Consequences of metapopulation collapse: comparison of genetic attributes between two Allegheny woodrat metapopulations |
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Authors: | Timothy J Smyser Joseph E Duchamp Scott A Johnson Jeffery L Larkin Jr" target="_blank">Olin E RhodesJr |
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Institution: | (1) Department of Forestry and Natural Resources, Purdue University, 715 West State Street, West Lafayette, IN 47907, USA;(2) Biology Department, Indiana University of Pennsylvania, 975 Oakland Avenue, Indiana, PA 15705, USA;(3) Indiana Department of Natural Resources, 553 East Miller Drive, Bloomington, IN 47401, USA;(4) University of Georgia’s Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA |
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Abstract: | Disruptions in metapopulation connectivity due to demographic pressure can leave genetically isolated subpopulations susceptible
to genetic drift, accumulation of deleterious alleles, and inbreeding depression. Such a scenario may be playing out within
Allegheny woodrat (Neotoma magister) metapopulations as a series of synergistic extrinsic pressures have contributed to the rangewide decline of the species
over the last 40 years. Our goal was to elucidate the effects of demographic collapse on metapopulation function by using
11 microsatellites markers to quantify differences in patterns of connectivity and genetic diversity between a demographically
stable metapopulation and one in severe demographic decline. The demographically diminished metapopulation had lower levels
of genetic diversity than the stable metapopulation at all levels evaluated (metapopulation-, subpopulation-, and individual-scales).
In contrast to patterns of connectivity observed within the stable metapopulation, peripheral subpopulations in the diminished
metapopulation had become completely isolated and were drifting toward genetic fixation, likely as a result of the extirpation
of stepping-stone subpopulations. The declining genetic parameters observed within these isolated peripheral subpopulations
suggest that inbreeding depression may be contributing significantly to their demographic decline. Allegheny woodrats readily
express the genetic consequences of metapopulation decline due to the low effective population sizes of subpopulations and
the species’ limited dispersal capacity. Differences in genetic parameters observed between demographically stable and diminished
Allegheny woodrat metapopulations emphasize the risks posed to metapopulation function and associated genetic processes introduced
with demographic decline. |
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