Ignacio De la Riva

Erosion of lizard diversity by climate change and altered thermal niches

Demise of the Lizards Despite pessimistic forecasts from recent studies examining the effects of global climate change on species, and observed extinctions in local geographic areas, there is little evidence so far of global-scale extinctions. Sinervo et al. (p. 894; see the Perspective by Huey et al.) find that extinctions resulting from climate change are currently reducing global lizard diversity. Climate records during the past century were synthesized with detailed surveys of Mexican species at 200 sites over the past 30 years. Temperature change has been so rapid in this region that rates of adaptation have not kept pace with climate change. The models were then extended to all families of lizards at >1000 sites across the globe, and suggest that climate change-induced extinctions are currently affecting worldwide lizard assemblages. A historical record of lizard populations in Mexico is used to parameterize models that predict global effects of climate change. It is predicted that climate change will cause species extinctions and distributional shifts in coming decades, but data to validate these predictions are relatively scarce. Here, we compare recent and historical surveys for 48 Mexican lizard species at 200 sites. Since 1975, 12% of local populations have gone extinct. We verified physiological models of extinction risk with observed local extinctions and extended projections worldwide. Since 1975, we estimate that 4% of local populations have gone extinct worldwide, but by 2080 local extinctions are projected to reach 39% worldwide, and species extinctions may reach 20%. Global extinction projections were validated with local extinctions observed from 1975 to 2009 for regional biotas on four other continents, suggesting that lizards have already crossed a threshold for extinctions caused by climate change.

The integrative future of taxonomy

BackgroundTaxonomy is the biological discipline that identifies, describes, classifies and names extant and extinct species and other taxa. Nowadays, species taxonomy is confronted with the challenge to fully incorporate new theory, methods and data from disciplines that study the origin, limits and evolution of species.ResultsIntegrative taxonomy has been proposed as a framework to bring together these conceptual and methodological developments. Here we review perspectives for an integrative taxonomy that directly bear on what species are, how they can be discovered, and how much diversity is on Earth.ConclusionsWe conclude that taxonomy needs to be pluralistic to improve species discovery and description, and to develop novel protocols to produce the much-needed inventory of life in a reasonable time. To cope with the large number of candidate species revealed by molecular studies of eukaryotes, we propose a classification scheme for those units that will facilitate the subsequent assembly of data sets for the formal description of new species under the Linnaean system, and will ultimately integrate the activities of taxonomists and molecular biologists.

High levels of diversity uncovered in a widespread nominal taxon: continental phylogeography of the Neotropical tree frog Dendropsophus minutus

Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally distributed in South America, that may represent a complex of multiple species, each with a more limited distribution. To understand the spatial pattern of molecular diversity throughout the range of this species complex, we obtained DNA sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and the 16S rhibosomal gene (16S) for 407 samples of D. minutus and closely related species distributed across eleven countries, effectively comprising the entire range of the group. We performed phylogenetic and spatially explicit phylogeographic analyses to assess the genetic structure of lineages and infer ancestral areas. We found 43 statistically supported, deep mitochondrial lineages, several of which may represent currently unrecognized distinct species. One major clade, containing 25 divergent lineages, includes samples from the type locality of D. minutus. We defined that clade as the D. minutus complex. The remaining lineages together with the D. minutus complex constitute the D. minutus species group. Historical analyses support an Amazonian origin for the D. minutus species group with a subsequent dispersal to eastern Brazil where the D. minutus complex originated. According to our dataset, a total of eight mtDNA lineages have ranges >100,000 km2. One of them occupies an area of almost one million km2 encompassing multiple biomes. Our results, at a spatial scale and resolution unprecedented for a Neotropical vertebrate, confirm that widespread amphibian species occur in lowland South America, yet at the same time a large proportion of cryptic diversity still remains to be discovered.

Deciphering the products of evolution at the species level: the need for an integrative taxonomy

Progress in molecular techniques together with the incorporation of phylogenetic analyses of DNA into taxonomy have caused an increase in the number of species’ discoveries in groups with morphological characters that are difficult to study or in those containing polytypic species. But some emerged criticisms plead for a taxonomic conservatism grounded either on the requirement of providing evidences of morphological distinctiveness or reproductive barriers to erect new species names. In a case study of taxonomic research on Neotropical frogs, we combine several lines of evidence (morphological characters, prezygotic reproductive isolation and phylogenetic analyses of mitochondrial DNA) to test the status of 15 nominal species and to assess the degree of agreement of the different lines of evidence. Our study reveals that morphology alone is not sufficient to uncover all species, as there is no other single line of evidence independently. Full congruence between lines of evidence is restricted to only four out of the 15 species. Five species show congruence of two lines of evidence, whereas the remaining six are supported by only one. The use of divergence in morphological characters seems to be the most conservative approach to delineate species boundaries because it does not allow the identification of some sibling reciprocally monophyletic species differing in their advertisement calls. The separate analysis of differences in advertisement calls (evidence of reproductive isolation) or of phylogenetic data alone also shows limitations, because they do not support some morphological species. Our study shows that only an integrative approach combining all sources of evidence provides the necessary feedback to evaluate the taxonomic status of existing species and to detect putative new ones. Furthermore, the application of integrative taxonomy enables the identification of hypotheses about the existence of species that will probably be rejected or changed, and those that can be expected to persist.

Systematics of spiny-backed treefrogs (Hylidae: Osteocephalus): An Amazonian puzzle

Spiny‐backed tree frogs of the genus Osteocephalus are conspicuous components of the tropical wet forests of the Amazon and the Guiana Shield. Here, we revise the phylogenetic relationships of Osteocephalus and its sister group Tepuihyla, using up to 6134 bp of DNA sequences of nine mitochondrial and one nuclear gene for 338 specimens from eight countries and 218 localities, representing 89% of the 28 currently recognized nominal species. Our phylogenetic analyses reveal (i) the paraphyly of Osteocephalus with respect to Tepuihyla, (ii) the placement of ‘Hyla’ warreni as sister to Tepuihyla, (iii) the non‐monophyly of several currently recognized species within Osteocephalus and (iv) the presence of low (<1%) and overlapping genetic distances among phenotypically well‐characterized nominal species (e.g. O. taurinus and O. oophagus) for the 16S gene fragment used in amphibian DNA barcoding. We propose a new taxonomy, securing the monophyly of Osteocephalus and Tepuihyla by rearranging and redefining the content of both genera and also erect a new genus for the sister group of Osteocephalus. The colouration of newly metamorphosed individuals is proposed as a morphological synapomorphy for Osteocephalus. We recognize and define five monophyletic species groups within Osteocephalus, synonymize three species of Osteocephalus (O. germani, O. phasmatus and O. vilmae) and three species of Tepuihyla (T. celsae, T. galani and T. talbergae) and reallocate three species (Hyla helenae to Osteocephalus, O. exophthalmus to Tepuihyla and O. pearsoni to Dryaderces gen. n.). Furthermore, we flag nine putative new species (an increase to 138% of the current diversity). We conclude that species numbers are largely underestimated, with most hidden diversity centred on widespread and polymorphic nominal species. The evolutionary origin of breeding strategies within Osteocephalus is discussed in the light of this new phylogenetic hypothesis, and a novel type of amplexus (gular amplexus) is described.

Recovering phylogenetic signal from frog mating calls

Goicoechea, N., De La Riva, I. & Padial, J. M. (2010). Recovering phylogenetic signal from frog mating calls. —Zoologica Scripta, 39, 411–154.

A Revision of Species Diversity in the Neotropical Genus Oreobates (Anura: Strabomantidae), with the Description of Three New Species from the Amazonian Slopes of the Andes

ABSTRACT We revisit species diversity within Oreobates (Anura: Strabomantidae) by combining molecular phylogenetic analyses of the 16S rRNA amphibian barcode fragment with the study of the external morphology of living and preserved specimens. Molecular and morphological evidence support the existence of 23 species within Oreobates, and three additional candidate species (Oreobates sp. [Ca JF809995], Oreobates sp. [Ca EU368903], Oreobates cruralis [Ca EU192295]). We describe and name three new species from the Andean humid montane forests of Departamento Cusco, southern Peru: O. amarakaeri New Species from Río Nusinuscato and Río Mabe, at elevations ranging from 670 to 1000 m in the Andean foothills; O. machiguenga, new species, from Río Kimbiri (1350 m), a small tributary of the Apurimac River, in the western versant of Cordillera Vilcabamba; and O. gemcare, new species, from the Kosñipata Valley at elevations ranging from 2400 to 2800 m. The three new species are readily distinguished from all other Oreobates by at least one qualitative morphological character. Three species are transferred to Oreobates from three genera of Strabomantidae: Hypodactylus lundbergi Pristimantis crepitans, and Phrynopus ayacucho (for which the advertisement call, coloration in life, and male characteristics are described for first time). Oreobates simmonsi is transferred to the genus Lynchius. Hylodes verrucosus is considered a junior synonym of Hylodes philippi. In addition, H. philippi is removed from the synonymy of O. quixensis and considered a nomem dubium within Hypodactylus. The inclusion of Phrynopus ayacucho in Oreobates extends the ecological range of the genus to the cold Andean puna. Oreobates is thus distributed from the Amazonian lowlands in southern Colombia to northern Argentina, reaching the Brazilian Atlantic dry forests in eastern Brazil, across an altitudinal range from ca. 100 to 3850 m.

Molecular systematics of teioid lizards (Teioidea/Gymnophthalmoidea: Squamata) based on the analysis of 48 loci under tree-alignment and similarity-alignment

We infer phylogenetic relationships within Teioidea, a superfamily of Nearctic and Neotropical lizards, using nucleotide sequences. Phylogenetic analyses relied on parsimony under tree‐alignment and similarity‐alignment, with length variation (i.e. gaps) treated as evidence and as absence of evidence, and maximum‐likelihood under similarity‐alignment with gaps as absence of evidence. All analyses produced almost completely resolved trees despite 86% of missing data. Tree‐alignment produced the shortest trees, the strict consensus of which is more similar to the maximum‐likelihood tree than to any of the other parsimony trees, in terms of both number of clades shared, parsimony cost and likelihood scores. Comparisons of tree costs suggest that the pattern of indels inferred by similarity‐alignment drove parsimony analyses on similarity‐aligned sequences away from more optimal solutions. All analyses agree in a majority of clades, although they differ from each other in unique ways, suggesting that neither the criterion of optimality, alignment nor treatment of indels alone can explain all differences. Parsimony rejects the monophyly of Gymnophthalmidae due to the position of Alopoglossinae relative to Teiidae, whereas support of Gymnophthalmidae by maximum‐likelihood was low. We address various nomenclatural issues, including Gymnophthalmidae Fitzinger, 1826 being an older name than Teiidae Gray, 1827. We recognize three families in the arrangement Alopoglossidae + (Teiidae + Gymnophthalmidae). Within Gymnophthalmidae we recognize Cercosaurinae, Gymnophthalminae, Rhachisaurinae and Riolaminae in the relationship Cercosaurinae + (Rhachisaurinae + (Riolaminae + Gymnophthalminae)). Cercosaurinae is composed of three tribes—Bachiini, Cercosaurini and Ecpleopodini—and Gymnophthalminae is composed of three—Gymnophthalmini, Heterodactylini and Iphisini. Within Teiidae we retain the currently recognized three subfamilies in the arrangement: Callopistinae + (Tupinambinae + Teiinae). We also propose several genus‐level changes to restore the monophyly of taxa.

A New Species of the discoidalis Group of Eleutherodactylus (Anura, Leptodactylidae) from Inner-Andean Dry Valleys of Bolivia

A new species of the Eleutherodactylus discoidalis group is described from the inner-Andean dry valleys of Bolivia. The new species is similar to Eleutherodactylus cruralis but differs from it in having the discs of fingers III and IV two times wider than the digits proximal to the discs, and the tympanum length being more than half the eye length. Moreover, the advertisement call of the new species is much shorter, has a lower dominant frequency, and fewer notes per call.

Systematics of Andean gladiator frogs of the Hypsiboas pulchellus species group (Anura, Hylidae)

Köhler, J., Koscinski, D., Padial, J. M., Chaparro, J. C., Handford, P., Lougheed, S. C. & De la Riva, I. (2010). Systematics of Andean gladiator frogs of the Hypsiboas pulchellus species group (Anura, Hylidae). —Zoologica Scripta, 39, 572–590.