Institute of Botany and Landscape Ecology, Greifswald University, Greifswald, Germany.
Department of Biology, University of Prince Edward Island, Charlottetown, PE, Canada.
PLoS One. 2020 Oct 26;15(10):e0241116. doi: 10.1371/journal.pone.0241116. eCollection 2020.
Non-indigenous species are often identified as threats to native species and communities. Yet, the mechanisms that enable many of these invaders to thrive and alter their newly invaded habitats are still not fully understood. This applies to habitats such as widespread sedimentary shorelines characterized by the presence of scattered biogenic clumps of blue mussels (Mytilus edulis) structurally more complex than bare sediments. In Atlantic Canada, some of these shorelines are numerically dominated by native mud crabs (Dyspanopeus sayi) but have been gradually invaded by the European green crab (Carcinus maenas). This study describes between-habitat (mussel clump vs. bare sediment) differences in density and diversity of invertebrates. It also tests the impact of juvenile green crabs in comparison to native mud crabs using two approaches: First, measuring habitat-related differences in these crabs' feeding rates on a common prey (soft-shell clams, Mya arenaria). Second, measuring their influence on invertebrate communities associated with mussel clumps. The results show that mussel clumps hold higher invertebrate density and diversity than surrounding sedimentary bottoms. In the laboratory, the feeding rates of native mud crabs were dependent on the type of habitat (sand flat > mussel clump), whereas those of green crabs were significantly higher and unrelated to the habitat in which predation occurred. In field experiments, juvenile green crabs were also the only predators that changed community structure in the mussel clump habitat. These results indicate that green crabs can cause a significant impact on native species and communities. Moreover, they suggest that the ability of this species to overcome the refuge provided by complex biogenic habitats for prey may represent an unexplored mechanism to explain this invader's expansion here and elsewhere.
非本地物种常被认为是对本地物种和群落的威胁。然而，许多这些入侵物种能够茁壮成长并改变它们新入侵的栖息地的机制仍未完全理解。这适用于广泛存在的沉积性海岸线等栖息地，这些栖息地的特征是存在结构比裸沉积物更复杂的分散生物成因贻贝（Mytilus edulis）丛。在加拿大大西洋沿岸，其中一些海岸线在数量上由本地泥蟹（Dyspanopeus sayi）占据主导地位，但已逐渐被欧洲绿蟹（Carcinus maenas）入侵。本研究描述了栖息地之间（贻贝丛与裸沉积物）无脊椎动物密度和多样性的差异。它还通过两种方法测试了幼体绿蟹与本地泥蟹相比的影响：首先，测量这些螃蟹在常见猎物（软壳蛤，Mya arenaria）上的摄食率与栖息地相关的差异。其次，测量它们对与贻贝丛相关的无脊椎动物群落的影响。结果表明，贻贝丛的无脊椎动物密度和多样性高于周围的沉积底层。在实验室中，本地泥蟹的摄食率取决于栖息地类型（沙滩>贻贝丛），而绿蟹的摄食率显著更高且与捕食发生的栖息地无关。在野外实验中，幼体绿蟹也是唯一改变贻贝丛栖息地群落结构的捕食者。这些结果表明，绿蟹可能对本地物种和群落造成重大影响。此外，它们表明，该物种克服复杂生物成因栖息地为猎物提供的避难所的能力可能代表了一个尚未被探索的机制，可以解释该入侵物种在此地和其他地方的扩张。
