A Latitudinal Cline in the Taxonomic Structure of Eelgrass Epifaunal Communities is Associated With Plant Genetic Diversity

Abstract

Aim: Biogenic structural complexity increases mobile animal richness and abundance at local, regional and global scales, yet an-imal taxa vary in their response to complexity. When these taxa also vary functionally, habitat structures favouring certain taxamay have consequences for ecosystem function. We characterised global patterns of epifaunal invertebrates in eelgrass (Zosteramarina) beds that varied in structural and genetic composition.Location: North America, Europe and Asia.Time Period: 2014.Major Taxa Studied: Peracarid crustaceans and gastropod molluscs.Methods: We sampled epifaunal invertebrate communities in 49 eelgrass beds across 37° latitude in two ocean basins con-currently with measurements of eelgrass genetic diversity, structural complexity and other abiotic and biotic environmentalvariables. We examined how species richness, abundance and community composition varied with latitude and environmentalpredictors using a random forest approach. We also examined how functional trait composition varied along with communitystructure.Results: Total species richness decreased with latitude, but this was accompanied by a taxonomic shift in dominance from pera-carid crustaceans to gastropods, which exhibited different sets of functional traits. Greater eelgrass genetic diversity was stronglycorrelated with both richness and abundance of peracarids, but less so for gastropods.Main Conclusions: Our results add to a growing body of literature that suggests genetic variation in plant traits influences theirassociated faunal assemblages via habitat structure. Because peracarids and gastropods exhibited distinct functional traits, ourresults suggest a tentative indirect link between broad-scale variation in plant genetic diversity and ecosystem function.