Genetic effects of habitat fragmentation and population isolation on Etheostoma raneyi (Percidae)

Abstract

The use of genetic methods to quantify the effects of anthropogenic habitat fragmentation on population structure has become increasingly common. However, in today's highly fragmented habitats, researchers have sometimes concluded that populations are currently genetically isolated due to habitat fragmentation without testing the possibility that populations were genetically isolated before European settlement. Etheostoma raneyi is a benthic headwater fish restricted to river drainages in northern Mississippi, USA, that has a suite of adaptive traits that correlate with poor dispersal ability. Aquatic habitat within this area has been extensively modified, primarily by flood-control projects, and populations in headwater streams have possibly become genetically isolated from one another. We used microsatellite markers to quantify genetic structure as well as contemporary and historical gene flow across the range of the species. Results indicated that genetically distinct populations exist in each headwater stream analyzed, current gene flow rates are lower than historical rates, most genetic variation is partitioned among populations, and populations in the Yocona River drainage show lower levels of genetic diversity than populations in the Tallahatchie River drainage and other Etheostoma species. All populations have negative F IS scores, of which roughly half are significant relative to Hardy-Weinberg expectations, perhaps due to small population sizes. We conclude that anthropogenic habitat alteration and fragmentation has had a profoundly negative impact on the species by isolating E. raneyi within headwater stream reaches. Further research is needed to inform conservation strategies, but populations in the Yocona River drainage are in dire need of management action. Carefully planned human-mediated dispersal and habitat restoration should be explored as management options across the range of the species.

Evolutionary history and population genetics of a cyprinid fish (Iberochondrostoma olisiponensis) endangered by introgression from a more abundant relative

“…Compared to other endangered freshwater fishes from Iberia or elsewhere, I. olisiponensis shows extremely low levels of genetic polymorphism and high population subdivision (e.g. Alves et al 2001a;Salgueiro et al 2003;Mesquita et al 2005;Sousa et al 2010;Dowling et al 2012;Lopes-Cunha et al 2012;Osborne et al 2012;Sterling et al 2012;Chen et al 2013). Furthermore, in addition to the suspected old hybridization events discussed above, we present clear evidence that I. olisiponensis is currently being subjected to strong genetic assimilation through hybridization with the sympatric I. lusitanicum (Gante et al 2010 and present study).…”

Distance, dams and drift: what structures populations of an endangered, benthic stream fish?

“…Such isolation is expected to accelerate genetic differentiation relative to a riverine connection (Bessert & Ort ı, 2008;Raeymaekers et al, 2008;Junker et al, 2012;Sterling et al, 2012). Such isolation is expected to accelerate genetic differentiation relative to a riverine connection (Bessert & Ort ı, 2008;Raeymaekers et al, 2008;Junker et al, 2012;Sterling et al, 2012).…”

“…In contrast, many small-bodied, benthic warm-water fishes undergo comparably minor ontogenetic shifts in habitat needs, which can be accommodated via localized movements (Winn, 1958;Hall, 1972;Rosenberger & Angermeier, 2003;Roberts & Angermeier, 2007), seemingly obviating extensive migration or dispersal. H€ anfling & Weetman, 2006;Beneteau et al, 2009;Lamphere & Blum, 2012;Sterling et al, 2012). Unfortunately, mark-recapture data seldom are useful for testing this assumption, due to the limited spatiotemporal scope of such studies (Fausch et al, 2002).…”

Pronounced genetic differentiation of small, isolated and fragmented tilapia populations inhabiting the Magadi Soda Lake in Kenya

“…Adverse effects of fragmentation may as well lead to loss of genetic diversity due to small effective population sizes, loss of allelic variation due to inbreeding, patterns of gene flow, all of which might lead to a decline in genetic variation and possibly fitness and could potentially even lead to local extinction (Sterling et al, 2012). Such effects are, of course, predicted to have adverse effects on small isolated populations living under stressful conditions where local selective pressures might differ and be particularly strong (Fraser et al, 2011).…”