Cryptic diversity in Lithobateswarszewitschii (Amphibia, Anura, Ranidae)

Amphibian diversity across three adjacent ecosystems in Área de Conservación Guanacaste, Costa Rica

Amphibians are the most threatened species-rich vertebrate group, with species extinctions and population declines occurring globally, even in protected and seemingly pristine habitats. These 'enigmatic declines' are generated by climate change and infectious diseases. However, the consequences of these declines are undocumented as no baseline ecological data exists for most affected areas. Like other neotropical countries, Costa Rica, including Área de Conservación Guanacaste (ACG) in north-western Costa Rica, experienced rapid amphibian population declines and apparent extinctions during the past three decades. To delineate amphibian diversity patterns within ACG, a large-scale comparison of multiple sites and habitats was conducted. Distance and time constrained visual encounter surveys characterised species richness at five sites-Murciélago (dry forest), Santa Rosa (dry forest), Maritza (mid-elevation dry-rain forest intersect), San Gerardo (rainforest) and Cacao (cloud forest). Furthermore, species-richness patterns for Cacao were compared with historic data from 1987-8, before amphibians declined in the area. Rainforests had the highest species richness, with triple the species of their dry forest counterparts. A decline of 45% (20 to 11 species) in amphibian species richness was encountered when comparing historic and contemporary data for Cacao. Conservation efforts sometimes focus on increasing the resilience of protected areas, by increasing their range of ecosystems. In this sense ACG is unique containing many tropical ecosystems compressed in a small geographic space, all protected and recognised as a UNESCO world heritage site. It thus provides an extraordinary platform to understand changes, past and present, and the resilience of tropical ecosystems and assemblages, or lack thereof, to climate change.

Peptidomic analysis of the host-defense peptides in skin secretions of the Amazon River frog Lithobates palmipes (Ranidae)

Skin secretions of certain frog species represent a source of host-defense peptides (HDPs) with therapeutic potential and their primary structures provide insight into taxonomic and phylogenetic relationships. Peptidomic analysis was used to characterize the HDPs in norepinephrine-stimulated skin secretions from the Amazon River frog Lithobates palmipes (Ranidae) collected in Trinidad. A total of ten peptides were purified and identified on the basis of amino acid similarity as belonging to the ranatuerin-2 family (ranatuerin-2PMa, -2PMb, -2PMc, and-2PMd), the brevinin-1 family (brevinin-1PMa, -1PMb, -1PMc and des(8-14)brevinin-1PMa) and the temporin family (temporin-PMa in C-terminally amidated and non-amidated forms). Deletion of the sequence VAAKVLP from brevinin-1PMa (FLPLIAGVAAKVLPKIFCAISKKC) in des[(8-14)brevinin-1PMa resulted in a 10-fold decrease in potency against Staphylococcus aureus (MIC = 31 μM compared with 3 μM) and a > 50-fold decrease in hemolytic activity but potency against Echerichia coli was maintained (MIC = 62.5 μM compared with 50 μM). Temporin-PMa (FLPFLGKLLSGIF.NH₂) inhibited growth of S. aureus (MIC = 16 μM) but the non-amidated form of the peptide lacked antimicrobial activity. Cladistic analysis based upon the primary structures of ranaturerin-2 peptides supports the division of New World frogs of the family Ranidae into the genera Lithobates and Rana. A sister-group relationship between L. palmipes and Warszewitsch's frog Lithobates warszewitschii is indicated within a clade that includes the Tarahumara frog Lithobates tarahumarae. The study has provided further evidence that peptidomic analysis of HDPs in frog skin secretions is a valuable approach to elucidation of the evolutionary history of species within a particular genus.

Performance of intron 7 of the β-fibrinogen gene for phylogenetic analysis: An example using gladiator frogs, Boana Gray, 1825 (Anura, Hylidae, Cophomantinae)

Boana, the third largest genus of Hylinae, has cryptic morphological species. The potential applicability of b-fibrinogen intron 7 – FGBI7 is explored to propose a robust phylogeny of Boana. The phylogenetic potential of FGBI7 was evaluated using maximum parsimony, MrBayes, and maximum likelihood analysis. Comparison of polymorphic sites and topologies obtained with concatenated analysis of FGBI7 and other nuclear genes (CXCR4, CXCR4, RHO, SIAH1, TYR, and 28S) allowed evaluation of the phylogenetic signal of FGBI7. Mean evolutionary rates were calculated using the sequences of the mitochondrial genes ND1 and CYTB available for Boana in GenBank. Dating of Boana and some of its groups was performed using the RelTime method with secondary calibration. FGBI7 analysis revealed high values at informative sites for parsimony. The absolute values of the mean evolutionary rate were higher for mitochondrial genes than for FGBI7. Dating of congruent Boana groups for ND1, CYTB, and FGBI7 revealed closer values between mitochondrial genes and slightly different values from those of FGBI7. Divergence times of basal groups tended to be overestimated when mtDNA was used and were more accurate when nDNA was used. Although there is evidence of phylogenetic potential arising from concatenation of specific genes, FGBI7 provides well-resolved independent gene trees. These results lead to a paradigm for linking data in phylogenomics that focuses on the uniqueness of species histories and ignores the multiplicities of individual gene histories.

Unveiling the evolutionary relationships and the high cryptic diversity in Andean rainfrogs (Craugastoridae: Pristimantis myersi group)

Background

Pristimantis is the most diverse genus of terrestrial frogs. Historically, it has been divided into several phenetic groups in order to facilitate species identification. However, in light of phylogenetic analysis, many of these groups have been shown to be non-monophyletic, denoting a high degree of morphological convergence and limited number of diagnostic traits. In this study, we focus on the Pristimantis myersi group, an assemblage of small rainfrogs distributed throughout the Andes of Ecuador and Colombia, whose external morphology is highly conserved, and its species diversity and evolutionary relationships largely unknown.

Methods

We inferred a new phylogenetic hypothesis for the frog genus Pristimantis, including all available sequences of the mtDNA 16S rRNA, as well as new DNA sequences from 175 specimens. Our sampling included 19 of the 24 species currently recognized as part of the Pristimantis myersi group.

Results

Our new evolutionary hypothesis recovered the P. myersi group as non-monophyletic and composed of 16 species. Therefore, we exclude P. albujai, P. bicantus, P. sambalan, and P. nelsongalloi in order to preserve the monophyly of the group. We discovered at least eight candidate species, most of them hidden under the names of P. leoni, P. hectus, P. festae, P. gladiator, and P. ocreatus.

Discussion

Our results reveal the occurrence of a high level of cryptic diversity to the species level within the P. myersi group and highlight the need to redefine some of its species and reassess their conservation status. We suggest that the conservation status of six species within the group need to be re-evaluated because they exhibit smaller distributions than previously thought; these species are: P. festae, P. gladiator, P. hectus, P. leoni, P. ocreatus, and P. pyrrhomerus. Finally, given that the Pristimantis myersi group, as defined in this work, is monophyletic and morphologically diagnosable, and that Trachyphrynus is an available name for the clade containing P. myersi, we implement Trachyphrynus as a formal subgenus name for the Pristimantis myersi group.