Trophic ecology of tadpoles in floodplain wetlands: combining gut contents, selectivity, and stable isotopes to study feeding segregation of syntopic species (original) (raw)
Related papers
South American Journal …, 2009
We determined microhabitat and diet niche for tadpoles from two ponds in an agricultural landscape. Additionally, we verified the intraspecific variation in resource use, and if diet and microhabitat use were correlated. Tadpoles found in the two ponds differed in microhabitat use, because in the larger pond they explored deeper places far from the margin. There were three groups with high microhabitat niche overlap. In both ponds, plant cover was the best descriptor to explain interspecific variation in microhabitat use. Tadpoles of all species ingested mainly bacillariophyceae and Trachellomonas however the diet differed intraspecifically in the species from the two ponds. Ten items in the temporary pond and 15 items in the permanent one were ingested by all species; however, the relative abundance of each item differed. Diet similarity was not correlated to similarity in microhabitat use. In this study, diet was as important as microhabitat use to explain resource partitioning.
Plastic changes in tadpole trophic ecology revealed by stable isotope analysis
2012
Amphibian larvae constitute a large fraction of the biomass of wetlands and play important roles in their energy flux and nutrient cycling. Interactions with predators and competitors affect their abundance but also their foraging behaviour, potentially leading to non-consumptive cascading effects on the whole trophic web. We experimentally tested for plastic changes in larval trophic ecology of two anuran species in response to competitors and the non-lethal presence of native and non-native predators, using stable isotope analysis. We hypothesized that tadpoles would alter their diet in the presence of competitors and native predators, and to a lesser extent or not at all in the presence of non-native predators. First, we conducted a controlled diet experiment to estimate tadpole turnover rates and discrimination factors using Pelobates cultripes and Bufo calamita. Turnover rates yielded a half-life of 15-20 days (attaining a quasi-isotopic equilibrium after 2 months), whereas discrimination factors for natural controlled diets resulted in different isotopic values essential for calibration. Second, we did an experiment with P. cultripes and Rana perezi (=Pelophylax perezi) where we manipulated the presence/absence of predators and heterospecific tadpoles using microcosms in the laboratory. We detected a significant shift in trophic status of both amphibian species in the presence of non-native crayfish: the d 15 N values and macrophyte consumption of tadpoles increased, whereas their detritus consumption decreased. This suggests that tadpoles could have perceived crayfish as a predatory risk or that crayfish acted as competitors for algae and zooplankton. No dietary changes were observed in the presence of native dragonflies or when both tadpole species co-occurred. Stable isotopic analysis is an efficient way to assess variation in tadpoles' tropic status and hence understand their role in freshwater ecosystems. Here we provide baseline isotopic information for future trophic studies and show evidence for plastic changes in tadpoles' use of food resources under different ecological scenarios.
Revisiting “what do tadpoles really eat?” A 10‐year perspective
Freshwater Biology, 2019
1. Tadpoles are diverse and abundant consumers, and knowledge of their feeding ecology and trophic status is essential in understanding their functional roles within aquatic habitats. Here we revisit Altig, Whiles, and Taylor (2007)'s paper, which highlighted the knowledge gaps in tadpole feeding ecology and the application of modern techniques, such as stable isotope and fatty acid analyses to better quantify dominant food resources, food assimilation, and the trophic status of tadpoles. 2. We reviewed the ecological studies that have been published since 2007 that used stable isotopes and fatty acid analyses, also metagenomics and ecological stoichiometry analyses. We describe the ecological roles of tadpoles in freshwater ecosystems and identify knowledge gaps regarding tadpole feeding ecology across biogeographic regions. 3. Worldwide declines in amphibian abundance and diversity create an urgent need to document their feeding ecology and trophic status. As consumers, tadpoles play important functional roles in nutrient cycling, energy flow, and bioturbation. They also exhibit context-dependent trophic plasticity in response to abiotic and biotic gradients, which complicates understanding of their trophic roles. 4. Most studies of tadpole trophic ecology have been conducted primarily on species from the families Ranidae, Bufonidae, and Hylidae from Neotropic and Nearctic regions, while species in tropical regions such as Africa and Asia lack ecological information for tadpoles. There continues to be a need for studies of tadpole diets and/or trophic ecology in Africa and Southeast Asia regions where species endemism is threated by the growth of anthropogenic activities. 5. The majority of studies have focused on trophic ecology of tadpoles from the perspective of single species or at relatively small spatial and temporal scales. Studies that address questions from an ecosystem perspective were scarce, but are critical for conservation and management. Future research should aim to address the role of tadpoles as consumers across broader spatiotemporal scales.
Frontiers in Environmental Science , 2021
The study of tadpole assemblages allows inferring habitat availability and using their occupation as a means of proxy for the effective reproduction of the species, contributing to complementary information for the study of their adult forms. Environmental variables, represented by abiotic variables, vegetation structure, matrix management, and landscape elements, affect species having reproductive modes associated with oviposition and development in bodies of water. In the Orinoco region, most amphibians have complex life cycles and deposit their eggs in highly dynamic lentic bodies of water. Therefore, it is important to know how larval assemblages change over short periods of water accumulation and their relationship with environmental variables. Fieldwork was conducted during 9 weeks of larval sampling, from the beginning of the rainy season. We evaluate changes in anuran assemblages associated with water accumulation in five temporary water bodies of anthropogenic (road or pasture) and natural (savanna or gallery forest) origin. Twenty environmental variables were evaluated and measured in the center of each water body. Of these, nine landscape variables were measured only once during the study. The other eleven variables, representing management practices, physicochemical and structural characteristics of the water bodies, were measured weekly during the 3 months of sampling. We explored differences in the structure and diversity of larval-stage anuran assemblages using statistical tests suitable for small sample sizes (i.e., permutational multivariate analysis of variance PERMANOVA and the distance-based linear modeling DistLM). Of the 14 species found, two species had remarkedly high abundances from which Rhinella humboldti (19% of the total tadpole abundance) was a generalist inhabiting the natural and anthropogenic water bodies, while Leptodactylus insularum (18% of the total tadpole abundance) was a specialist at a natural pond in the savanna. The natural water bodies contained the highest number of species (between 10 and 12) and a total abundance of larvae (between 847 and 485 individuals). In contrast, the anthropogenic water body tracks generated by tractors were only occupied by two species with 50 individuals in total, while the water body generated by the trampling of cattle in pastures had three species with 474 individuals. These three species that inhabited the anthropogenic puddles were also found in the natural ponds and none of the eight species of hylids inhabited the puddles. In each field trip, all the tadpoles were collected from the sampled bodies of water. However, a week later, we found that each of the water bodies had been recolonized by four species (Leptodactylus fuscus, Leptodactylus fragilis, Elachistocleis ovalis, and R. humbolti). The variables with the highest explanatory power on the variation of anuran assemblage structure throughout all the water bodies were height of plants, number of cattle, distance to the nearest native forest edge, distance to an anthropic lentic body of water, distance to a natural lentic body of water, and pH. The bodies of water immersed in the natural cover were more diverse and had a greater degree of spatial and temporal species turnover. Our study calls for the importance of understanding the turnover of larval stage anurans over short periods, associated with water accumulation, in highly dynamic systems such as natural ponds and anthropogenic puddles. The importance of species traits and local processes is also highlighted, from environmental variables to human management activities, in the conservation of amphibian assemblages.
Herpetological Journal, 2017
Published by the British Herpetological Society Anurans inhabiting lentic and lotic water bodies show distinct responses to environmental and spatial variables due to dispersal by adults and microhabitat selection by tadpoles, which creates a hierarchical structure in these metacommunities. Aiming to understand the influence of tadpole microhabitat selection and adult dispersal on species richness distribution, we tested the influence of microhabitat environmental variables and habitat spatial variables on tadpole richness in lentic and lotic water bodies located in the Atlantic Rainforest. We sampled tadpoles in 99 lentic microhabitats and 288 lotic microhabitats for seven months. We performed a Hierarchical Partitioning Analysis to test the influence of environmental and spatial variables. The percentage of aquatic vegetation within microhabitats and the main spatial gradient (dbMEM1) affected species richness in lentic water bodies. Sand percentage, aquatic vegetation, and depth in the microhabitat and small-scale spatial gradient (dbMEM4) affected species richness in lotic water bodies. Spatial processes indicate an influence of adult dispersal limitation in search of reproductive habitats. The influence of microhabitat variables was mostly related to the amount of aquatic vegetation, indicating the influence of environmental processes on the larval phase of anuran life cycle. In conclusion, both environmental and spatial processes are driving the species richness in microhabitats inside lentic and lotic water bodies in the Atlantic Rainforest.
TROPICAL TADPOLE ASSEMBLAGES: WHICH FACTORS AFFECT THEIR STRUCTURE AND DISTRIBUTION
Tropical tadpoles may occur in a range of aquatic habitats, from tree holes (e.g., fitolimns), to permanent ponds and streams. Thus, tadpoles are exposed to a different sort of biotic and abiotic factors, according to the habitat they develop, and these factors may also vary over time. What are these factors? What are their relevance for the distribution of tadpole species and local assemblages? How do they affect the structure of tadpole assemblages? In this review, we explore these questions and recognize some trends regarding the factors influencing tropical tadpole assemblages. We can recognize at least nine major trends regarding the distribution and structure of tropical tadpole assemblages: (1) stream size and microhabitat diversity are important abiotic features influencing species richness and composition; (2) in ponds, the permanence gradient (e.g., hydroperiod), and the heterogeneity of habitat are the main factors modeling tropical tadpole assemblages; (3) species composition seems to be a more relevant assemblage parameter than species richness and should be first considered when planning conservation of both pond and stream-dwelling anurans; (4) predation seems to be the most important biotic interaction structuring tropical tadpole assemblages, with vertebrate predators (e.g., fishes) being more voracious in permanent habitats, while invertebrates (e.g., odonate naiads) are the most important in temporary ones; (5) tadpoles may play a regulatory effect preying upon anuran eggs and recently hatched tadpoles (6) microhabitat use varies in function of breeding habitat choice by adults, presence of predators, phylogeny, stage of development and heterogeneity of the habitat; (7) historical factors restrict the breeding habitats that species may use, and impose behavioral and physiologic constrains; (8) temporal variation in biotic (e.g., risk factors) and abiotic factors (e.g., rainfall distribution), and the reproductive patterns of the species may interfere in the structure of tropical tadpole assemblages, and (9) food resource partitioning in tadpole assemblages may both be or not linked to microhabitat occupation, feeding behavior, and morphology. Future efforts regarding the study of tadpoles should contemplate assemblages associated with streams, and experimental studies. RESUMO ASSEMBLEIAS DE GIRINOS TROPICAIS: QUAIS FATORES AFETAM SUA ESTRUTURA E DISTRIBUIÇÃO? Os girinos tropicais ocorrem em uma variedade de habitats aquáticos. Os girinos são expostos a diferentes conjuntos de fatores (bióticos, abióticos), de acordo com o habitat em que vivem, os quais também podem variar temporalmente. Quais são esses fatores? Qual a sua relevância sobre a distribuição das assembleias de girinos? Como eles afetam a sua organização? Nesta revisão, exploramos essas questões e reconhecemos algumas tendências associadas aos fatores que influenciam as assembleias de girinos tropicais. Podemos reconhecer pelo menos nove tendências relacionadas à distribuição e a estrutura de assembleias de girinos: (1) o tamanho dos riachos e a diversidade de microhabitats são importantes características abióticas influenciando a riqueza e a composição de espécies; (2) em poças, o gradiente de permanência (e.g., hidroperíodo) e a heterogeneidade do habitat são os principais fatores moldando as assembleias de girinos; (3) a composição de espécies parece ser um parâmetro das assembleias mais relevante do que a riqueza de espécies e deve ser primeiramente considerado durante o planejamento de ações conservacionistas de anuros associados a poças e riachos; (4) a predação parece ser a interação biótica mais importante na estruturação das assembleias de
Diets of tadpoles from a temporary pond in southeastern Brazil (Amphibia, Anura)
Revista Brasileira de Zoologia, 2004
The diet of tadpoles of 13 anuran species was determined to verify whether food resource partitioning occurs and whether the degree of diet similarity is related to taxonomic affinity. Tadpoles of all species studied were mainly herbivorous, except for these of Leptodactylus fuscus (Schneider, 1799) which were mycophagous. Although some species had exclusive items in their diet, most tadpole species ingested the same items, but differed in the amount of each item consumed. Two guilds were found: tadpoles that feed on diatoms on the pond bottom, and tadpoles that feed on Oedogonium Link, 1820 algae in midwater. Diet similarity was related to the taxonomic relationship, microhabitat and feeding behavior of tadpoles indicating that the community organization is complex and resulting from the interaction of several parameters.
Diet of Tadpoles from a Pond in Iguazu National Park, Argentina
Gayana (Concepción), 2007
Gut contents of anuran larva (Elachistocleis bicolor, Chaunus schneideri, Odontophrynus americanus, Scinax fuscovarius, and S. granulatus) that coexist in a semi-permanent waterbody from Iguazú National Park (Misiones, Argentina) was analyzed. Our objective was analyse the gut contents of different tadpole species that coexist in the same water body during seasons of minimum and maximum precipitation, to increase the knowledge of the natural history of these tadpoles. Elachistocleis bicolor (obligate-suspension-feeder) it presents only planktonic algae in its gut (92%). In gut of S. fuscovarius and S. granulatus (nektonic) planktonic algae were abundant, especially in the rainy season (14 and 41%). The guts of C. schneideri and O. americanus (benthic) showed sediments (55% and 17.5%) and vegetable fibers (33 and 61%). The largest particle size (< 100 µm) was found in the guts of C. schneideri and the smallest (< 25 µm) in O. americanus and E. bicolor.