Plant Conservation and Population Biology, Department of Biology, University of Leuven, Heverlee, Belgium.
Leuven Plant Institute, Heverlee, Belgium.
J Hered. 2023 Mar 16;114(1):22-34. doi: 10.1093/jhered/esac059.
Habitat loss is threatening natural communities worldwide. Small and isolated populations suffer from inbreeding and genetic drift, which jeopardize their long-term survival and adaptive capacities. However, the consequences of habitat loss for reciprocal coevolutionary interactions remain poorly studied. In this study, we investigated the effects of decreasing habitat patch size and connectivity associated with habitat loss on molecular signatures of coevolution in the Alcon blue butterfly (Phengaris alcon) and its most limited host, the marsh gentian (Gentiana pneumonanthe). Because reciprocal coevolution is characterized by negative frequency-dependent selection as a particular type of balancing selection, we investigated how signatures of balancing selection vary along a gradient of patch size and connectivity, using single nucleotide polymorphisms (SNPs). We found that signatures of coevolution were unaffected by patch characteristics in the host plants. On the other hand, more pronounced signatures of coevolution were observed in both spatially isolated and in large Alcon populations, together with pronounced spatial variation in SNPs that are putatively involved in coevolution. These findings suggest that habitat loss can facilitate coevolution in large butterfly populations through limiting swamping of locally beneficial alleles by maladaptive ones. We also found that allelic richness (Ar) of the coevolutionary SNPs is decoupled from neutral Ar in the butterfly, indicating that habitat loss has different effects on coevolutionary as compared with neutral processes. We conclude that this specialized coevolutionary system requires particular conservation interventions aiming at generating a spatial mosaic of both connected and of isolated habitat to maintain coevolutionary dynamics.
生境丧失正在威胁着全球的自然群落。小而孤立的种群遭受近交和遗传漂变的影响，这危及它们的长期生存和适应能力。然而，生境丧失对互惠协同进化相互作用的后果仍研究不足。在这项研究中，我们调查了与生境丧失相关的生境斑块大小和连通性下降对阿尔康蓝蝶（Phengaris alcon）及其最有限的宿主沼泽龙胆（Gentiana pneumonanthe）协同进化分子特征的影响。由于互惠协同进化的特征是负频率依赖选择，作为一种特殊类型的平衡选择，我们调查了平衡选择的特征如何沿着斑块大小和连通性的梯度变化，使用单核苷酸多态性（SNPs）。我们发现，宿主植物的斑块特征对协同进化的特征没有影响。另一方面，在空间隔离和大的阿尔康种群中观察到更明显的协同进化特征，以及与协同进化有关的 SNP 明显的空间变化。这些发现表明，生境丧失可以通过限制本地有益等位基因被适应不良等位基因淹没，促进大蝴蝶种群的协同进化。我们还发现，协同进化 SNP 的等位基因丰富度（Ar）与蝴蝶中的中性 Ar 分离，表明生境丧失对协同进化过程的影响与中性过程不同。我们得出结论，这种专门的协同进化系统需要特殊的保护干预措施，旨在产生连接和隔离的栖息地的空间镶嵌，以维持协同进化的动态。
