Multigner Lola Fernández, Bras Audrey, DiLeo Michelle F, Saastamoinen Marjo
Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.
Mol Ecol. 2025 Jul 25:e70037. doi: 10.1111/mec.70037.
Habitat loss and fragmentation are considered key drivers of biodiversity loss. Understanding their relative roles is difficult as habitat loss and fragmentation tend to co-occur. It has been proposed that the total habitat amount available in the local landscape mainly drives species richness, while fragmentation per se-the breaking apart of habitat independent of habitat amount-has a negligible or even a positive effect on biodiversity. Several studies support this at the species richness level. Yet, the potential effects of fragmentation per se on genetic diversity at the landscape scale are understudied. Using the Glanville fritillary butterfly metapopulation in the Åland islands, we tested the effects of fragmentation on genetic diversity using a landscape-based approach and 2610 individuals genotyped at 40 neutral SNP markers. We assessed the independent effect of habitat amount and fragmentation (i.e., number of patches, habitat aggregation) within the local landscape on focal patch genetic diversity. The amount of habitat in the local landscape had a positive effect on genetic diversity. Fragmentation measured as the number of patches within the landscape had a negligible impact on genetic diversity, whereas habitat aggregation had a negative effect on genetic diversity when the available amount of habitat in the landscape was low. Focal patch size increased genetic diversity, whereas focal patch structural connectivity had no impact. Our results highlight that all fragments are important to contribute to the total amount of habitat available, and that the impact of habitat fragmentation matters more when the total amount of habitat available is low.
栖息地丧失和破碎化被认为是生物多样性丧失的关键驱动因素。由于栖息地丧失和破碎化往往同时发生，了解它们各自的相对作用颇具难度。有人提出，当地景观中可利用的栖息地总量主要驱动物种丰富度，而破碎化本身（即栖息地的破碎，与栖息地数量无关）对生物多样性的影响可忽略不计，甚至可能有积极影响。多项研究在物种丰富度层面支持了这一观点。然而，破碎化本身在景观尺度上对遗传多样性的潜在影响却鲜有研究。我们利用奥兰群岛的格兰维尔豹纹蝶复合种群，采用基于景观的方法，并对2610个个体进行40个中性单核苷酸多态性（SNP）标记的基因分型，来测试破碎化对遗传多样性的影响。我们评估了当地景观中栖息地数量和破碎化（即斑块数量、栖息地聚集度）对目标斑块遗传多样性的独立影响。当地景观中的栖息地数量对遗传多样性有积极影响。以景观内斑块数量衡量的破碎化对遗传多样性的影响可忽略不计，而当景观中可利用的栖息地数量较低时，栖息地聚集度对遗传多样性有负面影响。目标斑块大小增加了遗传多样性，而目标斑块的结构连通性则没有影响。我们的研究结果表明，所有碎片对于增加可利用的栖息地总量都很重要，而且当可利用的栖息地总量较低时，栖息地破碎化的影响更为显著。
