Defining conservation units in a stocking‐induced genetic melting pot: unraveling native and multiple exotic genetic imprints of recent and historical secondary contact inAdriatic grayling

Abstract

The definition of conservation units is crucial for the sustainable management of endangered species, though particularly challenging when recent and past anthropogenic and natural gene flow might have played a role. The conservation of the European grayling, Thymallus thymallus, is particularly complex in its southern distribution area, where the Adriatic evolutionary lineage is endangered by a long history of anthropogenic disturbance, intensive stocking and potentially widespread genetic introgression. We provide mtDNA sequence and microsatellite data of 683 grayling from 30 sites of Adriatic as well as Danubian and Atlantic origin. We apply Bayesian clustering and Approximate Bayesian Computation (ABC) to detect microgeographic population structure and to infer the demographic history of the Adriatic populations, to define appropriate conservation units. Varying frequencies of indigenous genetic signatures of the Adriatic grayling were revealed, spanning from marginal genetic introgression to the collapse of native gene pools. Genetic introgression involved multiple exotic source populations of Danubian and Atlantic origin, thus evidencing the negative impact of few decades of stocking. Within the Adige River system, a contact zone of western Adriatic and eastern Danubian populations was detected, with ABC analyses suggesting a historical anthropogenic origin of eastern Adige populations, most likely founded by medieval translocations. Substantial river-specific population substructure within the Adriatic grayling Evolutionary Significant Unit points to the definition of different conservation units. We finally propose a catalog of management measures, including the legal prohibition of stocking exotic grayling and the use of molecular markers in supportive- and captive-breeding programs.

High genetic diversity and demographic history of captive Siamese and Saltwater crocodiles suggest the first step toward the establishment of a breeding and reintroduction program in Thailand

“…Assessment of genetic diversity in natural and captive populations is an important step to understand population structure, history, and hybrid status better when developing breeding programs for conservation management of threatened species [ 21 – 23 ]. Molecular genetic markers such as mitochondrial DNA (mtDNA) and biparentally inherited nuclear DNA microsatellites can facilitate the ability to characterize population diversity, assign possible origins of individuals, and identify hybrids and their parents [ 14 , 15 , 24 , 25 ].…”

MitochondrialDNAanalysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia

“…Knowledge of genetic diversity and structure can help identify the most closely related populations or individuals for use in translocation and augmentation programs. Furthermore, examination of the genetic composition of existing captive breeding populations can help guide management practices for maintaining the genetic integrity of distinct genetic groups in captivity as well as assessing the suitability of captive individuals for population recovery and conservation strategies (e.g., Ruokonen et al 2000;Burns et al 2003;Gaur et al 2006;Ramirez et al 2006;Russello et al 2007;Beauclerc et al 2010;McGreevy et al 2011;Rold an et al 2011;Benavides et al 2012;Meraner et al 2014).…”

Global systematic diversity, range distributions, conservation and taxonomic assessments of graylings (Teleostei: Salmonidae; Thymallus spp.)

“…Conservation remarks River engineering measures, hydropower expansion and water pollution are among widespread threats that have reduced at least 50% of the species range; introgression with non-native lineages is a major threat to T. aeliani and there are few pure genetic populations left (Sušnik et al 2004;Meraner et al 2014). The area of aquatic occupancy may be as little as 100 sq.…”