The contribution of environmental and geospatial variation to multi-species genetic variation: a standardised seascape genetics meta-analysis

Genetic diversity in the sea varies spatially and temporally, and understanding which factors contribute to this variation helps inform management and conservation decision making, as well as contributing to our understanding of evolution. However, few studies have explicitly tested the relationship between genetic variation and geospatial/environmental variation across a wide range of coastal marine species. In the present study, we tested for the presence of consistent patterns of explanatory environmental and/or geospatial variables across multiple phyla for species-specific estimates of genetic diversity. We conducted a survey of published/unpublished results of genetic diversity indices for which we generated a standardised and spatially-explicit geospatial and marine environmental data set. Our seascape genetics analyses involved multiple regressions (GLMs) using 11 geospatial and environmental variables for 80 species-specific data sets of genetic variation for New Zealand coastal marine taxa from 9 phyla. Overall, we found very strong evidence to reject the null hypothesis of no significant effect of geospatial and/or environmental variation on the variation of the 9 genetic indices. Although all 11 geospatial and environmental variables explained significant variation in one or more of the genetic indices, our results identified six factors (two geospatial, three related to sea surface temperature, one related to currents) as explaining the greatest levels of significant variation in genetic variation. Generalised binomial testing confirmed that six of eight genetic indices exhibited consistent across-taxon patterns of variation in response to the 11 geospatial and environmental variables. The identification of such response patterns across multiple species and phyla is helpful in the broader context of better understanding how environmental variation - past, present and future - contributes to genetic diversity.