Abstract
Predation is one of the main barriers that exotic species may face in newly colonized areas and may help stop or control the potential negative impacts of invasive species in the environment. We evaluated if the consumption of an invasive prey (armored catfish: Pterygoplichtys sp.) affects the dietary niche breadth and trophic level of a native predator (Neotropical river otter: Lontra longicaudis) in northern Guatemala. We examined otter scats from three rivers: two where the invasive armored catfish occurred and one without the invasive fish. Samples were collected two and seven years after the first report of the catfish in the area. We performed gross scat analysis and stable isotope analyses of nitrogen and carbon of fecal matter. Where the invasive armored catfish occurred, it was the main prey item for L. longicaudis. Particularly in the river outside of protected areas seven years after the first report of the catfish, where it accounted for 49% of the otter diet. Concordance was found between the two techniques to estimate dietary niche breadth and trophic level. The dietary niche breath of otters was narrower seven years after the invasion in comparison to two years after the invasion in both invaded rivers, but the extent of the reduction was lesser inside the protected area. Finally, the trophic level of otters also showed a reduction related to the occurrence of the armored catfish in their diet.
Highlights
Predators may change their diet after an exotic prey species becomes established and abundant in the predator’s range [1,2,3,4]
The same pattern was observed in the standardized niche breadth index (Ba)
The wider niche breadth (Ba values) in the San Pedro River may be related to its higher environmental integrity that could help sustain the richness of native NRO prey or reduce the invasiveness of the ACF
Summary
Predators may change their diet after an exotic prey species becomes established and abundant in the predator’s range [1,2,3,4]. Inclusion of such a species in a predator’s diet can lead to a shift in the predator’s dietary niche, which may become wider or narrower, depending on the intensity of use of the new resource and changes in the use of alternative native prey [5]. The type of prey that a predator eats defines its trophic level (e.g., primary consumer, secondary consumer). Both niche breadth and trophic levels can be evaluated using gross scat analysis and stable isotopes analyses. An important group of invasive species in freshwater communities are the armored catfishes of the South American family Loricariidae, a diverse group of fishes with 928 valid
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