An assessment of seagrass evolutionary diversity in the Anthropocene

Seagrass meadows provide enormous ecosystem goods and services, ultimately establishing complex coastal habitats that support diverse collections of marine organisms. However, the future of seagrass communities under rapid shifts in climate in the Anthropocene—a period of pronounced human impact on biotic communities—has recently been questioned. Uncertainties from sampling biases present challenges to ecologists and evolutionary biologists in understanding species sensitivity to anthropogenic climate change. Here, we synthesize possible impediments that can constrain research to assess present and future seagrass responses to climate change. First, our knowledge of seagrass occurrence information is prevalent with biases, gaps and uncertainties that can influence inferences on species’ response to global change. Second, research on seagrass diversity has been focused on species-level metrics that can be measured with data from the present - but rarely accounting for the shared phylogenetic relationships and evolutionary distinctiveness of species. Third, compared to the mass production of species occurrence records, computational tools that can analyze these datasets in a reasonable amount of time are almost non-existent or do not scale well in terms of computer time and memory. These impediments mean that scientists must work with incomplete information and often unrepresentative data to predict how seagrass diversity might change in the future. In chapter one, we discuss these shortfalls and provide a framework for overcoming the impediments and diminishing the knowledge gaps they generate. Although climate change projections indicate significant threats to terrestrial biodiversity, shifts in species composition in marine environments might be equally profound. Here, we also explore how different facets of α-diversity (i.e., within all seagrass communities globally) and β-diversity (i.e., between seagrass communities) of seagrasses may respond to future climate change scenarios across the globe and compare them with the existing network of marine protected areas. By utilizing ensemble species distribution modeling under various scenarios of climate change, we observe widespread decreases in seagrass weighted endemism on a global scale. This projected loss in seagrass endemism will result in decreases in β-diversity within temperate regions resulting in the homogenization of seagrass communities in these regions. Regardless of the climate scenario, the hotspots and cold spots of these projected shifts in seagrass α- and β-diversity are predicted to occur outside the current network of marine protected areas, suggesting that these marine protected areas will be insufficient to safeguard the future of seagrasses. Our findings report species’ response for a group underrepresented in climate change assessments yet crucial in maintaining marine food chains.