The role of historic and climatic factors in the distribution of crustacean communities in Iberian...

The role of historic and climatic factors in the distributionof crustacean communities in Iberian Mediterranean ponds

MAR�IA SAHUQUILLO AND MARIA R. MIRACLE

Department of Microbiology and Ecology, Institut Cavanilles de Biodiversitat i Biologia Evolutiva, University of Valencia,

Burjassot, Spain

SUMMARY

1. We studied 140 freshwater ponds in eastern Spain spanning a wide range of water source,

hydroperiod and regional heterogeneity attributable to orographic and climatic differences. Our aim

was to provide a typology for Mediterranean ponds using crustacean assemblages and to find key

environmental thresholds that define these pond types.

2. To search for the environmental variables that define these communities, two complementary

analyses were used: correspondence analyses (CA) and multivariate regression trees (MRT). We

found a high level of specificity of crustaceans defining the different pond types. Three ponds, which

were not associated with any of the large set of environmental variables used, were clearly separated

from the rest in the CA. These held a very specific and probably relict community, characterised by

the large calanoid Hemidiaptomus: we refer to these as ‘Hemidiaptomus’ ponds. Taxonomic information

suggests a fundamental influence of historical events.

3. The MRT analysis applied to the rest of the ponds allowed us to create a hierarchical order of sev-

eral current environmental factors that account for their crustacean community composition. Thus,

we defined four further pond types. The most important factor structuring communities was hydro-

period, separating temporary ponds, mainly fed by rain, from permanent ponds, fed from more sta-

ble sources. Climate-related factors subsequently separated two groups of temporary ponds: (i)

temporary ponds in semi-arid areas (mean rainfall <600 mm year�1, spring rainfall <150 mm), which

contained Neolovenula alluaudi and (ii) temporary ponds in semi-humid areas, which contained Mixo-

diaptomus incrassatus. Amongst the permanent ponds, (iii) lowland coastal spring-fed ponds with

quite constant temperatures hosted a singular crustacean community that was well separated from

that found in (iv) inland mountain ponds consisting of more ubiquitous crustaceans.

4. These results provide a typology of ponds useful for conservation planning and freshwater biodi-

versity maintenance. Moreover, the identified ecological thresholds should be helpful in predicting

the communities to be expected as a result of changes to land use or climate.

Keywords: calanoid, cladoceran, environmental thresholds, Hemidiaptomus, hydroperiod, multivariateregression trees, turbidity

Introduction

Despite their small size, scientific interest in ponds has

risen recently because of their disproportionate contribu-

tion to biodiversity (Williams et al., 2004; De Bie et al.,

2008). Both their abundance and the broad geographical

ranges they cover account for the high overall contribu-

tion of ponds to biodiversity (De Meester et al., 2005).

The definition of a typology of small waterbodies is a

first step to understanding their contribution to biodiver-

sity (C�er�eghino et al., 2008). With this in mind, the Euro-

pean Ponds Conservation Network (EPCN) attempted a

preliminary classification of European ponds, based

upon both species distributions and specific biological

attributes (EPCN, http://campus.hesge.ch/epcn/pro-

jects_typology.asp). They divided ponds into three

subsets: Mediterranean, Atlantic and Alpine, and Conti-

nental ponds. First results from this project showed that

Correspondence: Mar�ıa Sahuquillo, Department of Microbiology and Ecology, Institut Cavanilles de Biodiversitat i Biologia Evolutiva,

University of Valencia, 46100 Burjassot, Valencia, Spain. E-mail: [email protected]; [email protected]

© 2013 Blackwell Publishing Ltd 1

Freshwater Biology (2013) doi:10.1111/fwb.12124

Mediterranean ponds hosted the richest and the most

unique fauna. It remains necessary to establish further

regional pond typologies within these three main groups

to take account of the diverse Mediterranean landscape,

as already concluded for Mediterranean streams

(S�anchez-Montoya et al., 2007).

Ponds are the most representative inland freshwater

lentic system in Mediterranean regions. They are extre-

mely important for their social and economic value as

well as for their ecological role in biodiversity mainte-

nance. The high biodiversity of ponds in the Mediterra-

nean region is the result of its ecological history and

landscape heterogeneity. The region served as a refuge

during ice age climatic fluctuations and preserves a very

specifically freshwater fauna, with typically Mediterra-

nean steppe taxa in the drier regions, which coexist with

Central European elements in wetter areas (Miracle,

1982). Mediterranean areas are characterised by signifi-

cant landscape heterogeneity that can be attributed to

both topographical–climatic variability and human influ-

ence (Cowling et al., 1996; Grove & Rackham, 2001).The

main characteristics of the Mediterranean climate are the

irregular occurrence of rainfall and the presence of a hot

and dry summer season. Ponds fed by rainfall are

expected to reflect these climate variations, with wide

fluctuations in environmental conditions, as is the case

for streams in a Mediterranean climate (Gasith & Resh,

1999). On the other hand, the Mediterranean basin has

many karstic areas with aquifers supplying spring-fed

ponds that are highly stable. Thus, depending on the

continuity or inconstancy of the water source, ponds

span a wide range of hydroperiods and hence a gradient

in environmental harshness that can be expected to

determine the relative importance of abiotic versus biotic

factors for community organisation (Arnott & Vanni,

1993).

Crustaceans, as permanent aquatic residents, are good

indicators of the ecological conditions of ponds. Our

overall objective was to determine a typology for Medi-

terranean ponds using crustacean assemblages and to

find key environmental thresholds that define these

pond types. We used a large data set of microcrustacean

communities for ponds in a varied and typical Mediter-

ranean area, the Comunitat Valenciana on the eastern

Iberian Peninsula. There have been several studies of

microcrustacean distributions on the Iberian Peninsula

(Miracle, 1982; Alonso, 1998) but none in the mountain-

ous inland part of our study area apart from our own

preliminary surveys (Miracle, Sahuquillo & Vicente,

2008; Sahuquillo & Miracle, 2010). This previous work

showed that the area hosted several rare and endemic

species. Within this heterogeneous area, we were able to

assess the differential influences on the distribution of

microcrustacean assemblages of external variables (such

as climate, orography and land use) together with inter-

nal physical and chemical conditions in the ponds. Land

use is important in our study area, which like other

Mediterranean areas, has been populated for a long

time, with human activities closely linked to water

sources. Our results may be applicable also to other

Mediterranean regions of the world, characterised by

predictable and seasonal droughts to which aquatic taxa

have become adapted (Gasith & Resh, 1999; Bonada

et al., 2007). On the other hand, comparisons with typol-

ogies obtained in non-Mediterranean regions would

emphasise the similarities and differences in factors that

constrain communities.

The specific aims of our study are as follows: (i) to

obtain a typology of ponds based on crustacean commu-

nities; (ii) to understand the factors accounting for these

typologies; (iii) to identify ecological thresholds associ-

ated with ‘break points’ in crustacean communities and

(iv) to identify the crustacean species characteristic of

each pond type. The resulting typology should be useful

for conservation planning and freshwater biodiversity

maintenance. Moreover, the identified ecological thresh-

olds should be helpful in predicting the communities to

be expected as a result of changes to land use or cli-

mate.

Methods

Study area

The study area (Comunitat Valenciana, Fig. 1) lies along

the centre of the Mediterranean coast of the Iberian Pen-

insula. Roughly 300 kilometres from north to south

(about 3° latitude) and 100 kilometres inland from the

coast, it consists of a narrow coastal plain and mountain-

ous inland territory (Iberian ranges in the north and

Sub-Betic ranges in the south). The region has a Mediter-

ranean climate, heavily influenced by the neighbouring

sea, but with very pronounced climatic differences

amongst areas due to continental influence and oro-

graphic effects. Annual precipitation ranges from semi-

arid (<400 mm year�1 precipitation) to subhumid

(>800 mm year�1) and mean annual temperatures from

8.6 °C in the northern mountains to 17.8 °C close to the

sea (P�erez Cueva, 1994). Precipitation peaks in late

autumn, with moderate rain in winter, a secondary peak

in early spring (depending on the year) and a very dry

summer. Rains are heavier in winter and early spring in

© 2013 Blackwell Publishing Ltd, Freshwater Biology, doi: 10.1111/fwb.12124

2 M. Sahuquillo and M. R. Miracle

wetter areas than in arid areas, where winter is dry. The

main shared characteristics of the studied waterbodies

are their small size and shallowness but they differ in

the source of their water (rainfall, streams or groundwa-

ter springs) and hydroperiod (from ephemeral to perma-

nent). Water source and hydroperiod are strongly

related.

Ponds fed by rain follow the Mediterranean rainfall

pattern, filling in late autumn to winter (autumnal

ponds sensu Wiggins, Mackay & Smith, 1980) and with

a water level that rises with early spring rains and then

lowers, drying gradually in the dry and hot summers

when evaporation exceeds rainfall. In more arid areas,

ponds may dry completely in winter and refill with

spring rains. Thus, rain ponds are temporary (with rare

exceptions) and highly fluctuating. Most of these ponds

are small and have been more or less modified by man

for watering livestock, although a few are well pre-

served natural rain ponds (some of them quite large)

associated with shallow aquifers. Ponds associated with

streams also follow the Mediterranean rainfall pattern

but to a lesser extent than rain ponds because the former

receive a more regular supply of water from drainage

basins associated with larger catchments. Most of these

ponds are depressions in temporary streams, where

water remains isolated when the main channel dries;

these ponds are usually semi-permanent. On the other

hand, ponds fed by groundwater springs are permanent

waterbodies with moderate seasonal fluctuations. In

inland mountainous areas, these ponds are mainly artifi-

cially constructed basins used to store water from natu-

ral springs, but they can reach a highly naturalised state

with dense macrophyte coverage. In lowland coastal

plains, spring ponds are natural basins fed by stable and

abundant vertical groundwater discharges from deep

aquifers, without significant seasonal changes in water

temperature or ionic composition. Information on limno-

logical variables from a representative set of these

ponds, corresponding to the same sampling campaign of

crustacean collections analysed in the present article, can

be found in Sahuquillo et al. (2012).

Crustacean sampling

We conducted several extensive surveys during winter–

spring 2006 and 2007, and a few additional ponds were

sampled in spring 2008. Overall, we sampled 140 ponds

(86 rainfall-fed ponds, 24 stream- or surface water–fed

ponds and 30 spring- or groundwater-fed ponds) in an

attempt to cover the different regions of the Comunitat

Valenciana where ponds are found (Fig. 1). Most of the

studied ponds are located in the inland mountainous

zone but we include also 10 ponds located in the coastal

plain. Sampling was performed between February and

early-May, to avoid the early and the late wet phases in

the temporary ponds. We established an order of sam-

pling according to different climatic conditions; at the

end of winter, we began to sample those ponds located

in lowland warmer areas, where seasonal warming

comes earlier, and as the spring progressed, we contin-

ued the survey to sample ponds at increasing altitudes

and latitudes. Most ponds were sampled once but about

20% were sampled twice (in two different years to pro-

vide samples from two late winter–early spring periods).

To obtain the fullest possible representation of the

planktonic and littoral microcrustacean communities in

each pond, we took semi-quantitative net samples from

different mesohabitats (open waters of the central area,

the vegetated littoral and very shallow shores). Littoral

800 mm

600 mm

400 mm

800 mm

400 mm

600 mm

10 km

Fig. 1 Geographical location of the 140 Mediterranean ponds stud-

ied in Comunitat Valenciana, eastern Spain. The isohyets show

mean annual precipitation based on data for a 30-year reference

period. Darker shading indicates higher precipitation.


Crustacean communities in Mediterranean ponds 3

and plant-associated microinvertebrates were sampled

by sweeping a 90-lm hand-net through the vegetated

areas and the shallow shores. The presence of large

branchiopods was determined in open water with a

250-lm towing net and by carrying out an exhaustive

visual examination along the very shallow shore areas

(especially to check for notostracans and conchostra-

cans). From open waters, we took 45-lm towing net

samples and quantitative samples. The latter were

obtained by in situ filtering through a 30-lm Nytal

mesh, between 4 and 16 L of depth-integrated water

samples with a transparent tube (1 or 0.5 m long and

5 cm internal diameter). All the material collected was

fixed in 4% formaldehyde and animals counted under

an inverted microscope. For net samples, we counted

subsamples until no substantial variation was observed

and no new species were found (always more than 300

individuals per sample). The remaining material was

examined at lower magnification to include less abun-

dant large-sized taxa. For quantitative samples, all speci-

mens were counted. Identification of branchiopod and

copepods followed mainly: Dussart (1967, 1969), Kiefer

& Fryer (1978), Negrea (1983), Stella (1984), Margaritora

(1985) and Alonso (1996) but we also used specific mon-

ographies and the ‘Guides to the identification of the

microinvertebrates of the continental waters of the

world’ (Dumont Ed., Volumes 1, 10, 11, 14, 15, 17 and 21).

Environmental variables

Two kinds of explanatory environmental variables were

used in multivariate analyses:

1. Limnological variables measured at each sampling

occasion:

Water depth was measured with a staked bar along

transects from the shore to maximum depth. Near this

point, at the centre of the open water area, we measured

in situ water temperature, dissolved oxygen, conductivity

and pH using WTW probes and we took a depth-

integrated sample of the water column with a transparent

tube (as described above) for laboratory analysis of tur-

bidity, alkalinity, planktonic chlorophyll-a, total phospho-

rus, total nitrogen and ammonium, following APHA

(1992). We estimated visually the percentage of pond area

covered by plants (including submerged and emergent

macrophytes) and the percentage of shores affected by

trampling, to indicate livestock pressure. We included

also information on fish predation pressure as a categori-

cal variable (0 = absent, 1 = present, 2 = abundant).

2. General geographical, climatic and hydrological

features assigned to each pond:

The hydrological features were categorical variables

indicating the main source of water (1 = rainfall,

2 = surface waters and 3 = ground waters) and hydrope-

riod. We assigned each pond to one of five hydroperiod

categories described in Table 1, based on our own obser-

vations. These categories are similar to those used by

other authors in studies of Mediterranean ponds (Ser-

rano & Fahd, 2005; Marrone & Mura, 2006; De Roeck

et al., 2007; Esta�un et al., 2010). The ponds were geo-

referenced in the field using a G.P.S. device (UTM coor-

dinates and altitude in m a.s.l.). Potential flooded pond

area (maximum area) was estimated using the Geo-

graphic Information System software from the Instituto

Cartogr�afico Valenciano (http://orto.cth.gva.es/). For

each pond, several climatic parameters related to rain-

fall, temperature and climate indices for a 30-year refer-

ence period (1960–1990) were obtained from the nearest

meteorological station in P�erez Cueva (1994). Note that

rainfall varies widely from year to year at any given

location, and it is not easy to separate changes in climate

from normal fluctuations of weather (Grove & Rackham,

2001). Our aim was to investigate the relationship

between crustacean assemblages and local variations in

climate, not temporal variations in weather, so we

selected a wide reference period for climatic data.

Data analysis

To obtain a representative composite sample for each

pond, the relative percentages of crustaceans in the dif-

ferent microhabitats were averaged for each pond and

date (all samples, except those taken with a 250-lm net,

were included). For multivariate analyses, the relative

percentages of crustacean species were arcsine square

root transformed to normalise the data. Explanatory

Table 1 Categories of pond, based on hydroperiod, used in this

study

CAT CODE Definition Hydroperiod

1 TS Temporary short

hydroperiod pools

<3 months

2 TM Temporary intermediate

hydroperiod pools

From 3 to 6 months

3 TL Temporary long

hydroperiod pools

Between 6 and more

than 9 months but

with annual summer

drying

4 SP Semi-permanent

ponds

Dry every few years

5 P Permanent ponds

feed springs

Permanent



variables were log (x + 1) transformed, except for rela-

tive variables (% trampling and% plant coverage), which

were arcsine square root transformed, and pH, climate

indices and hydrological categorical variables, which

were not transformed. Samples containing <3 species

were not included in these analyses. Large branchiopods

were not included in statistical analyses because sam-

pling was devised for collecting microcrustaceans. How-

ever, once the different typologies of ponds were

defined, for each typology the more frequent large bran-

chiopods were recorded.

We conducted an initial ordination of species and

ponds by detrended correspondence analysis (DCA by

segments) to check for differences in crustacean commu-

nity composition and to estimate the species gradient

length. Successive DCAs were performed excluding each

time those ponds well separated in a previous DCA,

until the axis of the analysis was smaller than 4 SD, con-

sidered a limit for a significant change in community

composition (ter Braak, 1995). Subsequently, we con-

ducted a canonical correspondence analysis (CCA), add-

ing the matrix of explanatory variables and calculating

Pearson correlations between sample and species scores

of the CA and CCA, to indicate how well the explana-

tory variables accounted for amongst-pond variation in

crustacean species composition (Leps & Smilauer, 2003).

The complementary use of unconstrained and con-

strained analyses can help to show whether important

explanatory variables have been overlooked (ter Braak,

1995). When fitting a constrained ordination model

(CCA), to avoid intercorrelation of variables, we reduced

the set of variables, one at time, so that no variable has

a VIF (variance inflation factor) larger than 20. The for-

ward selection procedure in CCA, with a Monte Carlo

permutation test for significance, was used to identify

the most important explanatory variables. Results were

expressed as the percentage of variance explained by the

conditional effect of each variable selected.

With multivariate regression tree (MRT) analysis, by

repeated splitting of the data, we looked for: (i) a hierar-

chical ordination of the variables affecting crustacean

composition; (ii) a threshold value (cut-off value) of

those variables that function as predictors and (iii) clus-

ters of sites (‘leaves’). The splits are chosen to minimise

the Bray–Curtis dissimilarity index within clusters, and

each split is defined by a simple rule based on environ-

mental variables (De’Ath & Fabricius, 2000; De’Ath,

2002). Predictive accuracy was estimated from the cross-

validated relative error (CVRE), and CVRE minimum

was used as the size of the best predictive tree (‘pruned

tree’, De’Ath, 2002). However the ‘un-pruned’ tree was

also shown to examine for subsequent explanatory vari-

ables affecting community composition within each leaf.

DCAs and CCAs were computed with CANOCO for

Windows version 4.5 (Biometrics, Wageningen) and

MRT analyses with the program R (Package mvpart ver-

sion 1.2-6).

Finally, to decide whether the solution of the obtained

typologies was satisfactory, we checked for nestedness

within the samples corresponding to each set of ponds

defined by the MRT nodes (and confirmed by CA and

CCA ordinations). With this analysis, we checked

whether the crustacean community corresponds to a

genuine typology, where species-poor samples are a

subset of species-rich samples in this typology. The

degree of nestedness was quantified by the matrix’s tem-

perature (Atmar & Patterson, 1993) from binary matrices

containing species and ponds using the BINMATNEST

program (Rodr�ıguez-Giron�es & Santamar�ıa, 2006). In

addition, the program calculated the probability that a

random matrix has the same level of nestedness as our

data (3rd null model following Bascompte et al., 2003).

The most characteristic species for each final pond

type was selected from those having the highest values

of the INDVAL index (Dufrene & Legendre, 1997) and

with a significance of taxa association to typology

P < 0.01. This analysis takes into account the relative

abundance and frequency of occurrence of each taxon

within the pond type and was performed using the soft-

ware PC-ORD for Windows, 4.20, Oregon.

Results

Environmental variables

The ponds were small (150 m2 median, only six ponds

exceeded 2 ha, the largest being a rain pond) and shal-

low (<5 m). Conductivity was lower in rain ponds, 75%

having conductivities from 150 to 300 lS cm�1, while

ponds associated with streams or ground water had

higher conductivities due to the influence of calcareous

mountains in the study area. Water temperatures in win-

ter–spring were generally mild (10–20 °C). Turbidity

showed a wide range of values in rain ponds. A large

proportion of ponds had high turbidity due to clay,

while both stream and spring ponds had characteristi-

cally low turbidities. Nutrient concentrations were gen-

erally low, except in a few rain ponds that were heavily

influenced by cattle and in the spring ponds in lowland

agricultural areas where total nitrogen concentration

was one order of magnitude higher than the mean

(Sahuquillo et al., 2012).



Crustacean communities

We recorded 69 crustacean taxa (Fig. 2): seven large

branchiopods, 33 cladocerans, six calanoid copepods, 17

cyclopoid copepods and six harpacticoid copepods.

Their occurrence follows a power law with a large tail

of low-occurrence taxa (60% of all taxa occurred at a fre-

quency lower than 5%).

Crustacean ordinations (CA-DCA). Results from CA1

applied to the whole data species matrix are shown in

Fig. 3a. The first two axes explained 17% of data varia-

tion, and the DCA gradient lengths for these were 5.9

and 5.3 SD units, respectively. Most samples were dis-

tributed along the first axis, while the second axis sepa-

rated a small group of three ponds (G1) from the rest.

Only this small group of samples had high values on

the 2nd axis, while the rest were located close to zero

without any loading on this axis. Sample and species

scores resulting from the unconstrained CA1 and the

constrained CCA1 showed a significant Pearson correla-

tion for axis 1 (sites r = 0.854, species r = 0.898, all

P = 0.000), but not for axis 2 (sites r = 0.147, P = 0.135,

species r = �0.011, P = 0.947). The explanatory variables

were not related to the 2nd axis, but they did explain an

important percentage of variance accounted for on axis

1. Amongst the three ponds separated by axis 2, two

hosted the calanoid Hemidiaptomus ingens and the cladoc-

eran Alona anastasia. These ponds were located in two

siliceous areas far from each other, and we have found

no other common feature apart from the composition of

crustaceans. The third pond was located near one of the

others, and although it has been recently deepened, it

shares the presence of the calanoid Mixodiaptomus

Fig. 2 Occurrence of branchiopod and copepod species in the 140 Mediterranean ponds. The dashed lines indicate frequency of occurrence

of 5% and 25%. Species occurring in 25–50% of sites are considered frequent, in 5–25% occasional and <5% rare.



laciniatus atlantis with the neighbouring pond, but it has

lost the species associated with temporary waters.

A second ordination (CA2, Fig. 3b) was then con-

ducted excluding data from the three ponds in G1

(CA1). The gradient lengths of the DCA2 (5 SD for axis

1 and 3.4 for axis 2) revealed important differences

regarding species composition between ponds. The first

two axes extracted from the CA accounted for 23.2% of

variance of species data (13.9 for the first axis and 9.3%

for the second). Correlations between sample scores of

an unconstrained CA2 and constrained CCA2 showed a

significant Pearson correlation for axis 1 (sites r = 0.890,

species r = 0.926, all P = 0.000) and also for axis 2 (sites

r = �0.536, species r = �0.746, all P = 0.000), showing

that the explanatory variables accounted for the varia-

tion amongst ponds in the crustacean community. For-

ward selection showed that 45% of that variance is

explained by four variables: hydroperiod (16%), altitude

(12%), annual precipitation (9%) and turbidity (8%). The

first axis of this analysis separated mainly temporary

ponds from permanent and semi-permanent ponds.

Additional ordinations were performed within both

the temporary and the permanent group of ponds sepa-

rately, giving a subdivision of two groups for each and

with different environmental variables explaining the

gradients (Fig. 3c and d). The forward selection of vari-

ables in the CCA for temporary ponds revealed that five

variables explained 50% of total variance explained

(water turbidity 19%, annual precipitation 10%, altitude

9%, hydroperiod 8% and water column depth 6%). The

CCA for permanent ponds revealed that altitude (14%),

water temperature (12%), dissolved oxygen (10%) and

chlorophyll (8%) accounted for 50% of total variance

explained. The DCA axis length from the analysis with

temporary ponds was 3.6 and 3.3 for axes 1 and 2,

respectively, and 3.4 and 3.8 for axes 1 and 2 from the

(b)(a)

G2

–3 3

–34

6

9

29

41

4748

49

51

Cyclops

A.robustus

P.aduncus

N.alluaudiD.obtusa

D.pulex

D.atkinsoniS.vetulus

Ceriodaphnia

M.brachiata

M.hirsuticornisC.sphaericus

D.crassa

A.elegans

M.incrassatus

M.minutusE.serrulatusT.prasinus

D.bicuspidatus

G3

Turbidity

Rainfall, Depth

Temporary ponds(c)–4 6

–212 Hemidiaptomus ingens

Mixodiaptomus laciniatus

T.ambigua

Alona anastasia

Canthocamptus staphylinus

G1

–4 6

–44 Hydroperiod

–2 2

–2

4

A.excisa

C.dubia

A.cambouei

C.uncinatus

I.sordidus

O.tenicauidis

P.laevis

C.numidicus

E.macruroidesD.crassa

P.affinis

Harpact. M.rubellus

B.longirostrisA.americanus

A.rectangula

S.vetulus

M.hirsuticornisP.aduncus

C.sphaericusA.guttata

Macrocyclops

E.serrulatusT.prasinus

32

33

51

G5

G4

Tem

pera

ture

Altitude

Semi-permanent ponds (d)

Altitude,

Hydroperio

d

Fig. 3 Biplots of samples (stars, squares and circles) and species (triangles) resulting from successive ordinations: (a) CA1 including all sam-

ples (stars: samples from the special group of ponds G1), (b) CA2 excluding the samples from the special group of ponds G1 (squares: tem-

porary ponds and circles: semi-permanent and permanent ponds, (c) CA3 including only the samples from temporary rainfall ponds

(samples from G2 in white and from G3 in grey), (d) CA4 including only samples from semi-permanent and permanent ponds (circles in

grey lowland coastal spring ponds, and inland mountain ponds are shown by white and black circles corresponding, respectively, to spring-

fed and stream-fed ponds).



analysis with permanent ponds. The length gradients

were now closer to the limit for a turnover of species.

We decided to finish the ordinations here and to check,

a posteriori, for the homogeneity and separation of the

clusters of ponds.

Forcing factors (MRT). We applied MRT analysis to all

ponds except the first group of three ponds separated

by the CA but not differentiated by the explanatory vari-

ables used. The MRT analysis with all variables gave a

four-leaf tree clearly identified as having the smallest

estimated predictive error (CV = 0.64) (Fig. 4a). The first

split was based on hydroperiod and separated two

groups of ponds: true temporary ponds (short, medium

and long hydroperiods) from semi-permanent and per-

manent ponds. Water supply, turbidity, depth and con-

ductivity were surrogate variables and defined

temporary ponds as fed by rainfall, with higher clay

Semi and permanentTemporary

Altitude < 58 m a.s.l.≥ 6.5 NTUTurbiditySpring Rainfall < 153 mm

Conductivity <395 µS cm-1Depth < 0.4 m

Plant <6%

Hydroperiod

Error: 0.485 C.V.Error: 0.636 SE: 0.0532

Hemidiaptomus ingensAlona anastasia

Ceriodaphnia sp.nov.several species and large branchiopods

Neolovenula alluaudiBranchipus schaefferi

Alona elegansDaphnia atkinsoni

Metacyclops minutus

Mixodiaptomus incrassatusChirocephalus diaphanusDiacyclops bicuspidatus

Dunhevedia crassa

Pleuroxus aduncusEucyclops serrulatus

Tropocyclops prasinus

Microcyclops rubellus majorAlona cambouei

Eucyclops macruroides

G1Special

“Hemidiaptomus ponds” G2

Temporary ponds in semi arid areas

G3Temporary ponds

in sub humid areasG4

Mountain semi and

permanent ponds

G5Lowland

permanent springponds

ponds = 50 ponds = 38 ponds = 39 ponds = 8ponds = 3

Chlorophyll-a > 7 µg L-1NH4 > 40 µg N L-1.pH >9.5

“Eutrophication”

Aridity Index< 30Mean annual temp.> 13ºCMinimum mean temp. >6.9ºC

“Aridity”

D.O. <9.4 mg L-1Area< 516 m2Plant <15 %

“Pond size reduction andEutrophication”

WaterTª > 19 ºCFish: abundantConduct. >813 µS cm-1Total Nitrogen>4 mgN L-1

(a)

(b)

X-Va

l Rela

tive E

rror

Size of tree

Min+1SE

0.20.4

0.61.0

0.8

1 2 876543 9 10 11 12

0

50

100

taxa

% po

nds

0

50

100

taxa

% po

nds

0

50

100

taxa

% po

nds

0

50

100

taxa

% po

nds

0

50

100

taxa

% po

nds

Fig. 4 (a) Pruned multivariate regression tree (MRT) with the greatest cross-validated accuracy (four leaves) based on crustacean commu-

nity composition from 140 ponds. At top left is the result of cross-validation of the MRT showing the relative error (open circles) and the

cross-validated relative error (filled circles). The vertical bars indicate one standard error, and the horizontal dashed line indicates one stan-

dard error above the minimum cross-validated relative error and suggests a tree size of four leaves. In the tree, the labels for each node

show the variable selected for the split and the threshold. The lengths of the vertical line segments are proportional to the drop in deviance

corresponding to each split. Below the name for each pond type is shown the number of studied ponds, a schematic view of the habitat

with more characteristic species, and at bottom, vertical bar plots showing the different relative frequencies of microcrustacean species in

each pond type. (b) Variables selected and thresholds for subsequent splits from the overlarge un-pruned tree. Main habitat stress associated

with the splits is also indicated.



turbidity and low conductivity. Both groups were split

again. Temporary ponds were separated by turbidity to

give a group (G2) with clay turbid waters (above 6.5

NTU) and a group (G3) with clearer waters. The ponds

of group G2 occurred in arid areas (mean spring rainfall

below 153 mm and mean annual rainfall below 600 mm)

and additional characteristics were their shallowness

and low conductivity (<339 lS cm�1). The group of non-

turbid temporary ponds (G3) occurred in wetter areas.

They were somewhat deeper (but not exceeding 1 m)

and had slightly higher conductivity and greater plant

cover than the turbid ponds (G2). The semi-permanent

and permanent ponds were split by altitude to give a

group of inland mountain ponds (G4) and another of

lowland ponds (G5, <58 m a.s.l.). Surrogate variables

define these lowland ponds as having higher water tem-

peratures, conductivity and total nitrogen and a higher

probability of fish presence.

The nestedness analysis of the binary matrix with spe-

cies/sites for each of these four groups of ponds gave a

temperature of 14–15 for temporary ponds in arid areas

and for the permanent and semi-permanent inland

ponds and 34 for coastal lowland spring ponds and for

temporary ponds in wetter areas. Temperature (0–100°)

indicates the degree of nestedness; the colder the system

is, the more fixed the order of the species extinction will

be (Atmar & Patterson, 1993). Thus, our low tempera-

ture values indicate that communities within groups are

highly nested. The species composition of communities

with a lower number of species was a nested subset of

the species composition of communities with a large

number of species. The estimated P value for the ‘third

null model’ (Bascompte et al., 2003) was significant in all

cases. Therefore, we can consider the groups of ponds

separated by MRT analysis and CA to represent truly

different pond types.

Pond types and their indicator species

The bar plots at the bottom of Fig. 4a show the relative

frequencies of each taxon for each pond type. A gradual

replacement of species across the different pond types

can be observed, indicating considerable specificity of

crustaceans amongst pond types. Table 2 shows the

results of an INDVAL analysis for each pond type and

provides the indicator taxa associated with each. Cala-

noids are good indicator species: Hemidiaptomus indi-

cates a singular type of Mediterranean ponds, and

Neolovenula and Mixodiaptomus (in our case) are sensitive

species that define pond types and can be used as

indicators of environmental/climatic conditions. In the

following paragraphs, we will characterise the five pond

types.

Hemidiaptomus ponds (G1). This first pond type is poorly

represented amongst the studied ponds (only three

ponds, accounting for 2%) and seems to be unrelated to

any limnological, climatic, geographical or hydrological

variables used. It corresponds to a very rich and uncom-

mon crustacean community in which the large H. ingens

was the best indicator taxon. In addition, a large pool of

six other species had high and significant INDVAL val-

ues (Table 2). Most species occurring in these ponds

were also rare, such as the recently described A. anastasia

(Sinev et al., 2012), a new species of Ceriodaphnia, Mixo-

diaptomus laciniatus atlantis and rare large branchiopods.

These species are restricted to temporary aquatic habitats

and show a very limited biogeographical distribution.

Temporary ponds in semi-arid areas (G2). This includes a

large number of very shallow temporary ponds, located

in areas with semi-arid climate (mean rainfall

<600 mm year�1, spring rainfall <153 mm) and having a

short or medium hydroperiod. A total of 18 cladocerans

plus copepods and four large branchiopods occurred,

but only nine appeared with a relative frequency above

15% and could be considered common species in this

typology. Significant and highest INDVAL values corre-

spond to species restricted to temporary waters and

mainly with planktonic affinities. The Paradiaptominae

species Neolovenula alluaudi had highest INDVAL values.

This is a steppic calanoid from temporary waters with a

circum-Mediterranean distribution and preference for

arid or semi-arid areas. A typical community composi-

tion would include, besides this calanoid, several large

planktonic cladocerans co-occurring simultaneously

(Daphnia pulex, Daphnia atkinsoni and Moina brachiata)

and typically some sediment-associated crustaceans

(Metacylops minutus, Alona elegans and Macrothrix hirsuti-

cornis). The anostracan Branchipus schaefferi was the char-

acteristic large branchiopod, and in few cases, the

notostracan Triops spp. also occurred.

Temporary ponds in subhumid areas (G3). These are tem-

porary rain-fed ponds located under relative wetter con-

ditions with respect to the study area (>600 mm year�1)

and mainly located in mountain areas. They were also

well represented, numerically, in the study area. Here,

the number of cladocerans plus copepods found was 24

together with three large branchiopods. Only 16 taxa

had a relative frequency above 15%, and three species

had a significant INDVAL value (Table 2). This commu-



Table 2 Results of the INDVAL analysis with species grouped according to pond types

Species INDVAL P

Relative frequency

Pond typesG1 G2 G3 G4 G5

Hemidiaptomus ingens 67 ** 67 ‘Hemidiaptomus’ ponds 2 (+1) ponds = 2%

63% planktonic speciesMixodiaptomus laciniatus atlantis 67 ** 67

Alona anastasia 50 ** 5

Ceriodaphnia sp. nova 37 ** 83 3 72 19

Diaptomus cyaneus 33 ** 33

Cyclops abyssorum divulsus 32 ** 5 2 7 2

Canthocamptus staphylinus 29 ** 33 2 21

Tretocephala ambigua 13 * 17 2

Neolovenula alluaudi 60 ** 64 2 Temporary ponds in semi-arid areas

with Neolovenula

36% of studied ponds

71% planktonic species

Alona elegans 46 ** 17 73 67 5

Metacyclops minutus 46 ** 67 84 49 7

Daphnia gr. pulex 27 * 17 59 47 36

Macrothrix hirsuticornis 21 ** 5 41 4 12 13

Moina brachiata 19 * 27 3

Daphnia atkinsoni 17 * 23 16

Mixodiaptomus incrassatus 74 ** 74 Temporary ponds in sub-humid areas

with Mixodiaptomus



Diacyclops bicuspidatus 37 ** 4 2

Dunhevedia crassa 27 * 28 19

Daphnia obtusa 16 * 14 23

Acanthocyclops robustus 7 2 12 1

Tropocyclops prasinus 54 ** 18 35 81 56 Mountain semi-permanent and permanent

ponds



Pleuroxus aduncus 42 ** 11 9 48

Eucyclops serrulatus 27 * 11 42 55 81

Chydorus sphaericus 26 17 11 28 45 1

Macrocyclops albidus 23 * 5 29 63

Simocephalus vetulus 22 5 16 33 19

Alona guttata 21 21

Ceriodaphnia dubia 17 * 17

Alona rectangula 13 2 9 21 5

Diacyclops bisetosus 7 7

Ceriodaphnia laticaudata 6 2 1

Megacyclops viridis 5 5

Paracyclops chiltoni 5 5

Leydigia leydigii 4 5 7

Alona cambouei 94 ** 94 Lowland spring ponds

6% of studied ponds


Harpacticoide 94 ** 94

Microcyclops rubellus major 73 ** 7 94

Eucyclops macruroides 38 ** 38

Ilyocryptus sordidus 31 ** 31

Oxyurella tenuicaudis 31 ** 31

Pleuroxus laevis 31 ** 31

Camptocercus uncinatus 25 ** 25

Paracyclops affinis 25 ** 25

Scapholeberis rammneri 25 ** 25

Copidodiaptomus numidicus 19 ** 19

Alonella excisa 14 * 5 25

Acanthocyclops americanus 8 2 1 44

Bosmina longirostris 3 2 13

Species with INDVAL values above 20 are shown in bold.

*P <0.05; **P <0.01. Relative frequencies for each species for the five pond typologies are also given.



nity shares nineteen species with those from temporary

ponds in arid areas and 17 species with permanent

ponds. This illustrates the intermediate position that this

pond type, which can have very long hydroperiods,

occupies between the temporary and permanent ponds.

A typical crustacean community includes the calanoid

Mixodiaptomus incrassatus and several large planktonic

cladocerans. The crustacean community is enriched by

the presence of numerous macrophyte-associated taxa

and some sediment-associated taxa, either that have a

preference for temporary habitats (A. elegans, Metacyclops

minutus) or permanent ones (Alona rectangula). The anos-

tracan Chirocephalus diaphanus was the characteristic

large branchiopod.

In the studied ponds, the occurrence of the calanoids

N. alluaudi or M. incrassatus clearly separated two eco-

logically different pond types. We found only one site

where N. alluaudi and M. incrassatus co-occurred simul-

taneously. The pond is located geographically in the

transitional area between wetter and a semi-arid climate,

and significantly, N. alluaudi made up a major propor-

tion of the plankton samples.

Permanent and semi-permanent ponds in mountain areas

(G4). These contained a community represented by a

large number of widespread species. The number of cla-

doceran and copepods found was 17 and 12, respec-

tively, 12 having a relative frequency above 15%. Ten

species had an INDVAL value higher than 20, but none

was exclusive to this group. Highest INDVAL values

correspond to a group of three widespread copepods of

different sizes, namely Macrocyclops spp., Eucyclops ser-

rulatus and Tropocyclops prasinus, as well as the macro-

phyte-associated cladoceran Pleuroxus aduncus. G4

communities can reach a high diversity and include

large planktonic cladocerans, such as Daphnia gr. pulex

and species in the genus Ceriodaphnia.

Lowland permanent spring ponds (G5). These are limnoc-

rene spring ponds located along the coast and charac-

terised by very stable conditions due to their

groundwater source. Temperature is warm and stable,

about 19 °C all year-round, and water level fluctuations

are small. Despite the low number of ponds in this

group (eight), we found a large number of taxa (22

taxa, considering harpacticoids as one taxa, but at least

four different species had been identified) and a large

number of species that occurred at high relative fre-

quencies (20 taxa with a relative frequency above 15%),

with 10 taxa exclusive to this pond type and thus a

large number of indicator species (Table 2). Like G4

permanent ponds, G5 ponds are characterised by the

presence of a group of copepods of different sizes, but

the G5 community is richer. Amongst cladocerans, we

found a rich community with mainly littoral-associated

species and only one small planktonic cladoceran spe-

cies, Bosmina longirostris, was found.

Differences within each pond type

When running an ‘un-pruned’ tree, variables selected for

the subsequent splits were quite different for each leaf

(Fig. 4b). Within temporary ponds in arid areas, abiotic

factors related to climate and depth (reflecting hydrope-

riod) constrained the communities. Where environ-

mental conditions were less harsh, biotic variables

constrained the communities, such as those related to

trophic level and food resource (plant coverage and

chlorophyll) in temporary ponds in wetter areas and in

permanent ponds in the mountains. On the other hand,

the group of lowland spring ponds was strongly homo-

geneous and could not be subsequently divided.

Discussion

An extensive survey of crustacean communities in an

area characterised by a wide variety of small temporary

and permanent aquatic environments allowed us to

detect differences that were great enough to clearly iden-

tify distinct pond types. Much of the fauna is very spec-

ialised and has specific ecological requirements and

especially so for those with a preference for temporary

waters. This specialisation is supported by the large

number of species with significant INDVAL values.

There is an interesting hierarchical order of factors

structuring these crustacean communities. First histori-

cal, and second climatic and hydrological factors, played

key roles in differentiating five major pond types. Third,

local factors, such as eutrophication, shaped communi-

ties within these major typologies. This contrasts with

previous results where the zooplankton community was

found to be shaped by biotic factors, such as fish and

macrophyte abundance (Davidson et al., 2010) or trophic

state (Cottenie et al., 2003). However, these studies

focused on permanent ponds in temperate regions

where environmental variation is not so marked. When

studies are carried out in environments where harsh

conditions prevail, such as Alpine ponds, or cover large

latitudinal gradients, they usually reveal the overriding

influence of abiotic factors, such as altitude (Hinden

et al., 2005; Catal�an et al., 2009) and water conductivity

(Bjerring et al., 2009).



Special ponds with Hemidiaptomus: the role of historical

factors

The first pond type (G1), named ‘Hemidiaptomus ponds’

due to the presence of this diaptomid genus or the asso-

ciated M. laciniatus, comprised only three ponds. This

pond type was clearly separated by CA according to the

species data matrix but we could not find any relation-

ship to the large set of environmental variables used in

this study. In contrast, the crustacean communities of

the other four pond types can be clearly related to cur-

rent environmental conditions. It is conceivable that the

G1 ponds represent examples of relict wetlands that still

harbour a primordial community. In addition to the

crustacean community, these ponds share a siliceous

substratum, which is not common in a predominantly

calcareous study area. However, these two features are

not enough to explain their uniqueness. Ponds with

Hemidiaptomus have been found also in calcareous sites

(H. roubaui author’s observations), and ponds in some

areas with identical climate, substratum and vegetational

structure do not have Hemidiaptomus at all.

The Hemidiaptomus ponds hold a rich and unusual

crustacean community (Sahuquillo & Miracle, 2010),

supporting the hypothesis that historical factors have

played a more important role than current environmen-

tal factors in these sites. Taxonomic information and

speciation rate provide clues to historical influence

(Ricklefs, 1987). The genus Hemidiaptomus by itself repre-

sents a case of high speciation and restricted distribu-

tion. The group of species H. ingens, found in these

ponds, is very rare with very few known localities, and

in the Iberian Peninsula, it has been found only in the

ponds of this study. Recent taxonomic and molecular

studies have highlighted the role of historical factors in

the distribution of the genus Hemidiaptomus (Marrone

et al., 2013). Their analysis included individuals collected

by us and revealed that the population from Cavall (one

of our ponds) clustered together with other populations

of the H. ingens species group from localities in Italy

and Corsica, while that from Sinarcas (another of our

ponds) is an independent evolutionary lineage only

found in this pond. Apart from this calanoid, other

accompanying taxa were also rare and of biogeographi-

cal interest such as the large branchiopods: Branchipus

cortesi, an Iberian endemic, or the western-Mediterra-

nean Maghrebestheria maroccana (Sahuquillo & Miracle,

2010). Moreover, uncommon taxa and high species rich-

ness have been reported in other ponds where Hemidia-

ptomus occurs (Gauthier, 1928; Alonso, 1987; Marrone &

Naselli Flores, 2004; Alonso & Garcia-de-Lomas, 2009;

Caramujo & Boavida, 2010), not only for crustaceans but

also for plants (Bagella et al., 2010). These Hemidiaptomus

ponds are a refuge for several peculiar species, suggest-

ing the existence of a former and ancient wetland area

with sufficiently low historical disturbance to maintain a

complexly structured crustacean community. Habitat

age is likely to be important in determining whether a

Hemidiaptomus pond community is present. The species

of the Diaptomidae family are characterised by limited

distribution ranges constrained by the legacies of histori-

cal biogeographical events (Leibold, Economo & Peres-

Neto, 2010). Other authors have noted how history mat-

ters. For example, Chase (2003) pictured the mechanism

of community assembly as a result of variation in the

timing and sequence of species invasions. Considering

its limited current representation, the community of

Hemidiaptomus ponds could be considered relict and

probably with low dispersal capacity. Kotov & Alonso

(2010) suggest that some Iberian endemics could be rem-

nants of a pre-Pleistocene fauna and that they did not

recolonise new territories after the deglaciation. The cal-

anoid Hemidiaptomus could be considered as a ‘sentinel’

or ‘indicator’ species for ancient Mediterranean ponds.

Environmental filters and ecological thresholds: the major

role of climate

Current environmental conditions have been shown to

be useful to predict and differentiate crustacean commu-

nity composition in the studied ponds, with the excep-

tion of Hemidiaptomus ponds. We established the

relationships between the species of crustacean commu-

nities and environment conditions using two comple-

mentary approaches: CCA to globally model the

continuous structure along environmental gradients and

MRT to predict where break points are. The existence of

break points is expected because species assemblages

tend to exhibit clear-cut discontinuous points even when

environmental variables show a continuous gradient.

Margalef (1974) explains this as a consequence of the

coincidence of species tolerance limits, due to their

co-adaptations to the most frequent combinations of

environmental factors. We found a gradual replacement

of species dominance, but we also identified environ-

mental thresholds that marked a notably change in spe-

cies composition. Because of the wide environmental

variability across the study area, thresholds of ecological

factors that are related to the stressful climate that cha-

racterises the Mediterranean landscape can be expected

to most important. The scarcity of water is a limiting

factor for aquatic Mediterranean habitats, and thus,



hydroperiod was the first structuring factor. Many studies

of Mediterranean aquatic habitats have pointed to tem-

porality and conductivity as major structuring forces

(Boronat, Miracle & Armengol, 2001; Frisch, Moreno-

Ostos & Green, 2006; Marrone, Barone & Naselli Flores,

2006; Boix et al., 2008; Waterkeyn et al., 2008; Caramujo

& Boavida, 2010). Although we were not expecting great

differences in conductivity, because only freshwater

ponds were included in this study, variation did exist

because of the contrasting sources of their water. The

first division into temporary and permanent ponds is to

be expected since temporary ponds hold species able to

withstand dry periods (Wiggins et al., 1980). The crusta-

cean assemblage of the semi-permanent ponds, whether

fed by rainfall, by streams or by springs, was quite simi-

lar to each other and also to the assemblages of perma-

nent ponds. Some pond features can explain this

similarity, such as the possibility of recolonisation by

hydrochory in the case of ponds fed by intermittent

streams. Moreover, in the case of rain-fed ponds that do

not dry totally every year, microcrustaceans may remain

in interstitial water or even in small wet cavities.

The subdivision of crustacean communities of tempo-

rary waters into semi-arid and subhumid types emphas-

ises the major role of climate in their distribution. Clay

turbidity was a principle determinant of communities in

temporary ponds in arid areas (a special habitat called

argillotrophic temporary ponds). The landscape of arid

areas is characterised by a sparse vegetation cover. In

these situations, ponds are usually shallow due to the

paucity of precipitation, and if they occur on clay, they

are more susceptible to increased water turbidity owing

to sediment suspension. Despite this harsh environment,

the ponds sustain a characteristic and specialised crusta-

cean community able to feed on organic matter

adsorbed to the suspended clay particles (Alonso, 1985;

Castelli et al., 2006). Some specialised taxa (e.g. Daphnia

atkinsoni) are nicely adapted to these conditions (Mar-

rone et al., 2006), and they thrive better than in clearer

and more macrophyte-rich waterbodies. Other variables

that separate the two types of temporary ponds are

clearly climatic, a ‘break point’ occurring at the thresh-

old of 600 mm mean annual precipitation. It is interest-

ing to note that spring rainfall explained more variation

in crustacean composition in temporary ponds than total

annual rainfall. Spring rainfall is more variable interan-

nually than autumn rainfall, and spring rainfall is more

influential in arid zones of the study area. Arid areas

with dry winters may have several short intermittent

wet phases with critically limited time available for

development and reproduction. In wet areas, spring

rainfall extends the wet period initiated in autumn to

the end of summer. Drought severity, hydroperiod

length and the predictability of flooding periods are

important factors for temporary pond dwellers, and

crustacean composition in this study emphasised the dif-

ferences between semi-arid temporary ponds, temporary

ponds in more humid areas and semi-permanent or per-

manent ponds. Our results corroborate other studies that

have reported that different climate zones with more or

less severe dry periods are strong determinants of crus-

tacean community composition (Gauthier, 1928; Alonso,

1998; Marrone et al., 2006).

Within the group of semi-permanent and permanent

ponds, a physical factor related to water source sepa-

rates the lowland spring ponds from permanent ponds

in mountains. Lowland spring ponds have slightly

higher conductivity with respect to other ponds and are

characterised by warm and stable temperatures.

Undoubtedly, these stable and milder conditions favour

a rich fauna with Mediterranean or tropical affinities. In

addition, the influence of a biotic factor also became

prominent in lowland spring ponds: the presence of fish.

Most rain ponds were isolated and endorheic, and fish

were absent. In mountain spring- and stream-fed ponds,

fish were scarce or absent because of inaccessibility or

only intermittent connections with permanent waterbod-

ies. However, in lowland spring ponds, a permanent

outflow provided connectivity with wetlands and

allowed fish colonisation. Fish presence can determine

zooplankton size distribution (Brooks & Dodson, 1965)

and may account for the absence of large planktonic

zooplankton in these ponds.

Variability within major pond groups

Beyond these five types of ponds, factors affecting the

crustacean communities within each typology are quite

different and reflect different habitat stressors. Since the

ponds within these groups are highly nested, the subse-

quent splits separate the more impoverished ponds from

the richer ones. Our results confirm that patterns of

community composition are better interpreted within

the broad context of regional and historical influences,

with local factors acting as a constraint for species rich-

ness (Ricklefs, 2004). In the temporary ponds of arid

areas, climatic factors and depth were again responsible

for splitting the groups, their communities being ‘physi-

cally controlled’ due to harsh environmental conditions,

with organisms primarily adapted to the physical envi-

ronment and biological interactions being less significant

(Sanders, 1968; Menge & Sutherland, 1976). The number



of crustacean species is reduced in ephemeral ponds

(Eitam et al., 2004), and these species are highly specific

and adapted to this extremely transient environment

(Williams, 2006). Conversely, more benign and predict-

able conditions drive adaptations primarily related to

success in interactions with other species (Sanders,

1968). Therefore, in ponds where climatic conditions are

not so stressful and hydroperiod is longer, eutrophica-

tion appears as an important factor for the subdivision

of major types. Communities with a reduced number of

species are separated from the richest ones, but in this

case, the species maintained in the most eutrophic or

altered conditions tend to be the most generalist and

widespread.

The severity of environmental conditions determines

the relative role of biotic and abiotic factors. Physical

factors have been suggested as major forcing factors

structuring communities where environmental condi-

tions are severe and unpredictable (Sanders, 1968), and

these are the determining factors in the crustacean typol-

ogy of our study area. Biotic factors (chlorophyll, fish)

had a relative smaller role but with their influence hier-

archically constrained by climatic conditions. In a wide-

ranging study of species richness in shallow lakes from

different European regions, Declerck et al. (2005) also

found different driving factors shaping crustacean com-

munities in relation to latitude, with the trophic state

proving important in northern European areas, whereas

in Spain, abiotic features, such as temperature and con-

ductivity, were more decisive factors.

Implications for management

In summary, in our study area, the composition of pond

crustacean communities is related to historical and cli-

mate-driven factors, with hydroperiod being of major

relevance. Our results emphasise the need to identify

relict sites, such as Hemidiaptomus ponds, that should be

strictly protected because of the high risk of losing them

and the difficulty of subsequent restoration. These pond

communities seem to be the result of undisturbed evolu-

tion, and their modification, such as by deepening

(Sahuquillo & Miracle, 2010) draining or polluting them,

will alter them irreversibly. Creation of new ponds in

other areas will favour current widespread species

(Jeffries, 2012), whereas relict ones will disappear if we

damage their last refuges.

The maintenance of original hydroperiods is of great

importance for biodiversity conservation and there is a

need for concerted effort to focus on all existing ponds,

including the smallest and the more ephemeral ones in a

network, since these could be important as a reservoir of

biodiversity. Future climate change scenarios forecast a

decrease in precipitation in southern Europe, with

subsequent changes to the distribution of community

types. Thus, it may be that communities lost from arid

areas have a chance of establishing in ponds of formerly

wetter areas. However, pollution and other human activ-

ities favour widespread tolerant species with rapid dis-

persion that outcompete specialised species, thereby

producing the impoverished communities that are com-

ponents of a nested structure within each main group.

Acknowledgments

The authors thank Eduardo Vicente and Sara Morata for

their help with fieldwork and laboratory analyses and

Ignacio Lacomba and Vicente Sancho for assistance with

fieldwork. Ricard Miracle is gratefully acknowledged for

his assistance with MRT and nestedness statistical analy-

ses. We also thank Federico Marrone for his valuable

comments. We greatly appreciate the language correc-

tion by Vicente Deltoro and the detailed editing job on

the manuscript by the editor Colin R. Townsend. This

research was supported by the EC projects LIFE05/

NAT/E/000060 and the LIFE04/NAT/ES/000048.

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(Manuscript accepted 29 January 2013)



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