No abstract

Patagonia was shaped by a complex geological history, including the Miocene uplift of the Andes, followed by volcanism, marine introgressions, and extreme climatic oscillations during Pliocene-Pleistocene glaciation-deglaciation cycles. The distributional patterns and phylogenetic relationships of southern patagonian animals and plants were affected in different ways, and those imprints are reflected in the seven phylogeographic breaks and eight refugia that have been previously proposed. In this study, we estimated time-calibrated phylogenetic/phylogeographic patterns in lizards of the Liolaemus lineomaculatus group and relate them to historical Miocene-to-Pleistocene events of Patagonia and the previously proposed phylogeographic patterns. Individuals from 51 localities were sequenced for the mitochondrial marker (cyt-b) and a subsample of individuals from each mitochondrial lineage was sequenced for one nuclear (LDA12D) and one slow evolving mitochondrial gene (12S). Our analyses revealed strong phylogeographic structure among lineages and, in most cases, no signal of demographic changes through time. The lineomaculatus group is composed of three strongly supported clades (lineomaculatus, hatcheri and kolengh + silvanae), and divergence estimates suggested their origins associated with the oldest known Patagonian glaciation (7-5 Ma); subsequent diversification within the lineomaculatus clade coincided with the large Pliocene glaciations (~3.5 Ma). The lineomaculatus clade includes nine strongly genetically and geographically structured lineages, five of which are interpreted as candidate species. Our findings suggest that some Liolaemus lineages have persisted in situ, each of them in a different refugium, through several glaciation-deglaciation cycles without demographic fluctuations. We also summarize and update qualitative evidence of some shared phylogeographic breaks and refugia among plants, rodents and lizards.

Accurately delimiting species is fundamentally important for understanding species diversity and distributions and devising effective strategies to conserve biodiversity. However, species delimitation is problematic in many taxa, including ‘non-adaptive radiations’ containing morphologically cryptic lineages. Fortunately, coalescent-based species delimitation methods hold promise for objectively estimating species limits in such radiations, using multilocus genetic data. Using coalescent-based approaches, we delimit species and infer evolutionary relationships in a morphologically conserved group of Central American freshwater fishes, the Poecilia sphenops species complex. Phylogenetic analyses of multiple genetic markers (sequences of two mitochondrial DNA genes and five nuclear loci) from 10/15 species and genetic lineages recognized in the group support the P. sphenops species complex as monophyletic with respect to outgroups, with eight mitochondrial ‘major-lineages’ diverged by ≥2% pairwise genetic distances. From general mixed Yule-coalescent models, we discovered (conservatively) 10 species within our concatenated mitochondrial DNA dataset, 9 of which were strongly supported by subsequent multilocus Bayesian species delimitation and species tree analyses. Results suggested species-level diversity is underestimated or overestimated by at least ~15% in different lineages in the complex. Nonparametric statistics and coalescent simulations indicate genealogical discordance among our gene tree results has mainly derived from interspecific hybridization in the nuclear genome. However, mitochondrial DNA show little evidence for introgression, and our species delimitation results appear robust to effects of this process. Overall, our findings support the utility of combining multiple lines of genetic evidence and broad phylogeographical sampling to discover and validate species using coalescent-based methods. Our study also highlights the importance of testing for hybridization versus incomplete lineage sorting, which aids inference of not only species limits but also evolutionary processes influencing genetic diversity.

Twenty‐one species of lizards are included in the southernmost clade of South America, the Liolaemus lineomaculatus section. There are two hypotheses of species‐grouping within this section, one based on morphological similarities and the other based on molecular phylogenetic relationships; although discordant, both are in use. The ‘morphological arrangement hypothesis’, which sorts the species of the section in three groups, was proposed ∼30 years ago; however, despite taxonomic changes and almost doubling the species diversity of this section since then, the hypothesis has never been tested. Here, we (1) present an updated chronological review of taxonomic changes, species descriptions, morphological groups, and genetic clades proposed for the L. lineomaculatus section, and (2) evaluate the accuracy of the ‘morphological arrangement hypothesis’. We show that the traditional practice of classifying 11 of these species in two of the three traditional morphological groups of the section (Liolaemus kingii and Liolaemus archeforus), which is not supported by molecular data, is also not supported by morphological data, and therefore should be abandoned; we suggest referring to this group of species as the L. kingii group. We characterized the Liolaemus magellanicus group based on morphology, and extend the previously published morphological characteristics of the L. lineomaculatus group. Finally, we comment on future prospects for studies of sexual dimorphism and its possible ecological implications. This paper provides a critical synthesis of our understanding of the morphological and phylogenetic patterns within the L. lineomaculatus section and presents a useful framework for future tests of taxonomic hypotheses and physiological, behavioural, and evolutionary questions within this section.  © 2013 The Linnean Society of London