Diversity: alpha – beta – gamma

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7

Area

Sp

ec

ies

ALPHA

BETA GAMMA

Beta diversity is a concept that helps us to cope with the fact that not every species lives everywhere

= avg +

= avg

Whittaker 1972

Lande 1996

Koleff et al. 2003 J anim Ecol 72:367

Beta diversity indices

Sorensen

Lennon et al.

Koleff et al. 2003 J anim Ecol 72:367

Jaccard"Broad sense" measuresincorporate differences in species richness as well as differences in composition

"Narrow sense" measuresindependent of differences in species richness

Example 1a = 10, b = 10, c = 100Jaccard = 10/120 = 0.08Sorensen = 20/130 = 0.15Lennon = 1- 10/20 = 0.5

1-

Example 2a = 10, b = 10, c = 1000Jaccard = 10/1020 = 0.010Sorensen = 20/1030 = 0.019Lennon = 1- 10/20 = 0.5

ßAB

A

FE

DC

B

ßBD

ßDF

ßAC

ßCE

ßEF

ßCDLa

titu

de

tem

pe

rate

tro

pic

al

Altitudelowland montane

Beta diversity along e.g. latitudinal gradient:• change in community composition measured by beta diversity• change in beta diversity

Latitudinal gradient in alpha diversity – owls

Koleff et al. 2003

focal area

Koleff et al. 2003

Latitudinal gradient in A, B, C parameters – owls

for adjacent pairs of quadrats

A

B C

Beta diversity A/(A+B+C) of owls along latitudinal gradient

Koleff et al. 2003

Amphibians

Birds

Mammals

Beta diversity of vertebrates

decrease in species overlap over 500 km

Reyers et al. 2000

Beta diversity and optimum selection of protected areas

1. select the most species rich plot2. add the plot bringing the highest

number of new species

1. select the plot with the rarest species 2. add the plot with the rarest

unrepresented species

richness-based algorithm rarity-based algorithm

Causes of species turnover in space

Speciation and dispersal limitation: species migration ability vs. barriers

Biological interactions: competitive exclusion from suitable habitats

Habitat availability: biotic and abiotic resources and limiting factors

Apparent species turnover:species too rare to be sampled

Speciation and dispersal limitation: the Hubbell’s (2001) neutral model

- all species ecologically identical - species turnover generated by dispersal limitation

The probability F(r) that 2 trees r km apart are conspecific is modelled as depending on: speciation rate , mean dispersal distance and population density is predicted to decrease linearly with log r

Habitat availability: altitudinal gradient, the mother of all environmental gradients

Ficus copiosa in New Guinea raingorest: 2 samples of 200 caterpillars 150 km apart

0

15

30

45

lowland x lowland lowland x montane

% o

f s

ha

red

sp

ec

ies

0

2

4

6

8

10

low high

Altitude

No.

of s

peci

es

0.0

0.2

0.4

0.6

0.8

1.0

low high

Altitude

Bet

a di

vers

ity [1

-Jac

card

] .

Two modes of altitudinal species turnover:with complete nestedness and zero nestedness

Identical altitudinal trends in species richness meandifferent trends in mean altitudinal range of species and beta diversity between adjacent altitudes

Species turnover along altitudinal gradients: Rhododendron spp. on Mt. Kinabalu

Rhododendrones: 900 spp. worldwide, 300 spp. in SE Asia, 50 spp. in Borneo, 25 spp. on Mt. Kinabalu, incl. 5 endemic spp.

Altitudinal distribution of 454 bird species in Papua New Guinea

0 m asl.

4500 m asl.

K. Tvardikova, unpubl. data

each row is 100 m elevation belt, each column a bird species

Biological interactions: “checkerboard” distributions

Altitudinal segregation of competing parrots in New Guinea:

Language distribution among tribal societies:

0

500

1000

1500

2000

2500

Mt. Niba SepikMts.

Mt.Karimui

KarkarIs.

Tolokiwa NewBritain

Alti

tude

(m

)

Charmosyna placentalis C. rubronotata C. rubrigularis

Diamond, J.M. (1975) Community Ecology

“Checkeboard distribution” - not predicted by island biogeography

Cockoo-dove Macropygia mackinlayi and M. nigrirostris

M. nigrirostris

M. mackinlayi

Checkerboard distribution: Zosterops birds in New Guinea

Zosterops chloris

Zosterops atriceps

Herpetofauna on British Virgin Islands:a nested pattern of species distribution

(a) a maximally cold matrix, (b) actual data, small mammals in Rocky Mts., (c), (d) matrices randomly filled under successively relaxed constraints [Patterson & Atmar 1986].

spec

ies

islands

Nestedness can be used to determine

extinction probabilities

U = 1/(mn) i j uij

T = U/Umax * 100

Matrix temperature T