4 research outputs found
Field evidence of caddisfly larvae (Trichoptera: Limnephilidae, Leptoceridae) using alien Crassula helmsii (Kirk) Cockayne fragments (Saxifragales: Crassulaceae) in case construction
We present the first field observations of caddisfly (Trichoptera) larvae using an invasive alien aquatic plant, Crassula helmsii (Kirk) Cockayne, in case construction. In samples from invaded ponds across the UK and Belgium, we have recorded the presence of C. helmsii fragments in cases from Limnephilus lunatus Curtis, Citation1834, Limnephilus marmoratus Curtis, Citation1834, Limnephilus flavicornis (Fabricius, Citation1787) (Limnephilidae), Triaenodes bicolor (Curtis, Citation1834), and Oecetis furva (Rambur, Citation1842) (Leptoceridae). Fragmentation of C. helmsii in case creation and augmentation may produce vegetative propagules, thus facilitating further dispersal of this invasive macrophyte
Quantifying the ecological impacts of alien aquatic macrophytes: a global meta-analysis of effects on fish, macroinvertebrate and macrophyte assemblages
1. Biological invasions constitute a pervasive and growing threat to the biodiversity and functioning of freshwater ecosystems. Macrophytes are key primary
producers and ecosystem engineers in freshwaters, meaning that alien macrophyte invasions have the capacity to alter the structure and function of recipient aquatic ecosystems profoundly. Although prevailing wisdom holds that alien
macrophyte invasions tend to compromise freshwater ecosystem structure and
function, the ecological impacts of alien macrophyte invasion have not been
quantitatively reviewed to date.
2. Here we present a global meta-analysis of 202 cases from 53 research articles,
exploring the impacts of alien macrophyte invasion on the abundance and diversity of three ubiquitous and ecologically important focal groups, which together comprise the bulk of non-microbial freshwater biodiversity: resident
macrophytes, macroinvertebrates and fish. Our synthesis includes data from all
continents except Antarctica and Asia, covering 25 alien macrophyte species,
but reveals considerable taxonomic and geographical biases in knowledge.
3. Meta-analysis results reveal that invasion by alien macrophytes has an overall
negative impact on taxonomic diversity of the three focal groups, but no consistent effect on abundance. At a finer resolution, we detect a strong negative
effect of alien macrophyte invasion on resident macrophyte abundance and diversity, and a significant but smaller positive effect of submerged alien macrophyte invasion on macroinvertebrates. Effects on fish appear inconsistent.
4. Our findings emphasise the importance of context- and taxon-specific ecological research in informing appropriate and proportionate management of alien
macrophyte invasions, since alien macrophyte impacts are not consistently
negative. We also identify significant geographical and taxonomic limitations in
existing studies, quantitative data being lacking for many alien taxa