Kendi F. Davies & Brett A. Melbourne

Habitat Fragmentation: Predicting Long Term Extinction Dynamics from Transient Dynamics and Species Traits

National Science Foundation, Division of Environmental Biology
$405,000 April 2009 - March 2012


Habitat loss and fragmentation continues at an accelerating rate and accounts for most biodiversity loss. Understanding how fragmentation affects population dynamics and drives extinction is thus vital for the management of endangered species and the conservation of biodiversity.

Experiments provide the strongest inferential framework in which to understand the dynamics of species in response to habitat fragmentation. Experiments of large spatial and long temporal scale are needed to disentangle the different factors contributing to the response of species to fragmentation, which include many unknown historical factors in non-experimental systems. Frequently, experimental studies have documented the decline of species towards extinction immediately following fragmentation. However, existing studies have not gone beyond short term, possibly transient, dynamics to determine the fate of declining species in the longer term. How many species that initially decline eventually go extinct? Do some species persist at a lower abundance? On the contrary, is there an extinction debt, such that some species do not respond initially but go extinct in the long term?

The Wog Wog fragmentation experiment (Australia) is the longest running experiment in temperate forest. Existing short term data from this experiment will be used together with a matching series of new data collected after long term fragmentation to answer two overarching questions. First, do the transient dynamics of beetle species through 5 years post experimental fragmentation predict their long term dynamics (23-25 years post fragmentation)? Second, do traits of species that predict transient dynamics also predict long term dynamics? Life-history traits are related to the dynamics of populations and could predict extinction risk when detailed data for population dynamics are lacking.

Short term responses of individual beetle species to habitat fragmentation will be quantified using a population dynamics model parameterized from the data. This model will be used to predict long term dynamics, particularly extinction, and the predictions will be tested against new long term data. To match the short term data, beetles will be sampled using permanent pitfall traps at 188 sample sites over three years. Traits of species, such as dispersal ability and body size, will be scored from the specimens or from the literature and related to dynamics using a regression approach. In the original data 655 beetle species were captured and about one third are expected to be suitable for these analyses.