Seagrasses play a vital role in structuring coastal marine ecosystems, but their distributional range and genetic diversity have declined rapidly in recent decades. 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, which can give rise to populations with 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. By retrieving and re-analysing microsatellite data from previous studies, we delimited 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, models for both levels predicted considerable range contraction in the future, but the lineage-level models predicted more severe habitat loss. Importantly, the two modelling approaches predicted opposite patterns of habitat change in the Western Tropical Indo-Pacific region. Our results highlight the necessity of conserving distinct populations and genetic pools to avoid regional extinction due to climate change and have important implications for guiding future management of seagrasses.

中文翻译：

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在预测气候变化下的海草分布时，种内遗传变异很重要

海草在构建沿海海洋生态系统方面发挥着至关重要的作用，但近几十年来它们的分布范围和遗传多样性迅速下降。为了改善海草物种的保护，重要的是预测气候变化如何影响它们的分布范围。此类预测通常使用相关物种分布模型 (SDM) 进行，该模型可以在给定物种存在数据和气候预测变量的情况下估计物种在当前和未来气候情景下的潜在分布。然而，这些模型通常是用物种水平的数据构建的，因此忽略了种内遗传变异，这可能导致种群适应异质气候条件。在这里，我们探讨了种内适应和生态位分化之间的联系海藻，一种广泛分布于热带印度洋-太平洋的海草，是众多海洋物种栖息地的重要提供者。通过检索和重新分析先前研究中的微卫星数据，我们在名义物种中划定了两个不同的系统地理学谱系，并在它们的多维环境生态位中发现了中间水平的分化，表明了局部适应的可能性。然后，我们使用物种级和谱系级 SDM 比较了气候变化情景下物种栖息地适宜性的预测。在中热带印度洋-太平洋地区，两个级别的模型都预测未来范围会出现相当大的收缩，但谱系级别的模型预测更严重的栖息地丧失。重要的，这两种建模方法预测了西部热带印度洋-太平洋地区生境变化的相反模式。我们的研究结果强调了保护不同种群和遗传库以避免因气候变化而导致区域灭绝的必要性，并对指导未来海草管理具有重要意义。