Intraspecific genetic variation matters when predicting seagrass
distribution under climate change
Abstract
Seagrasses play a vital role in structuring coastal marine ecosystems,
but their distributional range and genetic diversity have declined
rapidly over the past decades. In order to improve conservation of
seagrass species, it is important to predict how climate change may
impact their ranges. Such predictions are typically made with
correlative species distribution models (SDMs), which can estimate a
species’ potential distribution under present and future climatic
scenarios given species’ presence data and climatic predictor variables.
However, these models are typically constructed with species-level data,
and thus ignore intraspecific genetic variability of populations that
potentially have adaptations to heterogeneous climatic conditions. Here,
we explore the link between intraspecific adaptation and niche
differentiation in Thalassia hemprichii, a seagrass broadly distributed
in the tropical Indo-Pacific Ocean and a crucial provider of habitat for
numerous marine species. Using microsatellite-based genotyping, we
identified two distinct phylogeographical lineages within the nominal
species and found an intermediate level of differentiation in their
multidimensional environmental niches, suggesting the possibility for
local adaptation. We then compared projections of the species’ habitat
suitability under climate change scenarios using species-level and
lineage-level SDMs. In the Central Tropical Indo-Pacific region, both
models predicted considerable range contraction in the future, but the
lineage-level model predicted more severe habitat loss. The two
modelling approaches predicted opposite pattern in habitat change in the
Western Tropical Indo-Pacific region. Our results highlight the
necessity of conserving distinct populations and genetic pools under
climate change and have important implications for guiding future
management of seagrasses.