Data from: Three types of rescue can avert extinction in a changing environment

Setting aside high-quality large areas of habitat to protect threatened
populations is becoming increasingly difficult as humans fragment and
degrade the environment. Biologists and managers therefore must determine
the best way to shepherd small populations through the dual challenges of
reductions in both the number of individuals and genetic variability. By
bringing in additional individuals, threatened populations can be
increased in size (demographic rescue) or provided with variation to
facilitate adaptation and reduce inbreeding (genetic rescue). The relative
strengths of demographic and genetic rescue for reducing extinction and
increasing growth of threatened populations are untested, and which type
of rescue is effective may vary with population size. Using the flour
beetle (Tribolium castaneum) in a microcosm experiment, we disentangled
the genetic and demographic components of rescue, and compared them with
adaptation from standing genetic variation (evolutionary rescue in the
strictest sense) using 244 experimental populations founded at either a
smaller (50 individuals) or larger (150 individuals) size. Both types of
rescue reduced extinction, and those effects were additive. Over the
course of six generations, genetic rescue increased population sizes and
intrinsic fitness substantially. Both large and small populations showed
evidence of being able to adapt from standing genetic variation. Our
results support the practice of genetic rescue in facilitating adaptation
and reducing inbreeding depression, and suggest that demographic rescue
alone may suffice in larger populations even if only moderately inbred
individuals are available for addition.