Population genetics of south European Atlantic salmon under global change

Abstract

Populations at the edge of species distributions are especially vulnerable to climate change. Genetic changes as well as modification of their population structure are expected as reactions to global warming. Atlantic salmon (Salmo salar) inhabiting south France has been chosen as a model for studying the effect of global warming in marginal populations during the last 15 years. Increased gene flow between neighboring populations and dichotomy of maturation age between sexes have been identified as two main population changes significantly associated with high values of the North Atlantic Oscillation index, a global climate indicator. Although occurrence of isolated populations in each river (or even tributary) is a paradigm for this species, at least in northern areas, increased gene flow between rivers is forecasted as long as climate warming increases, favoring metapopulations at regional level.

Impact of climate change and human-mediated introgression on southern European Atlantic salmon populations

“…Long datasets of well-monitored populations (survival at hatching, juvenile growth, smolt age, age at maturity, fertility and many other traits) could serve for this purpose, and would facilitate investigation of the association of population data with various climate indices (NAOI, Atlantic Multidecadal Oscillation, others). Between-river migration of adults, or straying and entering a nonnatal river when returning from the sea, are possibilities; research by Valiente et al (2010) for another region at the same latitude demonstrated that warm conditions enhanced straying, contributing to increased gene flow. Valiente et al (2010) also reported indirect signals of increased contribution of freshwatermaturing males (juvenile-like or precocious parr) under warmer climate conditions; such a finding suggests that an increased contribution to spawning by mature male parr of foreign origin, which are known to be responsible for at least some genome introgression at this latitude (Moran et al, 1994), may also play a role in eroding population structuring.…”

“…Between-river migration of adults, or straying and entering a nonnatal river when returning from the sea, are possibilities; research by Valiente et al (2010) for another region at the same latitude demonstrated that warm conditions enhanced straying, contributing to increased gene flow. Valiente et al (2010) also reported indirect signals of increased contribution of freshwatermaturing males (juvenile-like or precocious parr) under warmer climate conditions; such a finding suggests that an increased contribution to spawning by mature male parr of foreign origin, which are known to be responsible for at least some genome introgression at this latitude (Moran et al, 1994), may also play a role in eroding population structuring. Thus, synergistic effects related to a warmer climate may act to accelerate the homogenizing effect of human-mediated introgression, even after the cessation of introductions of foreign stocks.…”

“…Recent stock declines have been attributed in part to global climate change, which affects both juveniles and adults in diverse ways, from growth to migratory behaviour (e.g. Friedland et al, 2003Friedland et al, , 2009Jonsson & Jonsson, 2004;Condron et al, 2005;Valiente et al, 2010). Another effect of climate change is the increase of sensitivity to invasions in aquatic ecosystems (e.g.…”

“…Gene flow does occur between salmon populations, but is constrained by local adaptation at the regional scale and is influenced by both coastal distance and temperature regime (Dionne et al, 2008). Valiente et al (2010) have recently demonstrated that warm climate conditions tend to increase straying and, consequently, gene flow among salmon in southern French rivers. It is also known that, as a consequence of the abundant deliberate stock transfers of the XX century, foreign genomes native to northern European countries have introgressed into southern European populations, contributing to the erosion of population structuring (Moran et al, 2005;Ayllon et al, 2006).…”

Evolution of limpet assemblages driven by environmental changes and harvesting in North Iberia

“…through changes in the geographical distributions of temperature-sensitive species (Thomas et al 2004), predator-prey relationships (Parmesan 2006), generation time (Gross 2011) and population structuring (Horreo et al 2011), or through asynchrony of life histories by delayed or advanced migrations (Valiente et al 2010), through replacement of a species by another with different environmental requirements (Erasmus et al 2002, Wilson et al 2007). In intertidal ecosystems, species diversity and composition change along with climate, more pronouncedly in the most recent decades (Helmuth et al 2006).…”