An investigation into the environmental drivers of evolution in marine predators

Understanding the key environmental drivers of population structure formation and evolution is a fundamental problem in evolutionary biology. Within marine environments, ocean frontal systems have been implicated in acting as a barrier to gene flow in a wide variety of marine taxa, yet their impact on population structure in marine predators remains unclear. Using a combination of genetic markers (SNPS and mtDNA loci) and stable isotope analysis (δ13C and δ15N) this study investigated the genetic and trophic population structure of the Yellowmouth Barracuda Sphyraena viridensis and the Bottlenose Dolphin Tursiops truncatus against the context of environmental variables. S. viridensis showed some limited evidence of geographic population structure but considerable evidence of differential feeding by geography and the presence of two clear haplogroups. By contrast, clear population structure was evident in T. truncatus with the Almería-Oran front presenting as a strong environmental influence. Further environmental factors (e.g. salinity) correlated with population structure, with its impact on prey distribution being a possible causal mechanism. Evidence for an offshore Azores-Sicily metapopulation of T. truncatus was discovered, possibly mediated by social and acoustic parameters, although data on this is limited. There was clear genetic differentiation between T. truncatus ecotypes but with evidence of ongoing gene flow. A possible sequence of events to explain gene flow patterns within the wider genus is explored. Investigations in to the timing of speciation between T. truncatus and T. aduncus revealed evidence for climate events being a key driver of evolution in this genus. This builds on previous evidence that climate is a fundamentally important driver in the evolution of cetaceans.