W. Ronald Heyer

Tadpoles, Predation and Pond Habitats in the Tropics

Tadpoles involved in predator-prey interactions were studied in tropical wet forest in Costa Rica under laboratory and field conditions. Larvae of the frog Leptodactylus pentadactylas and naiads of the odonate Pantala flavescens are important predators on larvae of several species of frogs. The predators discriminate the prey on the basis of size and species, but not type of habitat in which predation occurs. A graphical model is proposed to illustrate the relationships between species diversity and habitat complexity as they affect the composition of tadpole communities. The model is used to evaluate the relative importance of abiotic and biotic factors in determining the use of specific kinds of aquatic habitats by frogs with larval stages. Predation by permanent aquatic predators (primarily fish) is considered to be the most important biotic factor influencing the temporal and spatial composition of tadpole communities. The development and maintenance of predatory feeding modes, including cannibalism, in certain tadpoles is examined in light of the model. MOST TADPOLES are generalized herbivores (Jenssen 1967) that either scrape plant material from a substrate or filter planktonic food directly from the water. Only a few species are known to be carnivorous although some instances of cannibalism among tadpoles have been reported (Bragg 1964). We were surprised, therefore, to find a well-developed predator-prey system in which tadpoles of one species were carnivores on other tadpoles. This finding was unusual not only because documented instances of tadpoles feeding on other tadpoles are relatively rare, but also because the carnivorous tadpoles were found in relatively small puddles. The predator-prey interactions studied occur in small rain-filled tropical puddles characteristically utilized by opportunistic breeders. Experiments were run to study the relative ability of predators to capture prey and their preference for certain prey species, to ascertain the influence of microhabitat on predator-prey interactions, and to evaluate the influence of prey size on their ability to escape predation. Results of these experiments led to a consideration of tadpole habitats and to those factors controlling the diversity of tadpole communities. A model is used to illustrate the relationship between pond complexity and predation as they affect the species composition of a tadpole community. The predatory feeding mode of tadpoles is considered in light of this model.

THE ADAPTIVE ECOLOGY OF THE SPECIES GROUPS OF THE GENUS LEPTODACTYLUS (AMPHIBIA, LEPTODACTYLIDAE)

Frogs of the Neotropical genus Leptodactylus provide a clear example of one way in which a group of amphibians evolved from an almost aquatic to a terrestrial life history. The genus is comprised of approximately 30 species, but the taxonomy and relationships of many of these species are confused. My initial interest in the genus was to attempt to determine if clusters of related species (species groups) could be recognized, and if so, to determine the relationships among the species groups. The following discussion uses as a background the synthesis of the species groups and their interrelationships (Heyer, 1969).

Ecological Interactions of Frog Larvae at a Seasonal Tropical Location in Thailand

To determine the adaptive strategies frogs utilize to exploit tropical seasonal environments, a 10 month study of tadpole ecological interactions was undertaken at the Sakaerat Experiment Station, located approximately 250 km NE of Bangkok. The temporal distribution patterns of larval species occurrence for several ponds show the following: 1) all the species have seasonal reproductive cycles, which are correlated with the unavailability of aquatic habitats during the dry season; 2) the greatest number of species using ponds as larvae correlates with the first time that the aquatic habitats retain water long enough for the larvae to complete metamorphosis; 3) patterns of larval species occurrence in response to the same environmental stimuli are varied; and 4) the occurrence of larval species in any single pond seems due to chance. Food analyses and behavioral observations are compared with niche analyses of overlap based on larval species abundances. Food differences do not add any information to that obtained from occurrence patterns in characterizing larval niches. The frog fauna at Sakaerat divides the total environment spatially and temporally at several levels. The most distinctive partitioning of the environment occurs between the wet (14 species) and dry (3 species) season breeders. The rainy season breeders subdivide the available aquatic environment by: 1) utilizing different ponds within the total environment, 2) occupying a single pond at different times, and 3) dividing up the living space within a pond spatially, rather than by selecting different food categories. All species for which data were gathered have short larval life periods which correlate with the uncertain aquatic habitat due to sporadic rainfall. All of the ponds had a much greater larval biomass at an early time rather than at a later time. Perhaps by having a period of larval activity at the beginning of the wet season, newly metamorphosed frogs are assured of a favorable period of growth before having to survive the dry season. Alternatively, the period of heavy larval usage may occur at the beginning of the pond cycle to avoid heavy predation. The single physical factor of rainfall distribution regulates anuran reproductive patterns in tropical areas characterized by a pronounced dry season. The more northerly the environment, the greater the number of physical factors which control the anuran reproductive patterns. * * *

Variation and distribution in the tree-frog genus Phyllomedusa in Costa Rica, central America

Resume The frog genus Phyllomedusa is represented in Costa Rica by six species. Analysis of variation in coloration, webbing, and measurements delineates features that distinguish the various forms. The characteristics of the flank pattern in the nominal species P. callidryas and P. helenae, utilized by previous authors to separate them, are shown to be subject to individual and geographic variation. The two forms represent two of many populations within a single species, P. callidryas. Reasons for not using the term subspecies for geographic segments of callidryas are presented. The diagnostic features and the geographic and ecologic distribution of the Costa Rican species, P. annae, P. calcarifer, P. callidryas, P. lemur, P. saltator and P. spurrelli, based on the entire species ranges, are discussed.

Advertisement Call Variation in the Leptodactylus Mystaceus Species Complex (Amphibia: Leptodactylidae) with a Description of a New Sibling Species

Whereas morphological analysis of populations recognized as Leptodactylus mystaceus indicates there is one species with modest geographic variation, analysis of advertisement calls indicates there are at least two or perhaps three species involved. The differences found in advertisement calls are sufficient to act as species isolating barriers to recognize at least two species, which action is taken. A consequent result is the description of a new sibling species. The significance of sibling species in the genus Leptodacytylus is discussed briefly.

The American Herpetofauna and the Interchange

Amphibians and reptiles are treated together in this chapter because, overall, they have similar and complementary Zoogeographic patterns with respect to the faunal interchange of the Americas. We are each interested in amphibian and reptilian zoogeography, but because we are not systematic specialists in both groups, we have written this Chapter together. The basic amphibian data are discussed by Heyer and the reptile data by Vanzolini.

Variation and distribution in the tree‐frog genus Phyllomedusa in Costa Rica, central America: With 6 figures

Resume The frog genus Phyllomedusa is represented in Costa Rica by six species. Analysis of variation in coloration, webbing, and measurements delineates features that distinguish the various forms. The characteristics of the flank pattern in the nominal species P. callidryas and P. helenae, utilized by previous authors to separate them, are shown to be subject to individual and geographic variation. The two forms represent two of many populations within a single species, P. callidryas. Reasons for not using the term subspecies for geographic segments of callidryas are presented. The diagnostic features and the geographic and ecologic distribution of the Costa Rican species, P. annae, P. calcarifer, P. callidryas, P. lemur, P. saltator and P. spurrelli, based on the entire species ranges, are discussed.

Systematics of the Neotropical Genus Leptodactylus Fitzinger, 1826 (Anura: Leptodactylidae): Phylogeny, the Relevance of Non-molecular Evidence, and Species Accounts

Abstract. A phylogeny of the species-rich clade of the Neotropical frog genus Leptodactylus sensu stricto is presented on the basis of a total evidence analysis of molecular (mitochondrial and nuclear markers) and non-molecular (adult and larval morphological and behavioral characters) sampled from > 80% of the 75 currently recognized species. Our results support the monophyly of Leptodactylus sensu stricto, with Hydrolaetare placed as its sister group. The reciprocal monophyly of Hydrolaetare and Leptodactylus sensu stricto does not require that we consider Hydrolaetare as either a subgenus or synonym of Leptodactylus sensu lato. We recognize Leptodactylus sensu stricto, Hydrolaetare, Adenomera, and Lithodytes as valid monophyletic genera. Our results generally support the traditionally recognized Leptodactylus species groups, with exceptions involving only a few species that are easily accommodated without proposing new groups or significantly altering contents. The four groups form a pectinate tree, with the Leptodactylus fuscus group diverging first, followed by the L. pentadactylus group, which is sister to the L. latrans and L. melanonotus groups. To evaluate the impact of non-molecular evidence on our results, we compared our total evidence results with results obtained from analyses using only molecular data. Although non-molecular evidence comprised only 3.5% of the total evidence matrix, it had a strong impact on our total evidence results. Only one species group was monophyletic in the molecular-only analysis, and support differed in 86% of the 54 Leptodactylus clades that are shared by the results of the two analyses. Even though no non-molecular evidence was included for Hydrolaetare, exclusion of that data partition resulted in that genus being nested within Leptodactylus, demonstrating that the inclusion of a small amount of non-molecular evidence for a subset of species can alter not only the placement of those species, but also species that were not scored for those data. The evolution of several natural history and reproductive traits is considered in the light of our phylogenic framework. Invasion of rocky outcrops, larval oophagy, and use of underground reproductive chambers are restricted to species of the Leptodactylus fuscus and L. pentadactylus groups. In contrast, larval schooling, larval attendance, and more complex parental care are restricted to the L. latrans and L. melanonotus groups. Construction of foam nests is plesiomorphic in Leptodactylus but their placement varies extensively (e.g., underground chambers, surface of waterbodies, natural or excavated basins). Information on species synonymy, etymology, adult and larval morphology, advertisement call, and geographic distribution is summarized in species accounts for the 30 species of the Leptodactylus fuscus group, 17 species of the L. pentadactylus group, eight species of the L. latrans group, and 17 species of the L. melanonotus group, as well as the three species that are currently unassigned to any species group.

Does advertisement call variation coincide with genetic variation in the genetically diverse frog taxon currently known as Leptodactylus fuscus (Amphibia: Leptodactylidae)?

The frog Leptodactylus fuscus is found throughout much of South America in open and disturbed habitats. Previous study of genetic differentiation in L. fuscus demonstrated that there was lack of genetic exchange among population units consistent with multiple species, rather than a single species. We examine advertisement vocalizations of L. fuscus to determine whether call variation coincides with genetic differentiation. Calls were analyzed for 32 individual frogs from 25 localities throughout the distributional range of L. fuscus. Although there is variation in calls among geographic samples, call variation is not concordant with genetic variation or geographic distance and the call variation observed is less than that typically found among other closely related species of Leptodactylus. This study is an example of the rare pattern of strong genetic differentiation unaccompanied by salient differences in advertisement calls. The relative infrequency of this pattern as currently understood may only reflect the lack of detailed analyses of genetic and acoustic differentiation within population systems currently understood as single species with substantial geographic distributions.

A Functional Analysis of the Complex Call of the Frog Physalaemus pustulosus

Males of Physalaemus pustulosus are capable of producing two sounds simultaneously. All other known cases of complex frog calls are instances of the different sounds being produced serially. Comparison of call analyses and laryngeal morphology among Physalaemus gracilis, P. olfersi and P. pustulosus leads to the conclusion that the two sounds are produced by separate vibrating structures in the larynx. Lateral passageways bypassing the median free edges of the vocal cords in all three of these species are described, a feature not previously reported for any anuran larynx. A mechanism is suggested that integrates the available knowledge into a hypothesis of call production in P. pustulosus.