Genetic diversity of the killifish Aphanius fasciatus paralleling the environmental changes of Tarquinia salterns habitat

Abstract

The habitat in the Natural Reserve of the Tarquinia salterns, located on the Tyrrhenian coast of central Italy, has undergone dramatic alterations over the last 10 years. After salt production was terminated in 1997 the site was abandoned until 2002, with consequent degradation of habitat quality and stiffening of the environmental conditions. From 2003 to 2006 ecological rehabilitation of the site was carried out, restoring water circulation to its previous equilibrium. The genetic variation in the killifish Aphanius fasciatus inhabiting the salterns was monitored using allozymes from 1998. The results showed that the genetic variability of the killifish strongly reduced through time: a high number of rare alleles were lost and both heterozygosity and allele richness were significantly decreased. The most recent samples, taken after the ecological restoration, showed that to date the genetic erosion of A. fasciatus gene pool has slowed down, since no significant differences have been detected for any genetic variability parameter. Concerning the mechanisms leading to the impoverishment of the genetic variability, the strong loss of rare alleles suggests a role of genetic drift, which accords with the fluctuation of the effective population size recorded over the period of study and with the low gene flow typical of this species. The low levels of gene flow reported for this species imply that once lost, the genetic variability can rarely be restored through immigration from highly variable populations.

Genetic Diversity and Population History of the Endangered Killifish Aphanius baeticus

“…Consistent with the mtDNA data, the amount of genetic variability was very low (mean observed heterozygosity H O = 0.266) across loci and sampling sites, as would be expected for a species that is genetically depressed (Table 3), with Acebuche (ACB, ACO, and ACC sampling sites) being the locality with the lowest genetic diversity (H O = 0.081). However, these values are slightly higher than those reported previously for the same species (Schönhuth et al 2003) or for the closely related killifish, A. fasciatus (Angeletti et al 2010) at the allozyme variability level, which could indicate a possible genetic recovery of the species.…”

“…Also, we attempted to cover the entire distribution range of the species, increasing the number of individuals studied per locality with respect to previous molecular studies Schönhuth et al 2003). Previous studies in killifish species with similar habitat requirements to those of A. baeticus (i.e., coastal and high-salinity water bodies) showed striking differences in mitochondrial and nuclear genetic distribution, shifting from high to low genetic variability (Maltagliati et al 2003;Whitehead 2009;Angeletti et al 2010;Tatarenkov et al 2011;Ferrito et al 2013). Consequently, it has been argued that these differences in genetic variability patterns are not only determined by habitat adaptation but also by specific life-history traits and historical processes (Fuller et al 2007;Whitehead 2009;Strand et al 2012).…”

Genetic structure of the South European toothcarpAphanius fasciatus(Actinopterygii: Cyprinodontidae) populations in the Mediterranean basin with a focus on the Venice lagoon

“…The analysis of the genetic structure of A. fasciatus samples has revealed marked geographical differentiation among populations, while some aspects of its genetic structure have been used to detect environmental stress or specific adaptations with respect to certain parameters, such as temperature and salinity (Maltagliati 2002;Cimmaruta et al 2003;Angeletti et al 2010). Apart from the effect of the naturally fragmented distribution of the typical habitats of the species on its present-day structure, past geological events may also have contributed.…”

Distribution of natural populations of the killifishAphanius fasciatus(Valenciennes, 1821) (Teleostei: Cyprinodontidae) in Italy: past and current status, and future trends

“…The pre-1990s distributional map ( Figure 1B) can be assumed to be the oldest data on the species' historical range; along the coast of the peninsula, this map identifies the widest known range for the species, which seems to have been reduced and partially recovered in the last three C 1994;(Maltagliati 1998a, 1999) L 1983 (Castelli PO);1994-1995(Maltagliati 1998a, 1998b, 1999(Maltagliati & Camilli 2000; L 1997L -1998L (Cognetti et al 1998(Maltagliati 2002 Ombrone river mouth 42°40ʹN; 11°00ʹE M 2011 (Fastelli et al 2012) Orbetello lagoon 42°26ʹN; 11°12ʹE L 1957 (MSNM); 1962 (Cavicchioli 1962);1960s (USNM);1980 (Varisco PC);(NHM) 1994(Maltagliati 1998a, 1998b, 19991999 L 1994L : 1996L (Maltagliati 1998aL , 1998bL , 19992001(Mancini 2001 Tarquinia salterns 42°12ʹN; 11°42ʹE S 1980s (Mastrolia & Gallo 1989);2007(Cimmaruta et al 2003Angeletti et al 2010;Ferrito et al 2013); 2011 (Mosesso et al 2012) (Continued ) (Tigano & Ferrito 1984);1994;(Maltagliati 19991999); 2001 (Ferrito et al 2003);2006…”

“…Moreover, freshwater populations of A. fasciatus should be also considered of high conservation interest. In this regard, there are historical records from northern Italy freshwater habitats, as for instance from the Treviso town area at the end of 1800 (Ninni 1863) Moreover, in some populations of A. fasciatus that currently show good conservation conditions from a demographic point of view, past traumatic events may have caused bottlenecks with consequent irreversible genetic loss (Maltagliati 2002;Cimmaruta et al 2003;Angeletti et al 2010). Our survey also recorded cases of natural population resilience: apart from the abovementioned Sicilian inland water populations, which appear completely re-established (Lo Duca & Marrone 2009), we were able to locate A. fasciatus populations in northern Tuscany, where it was considered extinct.…”