Amphibian richness patterns inAtlanticForest areas invaded byAmerican bullfrogs

Abstract

The relationship between invasion success and native biodiversity is central to biological invasion research. New theoretical and analytical approaches have revealed that spatial scale, land‐use factors and community assemblages are important predictors of the relationship between community diversity and invasibility and the negative effects of invasive species on community diversity. In this study we assess if the abundance of Lithobates catesbeianus, the American bullfrog, negatively affects the richness of native amphibian species in Atlantic Forest waterbodies in Brazil. Although this species has been invading Atlantic Forest areas since the 1930s, studies that estimate the invasion effects upon native species diversity are lacking. We developed a model to understand the impact of environmental, spatial and species composition gradients on the relationships between bullfrogs and native species richness. We found a weak positive relationship between bullfrog abundance and species richness in invaded areas. The path model revealed that this is an indirect relationship mediated by community composition gradients. Our results indicate that bullfrogs are more abundant in certain amphibian communities, which can be species‐rich. Local factors describing habitat heterogeneity were the main predictors of amphibian species richness and composition and bullfrog abundance. Our results reinforce the important role of habitats in determining both native species diversity and potential invasibility.

Living in a changing world: effects of roads andPinusmonocultures on an anuran metacommunity in southern Brazil

“…Recent reviews confirm that invasive species use the breaches in the functional space as gateways to invade communities where they would not occur naturally or establish easily (Lososová et al, 2015;Finerty et al, 2016). For South American frogs this possibility is concrete, as several communities suffer from the invasion of the American bullfrog (Lithobates catesbeianus), including communities in the extreme south of Brazil (Both et al, 2014;Both & Melo, 2015). In terms of conservation, this is worrying, as the resilience of communities and the integrity of the ecosystem functions provided by native anurans may be compromised.…”

“…In terms of conservation, this is worrying, as the resilience of communities and the integrity of the ecosystem functions provided by native anurans may be compromised. Indeed, the American bullfrog, for example, is among the world's 100 most prominent aquatic invasive species causing negative direct and indirect effect on native aquatic fauna worldwide, particularly on native anurans (Bucciarelli et al, 2014), and Brazil is no exception (Both et al, 2014;Both & Melo, 2015). Exotic plantations -of the genera Pinus and Eucalyptus -alter soil characteristics through the release of toxic substances, also contributing to lower quality litter (Machado, Moreira & Maltchik, 2012;Ferreira et al, 2015), making these areas inhospitable for anurans dependent on higher soil/water quality or the presence of vegetation for foraging or reproducing.…”

“…These characteristics of the anuran life-cycle make them particularly vulnerable to anthropogenic modifications. Increased levels of ultraviolet (UV) radiation (Hite et al, 2016), pollution and the introduction of exotic species (Both et al, 2014;Both & Melo, 2015) are associated with the increased incidence of deleterious and lethal pathogens in anurans. The transformation of natural areas into monocultures and the expansion of the road network drastically modify the structure of the landscapes; consequently, species behaviour, population dynamics and gene flow between populations may be severely affected (Bitar et al, 2014;Berriozabal-Islas et al, 2018).…”

Functional distance to recipient communities may favour invasiveness: insights from two invasive frogs

“…However, we do not exclude that they could have shown some signal if they had been analysed at a finer resolution. For instance, a study on bullfrog in Brazil showed that spatial heterogeneity had a significant effect when analysed at the aquatic-habitat scale, being positively correlated with bullfrog presence (Both et al, 2014).…”

Reproductive phenology of the American Bullfrog in subtropical Brazil: photoperiod as a main determinant of seasonal activity

“…It has been suggested that bullfrogs might negatively affect various native species in Brazil, however there is a lack of evidence supporting such impacts (see Both et al 2014).…”