Abstract
Population structure has direct consequences on species evolution, local adaptation, and the capacity of a metapopulation to adapt to climate change. In this study we assess the genetic structure and demographic history of the Pacific angel shark, Squatina californica, along the northwestern coast of Mexico using the mitochondrial control region. Results showed high levels of genetic diversity and reveal genetic differentiation between the samples from the Pacific coast of the Baja California Peninsula and those from the Gulf of California. These genetic differences are consistent with ontogenetic differences previously reported for S. californica off the northwestern coast of Mexico. Our findings can be explained by the low dispersal ability and habitat preference of the angel shark and by the complex geomorphology off the northwestern coast of Mexico. Contrasting historical demographic patterns were observed: population expansion in the gulf and population stability, with a declining trend, in the Pacific; however, more studies are required to corroborate demographic patterns in both populations. Our results point to 2 distinct management units of the Pacific angel shark in the study area, and this may have direct implications for the management and conservation of this species in Mexico.
Highlights
Understanding the spatiotemporal patterns of gene flow among isolated populations has long been a major focus in ecology (Spaet et al 2015)
Absence of population structure was detected for the deep-water Centroscymnus coelolepis (Veríssimo et al 2011), whereas almost global panmixia was found for Cetorhinus maximus (Hoelzel et al 2006)
Knowing the processes that affect genetic diversity and population structure is crucial for the conservation of exploited species (Arenas et al 2012)
Summary
Understanding the spatiotemporal patterns of gene flow among isolated populations has long been a major focus in ecology (Spaet et al 2015). Absence of population structure was detected for the deep-water Centroscymnus coelolepis (Veríssimo et al 2011), whereas almost global panmixia was found for Cetorhinus maximus (Hoelzel et al 2006). These population patterns are commonly promoted by geographic barriers or dispersal, or can be influenced by environmental gradients throughout continuous areas (Spaet et al 2015). Understanding population structure and connectivity of marine resources is an essential prerequisite for devising effective fishery management strategies in at least 2 critical ways: (i) the delineation of an appropriate spatial scale for management and (ii) the specification of subareas, nested within broader management units, that must be protected from exploitation (Fogarty and Botsford 2007, Hilário et al 2015)
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