American bullfrog (Lithobates catesbeianus) distribution, impact on native amphibians and management priorities in San Carlos, Uruguay

Biological invasions are a major cause of biodiversity and ecosystem services loss. However, information on distribution and impacts is limited for many alien species, restricting the development of local management measures. The aim of this study is: to identify the current situation of the American bullfrog (Lithobates catesbeianus) invasion focus in San Carlos (Maldonado, Uruguay); to evaluate its impacts on native anurans; and to provide management tools. Between 2017 and 2019, 75 permanent ponds were sampled, finding an expanding bullfrog population (occupying 32 ponds, in 16.5 km 2 ). Results show that native anuran richness was lower in the invaded ponds. Observed impacts were greater for the aquatic frog Pseudis minuta, probably due to greater encounter rates with the invader. The abundance of tadpoles was also lower in the invaded ponds. The local pond network was explored using graph theory, evaluating its topological role and centrality. In this network, a list of priority ponds was generated to prevent local bullfrog expansion. Given the relatively small size of this population, eradication seems feasible. Focusing on the key nodes could prevent further expansion, by using spatial prioritization to organize the recommended management of the pond network.Agencia Nacional de Investigación e Innovació

Preserving Uruguay’s freshwater systems: the need to restrict invasive species introductions for sustainable production

This manuscript critically examines the history of non-native aquatic species introductions in Uruguay, emphasizing the role of public institutions. Despite global concerns about biodiversity threats from these introductions, Uruguay’s reliance on animal production and aquaculture involving non-native species has grown since the 1980s. State institutions, despite past failures, have promoted these introductions without comprehensive risk assessments. Notable cases, including failed attempts with species like the herbivorous carp, American bullfrog, Nile tilapia, Australian redclaw crayfish, and American mink, raise concerns about invasive populations due to a lack of proper risk assessments and prevention measures. Previous examples were deficient in escape monitoring, oversight of specimens after farm closures, and considerations for the presence of new pathogens. This highlights the need for more informed and responsible approaches to prevent invasive species’ establishment, advocating for rigorous analysis and risk assessments before any introduction. We propose overcoming historically fragmented decision-making processes by establishing a bridging structure that coordinates inter- and intra-institutional efforts, engages with the academic sector and social organizations, and evaluates the introductions. This platform can prioritize protecting aquatic ecosystems, fostering sustainable growth, and maintaining ecological balance, contributing to the solution of the problem by facilitating coordinated efforts and engaging diverse stakeholders

Invariant and vulnerable food web components after bullfrog invasion

Alien species introductions produce strong impacts on invaded communities, altering their structure, diversity and functioning. These impacts are interrelated with changes in food web architecture. However, the reorganization or robustness of food webs in the face of invasion is a phenomenon poorly considered in ecology and conservation practices. In this article, we analyze the effects of the invasion of the American bullfrog, Lithobates catesbeianus, on the structure and function of invaded food webs. Specifically, we analyzed the integration of energetic channels by top predators, the relative use of alternative energetic paths by different functional groups and its dependence on body size among invaded and uninvaded communities in Uruguay, South America. The integration of energetic paths at high trophic positions by large body sized consumers was a pervasive feature of food webs among all studied ponds, in spite of turnover in top predator identity and large changes in community composition. Bullfrog post-metamorphs presented high trophic positions, integrating the primary producers and detritus paths, acting as apex predators in invaded food webs. The bullfrog tadpoles presented intermediate positions and were associated with the detritivorous pathway. On the other hand, the relative importance of the primary producers and detritus as carbon sources assimilated into the biomass of fish and invertebrates was altered in invaded systems. The robustness in the integration pattern of energy channels is congruent with its proposed central role in the stability of food webs. These results advance the understanding of the effect of invasions on key structural features of food webs, notably underrepresented in the invasion literature.Agencia Nacional de Investigación e InnovaciónRufford Foundatio

First report of satellite males during breeding in <i>Leptodactylus latrans</i> (Amphibia, Anura)

A male Leptodactylus latrans was observed calling within a foam nest located at about 40 cm from the edge of the pond. The male was collected (voucher deposited at the Herpetological Collection of the Museo Nacional de Historia Natural, Montevideo, Uruguay, MNHN 9476). Ten minutes after the calling male was removed, we observed an amplectic L. latrans pair laying eggs in the same nest. In addition, a third male was at the edge of the foam nest and sporadically swam under the amplectic pair.Asociación Herpetológica Argentina (AHA

First report of satellite males during breeding in <i>Leptodactylus latrans</i> (Amphibia, Anura)

A male Leptodactylus latrans was observed calling within a foam nest located at about 40 cm from the edge of the pond. The male was collected (voucher deposited at the Herpetological Collection of the Museo Nacional de Historia Natural, Montevideo, Uruguay, MNHN 9476). Ten minutes after the calling male was removed, we observed an amplectic L. latrans pair laying eggs in the same nest. In addition, a third male was at the edge of the foam nest and sporadically swam under the amplectic pair.Asociación Herpetológica Argentina (AHA

Skin-mates or neighbors? A seasonal study of amphibian chytrid and dermocystid infection in <i>Boana pulchella</i> (Anura: Hylidae)

We studied in this work the prevalence of two eukaryotic skin pathogens in a population of the frog Boana pulchella (Anura, Hylidae) from southeastern Uruguay, the fungus Batrachochytrium dendrobatidis (Rhizophydiales) and the protoctistan Valentines rwandae (Ichthyosporea, Dermocystida), between 2012 and 2014. In both cases higher prevalences were recorded in cooler seasons, winter and early spring for B. dendrobatidis (0.78 and 0.95 respectively) and autumn for V. rwandae (0.33 and 0.49), with mean temperatures between 11.5 and 17.8°C. No cases of infection were detected in summer. In both cases the probability of infection was strongly influenced by season (and also the year for B. dendrobatidis), but in neither case the occurrence of the other pathogen was significant. The parasitic cycles seem to occur independently and are likely strongly associated to environmental temperatures. Future field studies on amphibian eukaryotic pathogens from temperate areas of South America should consider seasonal variations.En este trabajo se estudió la prevalencia de dos patógenos cutáneos eucariotas en una población de la rana Boana pulchella (Anura, Hylidae) del sureste de Uruguay, el hongo Batrachochytrium dendrobatidis (Rhizophydiales), y el protista Valentines rwandae (Ichthyosporea, Dermocystida), entre 2012 y 2014. En ambos casos las prevalencias más altas se registraron en épocas frías, invierno y primavera temprana para B. dendrobatidis (0,78 y 0,95 respectivamente) y otoño para V. rwandae (0,33 y 0,49), con temperaturas medias entre 11,5 y 17,8°C. No se detectaron casos de infección en verano. La probabilidad de infección en los dos casos está fuertemente influenciada por la estación (y además por el año para B. dendrobatidis), pero no por la ocurrencia del otro patógeno. Ambos ciclos parasitarios parecen ocurrir independientemente, y son probablemente condicionados en gran medida de la temperatura ambiental. Futuros estudios de campo sobre patógenos eucariotas en anfibios de zonas templadas de Sudamérica deberán tener en cuenta variaciones debidas a la época del año.Asociación Herpetológica Argentin

Graph theory as model to understand American bullfrog invasion in Uruguay

In this work it is presented a graph theory approach for the characterization of the data-set of ponds invaded by the aquatic amphibian Lithobates catesbeianus in the period 2007-2022 in Acegu´a (Uruguay). The topological characterization of the network of ponds with a mobility threshold distance of 700 m is presented. The vulnerability analysis of ponds is carried out using centrality metrics, community analysis and evaluating the connection probabilities between nodes, the goal is to classify nodes to prioritize the invasion control.Agencia Nacional de Investigación e Innovació