Genetic diversity and population structure of the size- selectively harvested owl limpet, Lottia gigantea

Size-selective harvesting is one of the most widespread anthropogenic impacts on marine species. The loss of larger (older) individuals due to such harvesting has numerous cascading effects on the biology of affected species and populations, including changes in life history, demography, reproductive output, and even ecological interactions (Fenberg & Roy 2008). Size-selective harvesting has been shown to elicit rapid microevolutionary responses in some wild populations (Coltman et al. 2003; Grift et al. 2003; Olsen et al. 2004; Kuparinen & Merila 2007; Nussle et al. 2009) and intense harvest-induced mortality (regardless of selectivity) over multiple generations should result in genetic changes (Allendorf et al. 2008). However, for the vast majority of affected species, we do not know whether observed changes have a genetic basis, represent phenotypic plasticity, or result from a combination of both (Kuparinen & Merila 2007; Allendorf et al. 2008; Fenberg & Roy 2008). The most powerful way to detect harvest-induced genetic changes is to analyze samples collected over an extended period of time as a species is exploited (Coltman et al. 2003; Kuparinen & Merila 2007; Allendorf et al. 2008). This approach has produced mixed results for harvested fish species, with some such studies showing a change in genetic diversity or structure over time (Smith et al. 1991; Hauser et al. 2002; Heath et al. 2002; Hutchinson et al. 2003) while others reveal no significant trends (Nielsen et al. 1999; Ruzzante et al. 2001; Chevolot