Is the exotic red swamp crayfish (Procambarus clarkii) a current threat for the Mediterranean tree frog (Hyla meridionalis) in the Camargue (Southern France)?

Abstract

International audienceThe non-indigenous red swamp crayfish (Procambarus clarkii) has been shown to be a threat for amphibian conservation. Many amphibian species breed in temporary ponds to diminish predation risk as such ecosystems are free of large predators. However P. clarkii, occurring as an invasive species in the Camargue delta, can readily disperse on the ground and thus colonize isolated ponds. We studied the current impact of the exotic crayfish on the reproduc- tive success of the Mediterranean tree frog (Hyla meridionalis). In a mesocosm experiment, we tested the effect of two crayfish densities (1 and 3 crayfish/ m2) on tadpole abundance. We also tested in a field experiment, within a temporary pond, the crayfish’s predation on the tree frog’s eggs. Finally, we devel- oped site occupancy models using data from 20 ponds to assess the effect of crayfish abundance on tadpole abundance. Neither the experiments, nor the site occupancy models showed a negative impact of the current crayfish abundance on the tree frog popula- tions breeding in ponds. We found that recorded crayfish densities were lower than in other areas where crayfish has impacted amphibian populations, but we hypothesize that current crayfish abundance in the area may increase in the future, thus impacting tree frog populations

Temporary pond ecosystem functioning shifts mediated by the exotic red swamp crayfish (Procambarus clarkii): a mesocosm study

“…A similar reduction occurred in our experiment (Fig. 4), but in contrast, grazers were still abundant because H. meridionalis tadpoles were not numerically affected by the presence of the red swamp crayfish, even in the D3 treatment (for further information, see Rodríguez-Pérez et al, 2014).…”

“…This ecosystem can be mimicked quite well with mesocosms (Blaustein & Schwartz, 2001). In the area of study, the Rhône delta (southern France), the crayfish actually colonizes temporary ponds (Meineri et al, 2014;Rodríguez-Pérez et al, 2014), and we aimed to test the effect of two different crayfish densities (1 and 3 crayfish/m 2 ) on the structure and functioning of the ecosystem.…”

The ecological role of ponds in a changing world

“…Colonization dynamics strongly influence within and among population genetic variation and evolutionary potential of populations (Ortells et al, 2013), and more specifically, predators play a key role in generating patterns of food web topology across regional environments (Dézerald et al, 2013). Like other freshwater (and terrestrial) habitat types, ponds are subjected to species introductions (Rodriguez-Perez et al, 2013). Species richness typically decreases when fish are present (Ruggiero et al, 2008).…”

Variable effects of an invasive species on the reproduction and distribution of native species in pond networks

“…Elsewhere, larval densities of the whole amphibian community, including the agile frog and the smooth newt Lissotriton vulgaris (a species very similar to the palmate newt), were negatively related to red swamp crayfish (Ficetola et al., ), even though crayfish densities were lower than in the present study (pipe sampling data used for the comparison: median density of 3 individuals/m 2 in colonised ponds, with a maximum of 23 individuals/m 2 ). The link between densities of larval amphibians and crayfish varied in intensity depending on species present in other studies (Cruz & Rebelo, ; Gamradt et al., ), and was not found for the Mediterranean tree frog Hyla meridionalis in the Camargue (Rodriguez‐Perez et al., ).…”