Tropical forests 1: Cradles or Arks Flashcards
Describe biogeography
The study of the distribution of organisms and genetic diversity across the Earth, in both time and space
How is biogeography studied?
The analysis of spatial distribution of organisms and the identification of the factors that influence the distribution.
Give examples of factors that are considered in biogeography
Ecological factors (control present distribution patterns) and historical factors (understanding how these ecological factors came to be)
How can biogeographic data be presented?
Biogeographic maps
What did ARW use to determine biogeographic realms?
Distributions and taxonomic relationships of particular vertebrate families
Describe the updated version of ARW’s realms by Holt et al. (2013).
20 zoogeographic regions within 11 larger realms
What is used to quantify biogeographic uniqueness of terrestrial zoogeographic regions?
Pairwise phylogenetic beta biodiversity (measures phylogenetic distance)
Name the three major types of biogeographic distributions
Cosmopolitan, endemic, disjunct
Describe a cosmopolitan biogeographic distribution
The state of being found almost anywhere around the world
What is the result of humans being cosmopolitan?
Species that are associated with humans are also endemic e.g. house dust mite
Describe an endemic biogeographic distribution and give an example
Unique to a defined geographic location e.g. lemurs in Madagascar
Describe a disjunct biogeographic distribution and give an example
Distribution with gaps e.g. alligators in North America and China
Define ecological niche
The space an individual species is able to occupy
Define fundamental niche space
The set of environmental and biotic conditions necessary for the existence of a species
Define realised environmental space
The set of conditions actually available within the resource space
What is phylogenetic niche conservatism?
The tendency of closely related species to occupy niches that are more similar than those of their more distant relatives
What is species number in a region related to?
Species number is correlated with the time since diversification in that region.
Name three historical factors that can affect geographic distributions
Extinction, dispersal, vicariance
Describe how extinction can affect geographic distributions
Either of some populations of a species or some species of a higher/lower taxon. e.g. Equidae spread from N.Am but then became extinct there
Describe how dispersal can affect geographic distributions
Range expansion into a favourable habitat or jump dispersal across an unfavourable habitat.
Give an example of a recent dispersal
Great American Interchange at the formation of the Isthmus of Panama
Give three examples of dispersal pathways
Corridors, filter routes (favours species over others), sweepstakes (hazardous e.g. island hopping)
Give three examples of things that can be dispersed by air currents
Seeds, spores, small animals
Give three examples of things that can be dispersed by ocean currents
Seeds, plankton, larvae
Describe vicariance
The splitting of a taxon’s range by barriers
Give three examples of causes of a barrier that leads to vicariance
Geology, climate, habitat
What can vicariance lead to?
Divergence and speciation
What are the four tropical forest classifications?
Tropical moist broadleaf forests, tropical moist deciduous forest, tropical dry forests, tropical/subtropical coniferous forests
Describe tropical moist broadleaf forests
Tropical rainforests, high levels of rainfall (>2,000mm/yr), low variability in annual temp, high biodiversity
Describe tropical moist deciduous forests
Monsoon forests, low variability in annual temp, 3-6mo dry season, 1,000-2,000mm/yr, mostly deciduous and semideciduous. Heavily impacted by teak logging in SE Asia
Describe tropical dry forests
5-8mo dry season, 1,000-1,500mm/yr, dominated by deciduous trees, sensitive to burning
Describe tropical/subtropical coniferous forests
Found at high altitudes, lower biodiversity by high endemism
What is the Latitudinal Biodiversity Gradient?
The pattern on having lots of species at the equator and fewer towards the poles
What are the three main hypotheses to explain the LBG?
Cradle, Ark, Out of the Tropics
Describe the Cradle Hypothesis to explain the LBG
There are higher rates of speciation at the tropics
Describe the Ark Hypothesis to explain the LBG
There is less extinction at the tropics
Describe the Out of the Tropics Hypothesis to explain the LBG
Speciation is high and extinction is low at the tropics. Species migration out of the tropics is high.
Was the LBG present in the late Cretaceous?
There was no relationship between biodiversity and latitude gradient
During the Phanerozoic ice ages, what was the relationship between biodiversity and latitude gradient?
Low levels of biodiversity at poles when temperatures were lower
What led up to the Quaternary ice ages?
Pliocene (5.4-2.4mya) Final stages of a global cooling trend
What was the trend of northern species during the Pleistocene (1.8m-10k ya)?
Lived far to the south of their present distribution during glacial periods
