Comparison of historical bottleneck effects and genetic consequences of re‐introduction in a critically endangered island passerine

Abstract

Re-introduction is an important tool for recovering endangered species; however, the magnitude of genetic consequences for re-introduced populations remains largely unknown, in particular the relative impacts of historical population bottlenecks compared to those induced by conservation management. We characterize 14 microsatellite loci developed for the Seychelles paradise flycatcher and use them to quantify temporal and spatial measures of genetic variation across a 134-year time frame encompassing a historical bottleneck that reduced the species to ~28 individuals in the 1960s, through the initial stages of recovery and across a second contemporary conservation-introduction-induced bottleneck. We then evaluate the relative impacts of the two bottlenecks, and finally apply our findings to inform broader re-introduction strategy. We find a temporal trend of significant decrease in standard measures of genetic diversity across the historical bottleneck, but only a nonsignificant downward trend in number of alleles across the contemporary bottleneck. However, accounting for the different timescales of the two bottlenecks (~40 historical generations versus <1 contemporary generation), the loss of genetic diversity per generation is greater across the contemporary bottleneck. Historically, the flycatcher population was genetically structured; however, extinction on four of five islands has resulted in a homogeneous contemporary population. We conclude that severe historical bottlenecks can leave a large footprint in terms of sheer quantity of genetic diversity lost. However, severely depleted genetic diversity does not render a species immune to further genetic erosion upon re-introduction. In some cases, the loss of genetic diversity per generation can, initially at least, be greater across re-introduction-induced bottlenecks.

The impact of translocations on neutral and functional genetic diversity within and among populations of the Seychelles warbler

“…; Grueber & Jamieson ; Bristol et al . ), and our results should therefore be of general applicability. Questions have been raised about inferring functional variation based solely on any one given locus, that is the MHC (Acevedo‐Whitehouse & Cunningham ; Radwan et al .…”

Evolutionary distinctiveness and historical decline in genetic diversity in the Seychelles Black Parrot Coracopsis nigra barklyi

“…Our detection of a recent population decline is also supported by observations from field records and surveys (Rocamora & Laboudallon 2009, Reuleaux et al 2013. Similar genetic analyses of temporal changes in N e for other Seychelles endemic birds such as the Seychelles Kestrel ), the Seychelles Warbler Acrocephalus sechellensis (Spurgin et al 2014) and the Seychelles Paradise Flycatcher (Bristol et al 2013b) suggest that substantial population declines within the last century are not uncommon on these islands. Indeed, the severe decline to a contemporary N e of only six individuals for the Seychelles Black Parrot is comparable to that genetically derived for the Kestrel, which experienced a decline to an N e of eight individuals prior to subsequent recovery ).…”

“…) and the Seychelles Paradise Flycatcher (Bristol et al . ) suggest that substantial population declines within the last century are not uncommon on these islands. Indeed, the severe decline to a contemporary N e of only six individuals for the Seychelles Black Parrot is comparable to that genetically derived for the Kestrel, which experienced a decline to an N e of eight individuals prior to subsequent recovery (Groombridge et al .…”

“…) and Seychelles Paradise Flycatcher (Bristol et al . ) have led to newly established populations and facilitated potential gene‐flow, furthering the persistence of these endangered island species. Encouragingly, a research programme focused on monitoring the population was launched in 2009 and has provided an increasing body of information on the ecology of these Black Parrots.…”

“…Consequently, we recommend maintaining and potentially expanding the habitat and range of Seychelles Black Parrots through continued protection and intensified restoration of endemic palm forest on Praslin and on islands identified as being appropriate for potential reintroduction. These practices should promote increased population size and subsequently minimize further loss of genetic diversity (Soul e 1976, Lacy 1987, Hedrick 2005 (Bristol et al 2013b) have led to newly established populations and facilitated potential gene-flow, furthering the persistence of these endangered island species. Encouragingly, a research programme focused on monitoring the population was launched in 2009 and has provided an increasing body of information on the ecology of these Black Parrots.…”