Empirical tests for ecological exchangeability

Abstract

The concept of ecological exchangeability, together with genetic exchangeability, is central to both the Cohesion Species Concept as well as to some definitions of Evolutionarily Significant Units. While there are wellestablished criteria for measuring genetic exchangeability, the concept of ecological exchangeability has generated considerable confusion. We describe a procedure that uses the complementary strengths, while recognising the limitations, of both molecular genetic data and ecological experiments to determine the ecological exchangeability of local populations within a species. This is the first synthesis of a combined approach (experiments and genetics) and the first explicit discussion of testing ecological exchangeability. Although it would be ideal to find functional genes that interact to influence quantitative traits resulting in ecological differences (e.g. growth, size, fecundity), we suggest that our current knowledge of functional markers is too limited for most species to use them to differentiate adaptively different local populations. Thus, we argue that ecological experiments using whole organisms combined with neutral markers that indicate evolutionary divergence, provide the strongest case for detecting adaptive differences among local populations. Both genetic divergence and ecological experiments provide the best information for infering ecological exchangeability. This procedure can be used to decide which local populations should be preserved to maintain intraspecific variation and to determine which populations would enhance captive-breeding programs, augment endangered local populations and could best be used to re-introduce native species into historically occupied areas.

Patterns of ancestry and genetic diversity in reintroduced populations of the slimy sculpin: implications for conservation

“…If this is the case, then mixing sources may be appropriate. If potentially adaptive trait differences are observed, and pilot studies in which reintroduced populations may be monitored are feasible, then phenotypic plasticity may be parsed out from genetically based local adaptation via common garden or reciprocal transplant experiments that measure differences in phenotypic traits (e.g., growth, body size, fecundity and survivorship; Rader et al 2005).…”

“…Evidence of ecological divergence among source populations should be carefully considered because it indicates the potential for disrupting unique local adaptations that may be worth preserving (Crandall et al 2000), and for outbreeding depression in intrapopulation hybrid individuals. Because of the variation in habitat and their degree of isolation, sculpin populations in the Driftless Region may not only have a unique evolutionary history, but they may also not be ecologically exchangeable with one another (Crandall et al 2000;Rader et al 2005). Mixing these sources may have the disadvantage of disrupting unique adaptations among populations and lead to decreased fitness.…”

Population genetics and conservation of the threatened southeastern beach mouse (Peromyscus polionotus niveiventris): subspecies and evolutionary units

“…There are, however, notable exceptions (Paetkau 1999;Crandall et al 2000;Kizarian and Donnely 2004), and arguments have been made that the inclusion of an ESU sensu Moritz (1994) in ESA legislation is problematic (Pennock and Dimmick 1997;Dimmick et al 1999) and that this definition overlooks nested units of diversity (Paetkau 1999;Crandall et al 2000;Kizirian and Donnelly 2004), thus negatively impacting the conservation of overall diversity. Many of these problems appear to be overcome with the recent more holistic approach of including both genetic and ecological exchangeability data in defining conservation units Fraser and Bernatchez 2001;Rader et al 2005).…”

Ecological and association genetics in two Mediterranean pine species

“…But molecular genetic markers alone do not provide a reliable tool for conservation geneticists wanting to measure a population's adaptive potential, as patterns identified in quantitative adaptive traits normally differ from those observed using neutral or weakly selected loci (Fraser and Bernatchez 2001;Frankham 2010;Mittell et al 2015). A combined approach including molecular, quantitative and ecological data, although rarely employed, is fundamental and would allow the integration of evolutionary processes in conservation planning (Rader et al 2005;Ouborg et al 2006;Sgrò et al 2011). Precise and integrated data in neutral and adaptive genetic patterns are essential to design effective tree dynamic conservation strategies to minimize biodiversity losses in the face of climate change.…”