Managing Polyploidy in Ex Situ Conservation Genetics: The Case of the Critically Endangered Adriatic Sturgeon (Acipenser naccarii)

Leonardo Congiu,Anna Forlani,Silvia Cenadelli,Jose Martin Pujolar,Francesco Fontana,Federica Barbisan,Andrea Galli,Isabelle Dupanloup,Simon Joly

doi:10.1371/journal.pone.0018249

Leonardo Congiu, Anna Forlani + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0018249

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Abstract

While the current expansion of conservation genetics enables to address more efficiently the management of threatened species, alternative methods for genetic relatedness data analysis in polyploid species are necessary. Within this framework, we present a standardized and simple protocol specifically designed for polyploid species that can facilitate management of genetic diversity, as exemplified by the ex situ conservation program for the tetraploid Adriatic sturgeon Acipenser naccarii. A critically endangered endemic species of the Adriatic Sea tributaries, its persistence is strictly linked to the ex situ conservation of a single captive broodstock currently decimated to about 25 individuals, which represents the last remaining population of Adriatic sturgeon of certain wild origin. The genetic variability of three F1 broodstocks available as future breeders was estimated based on mitochondrial and microsatellite information and compared with the variability of the parental generation. Genetic data showed that the F1 stocks have only retained part of the genetic variation present in the original stock due to the few parent pairs used as founders. This prompts for the urgent improvement of the current F1 stocks by incorporating new founders that better represent the genetic diversity available. Following parental allocation based on band sharing values, we set up a user-friendly tool for selection of candidate breeders according to relatedness between all possible parent-pairs that secures the use of non-related individuals. The approach developed here could also be applied to other endangered tetraploid sturgeon species overexploited for caviar production, particularly in regions lacking proper infrastructure and/or expertise.

Highlights

Management of captive breeding programs require routinely use of parentage analysis and, to a lesser extent, estimators of relatedness in order to evaluate the relationship among founders in the absence of parentage data
Parentage assignment using molecular markers implies that parents and offspring are all genotyped at a given number of unlinked genetic markers, and that the information on genotypes is used to assign progeny to the correct parental pair [1]
Alternative methods are necessary for genetic relatedness analysis in conservation programs for polyploid species

Summary

Introduction

Management of captive breeding programs require routinely use of parentage analysis and, to a lesser extent, estimators of relatedness in order to evaluate the relationship among founders in the absence of parentage data. In the only available study on the evolutionary history of the Adriatic sturgeon, Ludwig et al [12] examined a subset of the parental F0 Azienda Agricola VIP stock (N = 31) together with a sample from the Buna river (Albania, N = 17). The present study characterized the distribution of relatedness values within all remaining Adriatic sturgeons of certain wild origin This included most of the animals that were employed by Azienda Agricola VIP as F0 parents back in 1977, even if presently dead, and whose progeny was either released in the restocking practices conducted in the period 1988–2009 or reared to be part of the F1 stocks currently available as future source of breeders. We propose a standardized method for the analysis of genetic relatedness data in polyploid species to be used as a simple approach to support practical breeding activities

Results

Discussion

Materials and Methods