Spatial and temporal scales of adaptive divergence in marine fishes and the implications for conservation

Abstract

Knowledge of geographic and temporal scales of adaptive genetic variation is crucial to species conservation, yet understanding of these phenomena, particularly in marine systems, is scant. Until recently, the belief has been that because most marine species have highly dispersive or mobile life stages, local adaptation could occur only on broad geographic scales. This view is supported by comparatively low levels of genetic variation among populations as detected by neutral markers. Similarly, the time scale of adaptive divergence has also been assumed to be very long, requiring thousands of generations. Recent studies of a variety of species have challenged these beliefs. First, there is strong evidence of geographically structured local adaptation in physiological and morphological traits. Second, the proportion of quantitative trait variation at the among‐population level (QST) is much higher than it is for neutral markers (FST) and these two metrics of genetic variation are poorly correlated. Third, evidence that selection is a potent evolutionary force capable of sustaining adaptive divergence on contemporary time scales is summarized. The differing spatial and temporal scales of adaptive v. neutral genetic divergence call for a new paradigm in thinking about the relationship between phenogeography (the geography of phenotypic variation) and phylogeography (the geography of lineages) in marine species. The idea that contemporary selective processes can cause fine‐scale spatial and temporal divergence underscores the need for a new emphasis on Darwinian fishery science.

Fine-scale spatial and temporal genetic structure of Atlantic cod off the Atlantic coast of the USA

“…Mar Ecol Prog Ser 410: [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195] 2010 the importance of processes that limit dispersal and promote self-replenishment of local populations, such as sedentary adult life history strategies (Robichaud & Rose 2004, Howell et al 2008, spawning site fidelity (Taggart 1997), natal homing (Thorrold et al 2001, Svedäng et al 2007), egg and larval retention (Jones et al 1999, 2005, Bradbury et al 2008) and local adaptation (McIntyre & Hutchings 2003, Conover et al 2006, Hutchings et al 2007). The implications of such fine-scale population structure are important for effective management (Palumbi 2003, Bradbury et al 2008, Reiss et al 2009).…”

“…Adaptive divergence can occur over much shorter time scales than can neutral genetic differentiation (Endler 1986, Cano et al 2008, resulting in genetic differentiation of a greater magnitude for selected versus neutral loci (Beaumont & Balding 2004) : 177-195, 2010 therefore inappropriate for making inferences about population processes, such as migration rates and effective population size, they can serve an important function in genetic stock identification (Nielsen et al 2006, ICES 2009). The adaptive differences underlying variation at selected loci may have important management implications (Crandall et al 2000, Conover et al 2006, Hauser & Carvalho 2008, ICES 2009.…”

“…Although selected loci are therefore inappropriate for making inferences about population processes, such as migration rates and effective population size, they can serve an important function in genetic stock identification (Nielsen et al 2006, ICES 2009). The adaptive differences underlying variation at selected loci may have important management implications (Crandall et al 2000, Conover et al 2006, Hauser & Carvalho 2008, ICES 2009.…”

Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

“…This find is very interesting because previously several authors had defined different ecological requirements for the various Pomatochistus species; for example, P. marmoratus survives to higher salinities than P. microps, especially in habitats whose temperature and salinity change through the year, but do not vary abruptly (Berrebi et al 2005). Thereby, extreme environmental conditions could be acting on genetic structure of coastal lagoon populations of P. marmoratus causing genetic divergence (Conover et al 2006;Marshall et al 2010;Sanford and Morgan 2011).…”

“…Moreover, differences in reproductive strategy may have an important impact on genetic diversity and population structure (González-Wangüemert and Pérez-Ruzafa 2012; Portnoy et al 2013). In addition, there is evidence of genetic adaptation as result of natural selection capable of sustaining adaptive divergence on contemporary time scales (Conover et al 2006;Nielsen et al 2009;Yoboué et al 2012;Wang et al 2013). All these factors could have a profound effect on the arising of population differentiation.…”