Genetic Evaluation of Isolated Populations for Use in Reintroductions Reveals Significant Genetic Bottlenecks in Potential Stocks of Sacramento Perch

Abstract

New populations of threatened species are often established as a conservation measure. However, if only a few individuals contribute to subsequent generations, these populations may have limited genetic diversity. Such genetic bottlenecks can result in inbreeding depression, reduced fitness, and even extirpation of populations. Eight isolated populations of Sacramento perch Archoplites interruptus established through anthropogenic translocations were examined for evidence of genetic bottlenecks. Sacramento perch are endemic to two regions of California but have been entirely extirpated from their native range; the remaining populations are essential for conservation of the species. Using 12 microsatellite DNA loci, we determined that genetic bottlenecks occurred in six of the populations. Allelic richness, richness of private alleles, and effective population size differed significantly among populations. Strong differentiation among the extant populations probably resulted from differences in the sources used to establish the populations and from genetic drift due to the small population sizes. These results indicate that genetic bottlenecks are frequent when new, isolated populations of a species are established. Although these extant populations have persisted despite bottlenecks, future Sacramento perch populations should be established by drawing from the most diverse of the current populations and should be monitored with genetic markers to evaluate diversity and the possible need for further stocking. We combine three measures of genetic diversity (allelic richness, private allelic richness, and effective population size) to recommend potential source populations.

Developing major histocompatibility markers in a species of concern: the Sacramento perch Archoplites interruptus

“…Unfortunately, all the established populations were derived from one another, and were founded with <50 individuals. Genetic bottlenecks were identified in the majority of populations with microsatellite (Schwartz & May, ) and mitochondrial markers (Crain et al ., ). Due to the lack of genetic diversity, Schwartz & May () suggested drawing from multiple source populations in reintroductions to increase overall genetic diversity and avoid possible problems with inbreeding depression.…”

“…Genetic bottlenecks were identified in the majority of populations with microsatellite (Schwartz & May, ) and mitochondrial markers (Crain et al ., ). Due to the lack of genetic diversity, Schwartz & May () suggested drawing from multiple source populations in reintroductions to increase overall genetic diversity and avoid possible problems with inbreeding depression. They recommended striking a balance between increasing genetic diversity to ensure the potential for the ability to respond to future environmental change, while avoiding breaking up co‐adapted gene complexes and loss of local adaptation by breeding all homogenic populations with individuals only from the populations with highest genetic diversity.…”

“… Archoplites interruptus range and translocation sites (modified from Schwartz & May, ). Sampling sites are boxed.…”

“…2 locus. The overall pattern of differentiation across mhc loci significantly correlated ( r 2 = 0·83) to previous F ST estimates obtained for each of the sampling locations with neutral microsatellite markers (Schwartz & May, ) (Table ). The correlation between the two marker types suggests that demographic pressures [ e .…”

“…The optimum population model was two (Fig. ) and closely corresponded to population structure established with microsatellites for the four sampling locations (Schwartz & May, ). Specifically, all Sindicich and Crowley individuals comprised one cluster, while the other was composed of Jewel Lake individuals.…”