Myths and moderation in marine ‘metapopulations’?

Abstract

The metapopulation concept is appearing with increasing frequency in the marine population dynamics and genetics literature, though its applicability to marine systems remains an open question. Moreover, in recent years, the meaning of the term ‘metapopulation’ has become blurred, concomitant with its increasing use. In this paper, we summarize the concept of metapopulation dynamics and the associated theoretical assumptions. We call for a stricter definition and use of the term ‘metapopulation’, critically evaluate the applicability of metapopulation theory to marine population dynamics and its use in the related literature, and consider two published case‐studies that investigate metapopulation structuring in specific marine populations. Finally, we urge scientists to carefully articulate what is meant by the term ‘metapopulation’ and to use appropriate citations in the primary literature to circumvent the potential for nebulous (and possibly damaging) conclusions in the future.

Migratory behaviour of Atlantic cod Gadus morhua: natal homing is the prime stock-separating mechanism

“…Robichaud & Rose 2004). Nonetheless, if philopatric behaviour is recognised as the prime population structuring mechanism in marine fishes, it will have far-reaching consequences on the applicability of metapopulation theory to fishery science (McQuinn 1997, Smedbol et al 2002) and on our perceptions in fisheries management (Smedbol & Stephenson 2001). Importantly, if fish populations act as behavioural entities, degradation of population structures has to be considered as partly irreversible, at least on an ecological time perspective.…”

Theory, consequences and evidence of eroding population spatial structure in harvested marine fishes: a review

“…Many factors can blur the genetic signature of demographically isolated populations, such as markers used for examining the separation, population sizes, and the isolation time (Palumbi 2003, Hutchings et al 2007, Knutsen et al 2011. In contrast to this pattern of isolation, a metapopulation is defined by the presence of several locally breeding subpopulations linked to each other by individual dispersal and each having equal potential for independent extinction and re-colonization (Smedbol et al 2002). In a metapopulation, the internal dynamics of each composing subunit (deme) are still dominant compared to the dynamics caused by individual dispersal, but the level of dispersal is such that the genetic signature among the composing demes is blurred (McQuinn 1997).…”

“…Yet, grouping populations based on their spatial, demographic and genetic structures is a common practice in ecology (e.g. Pulliam 1988, Smedbol et al 2002 and in this review has been instrumental to describe the genesis and maintenance of spatial structure and the consequences of its erosion. However, in nature, individuals are not aware of our theoretical boundaries and behave in ways that may challenge their premises (Thomas & Kunin 1999).…”

“…Iles & Sinclair 1982), (2) spatially complex populations, e.g. metapopulations (Smedbol et al 2002) and source-sink populations (Pulliam 1988), and (3) panmictic populations (Table 1). In nature, these 3 levels of aggregations are present as a continuum rather than categorical groupings (Thomas & Kunin 1999) (Brown et al 1995), intra-and inter-specific interactions, and individual behavioral responses (Planque et al 2011).…”

Plasticity of European flounder life history patterns discloses alternatives to catadromy

“…This type of policy can induce selective fishing mortality on individuals that use 1 particular migratory tactic, with unpredictable consequences for flounder genetic diversity and stock structure (Olsen et al 2004, Thériault et al 2008. At the local scale, sustainable management of flounder stocks is contingent on both connectivity among coastal, brackish and freshwater habitats, which in dam-regulated ecosystems depends on maintaining water discharge below critical levels (Morais et al 2009), while from a metapopulation perspective, it is important to understand the roles of spatial heterogeneity in population structure and connectivity (Smedbol et al 2002). Ultimately, flounder fishery management must be supported by solid population trait data, and future work should investigate the mechanisms underlying migratory plasticity in European flounder.…”