Invasive crayfish does not influence spawning microhabitat selection of brown frogs

Abstract

Microhabitat selection is a key component of amphibian breeding biology and can be modulated in response to the features of breeding sites and the presence of predators. Despite invasive alien species being among the major threats to amphibians, there is limited information on the role of invasive species in shaping amphibians' breeding microhabitat choice. The invasive red swamp crayfish (Procambarus clarkii) is a major predator of amphibians' larvae, including those of the brown frogs Rana dalmatina and Rana latastei. Although qualitative information about the spawning site preferences and breeding microhabitat choice of brown frogs is available in the literature, only a few studies performed quantitative analyses, and the relationship between microhabitat choice and the presence of alien predators has not been investigated yet. The aims of this study were: (1) to characterize the microhabitats selected for clutch deposition by R. dalmatina and R. latastei and (2) to test if the position and the aggregation of egg clutches differ in sites invaded or not invaded by P. clarkii. During spring 2017, we surveyed multiple times 15 breeding sites of both brown frogs in Northern Italy; in each site we assessed the features of the microhabitat where each egg clutch was laid, considering its position (distance from the shore, depth of the water column) and the degree of aggregation of clutches. In each site we also assessed the presence/absence of the invasive crayfish and the relative abundance in the breeding period. We detected egg clutches in all sites; the crayfish occurred in eight ponds. Our results showed substantial differences between the spawning microhabitat features of the two brown frogs: Rana latastei clutches showed a higher degree of aggregation and were associated with deeper areas of the ponds , while Rana dalmatina deposited more spaced out clutches in areas of the ponds that were less deep. For both species, spawning microhabitat features were not significantly different between sites with and without P. clarkii. Although we did not detect behavioural responses to P. clarkii in the choice of spawning microhabitat , additional studies are required to assess whether these frogs modulate other behavioural traits (e.g. during larval development) in response to the invasive predator. How to cite this article Romagnoli S, Ficetola GF, Manenti R. 2020. Invasive crayfish does not influence spawning microhabitat selection of brown frogs. PeerJ 8:e8985 http://doi.org/10.7717/peerj.8985 Romagnoli et al. (2020), PeerJ, DOI 10.7717/peerj.8985 2/16Arribas R, Díaz-Paniagua C, Gomez-Mestre I. 2014. Ecological consequences of amphibian larvae and their native and alien predators on the community structure of temporary ponds.

Morphological and life-history plastic responses to predators and competitors in two brown frogs, Rana dalmatina and R. latastei

“…Both species survived the Pleistocene glaciations in single refugia in southern Europe (Ficetola et al 2007;Vences et al 2013), but while R. dalmatina has expanded its range to much of the territories of central Europe, R. latastei has remained endemic to northern Italy and to neighboring territories (Sillero et al 2014). In sympatry, the two species often share the same breeding site, although R. latastei lays eggs in deeper water, farer from the shoreline (Romagnoli et al 2020). In previous studies (Castellano et al 2022;Castellano et al 2023), we showed that tadpoles of the two species differed in their behavior, both quantitatively (the amount of swimming) and qualitatively (speed and duration of swimming), with R. dalmatina moving more and faster than R. latastei.…”

Similar species, different fates: Abundance dynamics in spatially structured populations of common and threatened frogs

“…Such an effect could occur because adult females might be able to detect the presence of crayfish and prefer to breed in uninvaded wetlands, or because the crayfish reduces recruitment of juveniles, hampering population growth over time. Brown frog tadpoles can modify development rates in the presence of the alien crayfish (Melotto et al, 2020; Muraro et al, 2021), but no information is available about the ability of adults to detect the predator (Ficetola et al, 2011; Romagnoli et al, 2020). Evidence from related frog species suggested that adults are not able to recognize predators inside breeding wetlands (Laurila & Aho, 1997), still some amphibian species can detect predators and prefer predator‐free ponds for laying eggs (Resetarits, 2005).…”

“…The two species have different dispersal abilities and lifespan: ~1500 m dispersal and 5–7 years lifespan for R. dalmatina while for R. latastei dispersal ability is ~1000 m and lifespan is 3–4 years (Bernini, Guarino, et al, 2007; Guarino et al, 2003). They very often breed in the same sites, but they exploit different sectors of ponds, with R. dalmatina mostly laying clutches close to the shoreline, while within the same pond, R. latastei prefers sectors far from the shoreland and with deep water (Romagnoli et al, 2020). The two species also have different conservation statuses.…”

“…Such an effect could occur because adult females might be able to detect the presence of crayfish and prefer to breed in uninvaded wetlands, or because the crayfish reduces recruitment of juveniles, hampering population growth over time. Brown frog tadpoles can modify development rates in the presence of the alien crayfish (Melotto et al, 2020;Muraro et al, 2021), but no information is available about the ability of adults to detect the predator (Ficetola et al, 2011;Romagnoli et al, 2020).…”

“…Differences in life history or microhabitat selection could influence sensitivity to dry years, determining divergent demographic trends between species. The two frog species lay eggs in different locations within the same pond, with R. latastei preferring sectors with deep water and further from the shoreline (Romagnoli et al, 2020). So, microhabitat differences do not explain divergent trends of abundance because egg masses laid in deep water should suffer a lower desiccation risk.…”