Pond characteristics influence the intraspecific variation in the morphometry of the tadpoles of two species of Dendropsophus (Anura: Hylidae) from the Cerrado savanna of northeastern Brazil.

Spatial variation in the environment may be an important source of morphological variation in many organisms. Tadpoles are valuable model organisms for studies of morphological variation, and in particular, the evaluation of the relationship between environmental and morphological variables. In heterogeneous environments, such as the temporary ponds found in the Cerrado savanna of central Brazil, understanding how environmental variables influence the morphological variation found in tadpole populations can provide important insights into this phenomenon. The present study thus aimed to (i) describe the morphometric variation in tadpoles found in different populations of Dendropsophus nanus and Dendropsophus minutus in the Cerrado of southern Maranhão state (Brazil), and (ii) relate this variation in tadpole morphology to the characteristics of the local ponds. Tadpoles were collected from 11 pounds in southern Maranhão, and the morphological space among the different populations was compared using NPMANOVA, separately for each species. The degree of association between the environmental and morphological matrices was then tested using a Stepwise Multiple Linear Regression. The morphological (tadpole morphometry) and environmental (pond characteristics) data matrices were obtained by ordination techniques. Considerable morphometric differences were found among populations in both species. In D. nanus, the morphometric variation was correlated with that of the substrate, whereas in D. minutus, morphometry was associated with the vegetation found in the pond. Overall, then, the study demonstrated that distinct environmental variables influenced significantly the morphometry of the tadpoles of each frog species.

Phylogeny of frogs from the genus Physalaemus (Anura, Leptodactylidae) inferred from mitochondrial and nuclear gene sequences.

Although some species groups have been recognized in the leiuperine genus Physalaemus, no phylogenetic analysis has previously been performed. Here, we provide a phylogenetic study based on mitochondrial and nuclear DNA sequences from 41 of the 46 species of Physalaemus. We employed the parsimony criterion using the software TNT and POY and the Bayesian criterion using the software MrBayes. Two major clades were recovered inside the monophyletic Physalaemus: (i) the highly supported Physalaemus signifer Clade, which included P. nattereri and the species previously placed in the P. deimaticus and P. signifer Groups; and (ii) the Physalaemus cuvieri Clade, which included the remaining species of Physalaemus. Five species groups were recognized in the P. cuvieri Clade: the P. biligonigerus Group, the P. cuvieri Group, the P. henselii Group, the P. gracilis Group and the P. olfersii Group. The P. gracilis Species Group was the same as that previously proposed by Nascimento et al. (2005). The P. henselii Group includes P. fernandezae and P. henselii, and was the sister group of a clade that comprised the remaining species of the P. cuvieri Clade. The P. olfersii Group included P. olfersii, P. soaresi, P. maximus, P. feioi and P. lateristriga. The P. biligonigerus Species Group was composed of P. biligonigerus, P. marmoratus, P. santafecinus and P. riograndensis. The P. cuvieri Group inferred here differed from that recognized by Nascimento et al. (2005) only by the inclusion of P. albifrons and the exclusion of P. cicada. The paraphyly of P. cuvieri with respect to P. ephippifer was inferred in all the analyses. Distinct genetic lineages were recognized among individuals currently identified as P. cuvieri and they were congruent with cytogenetic differences reported previously, supporting the hypothesis of occurrence of formally unnamed species.

Multiple contact zones and karyotypic evolution in a neotropical frog species complex.

Previous studies of DNA sequence and karyotypic data have revealed high genetic diversity in the Physalaemus cuvieri - Physalaemus ephippifer species complex-a group of small leptodactylid frogs in South America. To date, seven major genetic lineages have been recognized in this group, with species delimitation tests supporting four to seven of them as valid species. Among these, only P. ephippifer shows heteromorphic sex chromosomes, but the implications of cytogenetic divergence for the evolution of this group are unknown. We analyzed karyotypic, mitochondrial DNA, and 3RAD genomic data to characterize a putative contact zone between P. ephippifer and P. cuvieri Lineage 1, finding evidence for admixture and karyotypic evolution. We also describe preliminary evidence for admixture between two other members of this species complex-Lineage 1 and Lineage 3 of P. cuvieri. Our study sheds new light on evolutionary relationships in the P. cuvieri - P. ephippifer species complex, suggesting an important role of karyotypic divergence in its evolutionary history and underscoring the importance of hybridization as a mechanism of sex chromosome evolution in amphibians.

Polytypic and polymorphic cytogenetic variations in the widespread anuran Physalaemus cuvieri (Anura, Leiuperidae) with emphasis on nucleolar organizing regions.

We investigated the NOR distribution in ten populations of Physalaemus cuvieri from different regions of Brazil and Argentina. A high variability in NOR pattern was observed and provided a useful tool in grouping several populations. The specimens from the state of Tocantins, northern Brazil, could easily be distinguished from all the other analyzed populations, since its karyotype presented NORs in the chromosome pairs 1,3,4 and 10 (and sometimes also in chromosome 5), and several pericentromeric C-bands. A NOR-site in chromosome 9 characterized three populations from the northeastern region of Brazil. Interestingly, the P. cuvieri populations located in opposite extremes of the geographic distribution had, as a fixed condition, the presence of NORs in 8q int and llp. Besides interpopulational divergences, intrapopulational variability was observed in the number of NORs, except for populations from the states of Bahia and Minas Gerais, which are boundary states respectively in the northeastern and southeastern regions of Brazil. In relation to NOR size, interindividual variations occurred in all Brazilian and Argentinean populations. Additionally, intraindividual variability in NOR size was detected in specimens from Minas Gerais. The data presented herein revealed substantial geographic polytypic variation in P. cuvieri and indicated that a taxonomic reexamination of this species is necessary.

Extensive Cryptic Diversity Within the Physalaemus cuvieri-Physalaemus ephippifer Species Complex (Amphibia, Anura) Revealed by Cytogenetic, Mitochondrial, and Genomic Markers.

Previous cytogenetic and phylogenetic analyses showed a high variability in the frog taxa Physalaemus cuvieri and Physalaemus ephippifer and suggested the presence of undescribed diversity in this species complex. Here, by 1) adding specimens from the Brazilian Amazon region, 2) employing sequence-based species delimitation approaches, and 3) including RADseq-style markers, we demonstrate that the diversity in the P. cuvieri-P. ephippifer species complex is even greater than previously suspected. Specimens from Viruá and Western Pará, located at the Guiana Amazonian area of endemism, were recovered as distinct from all previously identified lineages by the phylogenetic analyses based on mitochondrial DNA and RAD markers, a PCA from RAD data, and cytogenetic analysis. The sequence-based species delimitation analyses supported the recognition of one or two undescribed species among these Amazonian specimens and also supported the recognition of at least three other species in the P. cuvieri-P. ephippifer species complex. These new results reinforce the need for a comprehensive taxonomic revision.

Differential effects of temperature on the feeding kinematics of the tadpoles of two sympatric anuran species.

Temperature impacts ectotherm performance by influencing many biochemical and physiological processes. When well adapted to their environment, ectotherms should perform most efficiently at the temperatures they most commonly encounter. In the present study, we tested how differences in temperature affects the feeding kinematics of tadpoles of two anuran species: the benthic tadpole of Rhinella schneideri and the nektonic tadpole of Trachycephalus typhonius. Benthic and nektonic tadpoles have segregated distributions within ponds and thus tend to face different environmental conditions, such as temperature. Muscle contractile dynamics, and thus whole organism performance, is primarily temperature dependent for ectotherms. We hypothesized that changes in mean temperatures would have differential effects on the feeding kinematics of these two species. We conducted a laboratory experiment in which we used high-speed videography to record tadpoles foraging at cold and warm temperatures. In general, tadpoles filmed at warm temperatures opened their jaws faster, attained maximum gape earlier, and exhibited shorter gape cycles than tadpoles in cold temperatures, irrespective of species. We also found species x temperature interactions regarding the closing phase velocity, and the percentage of time it takes tadpoles to achieve maximum gape and to start closing their jaws. These interactions could indicate that these two co-occurring species differ in their sensitivity to differences in water temperature and have temperature-dependent feeding strategies that maximize feeding performance in their preferred environment.

Benefits for plants in ant-plant protective mutualisms: a meta-analysis.

Costs and benefits for partners in mutualistic interactions can vary greatly, but surprisingly little is known about the factors that drive this variation across systems. We conducted a meta-analysis of ant-plant protective mutualisms to quantify the effects of ant defenders on plant reproductive output, to evaluate if reproductive effects were predicted from reductions in herbivory and to identify characteristics of the plants, ants and environment that explained variation in ant protection. We also compared our approach with two other recent meta-analyses on ant-plant mutualisms, emphasizing differences in our methodology (using a weighted linear mixed effects model) and our focus on plant reproduction rather than herbivore damage. Based on 59 ant and plant species pairs, ant presence increased plant reproductive output by 49% and reduced herbivory by 62%. The effects on herbivory and reproduction within systems were positively correlated, but the slope of this relationship (0.75) indicated that tolerance to foliar herbivory may be a common plant response to absence of ant guards. Furthermore, the relationship between foliar damage and reproduction varied substantially among systems, suggesting that herbivore damage is not a reliable surrogate for fitness consequences of ant protection. Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems. Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals. These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.

Polytypic and polymorphic cytogenetic variations in the widespread anuran Physalaemus cuvieri (Anura, Leiuperidae) with emphasis on nucleolar organizing regions

We investigated the NOR distribution in ten populations of Physalaemus cuvieri from different regions of Brazil and Argentina. A high variability in NOR pattern was observed and provided a useful tool in grouping several populations. The specimens from the state of Tocantins, northern Brazil, could easily be distinguished from all the other analyzed populations, since its karyotype presented NORs in the chromosome pairs 1,3,4 and 10 (and sometimes also in chromosome 5), and several pericentromeric C-bands. A NOR-site in chromosome 9 characterized three populations from the northeastern region of Brazil. Interestingly, the P. cuvieri populations located in opposite extremes of the geographic distribution had, as a fixed condition, the presence of NORs in 8q int and llp. Besides interpopulational divergences, intrapopulational variability was observed in the number of NORs, except for populations from the states of Bahia and Minas Gerais, which are boundary states respectively in the northeastern and southeastern regions of Brazil. In relation to NOR size, interindividual variations occurred in all Brazilian and Argentinean populations. Additionally, intraindividual variability in NOR size was detected in specimens from Minas Gerais. The data presented herein revealed substantial geographic polytypic variation in P. cuvieri and indicated that a taxonomic reexamination of this species is necessary.