The reduction of genetic diversity in threatened vertebrates and new recommendations regarding IUCN conservation rankings

Abstract

Genetic diversity is necessary for evolutionary response to changing environmental conditions such as those facing many threatened and endangered species. To investigate the relationship between genetic diversity and conservation status, we conducted a systematic, quantitative review of vertebrate microsatellite data published since 1990: we screened 5165 previously published articles and identified 1941 microsatellite datasets spanning 17,988 loci that characterized wild populations distributed among five vertebrate classes. We analyzed these data in the context of conservation by comparing empirical estimates of heterozygosity and allelic richness between threatened and non-threatened species. We found that both heterozygosity and allelic richness are reduced in threatened species, suggesting that inbreeding and drift are both effective at removing genetic diversity in endangered populations. We then considered the criteria typically used to rank species of conservation concern (including declining population size, species range extent, and the number of mature individuals) to determine which of these criteria are most effective at identifying genetically depauperate species. However, we found that the existing criteria failed to systematically identify populations with low genetic diversity. To rectify this, we suggest a novel approach for identifying species of conservation need by estimating the expected loss of genetic diversity. We then evaluated the efficacy of our new approach and found that it performs significantly better than the existing methods for identifying species that merit conservation concern in part because of reduced genetic diversity.

Conservation genetics of the Mary River turtle (Elusor macrurus) in natural and captive populations

“…). The low microsatellite-based estimate of heterozygosity (Hs = 0.55) found in MRTs is close to the threshold of 0.54 identified byWilloughby et al (2015) as symptomatic of a species that merits conservation concern as Critically Endangered.The estimate of N e obtained for the extant wild population of MRTs (~150) is relatively low for a turtle species. Likewise, the timescale of divergence between Tinana and Mary populations of Australian lungfish is relatively recent (less than 10,000 years) and linked to periods of lowered sea level in the late Pleistocene(Bishop et al, in press).Overall estimates of genetic diversity based on microsatellite data (average Hs = 0.55) were similar to values estimated for Elseya albagula, an endangered freshwater turtle co-distributed with MRT (average Hs = 0.57;Todd et al, 2013), but lower than values observed in a range of other threatened turtle species(Davy, Bernardo, & Murphy, 2014;Escalona et al, 2009;Petre, Selman, Kreiser, Pearson, & Wiebe, 2015).…”

“…Based on low levels of microsatellite diversity observed in the wild population, Mary River turtles meet criteria for Critically Endangered proposed by Willoughby et al (2015). Based on low levels of microsatellite diversity observed in the wild population, Mary River turtles meet criteria for Critically Endangered proposed by Willoughby et al (2015).…”

Persistence of an endangered native duck, feral mallards, and multiple hybrid swarms across the main Hawaiian Islands

“…Efforts to conserve many endangered species are hindered by a lack of genetic variation (Willoughby et al, ). Though not the focus of this study, we report the first genomic data for the endangered Laysan duck, which yield exceptionally low estimates of standing genetic variation (π = 0.00046 for autosomal ddRAD‐seq loci; Figure ), consistent with the results of earlier studies based on different kinds of genetic data (Browne et al, ; Lavretsky, Engilis, et al, ; Lavretsky, Engilis, & Peters, ; Reynolds et al, ; Rhymer, ) and with records of a severe population decline (to n = 7) in 1912 (Warner, ).…”

New altitudinal record for white-lipped peccary Tayassu pecari (Link, 1795) in Ecuador, with notes about activity patterns and herd size

“…Our new data on reduced herd size calls into question the genetic viability of these populations, which could face problems such as low genetic diversity, inbreeding and reduced gene flow, which may affect population persistence (Doyle et al 2015, Willoughby et al 2015, Li et al 2016). Even with the data presented herein, some questions remain regarding the threats these populations are facing, such as: how is population genetic structure being maintained for such small populations and are there reproductive problems or diseases in the populations, as have been reported elsewhere in their distribution (Fragoso 2004; de Freitas et al 2010, Altrichter et al 2012)?…”