Temporal changes in allele frequencies in a small marble trout Salmo marmoratus population threatened by extreme flood events

Abstract

The effect of extreme floods on the genetic composition of marble trout Salmo marmoratus living in Lipovscek, a tributary of the Soca River in Slovenia, which has been affected by multiple destructive flood events for centuries was investigated. By monitoring genetic variability during the period 2004-2011, apparent signatures of genetic erosion including a decline in observed and expected heterozygosities and allelic richness were observed. Contemporary effective population size was estimated between 11 and 55 individuals, which is congruent with census data. The data suggest asymmetric gene flow between the two sections of the river. The existence of substantial downstream migration (15-19%) was confirmed by paternity analysis. A small (1-3%) upstream migration was also suggested, which was confirmed by tagging data. Overall, low genetic diversity has not prevented the survival of the Lipovscek population, which might be a common feature of salmonid freshwater populations.

Investigating the genetic structure of trout from the Garden of Ninfa (central Italy): Suggestions for conservation and management

“…Stocking with hatchery fish, even when originating from a native taxon, should also be a topic of major concern. Even natural events such as extreme variations in hydrographic regimes can drastically reduce the size of a population, leaving only few adults able to contribute to the progenies, with a consequent decrease in genetic variation (Pujolar, Vincenzi, Zane & Crivelli, 2016). Finally, populations of freshwater salmonids are often small and fragmented, characteristics that make them particularly prone to the effects of genetic drift.…”

“…Finally, populations of freshwater salmonids are often small and fragmented, characteristics that make them particularly prone to the effects of genetic drift. Even natural events such as extreme variations in hydrographic regimes can drastically reduce the size of a population, leaving only few adults able to contribute to the progenies, with a consequent decrease in genetic variation (Pujolar, Vincenzi, Zane & Crivelli, 2016). For these reasons, the documentation of species introductions, the genetic detection of illegal fish stocking and the environmental changes of the habitat should be monitored over a long-time frame.…”

Genetic diversity of a Daugava basin brown trout (Salmo trutta) brood stock

“…Thus, maintenance or establishment of high levels of genetic diversity is a common aim of conservation efforts (Saura and Faria, 2011). Nevertheless, low genetic diversity may occur in small, wild salmonid populations without preventing survival and adaption (Pujolar et al, 2016) and citations therein), so that the comparatively low genetic diversity of the Virgulica brood stock itself is not necessarily a major concern.…”

Morphological evolution reduces downstream displacement in juvenile landlocked salmon

“…We suggest that downstream displacement of O. masou ishikawae directly facilitates the local evolution of traits that are adaptive against flooding displacement, and thereby creates interpopulation variation. Downstream displacement from abovebarrier to below-barrier populations can be viewed as a gene flow system (see Pearse et al 2009;Plath et al 2010;Pujolar et al 2016). In general, gene flow is thought to homogenize any interpopulation variability created by local adaptations (Kawecki and Ebert 2004) by counteracting the effects of natural selection in local environments (Lenormand 2002;Kawecki and Ebert 2004).…”

“…We expect spatial sorting after flooding events to drive evolution in populations of landlocked salmonids. Salmonids are well known as anadromous fishes, but they also establish landlocked populations composed entirely of fluvial forms upstream of tall barriers, such as artificial check dams and/or natural waterfalls, that completely block fishes from returning to their original populations after downstream displacement (Morita et al 2000;Morita and Yamamoto 2002;Sakata et al 2005;Girman et al 2006;Sato 2006;Kikko et al 2008;Makiguchi et al 2009;Pearse et al 2009;Kawamura et al 2012;Pujolar et al 2016). These landlocked populations are found even in areas with heavy rainfall and frequent flooding (Sato 2006;Makiguchi et al 2009;Kawamura et al 2012;Pujolar et al 2016).…”