INFLUENCE OF MICROHABITAT ON THE TROPHIC ECOLOGY OF TWO LEPTODACTYLIDS FROM NORTHEASTERN ARGENTINA

Acoustic partitioning explains the coexistence between two Physalaemus species (Anura, Leptodactylidae) in the Atlantic Forest in Eastern Bahia State, Brazil

In this study we investigate the niche interaction between the frogs Physalameus cuvieri and Physalaemus kroyeri that occur in syntopy in water bodies of the Atlantic Forest located in the eastern Bahia State, Brazil. We investigated the niche width and overlap in the calling activity time, microhabitat use, diet composition, advertisement call, and body size. Both species preferred the same substrate and calling substrate categories, and showed low niche width values and high spatial niche overlap values. The pseudocommunity analysis revealed the absence of competition in space use. Ants and termites were the most important items in the diet of both species with the pseudocommunity analysis indicating an absence of competition in the diet. The two species demonstrate a greater similarity in body proportions and a high overlap in the calling activity time. However, they showed divergence in acoustic parameters, especially in the dominant frequency and call duration. Our results reinforce the role of advertisement call as a relevant attribute for anuran coexistence and highlight the importance of analyzing the various axes of the multidimensional niche for the most reliable description of the existence and magnitude of niche partitioning.

Feeding ecology of endemic frogs of the Atlantic Forest in southern Brazil

Our objective was to describe and compare the diet of endemic anurans of the Atlantic Forest, as well as to evaluate the influence of biotic factors on the trophic ecology of the species. We conducted the study in Mananciais da Serra (Piraquara-PR), a transition region between mixed and dense ombrophilous forest, between January 2019 and February 2020. In this work, we describe the diet of eight species: Aplastodiscus albosignatus, Boana semiguttata, Bokermannohyla circumdata, Ischnocnema henselii, Leptodactylus notoaktites, Proceratophrys boiei, Rhinella abei and Scythrophrys sawayae. Coleoptera were important prey in the diet of most species, except for B. circumdata and L. notoaktites. All species showed potential selection for some category of prey. We observed a correlation between the size of the individuals and the volume of consumed prey in I. henselii. In general, the niche overlap between species was low, and most species had a broad trophic niche.

Contrasting life-histories in two syntopic amphibians of the Leptodactylus fuscus group (Heyer 1978)

We used skeletochronology to compare age, size, reproductive parameters and growth patterns of two related, anuran amphibians from Northern Argentina: Leptodactylus bufonius (n=69) and L. latinasus (n=56), in order to better understand their coexistence in syntopy. Previous studies showed that the two species overlap in their dietary requirements and utilize the same habitats for feeding and breeding. We found that their life-history patterns are significantly different, L. bufonius being larger, and having a higher reproductive output and lifespan, compared to the smaller and shorter-living L. latinasus. Since none of the species exhibited sexual size dimorphism, and both acquired sexual maturity after the first year of life, we suggest that the differences in the observed life-history parameters must appear during early stages of development, during larval and/or juvenile stages.

Dietary relationships among coexisting anuran amphibians: a worldwide quantitative review

Anuran amphibians have traditionally been considered suitable model organisms for community ecology studies. In this paper, we review and quantitatively re-analyze the original studies published on dietary relationships among anuran communities worldwide. We re-analyzed 33 independent communities from all continents, including data on prey numbers and/or prey volumes. All datasets underwent null model re-analysis using two randomization algorithms. In addition, logistic regression models were used to identify specific assemblage patterns. We discovered three main patterns: (1) one particular algorithm (RA2, which replaces every cell in the matrix with one randomly chosen, but retains the zero structure of the matrix) performed much better at uncovering community structure; (2) nonrandom structure was more likely to occur in tropical than in nontropical regions; (3) prey volume was a better descriptor of dietary relationships than prey number when attempting to detect nonrandom structure. We showed that: pattern (1) depended on both the overall generalist nature of the anurans in general and on the mathematical properties of RA2; pattern (2) was consistent with theoretical attributes of tropicality; and pattern (3) was due to the intrinsic ecological properties of generalist organisms, which forage more or less opportunistically on prey of very different sizes; hence, when prey number is used as a diet descriptor, there is a risk of approximating different prey taxa that make different relative volume contributions to the overall diet as being of similar relevance .

História natural de Leptodactylus mystacinus e Leptodactylus fuscus (Anura: Leptodactylidae) no Cerrado do Brasil Central

Aspectos da ecologia de Leptodactylus mystacinus e Leptodactylus fuscus foram investigados em uma área de Cerrado do Brasil Central. O estudo incluiu o uso do microhábitat, padrões de atividade, dieta e morfometria. As observações foram conduzidas entre abril de 2006 a fevereiro de 2007. As espécies são sexualmente dimórficas - fêmeas maiores que os machos - e o tamanho do corpo em L. mystacinus é maior do que o de L. fuscus. Ambas as espécies preferiram a superfície do solo (microhábitat) de hábitats brejosos com vegetação herbácea próximos a corpos lênticos de água. Leptodactylus mystacinus foi mais observado em Outubro e Novembro (20:00-20:59 e 23:00-23:59 horas) e L. fuscus em Novembro e Outubro das 19:00 às 20:59 horas. A dieta destas populações foi baseada em Arthropoda, primariamente Coleoptera, a qual foi a mais importante ordem (IVI). Diferenças nas proporções volumétricas das categorias de presas utilizadas, e nos períodos em que são mais observadas, provavelmente sejam os fatores que mais contribuem para a coexistência das duas espécies na área. Diferenças intersexuais na dieta foram observadas para estas espécies. Estas diferenças estão provavelmente associadas à alocação diferencial de recursos para a produção de gametas ou diferenças ocasionais no uso do espaço pelos dois sexos.

Diet and microhabitat use by two Hylodinae species (Anura, Cycloramphidae) living in sympatry and syntopy in a Brazilian Atlantic Rainforest area

We analyzed the diet and microhabitat use for two Hylodinae anurans (Cycloramphidae), Hylodes phyllodes Heyer & Cocroft, 1986 and Crossodactylus gaudichaudii Duméril & Bibron, 1841, living in sympatry at an Atlantic Rainforest area of Ilha Grande, in southeastern Brazil. The two species live syntopically at some rocky streams. The two species differed strongly in microhabitat use. Hylodes phyllodes occurred mainly on rocks, whereas C. gaudichaudii was observed mostly on the water. Regarding diet, coleopterans, hymenopterans (ants), and larvae were the most important prey item consumed by both species. Data suggest that microhabitat use appears to be an important parameter differentiating these frogs with respect to general resource utilization.