Tropical ecology

Tropical biodiversity: species richness,

diversity of life strategies(January Weiner)

J. Weiner, "śycie i ewolucja biosfery", 2nd ed/PWN (2003)

Rozdz. 11

READINGS

Part TwoChapters 4 - 7

2009

1992

19992010

Simon & Schuster 1984, 1985

(appr. $10 at Amazon.com)

Princeton University Press1997

2005

Journal papers• Willig MR, Kaufman DM, Stevens RD (2003):

Latitudinal gradients of biodiversity: pattern, process, scale and synthesis . Annu. Rev. Ecol. Evol. Syst. 34: 273-309

• Turner JRG (2004): Explaining the globalbiodiversity gradient: energy, area, history and natural selection . Basic andApplied Ecology 5: 435-445

• Mittelbach GG et al. (2007): Evolution andthe latitudinal diversity gradient: speciation, extinction and biogeography. Ecology Letters, 10: 315–331

Classic text to read:

Joseph H. Connel, 1978:

Diversity in Tropical Rain Forestsand Coral Reefs

Science, V. 199, 4335: 1302-1310

Problems:

• Clinal variation of biotic diversity on Earth• Hypotheses explaining species richness in

the tropics• Adaptive strategies of tropical biota

Problems:

• Clinal variation of biotic diversity on Earth• Hypotheses explaining species richness in

the tropics• Adaptive strategies of tropical biota

Alfred Russel Wallace (1823 – 1913)

Darwin, Wallace and others:

• Adaptations in temperate zone depend on abiotic factors (climate);

• In the tropics – on the interactions between organisms;

• Fischer (1960): [therefore in the tropics] faster differentiation, more quiet time...

Kier et al. 2005

Global diversity of vascular plants

Kier et al. 2005

AVAILABILITY ADN QUALITY OF DATA CONCERNING PLANT DIVERSITY

Number of species per 10000 km2

<100 100-200200-400400-1000

1000-15001600-20002000-30003000-4000

4000-6000>5000

Latitudinal diversity gradient of fossilForaminifera (after Stehli et al. 1969)

Amphibians

Reptiles Mammals

Gaston et al.. 1995

LATITUDINAL GRADIENT OF FAMILY RICHNESS

Vascular plants

LATITUDINAL GRADIENT OF SPECIES (a) AND GENERIC (b) RICHNESS OF BIVALVES

(Flessa & Jablonski 1995)

Latitudinal gradient of extant species of corals(Fraser & Currie 1996)

Taxonomic diversity of the tropics: Phyla

• Annelida• Arthropoda• Chordata• Mollusca• Nematoda• Platyhelminthes• Rotifera

• Acanthocephala• Brachiopoda• Bryozoa• Cnidaria• Ctenophora• Echinodermata• Echiura• Ectoprocta• Gastrotricha• Kinoryncha• Loricifera• Nemertea• Phoronida• Pogonophora• Porifera• Priapulida• Sippuncula

• Onychophora

ONLY OCEANIC

ONLY TERRESTRIAL

TERRESTRIAL AND AQUATIC

BIRDS OF POLAND:

227 breeding specoes(Tomiałojć & Stawarczyk 2003)

Birds of Venezuela:

1382 species(Hilty, 2003)

CLOUD FOREST IN VENEZUELA (Rancho Grande)

Number of plant species in equatorial forests(after Primack i Corlett, 2005)

25061700Total Asia and Pacific

830175200Total

1000Pacific Islands

700Australia

1000Sri Lanka

4000S. India

10000Indochina etc.

45000Malaysia

18020000Africa total

4000Madagascar

16000Africa (land)

40093500Neotropics

Area forested (mln ha)Number ofspecies

Region

Number of tree species per hain rain forests of different continents

Primack i Corlett 2005

Other dataGentry 1988: 580 trees of 283 species/ha(Amazon, border of Venezuela and Brasil)

Speciesdiversity of

ants invariousregions

42Polynesia

23New Zealand

9667TOTAL

1100Australia

275New Guinea, New Britian and New Ireland

2080Asia (parts of this region)

2500Africa (sub-saharan)

429Europe

400USA

585North America, North of Mexico

2233West Indies, Mexico, Central andSouth America

No. sp.Region

From Holldoblerand Wilson (1991) andGroombridge(1992).

Number of coral genera in frelation to surfacetemperature of the see (Fraser & Currie 1996)

DIFFICULTIES WITHBIODIVERSITY MEASUREMENT

• How to measure species number withregard to area? (ecoregions, latitudinalzones, longitudinal belts, meridian, mapswith species density contours)

• The majority of tropical species are not known yet!

Okapi (Okapia johnstoni)Giraffidae

discovered in Congo in 1900

Pseudoryx nghetinhensis

1992

wstawić przyrost l. gat. ptaków (jak w podręczniku)

odkrywane ostatnio gatunki (liczby, przykłady, antylopa z Wietnamu, ośmiornice głębinowe

Wollemia nobilis Anonymus 1999 (Araukariaceae);

discovered in Australia : 1994

T.L.Erwin

19 treesLuehea seemani (Panama) fumigatedspecies of beetles collected .................................1200

Assumption 1: Average specifity of beetles = 13.5%ergo: No. of specialised species .............................163

Assumption 2: 50000 tree species in rein forests, on each specialisedspecies of beetles

ergo: total No. of species specialised .......... 8150000

Assumption 3: Beetles make up 40% spesies of arthropodsergo: No. of arthropod species ................... 20000000

Assumption 4: 2 × more species in tree canopies than on forest floorergo: total No. of species in rain forest ............ 30 mln

ERWIN’S ESTIMATE OF THE TOTAL SPECIES RICHNESS

Problems:

• Clinal variation of biotic diversity on Earth• Hypotheses explaining species richness in

the tropics• Adaptive strategies of tropical biota

Hillebrand, 2004:meta-analysys of 600 data sets confirms gradient properties:

• at regional scale are stronger and steeper than atlocal one;• strength and steepness increases with body size ofthe group studied;• strength increases with trophic level;• taxonomic effect (poikilo- vs. homeotherms);• in freshwater environments weaker than in marineand terrestrial ones;• differs between continents and environments;• hemispheres (S or N) do not matter.

LATITUDINAL BIODIVERSITY GRADIENTSARE UNIVERSAL

HISTORY OF THE RESEARCH CONCERNING THEGEOGRAPHY OF SPECIES DIFERSITY

• Wallace 1878• Dobzhanski 1950• Hutchinson 1959• MacArthur (et all.) 1965, 1969, 1972• Pianka 1966• RECENT REVIEWS (WITH NEW HYPOTHESES)

– Rosenzweig 1992– Brown 1988– Currie 1991– Rohde 1992– Wright, Currie & Maurer 1993– Turner, Lennon & Greenwood 1996– Fraser & Currie 1996– Rohde 1999– Kaspari et al. 2000– Willig et al. 2003– Turner 2004– Mittelbach et al. 2007

LOCALCOMMUNITY

LIMBOSPECIATION EXTINCTION

SPECIESPOOL

evolutionarytime scale

„ASSEMBLYRULES”environmental filtering

dispersal limitation

interactions

ecologicaltime scale

history = randomness

SUCCESSION

Continental spatial scale

MAJOR APPROACHES ANDCONTROVERSIES

• Neutral theories (MacArthur & Wilson, Hubbell)

• Niche-based theories (competition, specialization)

• Equilibrium vs. Non-equilibrum communities

GROUPS OFHYPOTHESES

ECOLOGICAL FACTORS(carrying capacity)

VARIOUS RATE OFSPECIESDIFFERENTIATION(speciation and extinction)

MORE TIME FOR DIFFERENTIATION IN THE TROPICS

Mittelbach et al. 2007

Differentiation rate similar, but more time in the tro pics:1. Tropical environments are older, many extant clades originated there 2. Clade dispersal from the tropics is limited and only recent

Differentiation rate in the tropics is higher...

...because speciation is faster1. Genetic drift in small populations 2. Climatic changes accelerate speciation3. Higher likeness of para- and sympatric speciation4. Larger area of the tropics – more chances for isolation5. Narrower physiological tolerance of tropical biota6. Higher temperature accelerates evolution7. Stronger interactions – narrower specialisation and faster speciation

...because extinction rate is lower1. Stable climate2. Larger area – more numerous populations – lower risk of extinction

EVOLUTIONARY HYPOTHESES CONC. BIODIVERSITY GRADIENT

Most important hypotheses explaininggeographical biodiversity gradient

• Geographical area• History• Productivity• Environmental energy• Rapoport’s rule• The rate of evolution• Geometric limitation• Continuous disturbance

• The geometry of the globe implies that thearea of equatorial zone is the largest;

• This area is thermally most uniform andstable;

• The number of species increases witharea;

• Large area has more diverse habitats.

Geographical area(Terborgh; Rosenzweig)

Rosenzweig 1995

SPECIES RICHNESS (S) IN RELATIONTO THE SURFACE AREA (A)

S = cAz log S = log c + z log A

NUMBER OF TREE SPECIESIN RELATION TO ISLAND AREA (AUSTRALIA)

LARGER AREAS OF RAIN FORESTS MAINTAINT MOREPRIMATE SPECIES

Primack i Corlett 2005)

NUMBER OF PRIMATE SPECIES CORRELATES ALSOWITH RAINFALL (EXCEPT FOR ASIA)

Primack i Corlett 2005

THE EFFECT OF LATITUDE UPON

„species-area” RELATIONLyons & Willig 2002

• data: marsupials and bats of Americas

• relation: S = C Az

where S = species number, A = areaC, z = parameters

log S

log A

1 2 3

C1 > C2z2 > z3

1. A clear latitudinal gradient of z (Lyons & Willig 2002)

pasami

kwadratami

1. A clear latitudinal gradient of C (Lyons & Willig 2002)

Conclusions:• Biotic diversity in the tropics is higher but less dependent on area;• This effect should be taken into account atany comparisons;

log S

log A

tropics

other

HISTORY(Rosenzweig)

• Tropical area was not subjected to deepclimatic changes during a long time;

• Climatic changes caused fragmentation oftypical tropical environments (rain forests) and enhanced speciation;

• In the tropics the number of speciesincreases with time (many old taxons).

The extent of recent glaciation, 18000 y. ago

CHANGES OF THE RAIN FOREST EXTENTIN SOUTH AMERICA

DURING PEISTOCENE RECENTLY

Mittelbach et al. 2007

HISTORY: thermal maximum in eocene,maximum extent of tropical environments

Average age of avian taxain relation to latitude

Weiner 2003 from Gaston & Blackburne 1996

Stebbins: „cradle or museum?”

latitude

log

(av.

age

ofta

xon)

Productivity

• Higher primary production (Pp) enables to maintain more species populations (S) (Hutchinson 1959, „Santa Rozalia”)

• S correlates (in large spatial scale) with Ppand AET

• No correlation of Pp i S in small scale• No explanation of the mechanism

Daniel Simberloff: „Santa Rozalia was a goat”

Environmental energy(Turner)

• Thermal conditions in the tropics are closeto thermoneutrum and stable

• Individual energy budget is less loadedenabling more expensive specialisations

• Temperature and PET correlate with S

Rapoport’s rule

• Species ranges close to equator are smaller• Species ranges at low elevations are smaller

• „Mountains in the tropics are higher” (Janzen)• Mechanism: seasonal climate suports broader

adaptations, enabling greater geographicalranges

• Stronger endemism in tropical climate

• Critics: contradictory examples, no evidence for the mechanism postulated

Rapoport’s rule

Ranges of the taxonswith the centres distantfrom equator are larger.

TreesSea molluscs

Fishes Reptiles and amphibians

Mammals

from Stevens 1989; Weiner 2003

Rapoport’s ruleon elevation gradient

Vertical ranges of species arelarger if their centre is locatedat higher elevation a.s.l.;With increasing elevation thediversity decreases.

Stevens 1992; Weiner 2003

Trees in Costarica

Mammals in Colorado

Birds in Venezuela

The rate of evolution

• The rate of speciation is supposed to increase with temperature: – shorter generation time,

– higher mutation rate, – stronger selection pressure

(Rohde 1992)

• Critics: The evidence not convincing

Geometric limitation

• Ranges randomly distributed over a largebut limited area make up a gradient oflocal diversities because of purely„mechanical” reasons.

Intermediate Disturbance Hypothesis(Connel)

• Rain forest: non-equilibrium; • „Gaps” continuously colonized (succesion)• Coral reef: non-equilibrium• Intermedite disturbances (hurricanes) and

continuous succesion

Classic text to read:

Joseph H. Connel, 1978:

Diversity in Tropical Rain Forestsand Coral Reefs

Science, V. 199, 4335: 1302-1310

FUNCTIONAL SIGNIFICANCE OFBIODIVERSITY

IN THE TROPICS

• Global carbon balance• Global water circulation• Local trophic cascade• Local biogeochemical balance

Tree biodiveersity efect uponbiomass carbon accumulation in

equatorial forest (Panama)Bunker et al. 2005; SCIENCE 310:1029-1031

• Mid column : average and c.v.• Number of tree species: 1 ... 126• Carbon accumulation: Mg/ha• Simulated sequence of spiecies loss:

• random• large-statured first• low density ‘’• high density ‘’• slow-growing ‘’• drought sensitive ‘’• endemic ‘’• widespread ‘’

Species richness

The effuct of mammals and birds uponherbivores, soil fauna and phosphorus

balance (Dunham, 2008)[exclusion experiment]

• Study area: equatorial rain forest(Ivory Coast, W. Africa)

• Mammals and birds excluded from study plots;• Studied were:

• plant consumption• faunal composotion• decomposition rate• phosphorus balance

Microfaunal sbundance drops, macrofaunal (earthworms) inceases on the plots void of mammale and birds (Dunham, 2008)

Percent loss of leaf biomass and morality of seedlings in he plotswithout mammals and birds

(Dunham, 2008)

Changes in the amount ofthe available inorganicphosphorus (P) andnitrogen (N) in the soildepending on the presenceof mammals and birds, after 8 month of exclusion.

(Dunham, 2008)

Trophic cascade in the rain forest

positive effects

negative efects

(Dunham, 2008)