Abstract
The uptake of natural living resources for human consumption has triggered serious changes in the balance of ecosystems. In the archipelagos of Macaronesia (NE Atlantic), limpets have been extensively exploited probably since islands were first colonized. This has led to profound consequences in the dynamics of rocky shore communities. The Patella candei complex includes various subspecies of limpets that are ascribed to a particular archipelago and has been the focus of several taxonomic surveys without much agreement. Under a conservational perspective, we apply morphometric and genetic analyses to test subspecies boundaries in P. candei and to evaluate its current population connectivity throughout Macaronesia (Azores, Madeira, and Canaries). A highly significant genetic break between archipelagos following isolation by distance was detected (F ST = 0.369, p < .001). Contrastingly, significant genetic differentiation among islands (i.e., Azores) was absent possibly indicating ongoing gene flow via larval exchange between populations. Significant shell‐shape differences among archipelagos were also detected using both distance‐based and geometric morphometric analyses. Adaptive processes associated with niche differentiation and strong barriers to gene flow among archipelagos may be the mechanisms underlying P. candei diversification in Macaronesia. Under the very probable assumption that populations of P. candei from each archipelago are geographically and/or ecologically isolated populations, the various subspecies within the P. candei complex may be best thought of as true species using the denomination: P. candei in Selvagens, Patella gomesii in Azores, Patella ordinaria in Madeira, and Patella crenata for Canaries. This would be in agreement with stock delimitation and units of conservation of P. candei sensu latu along Macaronesia.
Highlights
Conservation efforts applied to human-exploited and threatened species require a comprehensive knowledge about population structure and factors that shape differentiation within a species (Lande, 1988)
Besides the assessment of genetic diversity and structure of P. candei populations across archipelagos, and given the importance of defining conservation units in fisheries planning (Hawkins et al, 2016), we provide discussion and guidance about protective measures of such threatened marine resource, highlighting the importance of considering levels of genetic diversity in populations as well as their uniqueness
Our results revealed highly structured populations among archipelagos, which are likely associated with strong barriers to gene flow
Summary
Conservation efforts applied to human-exploited and threatened species require a comprehensive knowledge about population structure and factors that shape differentiation within a species (Lande, 1988). The complex interplay between physical processes (e.g., coastal topography, stratified water columns, tidal forces, wind, buoyancy, surface waves, and turbulence) and life-history traits (e.g., time of spawning, larval behavior, growth and survival rates, pelagic larval duration), often interacting at fine to mesoscales, can result in a broad range of dispersal and metapopulation connectivity patterns (see review in Cowen & Sponaugle, 2009). Historical events such as past glaciations and changes in sea level can determine the contemporary distribution of populations (e.g., Portnoy et al, 2014). Besides the assessment of genetic diversity and structure of P. candei populations across archipelagos, and given the importance of defining conservation units in fisheries planning (Hawkins et al, 2016), we provide discussion and guidance about protective measures of such threatened marine resource, highlighting the importance of considering levels of genetic diversity in populations as well as their uniqueness
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