Intraspecific genetic variation matters when predicting seagrass distribution under climate change

Abstract

Seagrasses play a vital role in structuring coastal marine ecosystems,\nbut their distributional range and genetic diversity have declined\nrapidly over the past decades. In order to improve conservation of\nseagrass species, it is important to predict how climate change may\nimpact their ranges. Such predictions are typically made with\ncorrelative species distribution models (SDMs), which can estimate a\nspecies’ potential distribution under present and future climatic\nscenarios given species’ presence data and climatic predictor variables.\nHowever, these models are typically constructed with species-level data,\nand thus ignore intraspecific genetic variability of populations that\npotentially have adaptations to heterogeneous climatic conditions. Here,\nwe explore the link between intraspecific adaptation and niche\ndifferentiation in Thalassia hemprichii, a seagrass broadly distributed\nin the tropical Indo-Pacific Ocean and a crucial provider of habitat for\nnumerous marine species. Using microsatellite-based genotyping, we\nidentified two distinct phylogeographical lineages within the nominal\nspecies and found an intermediate level of differentiation in their\nmultidimensional environmental niches, suggesting the possibility for\nlocal adaptation. We then compared projections of the species’ habitat\nsuitability under climate change scenarios using species-level and\nlineage-level SDMs. In the Central Tropical Indo-Pacific region, both\nmodels predicted considerable range contraction in the future, but the\nlineage-level model predicted more severe habitat loss. The two\nmodelling approaches predicted opposite pattern in habitat change in the\nWestern Tropical Indo-Pacific region. Our results highlight the\nnecessity of conserving distinct populations and genetic pools under\nclimate change and have important implications for guiding future\nmanagement of seagrasses.