BIOL 2060 Lecture Notes - Lecture 6: Insular Biogeography, Environmental Niche Modelling, Species Richness

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2 Aug 2016
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Ecology – Unit 6
6.1 – Geographic ecology
Equilibrium model of island biogeography
-predicts species diversity and rates of turnover on islands as a function of islands sizes
and location
othe number of species on an island of a given size should remain constant
ospecies composition should change (i.e., species turnover) as some species go
extinct while others colonize.
Species turnover: change sin species composition on islands resulting
from some species becoming extinct and other immigrating
-One additional pattern that emerges when examining species richness on discrete
geographic patches is isolation, or distance from a source of migrants
ospecies number often decreases with increasing isolation because of barriers to
dispersal
-Island biogeography represents a new way of explaining species richness
oIs a neutral model not a niche model: explanations about mechanisms
influencing species richness that don’t rely on identity or phenotype of species
Niche model: explanations about mechanisms influencing species
richness that rely on the physiological tolerances of organisms
predictions from island biogeography theory rely only on the assumptions
that species can immigrate and go extinct locally
Application of island biogeography theory
-if habitat patches (discrete areas of habitat separated from other such patches) hold
more species  point of large nature reserves?
oWilliam Newmark (1987) examined the effects of North American national park size
on the number of species gained or lost since establishment: the number of natural
post-establishment extinctions decreased as park area increased (Figure 6.1).
concluded that all but the largest western North American national parks are
too small to maintain their mammalian fauna.
Ch.22
22.1 – ecological niche modelling
-information about a species current distribution and niche requirements can be
combined with spatial information to predict invasions and range expansion
ouse pop. Growth models but models don’t include on species of interest and
niche requirements
-making predictions on how a specie’s specific may change over time
oidentify the niche of the species of concern
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odetermine the distribution of the distribution of environmental conditions
throughout the geographic area of concern
ocombine info to make a map
predicting the spread of invasive crab species throughout North America
-Chinese mitten crab: spotty distribution  need to predict a future invasion
oNeed to determine niche:
List all locations where organism has been found
Specially explicit environmental info for the region
Similar env. Info for areas where organism has not been found
oFound that a lot of the US and Canada are suitable for crab
Areas that are farther than 355km from sea are unlikely to be invaded
Influence of species being introduced at different locations
Dominant vector: ship ballasts with water form Europe or asia
Using ecological niche modelling to predict distributions of crypto-zoological species
-Use: identify niche conditions for rare or at-risk species  more accurate conservation
plans
-Can highlight areas in which rare species are likely to occur and where they could move
under future environmental conditions
22.2 – Area, isolation and species richness
-on islands and habitat patches on continents, species richness increases with area and
decreases with isolation
Island area and species richness
-Kalmar and Currie: island area results in an upper bound to diversity, other factors such
as precipitation and extreme temps can also suppress diversity
-Nilsson et al (1988): island area = single predictor of species richness
Habitat patches on continents: mountain islands
-Pleistocene ended: climate warmed, forest and alpine areas retreated to higher
elevations at the tops of mountains  continuous forest converted into island-like
patches associated with mountains, montane
Lakes as islands
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-lakes can be considered islands as they are aquatic environments separated from other
aquatic environments
-seepage lakes: receive no surface water drainage are completely isolated
-drainage lakes: have stream inlets and/or outlets are less isolated
-Tonn and Magnus (1982) and Barbour and Brown (1974):
oPositive relationship with lake size and species richness
Island Isolation and species richness
Marine islands
-Kalmar and Currie (2006): the more isolated the island, the fewer bird species that will
be found
-Williamson (1981): species richness in Azore Channel: pteridophytes and water-breeding
birds
oPositive relationship between area and species richness
oPteridophytes: no clear effect from isolation
Spores are dispersed by wind, some have been found great distances
away
Must consider dispersal capabilities of organisms
oBirds: clear influence of isolation on diversity
Isolation of thermophilic bacteria
-springs heated by tectonic activity (ex. Hot springs): extreme environmental conditions
othermophilic bacteria that have narrow niche requirements, many cant live
outside of hot springs
scattering of bacteria living in hot springs around the world are like plants
on top of mountains
isolation from other habitats can cause shifts in community composition
of the microbial populations in
isolation occurred on largest scale (ex. Continents apart)  variation
22.3 – the equilibrium model of island biogeography
-species richness on islands can be modelled as a dynamic balance between immigration
and extinction
othe equilibrium model of island biogeography
model represents rates of immigration and extinction as a function of
numbers of species on islands
rate of immigration: rate at which new species arrive on island
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