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Advisor(s)
Abstract(s)
1. Invasive alien species (IAS) are leading to the homogenisation of taxonomic
and functional biodiversity, with negative consequences for key ecosystem
processes in fresh water. Invasive signal crayfish (Pacifastacus leniusculus) is expected
to disrupt detritus-based
food webs by affecting leaf breakdown and/or
by decreasing invertebrate density and diversity through predation. The combination
of per-capita
and abundance effects of P. leniusculus in invaded ecosystems
is still largely unknown.
2. A four-week
field experiment was established in Rabaçal and Tuela Rivers (NE
Portugal) to assess effects of P. leniusculus on invertebrate taxonomic and functional
diversity and leaf litter breakdown following a gradient of invasion. We
controlled the presence and absence of crayfish by placing the animals and leaf
litter inside cages at six sites (three sites per river) according to the crayfish in
situ abundance (absent, low, high). Cages were covered with coarse-or
fine-mesh
net to allow or prevent invertebrates from accessing the leaves.
3. Results showed that higher crayfish in situ abundance led to a decrease in abundance,
richness and Shannon diversity of invertebrates and to changes in the
communities’ structures. Higher crayfish abundance led also to a decrease in invertebrate
functional redundancy and an increase in the percentage of invertebrate
taxa with resistance forms. Leaf litter breakdown increased with crayfish
presence and decreased at sites with higher crayfish abundance.
4. Overall, signal crayfish changed the community structure of invertebrates, with
potential severe long-term
effects on native communities and leaf litter breakdown.
Given the widespread distribution of signal crayfish (and other crayfish
species), their ecological impacts should be assessed carefully, especially in pristine
freshwater ecosystems such as those described here.
Description
Keywords
Functional diversity Leaf litter breakdown Signal crayfish Streams Taxonomic diversity
Citation
Carvalho, Francisco; Pascoal, Cláudia; Cássio, Fernanda; Teixeira, Amílcar; Sousa, Ronaldo (2022). Combined per‐capita and abundance effects of an invasive species on native invertebrate diversity and a key ecosystem process. Freshwater Biology. ISSN 0046-5070.