Spatial patterns of genetic diversity in habitat-forming marine species and their overlap with Marine Protected Areas

Abstract

Genetic diversity is considered an essential level of biodiversity, supporting the responses of natural populations to environmental changes. In spite of the recent call to monitor global genetic diversity to fully understand the impacts of global change, the pattern of genetic diversity is largely unknown, especially in the oceans. In this study we conducted a meta-analysis to explore the global patterns of genetic diversity in habitat-forming marine species, which are key organisms providing structural complexity and increasing the biodiversity of benthic ecosystems. We mapped the expected heterozygosity (He) for more than 9.300 populations of 141 species - extracted from 269 papers – that belongs to seven taxa (bryozoans, hexacorals, hydrozoans, octocorals, seagrasses, seaweeds and sponges). We overlapped this data with the distribution of Marine Protected Areas (MPAs) using Protected Planet database at global scale, and MAPAMED from MEDPAN databases at Mediterranean Sea. Differences in genetic diversity were analyzed: i) among taxa; and ii) between protected and non-protected areas for each taxa, using a Generalized Linear Models. North-western Mediterranean and north-eastern Atlantic are the areas with the highest number of studies and populations, followed by the Gulf of Mexico, North-eastern Pacific and South-western Pacific. The expected heterozygosity is significantly different among the seven taxa, with Sponge and Seaweed showing the highest and lowest mean values, respectively. The number of studied populations is higher inside MPAs, but genetic diversity was not different between protected and non-protected areas. This fact challenges the idea that a high genetic diversity inside MPAs can enhance the resilience of marine species to global warming. Our work represents the first approximation of the global patterns of genetic diversity in habitat-forming marine species. It opens an opportunity to investigate the biotic (e.g. longevity) and abiotic (e.g. temperature) drivers of genetic diversity in these species and to monitor the genetic consequences of global change