ESTRATÉGIAS E MODOS REPRODUTIVOS DE ANUROS (AMPHIBIA) EM UMA POÇA PERMANENTE NA SERRA DE PARANAPIACABA, SUDESTE DO BRASIL

José P. Pombal Jr. and Célio F. B. Haddad

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Abstract: southeastern Brazil. This study describes the temporal patterns, behavioral strategies, reproductive modes, and fecundity of an anuran assemblage in a permanent pond in Serra de Paranapiacaba, municipality of Ribeirão Branco, south of São Paulo State (approximately 24º13'S; 48º46'W; ca. 800m above sea level). Field work was carried out between January and December 1993, totaling 40 nights of observation. Seven preliminary visits were made before this period and seven additional ones after December 1993. Naturalistic observations usually began before sunset and were concluded around 24:0001:00h. On three occasions the observations lasted the entire night. The commonest reproductive strategy among males of different species was that performed by calling male, but the satellite behavior was observed in some species. The calling temporal pattern was prolonged for the species of the assemblage; however, some species called only occasionally. Six different reproductive modes were observed in the pond or on its margins. The SVL of females of different species was positively correlated with egg clutch volume, irrespective of the reproductive mode. The SVL of females was also positively correlated with the number of eggs per clutch, although the correlation is stronger for species with a generalized reproductive mode. However, for species with specialized reproductive mode the number of eggs per clutch was not correlated with the SVL of females. A significant and positive correlation between female SVL and egg diameter was also detected for species with generalized reproductive mode. On the other hand, for species with specialized reproductive mode, female's SVL and egg diameter were negatively correlated. Terrestrial reproductive modes are possibly restricted to small-sized species. Large eggs may face problems of gas exchange due to their longer development period and lower surface/volume ratio.

Notas Sobre Predação em uma Taxocenose de Anfíbios Anuros no Sudeste do Brasil

José P. Pombal Jr.

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Abstract: Anuran amphibians are preyer by all vertebrate groups and several invertebrates. However, predation studies on amphibians are still occasional and anecdotic. Herein, informations on predation of an anuran assemblage of southeastern Brazil are provided. Invertebrates (spiders and water bugs), the frog Leptodactylus cf. ocellatus, and five snake species (four Colubridae and one Viperidae) preyer on small individuals or small anuran species.

Utilização de Habitats Reprodutivos e Micro-Habitats de Vocalização em uma Taxocenose de Anuros (Amphibia) da Mata Atlântica do Sudeste do Brasil

Jaime Bertoluci and Miguel Trefaut Rodrigues

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 Abstract: Breeding and calling site utilization were studied for an anuran community of the Parque Estadual Intervales, an Atlantic Rainforest reserve located in Southeastern Brazil (24°12'-24°25'S, 48°03'-48°30'W). Field work was carried out between April 1990 and March 1991. Forty-seven species from four families were recorded in the study site: Bufonidae (4), Hylidae (24), Leptodactylidae (18), and Microhylidae (1). We were able to obtain data on breeding habitat and microhabitat distribution for 26 species by monitoring six breeding sites year-round on a monthly basis. The number of species in the sites varied from 7 to 22. Species were classified as habitat generalists and specialists based on breeding site utilization. Most species showed preferences for certain calling sites. For some species calling site specificity seemed to depend on the density of the male aggregations rather than on the species composition of the assemblages.

Abiotic Correlates of Anuran Calling Phenology: The Importance of Rain, Temperature, and Season

Daniel Saenz, Lee A. Fitzgerald, Kristen A. Baum and Richard N. Conner

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Abstract: We surveyed anuran calls nightly at eight ponds in eastern Texas from 1 January 2001 through 31 December 2002. Air temperatures and daily rainfall also were recorded for each of the sites. Eastern Texas contains a diverse temperate anuran fauna and a climate that provides a range of conditions for anuran reproduction. During our study, we measured air temperatures that fluctuated seasonally with extremes from 0 to 29 C at 2100 h. We found rainfall to be generally abundant with occasional flooding events, however, prolonged periods of no precipitation were also observed. Given the level of anuran diversity and the amount of seasonal variation in temperature and rainfall in our temperate climate we expected to find a variety of breeding strategies. Results from our analyses did indeed suggest five basic breeding strategies based on anuran calling: (1) breeding within a predictable season (summer) independent of local weather patterns; (2) breeding opportunistically within a predictable season (summer) dependent on local rainfall; (3) breeding opportunistically within a predictable season (winter) dependent on local temperature; (4) breeding opportunistically dependent on local flood level rainfall events; (5) breeding opportunistically year round dependent on local temperature in the winter and local rainfall in the summer.

Comparison of Methods for Monitoring Reptiles and Amphibians in Upland Forests of the Ouachita Mountains

Doyle L. Crosswhite, Stanley F. Fox and Ronald E. Thill

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Abstract: We compared drift fence arrays (employing pitfalls and double-ended funnel traps), double-ended funnel traps without drift fences, and time-constrained searching as methods for capturing reptiles and amphibians in upland forests of the Ouachita Mountains, Arkansas. Taxonomic groups (anurans, salamanders, and squamates) were appraised for heterogeneity of susceptibility to capture among different methods. Also, capture success for types of funnel traps were compared across different size classes of squamates. We sampled a total of 91 days during six trapping periods over the spring and summer months of 1993 and 1994. Eight-hundred eighty-six individuals representing 38 species of reptiles and amphibians were captured. Standardizing captures by common unit effort (captures/trap-day or captures/person-day) shows that time-constrained searching was overall the most efficient, followed by drift fence arrays, then stand-alone funnel traps. However, more herps can be captured by trapping (especially when associated with drift fences) than searching, because of personnel limitations. Pitfall traps more effectively captured most anurans, salamanders, lizards, and small snakes, while double-ended funnel traps effectively captured most large squamates. Funnel traps made of aluminum window screen were significantly better for catching small squamates than funnel traps made of hardware cloth because small individuals could pass through the larger mesh of the latter.

Metapopulation Dynamics and Amphibian Conservation

David M. Marsh and Peter C. Trenham

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Abstract: In many respects, amphibian spatial dynamics resemble classical metapopulation models, in which subpopulations in breeding ponds blink in and out of existence and extinction and colonization rates are functions of pond spatial arrangement. This "ponds-as-patches" view of amphibian spatial dynamics is useful in several respects. First, it highlights the importance of regional and landscape processes in determining local patterns of abundance. Second, it offers a straightforward, pond-based approach to monitoring and managing amphibian populations. For many species, however, the ponds-as-patches view may be an over-simplification and metapopulation structure may be more apparent than real. Changes in distribution may be caused by processes other than extinction and recolonization, and most extinctions probably result from deterministic factors, not stochastic processes. In addition, the effects of pond isolation appear to be important primarily in disturbed environments, and in many cases these isolation effects may be better explained by the distribution of terrestrial habitats than by the distribution of breeding ponds. These complications have important implications for both researchers and managers. For researchers, future efforts need to determine the mechanisms underlying patterns of abundance and distributional change and patterns in amphibian populations. For managers, effective conservation strategies must successfully balance metapopulation considerations with careful attention to local habitat quality. Furthermore, translocations and active management may be indispensable tools for conserving amphibians in landscapes containing multiple breeding ponds.

Sexual Selection and Signal Evolution: The Ghost of Biases Past

Michael J. Ryan and A. Stanley Rand

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Abstract: The evolution of female mating preferences is an important key to understanding the evolution of signal diversity. Several hypotheses for preference evolution invoke different processes but all can produce the same end results: thus comparisons of extant traits and preferences within and among populations have made little progress in discriminating among competing hypotheses. Some of these hypotheses, however, do make different predictions as to the historical sequence of trait-preference evolution, and thus can be discriminated with appropriate phylogenetic analyses. We explore this approach in an analysis of the evolution of calls and call preferences in a monophyletic group of frogs, the Physalaemus pustulosus species group. In this clade there are pre-existing preferences for four call traits. These data reject hypotheses that invoke coevolution (good genes, runaway sexual selection) and females evolving preferences to choose males providing better resources, and instead support the hypothesis of sensory exploitation that suggests that males evolve traits that match pre-existing biases in the female's sensory system. We suggest that some of the difficulty in understanding preference evolution might derive from defining a preference only by those extant stimuli that elicit the preference. Our results suggest that preferences might be more general, and that signal diversity might arise from alternative means for eliciting the same preference. Furthermore, we discuss some difficulties with utilizing both population-based comparisons and phylogenetic approaches and suggest that the greatest progress will be made by addressing the problem of preference evolution at several levels of analysis.