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Description:
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Multiple ecological factors can simultaneously affect species activity and
community structure . The goal of my dissertation was to examine the effects of abiotic
factors , biotic factors , and succession on anuran communities . I took a three pronged
approach dividing the study into three major chapters .
First I focused on abiotic factors that affect anuran breeding activity . I found that
weather , rainfall and temperature affect the breeding activity of each species differently ,
and species in my study area can be placed into 5 different groups based on their
association with weather and season : 1 ) breed within a predictable season (summer )
independent of local weather patterns 2 ) breed opportunistically within a predictable
season (summer ) dependent on local rainfall 3 ) breed opportunistically within a
predictable season (winter ) dependent on local temperature 4 ) breed opportunistically
dependent on local flood level rainfall events and 5 ) breed opportunistically year round
dependent on local temperature in the winter and local rainfall in the summer .
In the second part of the study , I created a simulation model of an anuran
community using published life history parameters of the anuran species in my study
system . Results of the model suggest colonizing ability is important for species with
low fecundity and high susceptibility to predation . These early succession species tend
to be constrained from later stages of succession by predators . Species that are resistant
to predators are generally poor colonizers and tend to arrive late in succession , but once
they colonize a pond they tend to persist and recruit successfully .
Finally , I explored biotic mechanisms that might be important in structuring
anuran communities . I found that with the exception of Rana sphenocephala , anuran
species occupying sites with shorter hydroperiods had higher activity rates and were
more susceptible to predation . Rana sphenocephala appeared to be better at escaping
predation than the other species despite a relatively high activity rate . Examination of
published phylogenies indicates R . sphenocephala is derived from a species group that
uses permanent water suggesting that R . sphenocephala has retained many anti -predator
defenses inherited from its ancestors , even though the species now exploits sites with
low predator densities . |