The importance of the Andes in the evolutionary radiation of Sigmodontinae (Rodentia, Cricetidae), the most diverse group of mammals in the Neotropics.

The Andean mountains stand out for their striking species richness and endemicity that characterize many emblematic Neotropical clades distributed in or around these mountains. The radiation of the Sigmodontinae subfamily, the most diversified mammalian group in the Neotropics, has been historically related to Andean orogenesis. We aim to evaluate this interplay between geological processes and biological responses through the diversification dynamics, the biogeographical history, and the range evolution of the subfamily. For these, we built the most comprehensive phylogeny and gathered 14,836 occurrences for the subfamily. We identified one shift in the speciation rate in the genus Akodon, which suffered their Andean radiation after the arrival of non-Andean ancestors. Our biogeographic analyses show multiple dispersal paths throughout the evolution that allowed this subfamily to colonize all Neotropics. The Northern Andes and Central-Southern Andes were the most important sources of diversity. In addition, the Central-Southern Andes were the most relevant sink, receiving the highest number of lineages. The Andean region exhibited higher speciation and turnover rates than non-Andean regions. Thus, our results support the crucial role of the Andean Mountains in the Sigmodontinae radiation, acting as a "macroevolutionary cradle" and "species attractor" for several sigmodontine lineages at different times, and as a "species pump" becoming the biogeographic source of multiple widely distributed neotropical lineages. Then, complex macroevolutionary dynamics would explain these rodents' high extant Andean diversity and their wide distribution in the Neotropics.

Phylogenetic evaluation of taxonomic definition of didelphid mouse opossum of the genus Thylamys from valleys of Coquimbo region, Chile.

Only two species of Didelphidae are currently recognized in Chile, the sister species Thylamys elegans, endemic of Mediterranean ecorregion and Thylamys pallidior, the inhabitant of the Puna and desert canyons. Three subspecies have been described for T. elegans: T. e. elegans, T. e. coquimbensis and T. e. soricinus. However, a recent study based on morphological analyses, synonymized T. elegans coquimbensis from the Coquimbo valleys (30-31° S) with T. pallidior and proposed that T. elegans and T. pallidior could be in sympatry at Coquimbo valleys between Fray Jorge (30°40'S) and Paiguano (30°02' S). We assess the current definition of T. e. coquimbensis and T. e. elegans, as well as this taxonomical conflict among the mouse opossums from the Coquimbo valleys through phylogenetic analyses of cytochrome b mitochondrial gene sequences. In this study, for the first time, we used specimens from the type localities of T. e. coquimbensis and T. e. elegans. In addition, we analyzed diagnostic cranial structures for this taxonomic revision. The results supported two allopatric clades, allowing us to keep the taxonomic definition of T. e. elegans and T. e. coquimbensis as phylogenetic reciprocal monophyletic clades and polyphyletic with T. pallidior. This result corroborates previous morphological analyses, which support that mouse opossums from the Coquimbo valleys are T. e. coquimbensis, thus extending its geographic distribution to the coast of Coquimbo and Atacama regions. We don´t have evidence for sympatric distribution between T. elegans and T. pallidior in the Coquimbo region.

The influence of ecological and geographical context in the radiation of Neotropical sigmodontine rodents.

BACKGROUND: Much debate has focused on how transitions in life history have influenced the proliferation of some clades. Rodents of the subfamily Sigmodontinae (family Cricetidae) comprise one of the most diverse clades of Neotropical mammals (~400 living species in 86 genera). These rodents occupy a wide range of habitats and lifestyles so that ecological context seems relevant to understand the evolution of this group. Several changes in the landscape of South America through the Neogene might have provided vast resources and opportunity to diversify. The aim of this study was to examine whether transitions between i) lowland and montane habitats, ii) open vegetation and forest, and iii) distinct molar architectures are correlated with shifts in diversification rates and to characterize the general pattern of diversification. RESULTS: Based on a dense taxon sampling of 269 species, we recovered a new phylogeny of Sigmodontinae that is topologically consistent with those of previous studies. It indicates that the subfamily and its major lineages appeared during the Late Miocene. Analyses suggest that vegetation type and elevational range are correlated with diversification rates, but not molar architecture. Tropical lowlands accumulated more lineage diversity than other areas and also supported high speciation rates. Across the radiation the subfamily Sigmodontinae appear to have experienced a decline in diversification rate through time. We detected mixed evidence for lineage-specific diversification rate shifts (e.g., leading to the clades of Akodon, Bibimys, Calomys and Thomasomys). CONCLUSION: We report that the evolution of habitat preference (considering vegetation type and elevational range) was associated with diversification rates among sigmodontine rodents. We propose that the observed diversification slowdown might be the result of ecological or geographical constraints. Our results also highlight the influence of the tropical lowlands -which might have acted as both "a cradle and a museum of species." The tropical lowlands accumulated greater diversity than the remainder of the group's range.

Dating an impressive Neotropical radiation: Molecular time estimates for the Sigmodontinae (Rodentia) provide insights into its historical biogeography.

With about 400 living species and 82 genera, rodents of the subfamily Sigmodontinae comprise one of the most diverse and more broadly distributed Neotropical mammalian clades. There has been much debate on the origin of the lineage or the lineages of sigmodontines that entered South America, the timing of entrance and different aspects of further diversification within South America. The ages of divergence of the main lineages and the crown age of the subfamily were estimated by using sequences of the interphotoreceptor retinoid binding protein and cytochrome b genes for a dense sigmodontine and muroid sampling. Bayesian inference using three fossil calibration points and a relaxed molecular clock estimated a middle Miocene origin for Sigmodontinae (∼12Ma), with most tribes diversifying throughout the Late Miocene (6.9-9.4Ma). These estimates together results of analyses of ancestral area reconstructions suggest a distribution for the most recent common ancestor of Sigmodontinae in Central-South America and a South American distribution for the most recent common ancestor of Oryzomyalia.

Phylogeographical analysis of neotropical Rhagoletis (Diptera: Tephritidae): did the Andes uplift contribute to current morphological differences? / Análisis filogeográfico de Rhagoletis neotropicales (Diptera: Tephritidae): ¿ha contribuido el levantamiento de los Andes a explicar las actuales diferencias morfológicas?

Neotropical Rhagoletis species are arranged in four groups: nova,psalida,striatella and ferruginea, which include 18 species. On both sides of the Andes, the evolution of morphological differences among these groups has been suggested to be related to the Andes uplift process. In order to test this hypothesis, a phylogenetic analysis of morphological and molecular data was performed. The results suggest that: 1) Neotropical species of Rhagoletis constitute a separate group from Paleartic and North American species, with the only exception being a member of the striatella group having a certain association with the northern species. 2) Neotropical species seem to form a monophyletic clade, although statistical support for this is weak. 3) The split of South American Rhagoletis from other groups was dated at 4.333 million years ago, which is before the emergence of a continuous landbridge between Central and South América. 4) Within species distributed in South América, morphological and molecular data were coincident, placing species of the ferruginea group separate from the other Neotropical Rhagoletis. 5) The divergence of the ferruginea group from the other groups was dated at 3.882 million years ago, which is before the last uplift of the Andes. These results suggest that diversification of the ferruginea,psalida and nova groups, on each side of the Andes, was the result of a vicariant separation followed by dispersal and isolation processes. Thus, these results support the hypothesis that the Andes uplift has played an important role in Neotropical Rhagoletis diversification.

Las especies de Rhagoletis neotropicales han sido agrupadas en cuatro grupos: nova,psalida,striatella y ferruginea, constituyendo 18 especies. Se han descrito diferencias morfológicas entre estas especies a ambos lados de la cordillera de los Andes que podrían relacionarse con el proceso de levantamiento cordillerano. En este trabajo se evalúa esta hipótesis usando análisis filogenético de atributos morfológicos y moleculares. Los resultados muestran que: a) las especies Neotropicales de Rhagoletis constituyen un grupo separado de las especies Palearticas y Norteamericanas, con la excepción de un miembro del grupo striatella el cual presenta cierta asociación con las especies Norteamericanas; 2) Las especies Neotropicales parece conformar un clado monofilético; 3) La separación de los grupos Sudamericanos de otros grupos fue estimada en 4.333 millones de años antes del presente, proceso anterior a la emergencia del puente de tierra entre América Central y Sudamérica; 4) Dentro de las especies con distribución Sudamericana, los caracteres morfológicos y moleculares coinciden en ubicar algunas especies del grupo ferruginea separadas de especies de Rhagoletis Neotropicales. 5) La separación del grupo ferruginea fue estimada en 3.882 millones de años antes del presente, evento que precede al último levantamiento de los Andes. La diversificación de los grupos ferruginea,psalida y nova a uno y otro lado de la cordillera de los Andes parece responder inicialmente a un proceso vicariante y posteriores eventos de dispersión y aislamiento. Estos resultados sugieren que el levantamiento de los Andes habría participado en los patrones de diversificación de las Rhagoletis Neotropicales.