Functional response predicts invasiveness but not trophic impact.

Area of Science:

• Ecology
• Invasive Species Biology
• Biodiversity Research

Background:

• Biological invasions significantly erode biodiversity, with invasive species often exhibiting greater trophic impacts than native species.
• Functional response (FR) tests, measuring consumption rates relative to prey density, are key to assessing these impacts.
• FR parameters like attack rate (a) and handling time (h) are used to compare species' predatory efficiency.

Purpose of the Study:

• To investigate if functional response (FR) parameters differ between invasive species in their native versus invaded ranges.
• To test the assumption that FR measures are directly extrapolable across a species' distribution.
• To understand the role of biogeographic context in invasion success and ecological impact.

Main Methods:

• A phylogenetically corrected comparative analysis was performed on 269 FR observations from 45 freshwater fish species.
• Species were categorized as non-invasive or invasive, with invasive species further distinguished by sampling location (native vs. invasion range).
• Key FR parameters (attack rate and handling time) were analyzed in relation to species type and sampling range.

Main Results:

• Invasive species showed higher FR than non-invasive species, but only when sampled in their native range.
• Invasive species in their invasion range exhibited FRs comparable to non-invasive species.
• Attack rates decreased with temperature in non-invasive species but tended to increase in invasive species from introduction ranges, suggesting climate change impacts.

Conclusions:

• High FR predisposes species to invasiveness, but these traits may not persist or manifest identically in invaded ecosystems.
• The biogeographic context is crucial; FRs measured in native ranges cannot be directly extrapolated to predict trophic impacts in new environments.
• Future invasion risk assessments must incorporate biogeographic factors and consider how environmental conditions in the invasion range influence species interactions.