Translocations spur population growth but exacerbate inbreeding in an imperiled species

Abstract

Land and natural resource usage that supports human society can pose a risk to the survival of other species, spurring biodiversity loss. In extreme cases, when development threatens the existence of individuals, wildlife managers may perform mitigation translocations, relocating individuals out of harms way. We investigated the efficacy of mitigation translocations as a conservation strategy in Federally Threatened Florida Scrub-Jays using a dataset that provided unprecedented resolution into both the demographic and genomic outcomes of translocations. Over the course of seven years, a total of fourteen groups (51 jays) from five subpopulations that had been declining from agriculture and lack-of-fire driven habitat degradation were translocated to a larger site of more contiguous restored habitat with only four family groups, to mitigate for loss of these subpopulations from mining activity. Habitat restoration and translocations established a core population that increased 10-fold in size after only 17 years from the first translocations. Pedigree analyses of this population revealed that a small subset of mostly translocated individuals fueled the demographic expansion, with a single breeding pair responsible for [~]24% of the ancestral genetic contributions since 2008. Genomic comparisons between translocated individuals and individuals from the core population before and after translocations revealed that the high reproductive skew led to increased inbreeding and loss of genetic diversity. This study stresses the importance of demographic and genetic monitoring following translocations, and that subsequent, genetic-rescue-oriented translocations may be necessary in mitigation scenarios to counter the genetic consequences of reproductive skew in fragmented populations. Significance StatementThere is ongoing debate surrounding the effectiveness of mitigation-driven translocations for conservation, however we show that translocations to mitigate the effects of mining on Federally Threatened Florida Scrub-Jays spurred population growth; a major boon to the viability of this species. We translocated individuals from at-risk subpopulations that were demographic sinks into recently restored habitat, which quickly established a rapidly growing core population. We demonstrate that demographic and genetic recovery do not necessarily go hand-in-hand, as reproduction was highly skewed towards a small subset of mostly translocated individuals, which increased inbreeding and eroded genetic diversity. This stresses the importance of demographic and genetic monitoring for identifying reproductive skew, allowing for adaptive management that addresses inbreeding and achieves broader conservation goals.