Phylogenomic analysis of evolutionary relationships in Ranitomeya poison frogs (Family Dendrobatidae) using ultraconserved elements

A remarkable new blue Ranitomeya species (Anura: Dendrobatidae) with copper metallic legs from open forests of Juruá River Basin, Amazonia

Poison dart frogs (Dendrobatidae) are known for their aposematic coloration and toxic skin, making them a frequent subject of interest and research. However, descriptions of new species of Ranitomeya were interrupted for more than a decade. The implementation of a RAPELD (Rapid Assessment surveys of Long-Term Ecological Research) module in the Juruá River basin, a highly biodiverse and underexplored region, led to the record of a Ranitomeya species with blue dorsal stripes and coppery limbs. Herein we use morphological, morphometric, advertisement call, natural history, tadpole data and genetic data to describe the new species. Our phylogenetic analysis places the species within the Ranitomeya vanzolinii clade, and all delimitation methods confirmed its status as a new species. The species is characterized by its (i) small size (snout-vent length: males 15.2-17.0 mm, females 14.4-16.9 mm), (ii) dorsum with light sky-blue stripes on a reddish-brown ground, and metallic copper limbs with reddish-brown spots, (iii) ring-shaped granular region on the belly, (iv) toes with poorly developed lateral fringes, (v) later tadpole stages with tooth rows P1 = P2 > P3, P3 of 83-87% of P1, and conspicuous light sky-blue dorsal stripes, and (vi) cricket-like advertisement call consisting of 16-35 notes, call duration of 490-1,005 ms, note duration of 8.2-16.9 ms and dominant frequency of 5,168-6,029 Hz. The discovery of the new species emphasizes the significance of researching under-sampled regions like the Juruá River basin, and the usefulness of using a multidisciplinary approach to reveal new dendrobatid species.

An Amazonian hidden gem: a new metallic-colored species of Ranitomeya (Anura, Dendrobatidae) from Juruá River basin forests, Amazonas state, Brazil

The genus Ranitomeya has 16 known species, and the last of them was described 13 years ago. The forests of the Juruá River basin are known for their enormous vertebrate diversity, despite being one of the least sampled regions in the entire Amazonia. Our recent expeditions to the region resulted in the discovery of a Ranitomeya species with blue-green dorsal stripes and quite peculiar behavior. Here, it is described as a new species using morphological, morphometric, advertisement call, natural history, and genetic data. This new species is strongly nested within the R.vanzolinii clade, with interspecific p-distances ranging from 2.94 to 3.91%, and it was confirmed in all the delimitation methods used. It differs from its closest relatives mainly by (i) its size (male SVL 15.4-17.7 mm, n = 8; female SVL 17.3-18.5 mm, n = 5), (ii) its unique color pattern that is metallic pale yellowish green to metallic pale turquoise-green dorsal stripes pattern, limbs metallic chrome with dark carmine spotting), (iii) presence of a conspicuous sulfur yellow spot on the dorsal surface of the thighs, (iv) tadpoles with posterior tooth rows P1 > P2 > P3 in all stages, head translucent brownish and lack of emarginate lateral papillae, and (v) its advertisement call (composed of 21-45 notes, call duration of 647-1,424 ms, note rate of 28-36 notes/s and dominant frequency of 4,996-6,288 Hz).

The importance of reproductive isolation in driving diversification and speciation within Peruvian mimetic poison frogs (Dendrobatidae)

To explain how populations with distinct warning signals coexist in close parapatry, we experimentally assessed intrinsic mechanisms acting as reproductive barriers within three poison-frog species from the Peruvian Amazon belonging to a Müllerian mimetic ring (Ranitomeya variabilis, Ranitomeya imitator and Ranitomeya fantastica). We tested the role of prezygotic and postzygotic isolation barriers between phenotypically different ecotypes of each species, using no-choice mating experiments and offspring survival analysis. Our results show that prezygotic mating preference did not occur except for one specific ecotype of R. imitator, and that all three species were able to produce viable inter-population F1 hybrids. However, while R. variabilis and R. imitator hybrids were able to produce viable F2 generations, we found that for R. fantastica, every F1 hybrid males were sterile while females remained fertile. This unexpected result, echoing with Haldane's rule of speciation, validated phylogenetic studies which tentatively diagnose these populations of R. fantastica as two different species. Our work suggests that postzygotic genetic barriers likely participate in the extraordinary phenotypic diversity observed within Müllerian mimetic Ranitomeya populations, by maintaining species boundaries.

Multiple Routes to Color Convergence in a Radiation of Neotropical Poison Frogs

Convergent evolution is defined as the independent evolution of similar phenotypes in different lineages. Its existence underscores the importance of external selection pressures in evolutionary history, revealing how functionally similar adaptations can evolve in response to persistent ecological challenges through a diversity of evolutionary routes. However, many examples of convergence, particularly among closely related species, involve parallel changes in the same genes or developmental pathways, raising the possibility that homology at deeper mechanistic levels is an important facilitator of phenotypic convergence. Using the genus Ranitomeya, a young, color-diverse radiation of Neotropical poison frogs, we set out to 1) provide a phylogenetic framework for this group, 2) leverage this framework to determine if color phenotypes are convergent, and 3) to characterize the underlying coloration mechanisms to test whether color convergence occurred through the same or different physical mechanisms. We generated a phylogeny for Ranitomeya using ultraconserved elements and investigated the physical mechanisms underlying bright coloration, focusing on skin pigments. Using phylogenetic comparative methods, we identified several instances of color convergence, involving several gains and losses of carotenoid and pterin pigments. We also found a compelling example of nonparallel convergence, where, in one lineage, red coloration evolved through the red pterin pigment drosopterin, and in another lineage through red ketocarotenoids. Additionally, in another lineage, "reddish" coloration evolved predominantly through structural color mechanisms. Our study demonstrates that, even within a radiation of closely related species, convergent evolution can occur through both parallel and nonparallel mechanisms, challenging the assumption that similar phenotypes among close relatives evolve through the same mechanisms.

Captive breeding, embryonic and larval development of Ranitomeyavariabilis (Zimmermann & Zimmermann, 1988), (Anura, Dendrobatidae)

A solid basis to address the conservation challenges of amphibians requires an increased knowledge on their natural history and biology. Recent data on reproductive modes in amphibians suggest that they are much more complex and variable than previously thought but understudied. However, detailed information on the reproductive history is especially important to fill the current knowledge gaps. Following recent taxonomic changes in Ranitomeyavariabilis, information about captive-breeding management, image-based measurements of total length and surface area of the silhouette for individuals from embryonic to metamorphic development, and detailed larval staging for captive-bred specimens are provided from French Guiana. The development of R.variabilis from the stage eight (Gosner 1960) through metamorphosis took 79 to 91 days (n = 6) with a survival rate of 46%. The developmental stages largely matched those of the generalized staging system of Gosner (1960), with differences in the stages when labia and teeth differentiation and atrophy of the oral apparatus occurred. Compared with other studies the total length of R.variabilis tadpoles was greater at given stages than those of R.variabilis from a Peruvian population and those of the sister species, R.amazonica. Other studies concerning growth curves based on surface area data revealed that R.variabilis tadpoles at peak size were larger than those of R.amazonica, R.imitator, R.reticulata, R.sirensis, and R.vanzolinii, but smaller than R.benedicta. Our results represent the first embryonic and larval staging for R.variabilis, and detailed information is provided on their initial life phases. These data may facilitate the identification of R.variabilis tadpoles in the wild, as well helping to clarify the biogeographical distribution and taxonomic arrangement of the species. In addition, knowledge is added to the captive-breeding methodology for the species.