Marine Biology and Ecology Research Centre, School of Biological and Marine Sciences, University of Plymouth, Plymouth PL3 4LL, Devon, United Kingdom.
Freshwater Habitats Team, Institute for Nature and Forest Research (INBO), Havenlaan 88, Box 73, 1000 Brussels, Belgium.
Sci Total Environ. 2024 Feb 25;913:169667. doi: 10.1016/j.scitotenv.2023.169667. Epub 2023 Dec 30.
Invasive alien species are considered one of the greatest threats to global biodiversity, and are particularly problematic in aquatic systems. Given the foundational role of macrophytes in most freshwaters, alien aquatic plant invasions may drive strong bottom-up impacts on recipient biota. Crassula helmsii (New Zealand pygmyweed) is an Australasian macrophyte, now widespread in northwest Europe. Crassula helmsii rapidly invades small lentic waterbodies, where it is generally considered a serious threat to native biodiversity. The precise ecological impacts of this invasion remain poorly understood, however, particularly with respect to macroinvertebrates, which comprise the bulk of freshwater faunal biodiversity. We conducted a field study of ponds, ditches and small lakes across the core of C. helmsii's invasive range (United Kingdom, Belgium and the Netherlands), finding that invaded sites had higher macroinvertebrate taxon richness than uninvaded sites, and that many infrequent and rare macroinvertebrates co-occurred with C. helmsii. Alien macroinvertebrates were more abundant in C. helmsii sites, however, particularly the North American amphipod Crangonyx pseudogracilis. At the order level, water beetle (Coleoptera) richness and abundance were higher in C. helmsii sites, whereas true fly (Diptera) abundance was higher in uninvaded sites. Taxonomic and functional assemblage composition were both impacted by invasion, largely in relation to taxa and traits associated with detritivory, suggesting that the impacts of C. helmsii on macroinvertebrates are partly mediated by the availability and palatability of its detritus. The nuanced effects of C. helmsii on macroinvertebrates found here should encourage further quantitative research on the impacts of this invasive plant, and perhaps prompt a more balanced re-evaluation of its effects on native aquatic macrofauna.
入侵的外来物种被认为是对全球生物多样性的最大威胁之一，尤其在水生系统中问题更为突出。由于大型水生植物在大多数淡水中起着基础性作用，因此外来水生植物的入侵可能会对受纳生物群产生强烈的自下而上的影响。皱叶冷水花（新西兰小矮蒲苇）是一种澳大拉西亚的大型水生植物，现在广泛分布于西北欧。皱叶冷水花迅速入侵小型静水水体，在那里它通常被认为是对本地生物多样性的严重威胁。然而，这种入侵的精确生态影响仍知之甚少，特别是对于构成淡水动物区系生物多样性主体的大型无脊椎动物。我们在皱叶冷水花入侵范围的核心地区（英国、比利时和荷兰）开展了一项池塘、沟渠和小湖泊的实地研究，发现入侵点的大型无脊椎动物分类群丰富度高于未入侵点，并且许多不常见和罕见的大型无脊椎动物与皱叶冷水花共存。然而，外来大型无脊椎动物在皱叶冷水花点更为丰富，特别是北美的片脚类动物 Crangonyx pseudogracilis。在科级水平上，皱叶冷水花点的水甲虫（鞘翅目）丰富度和丰度较高，而未入侵点的真蝇（双翅目）丰度较高。分类和功能组合组成都受到了入侵的影响，主要与与碎屑食性相关的类群和特征有关，这表明皱叶冷水花对大型无脊椎动物的影响部分是通过其碎屑的可用性和可食性来介导的。这里发现的皱叶冷水花对大型无脊椎动物的细微影响应鼓励进一步对这种入侵植物的影响进行定量研究，也许还会促使对其对本地水生大型动物群的影响进行更平衡的重新评估。
