NATF320 L5 Biogeography of tropical rainforests

5 main rainforest regions

amazon, central america, and brazilian atlantic forest

congo basin and west africa

south-east asia

new guinea and australia

madagascar

biogeography

the large-scale geographic pattern in the distribution of species and the causes and history of this distribution

biogeograpy looks at fundamental process

dispersal

colonization

extinction

evolution

dispersal

movement of organisms from a apoint of origin (location of source, ancestral, population) to a new location

colonization

organisms reaches new location, survices, reproduces and establishes new population

extinctione

species is elimated from a patticular area, species may survive elsewhere and may recolonize area where it went extinct

evolutin

surviving populatin in a particular area undergoes cahanges in frequency of gene alleles, may result in altered phenotype and given sufficient time, possiblyt the formation of new species (speciation)

biogeographica; regions

earth can be divided into regions based on assemblages of plants and animals 0 biogeographical regions

biogeographic realms are based on evolutionary relationships and morphological similarities

biogeographical regions differ for flora and fauna

not always clear, since there are different lines, e.g. borneo

vegetation composition

pantropical famiies

many genera are also shared by two or more continents, but very few species

symphonia globulifera is an exception and is widely distributed in African and Neotropical rainforests

neotropics - characteristics

important woody families: Vochysiaceae, Bignoniacea, lecythidacea and chrysobalanaceae

large number of palms - 857 speceis in 64 genera

large number of orchids 41% of world

hummingbird pollinated plants, such as heliconia and passiflora

large number of bromeliads

SE asia characteristics

dominated by dipterocarps

mast fruiting eery 2-7 years

presence of oaks and chestnuts

large number of epiphytes and palms

africa characteristics

impoverished flora, particularly palms, orchids, lauracaea, myrtaceae, mristicaecae as wel as epiphyes and vines in general

low species numbers even in pantropical families

piper genus 1000 speceis in neotropics, several hundred in Asia, only 3 in Africa

large ares of single species dominance

new guinea and australia characteristics

new guinea floral composition a mix, but similar to Asian flora at afamily and genus level

dipterocaprs less important than se asia

australia noticable for its primitive plant families of gondwanic origin

little influence form asia

half ot the species are endemic

madagascar characteristics

high endemism -96% of trees and shrubs

most species in genera shared with africa, but diverse palm flora including genera of asian affinity

few figs and a paucity of edible fruits

vertebrates primates

new world vs old world

new world

• broad nostrils pointing to the sides

• three premolars

• lack opposable thumg

• all have tail, some prehensile

• variable colour vision, some tri, some dicrhromatics

old world

• narrow nostrils pointing forward

• two premolars

• opposable thumbs

• many lack tail

• all have trichromatic colour vision

other dissimilarites

fruit-eating primates mare abundan tin the neotropics

leaf-eating primates more promiment in the old world

new world priamtes all live in forest 0 old world priamtes use a variety of habitat

new wolrd primates rarely descend to the ground whereas many old world onkeys may be found more often on the round thant in trees

new guinea and australia have no primates, they ahve marsuipial equivalanets in tree kangeroos and possums

interestingly marsupials also occur in neotropical forests

other vertebrates

number of carnivores highest in asia and neotropics

africa has lower diversities, no dogs, no bears and only two cats

cats completely absent from madagascar, its own endemic canrivores

large or middle sized carnivores are completely absent form new guinea and australia, largest are reptiles and birds

new guinea and australia lack ntive members of the order carnivora altogether

forest floor herbivores are scare, but africa shows the highest species richness

neotropics lack bovids, rhinos and elephants and support relatively low biomass of browsers and grazers

in new guiea and australia, kangaroos and wallabies occupy this niche in additon to large flightless birds

madagascar lacks ground-dwelling browsers and grazers

bats

megachriptera (true fruit abts) restricted to the old world tropics

new world bats are much smaller, do not roost in huge tree colonies and belong to entirely different gorup of bats (microchroptera)

they also include bats that eat insects, fruits, blood, nectar and small vertebrates or a combination of these

gliders

predominantly SE asia

birds

birds radiated in the tertiary (65-35 Ma) when S. America and Australai were more isolated, madagascar already separated from africa

rainforest bird diversities radiated in each forest block relatively independently, altough africa and asia bcecame connected early and are similar to each other

only few bird families found in all rainforest regions: swifts, swallows, pigeons, parrots, cuckoos, hawks, falcons, owls and nightjars

new world most spcies rich

what are the origins of similarities and differences among rainforest regions

biogeographic

evolutionary

ecological (anthropological)

biogeographic factors

a modern pantropical distribution of a genus or family could reflect

an origin on Gondwana before the breakup of the continents

dispersal via high latitude land bridges in the earl eocene

more recent trans-oceanic dispersal

combi of 3e

earths tectonic history

late permian (260Ma)

• all earths major landmassess were collected into a single supercontinent - pangea, single ocean, largest mass extinction known to science

early jurassic (200Ma)

• supercontinent pangea broke up into laurasia (north) and gondwana (south)

late jurasic (150 Ma)

• godnwana inclueded most of the landmasses in the todays southern hemispere, Antartica, South america, africa, madagscar, australia, arabian penisula, indian subcontinent

late cretaceous (90MA)

• africa and south america has split, india and madagscare and india moves north, australia separates antartica

K-T boundary (65Ma)

• india migrates norths, meteorite impact, mass ectinction dinos and marine organisms 40% of paleoflora goes extinct

eocene

• antartica and australia split, antartica region starts to freeze, pleostence glaciations, india crash with asia and himalyas uplift begines

miocene (20Ma)

• india and asia collide, uplate of east africa, tethys ocean continues to shrink and then dissappear aas africa collides with eurasia

pleistocene (50Ka)

• repeated glaciations, modern continetsns at their plates, north and south america connected

holocene 0 present

• interglacial period

plants

annonaceae, aracaceae, lauraceace, yristicaecae, and proteacae may be old enough to have spread across continents while they still formed part of gondwana

modern plants

most modern groups of platns and naimlas originated after the break up was compelte and radaition during the teritary following the mass extinction at the end of the Cretaceous (K/Tboundary), 65Ma

e.g. burseraceace, moracea, melicaeca and saptoceac appear to have diversified well after thebreak up of gondawana

the legume familys current pantropical distribution may be a results of dispersal across northern land routes in the early eocene thermal maximum or trans oceanic dispersal

new guinea and australia

new guinea and australia moved north during the tertiary, resulting in a marjo influx of asian rainforest platns to new guinea

no dry land connection ever consisted, but as collission progressed, echanges would have become easier - still included several water crossing

australia was spared many incursion sby asian floral components - allowing plants of gondwanic origin to persistsp

plants better adapted to long-distance travel and colonization

only one seed may be required for successful establishment, colonizatoin

many seeds and spores can be carrier airborne for hundreds of miles (ceiba pentandra)

some seeds may be carried unahrmed in the ocean currents for long periods and distances (coconut)

this may account for the general floral similarities between Asia and New Guinea, but their faune being very different

Africa

the poor species richness of afircan forests is largely a result of extinctions in the last 30 million years

uplift of the continetn making it drier and more seasonal than other rainforest regions - leading to absence of drought sensitive species, such as epiphytes

more strongly affected during the past glacial periods

trans-oceanic dispersal

the new world priamtes share anatomical features that suggest they descended from a single species which arrived in south america 30-35 Ma

caviomorph rodents arrived in south america round the smae time as primates

molecular evidence also suggeste that madagascan lemurs ahve derived from a signle species that rrived around 65 ma

the radiation of madagascan carnivores are from a single colonization event

must have cross large expenses of ocean as bouth south american and madagascar has been separated from afria for 100 million years

evolutionary aspects and extinction - suth america

an island for most of the last 70 million years, giving rise to many endemic radiations

it became connected to north america only 3-4 ma enabling a dramatic intermingling of biotas known as the great american interchange

for example: south americas cats are recent arrivals from north america due to the formation of the land bridge about 3 Ma

south america had many large terrestrail herbivores until recently (10.000-12.000 years ago), ground sloths, mastodons, gomphotheres

Africa and madagascar

africa was an insland in the late cretaceous and early tertiary (90-24 Ma)

in this perido prouduced an mamlaian radiation in an endemic group called afrotheria (elephants, hyraxes, elephant shrews, aardvark, golden moles)

connected to asia, the alst 24 million years, but tropical forest biota exchanges were limited due to dry belt, non0forest excahnges probably easier

madagascar has been an island for almost 90 million yeara

few vertebrates made it and radiation in isolation

large femurs and hippos survived until recently, buta re now extinct

new guinea and australia

marsupials dominate in the absence of placental mammals

the drying of australia elimated most of the forest and the species with it

humans and the introduction of dogs and otehr domestic animals wiped out several specieseco

ecological factors

low number of browsers and grazers since most foliar biomass is in the canopy - little light penetration means scaricity of good quality forage

african forests may support more terrestrial herbivores due to the disturbances caused by elephants

the general paucity of frui in asian and african tropical rainforests hs probabily limited the use of fruit by local priamtes and folivory is therefore more prominent

alternative hypotheis: lack of folivorus primate sin the neotropics may be due to sloths who already occupied that arboreal folivore niche

bats

common ancestor lived around 65 Ma

thus, the fruit and nectar feeding habits ahve developed entirely independently in Old and New world, so has the size spectrum

small sizes in neotropics due to dense forest and need of manouevarbility and easy year-round access to fruit resources

large sizes in old world due to the long distances vcovered to find fruit resources

gliders

leaf eaters and insectivores

dipterocapr leaves are unpalatable due to toxic chemicals, but represent 95% of all tall trees

gliding may be an efficient manner to move between feeding trees

due to irregular flowering and fruiting cycles of dipterocarps, there is a scarcity of insects

insectivorus giders may need to search widely for food and gliding is again an efficnet manner to move

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similarites through convergent evolution

the process by which species evolve in different palces and times, and altough they have different genetic heritages, develop similar external forms and structures as a result of adaptation ot similar enviornments

in summary

rainforest faunas and floras have radiated very much in isolation in different regions, thus have many unique species

composition also dependent on mnay change dispersal events

that a species or gourp is not rpesent does not mean it was not there in the past

local ecological conditions have had big influence on local fauna - often with similar outcomes across the different rainforest regions