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What determine the current distribution of animals and plants?. 1. Habitat today: physical setting - climate, soil biotic setting - vegetation type, food availability, mutualistic relationships. 2. History: antiquity - the place of origin.

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what determine the current distribution of animals and plants
What determine the current distribution of animals and plants?

1. Habitat today: physical setting - climate, soil

  • biotic setting - vegetation type, food availability, mutualistic relationships.

2. History: antiquity - the place of origin.

  • availability of dispersal routes (barriers, land bridges, water ways)
  • climate change
  • island effects (extinction)
geological history of tropical biota generalizations
Geological history of tropical biota: generalizations

1. Animals move more than land moves (Darlington 1959, "Zoogeography")

2. Sahara has vast petrified logs and major (dry) river drainage systems indicating much rain and lush forest in the past. (Did climates change or did land move?)

3. The tropical regions share few mammal families but many plant families.

type of changes latitudinal separations later reunions
Type of changes - latitudinal, separations, later reunions
  • Collision of continents: e.g., India.
  • Temporal land bridges due to lowering sea level during cold climates
  • Stepping stones: Antilles archipelago (80 my BP-)
slide4

Continental collision

Ocean ridge (divergent zone)

slide7

Mammal families that evolved after separation of continents (many during 25-5 Ma) are not shared between continents.

Many angiosperm families that had evolved before separation of continents are shared among them.

(Terborgh, 1992)

convergence of forms in relation to their ecological niches of mammals

Paleotropics

Neotropics

Convergence of forms in relation to their ecological niches of mammals

Pigmy hippopotamus vs. Capybara

Water chevrotain vs. Paca

Royal antelope vs. Agouti

Yellow-backed Duiker vs. Red brocket deer

Giant ground pangolin vs. Ginant armadilo

(Terborgh, 1992)

wallace s and weber s lines faunal and floral demarcation knots of malesian flora
Wallace’s and Weber’s lines (faunal) and floral “demarcation knots” of Malesian flora

(Whitmore 1998)

what characterize today s tropical rain forest angiosperms
What characterize today’s tropical rain forest angiosperms?
  • Tall trees, multi storied closed forests
  • Lianas (often with palmately veined leaves)
  • Cauliflory
  • Medium to large leaves with entire margin and drip tips
  • Animal-dispersed large seeds for mature forest species
tall multi storied closed rain forests appeared after k t extinction morley 2000
Tall, multi-storied closed rain forests appeared after K-T extinction. (Morley 2000)

Emergent

Canopy

Subcanopy

Understory

-shrubs

- herbs

slide14

Fossil pollens from Tertiary South America.a.Bombax (Bombacaceae)b. Mauritia palmc. Amanoa (Euphorbiaceae)d. CrudiaLeguminosae)e. Albizia(Leguminosae)f. Alnus (after closure of Panama isthmus)

(Moreley 2000)

slide15
Megathermal plant taxa originally developed at both sides of subtropical high pressure belts by mid-Cretaceous (100 My BP)
  • Northern belt: mid-altitude of N. America and Europe (Bombaceae)
  • Equatorial (Palms)
  • Southern Belt: southern South America and eastern Gondwana (Proteaceae)
the three latitudinal belts within which moist megathermal angiosperm taxa first evolved
The three latitudinal belts within which moist megathermal angiosperm taxa first evolved

(Morley 2000)

angiosperm dominance established ca 110 90 ma
Angiosperm dominance established ca. 110-90 Ma

(Moreley 2000, after Crane 1987)

among present day tropical rain forests which are the oldest
Among present day tropical rain forests, which are the oldest?

Islands around Coral Sea (e.g., New Caledonia) and Madagasar (Morley 2000)

  • Most megathermal forests developed at mid-latitudes before the climate became suitable at the equator in Tertiary.
  • Areas of plate disassembly, rather than collision, restricting the opportunity of dispersal by more aggressive megathermal floras.
  • The northward Tertiary drift of the Australian Plate, Madagascar kept these zones to stay in warm climatic zones during Tertiary global cooling.
  • Oceanic climate protected these ancient floras rich in gymnosperms and archaic angiosperms.
how ancient is the se asia rain forest
How ancient is the SE Asia rain forest?
  • Some ancient taxa (e.g., gymnosperm Dacrydium in heath forests of Borneo, Richard 1996) present.
  • But, it probably developed in mid Miocene (16-10 Ma) replacing seasonal monsoon forests in Oligocene and early Miocene (Morley 2000).
    • mid-Eocene (45Ma) collision of India brought elements of African Cretaceous flora
    • 25-15 Ma - collision of Australian and Sunda plate brought dispersal of Gondwanan elements
    • Continuous continental connection from equator to 60ºN allowed survival of Boreotropical elements
slide21
Paleocene (65-54 Ma): the first appearance of closed-canopy tropical rain forests in ‘greenhouse’ climate

(Morley 2000)

slide22
Generalized oxygen isotope curve for Benthic foraminifera predicts continuous cooling during the last 60 My.

Eustatic curve(sea level)

slide23

Late Cretaceous vegetation of North America: T: tropical forestP: paratropical forestD: polar broadleaved deciduous forest(Upchurch and Wolfe 1987)

early ecocene thermal maximum 54 49 ma super greenhouse climate
Early Ecocene thermal maximum (54-49 Ma): ‘super-greenhouse’ climate

(Morley 2000)

slide25

Early Oligocene (36-30 Ma) after disappearance of mid-latitude megathermal forests at the terminal Ecocene cooling (36 Ma):‘interglacial’ model

(Morley 2000)

climatic deterioration and disappearance of mid latitude megathermal paratropical forests
Climatic deterioration and disappearance of mid-latitude Megathermal (=paratropical) forests

(Morley 2000)

slide27
Mid-Miocene (16-10 Ma) thermal maximum: reappearance of megathermal elements beyond subtropical high pressure zones

(Morley 2000)

slide28
Pleistocene glacial maximum (3 Ma-) noteworthy dispersal of temperate species to low latitude along mountain ranges

(Morley 2000)

slide31
At the last glacier maximum (B), only 15% of Africa could have supported tropical rain forests due to higher elevation of the continent.

(Morley 2000)

slide32

Altitudinal and latitudinal forest zones in SE and E Asia.The limit of evergreen broad leaved trees = -1 º C for the coldest mo.The limit of heat requirement for all trees = 15ºC month temperature sum (or the annual sum of mean monthly temperatures over 5 º C)

(Osawa 1990 adopted in Morley 2000)

contraction of lowland tropical forest and expansion of montane forests during the glacial episodes
Contraction of lowland tropical forest and expansion of montane forests during the glacial episodes

(Whitmore 1998, adopting Hammen 1969)

slide34
Uplifting of Andes (25-1.6 Ma) Vicariance – disjunct distribution of taxa Amazon river changed the direction of flow
pleistocene refugia and species pump
Pleistocene refugia and species pump
  • Repeated fragmentation of rain forests due to the expansion of savanna during the glacier periods facilitated speciation through vicariance (reproductive separation).
  • Proposed by Haffer (1969) based on the coincidence of bird distribution and estimated position of the rain forest fragments with an assumption of savanna forest boundary to be at 1500 mm precipitation and 25% reduction in precipitation during glacier.
support
Support?
  • Existence of high diversity hot spots with high degree of endemism for multiple rain forest organisms (birds, butterflies, plants)
  • Savanna expansion suggested by migration of savanna animals during the early phase of the Great American Faunal Interchange (Webb 1996).
critique collinvaux et al 2000
Critique (Collinvaux et al. 2000)
  • 1) Many vertebrates and plants evolved before Pleistocene (e.g., Miocene 16-10 Ma).
  • 2) Pollen analysis shows that some areas that are postulated to be savannas supported forests during the glaciers
  • 3) Cooling, rather than drying was the dominant pattern
new view
New view
  • Tropical rain forest refugia conserved megathermal species during global cooling.
  • They were not necessarily isolated, and definitely did not serve as speciation mechanisms.
  • Biogeographical patterns of species may reflect ecological mechanisms, such as competitive exclusion and immigration.
implication of new view
Implication of new view
  • Over emphasis on refugia may help conservation of tropical species.
  • Conservation of eastern Amazonina forest may have higher priority to maintain the health of regional hydrological regime than mere protection of western Amazonian high diversity spots (Bush et al. 2000)