Background: The Chilean Altiplano and the Atacama Desert in northern Chile harbor isolated hydrological systems or oases where it is possible to find minute aquatic snails of the genus Heleobia whose taxonomy is uncertain and where many populations remain unknown. Here, we obtained samples from 30 localities distributed in the region and used molecular (12S and 16S mitochondrial genes) and morphological (penis) characters to investigate diversity of this poorly known fauna. Results: Molecular phylogenetic analysis consistently recovered five clades, one of which constitutes a cryptic species previously assigned to a species recognized in the area. Four other clades contained sequences of one nominal species consistent with its type locality and at least two additional candidate species, which were corroborated by a particular penis morphology. Furthermore, some morphological differences in penis morphology were observed in two Altiplano populations not resolved by the DNA sequences, providing support for two additional candidate species in the genus. A molecular clock analysis allowed tracing the origin of lineages back to the Early Pleistocene.
AimAntarctica's remote and extreme terrestrial environments are inhabited by only two species of native vascular plants. We assessed genetic connectivity amongst Antarctic and South American populations of one of these species, Colobanthus quitensis, to determine its origin and age in Antarctica.LocationMaritime Antarctic, sub‐Antarctic islands, South America.TaxonAntarctic pearlwort Colobanthus quitensis (Caryophyllaceae).MethodsFour chloroplast markers and one nuclear marker were sequenced from 270 samples from a latitudinal transect spanning 21–68° S. Phylogeographic, population genetic and molecular dating analyses were used to assess the demographic history of C. quitensis and the age of the species in Antarctica.ResultsMaritime Antarctic populations consisted of two different haplotype clusters, occupying the northern and southern Maritime Antarctic. Molecular dating analyses suggested C. quitensis to be a young (<1 Ma) species, with contemporary population structure derived since the late‐Pleistocene.Main conclusions.The Maritime Antarctic populations likely derived from two independent, late‐Pleistocene dispersal events. Both clusters shared haplotypes with sub‐Antarctic South Georgia, suggesting higher connectivity across the Southern Ocean than previously thought. The overall findings of multiple colonization events by a vascular plant species to Antarctica, and the recent timing of these events, are of significance with respect to future colonizations of the Antarctic Peninsula by vascular plants, particularly with predicted increases in ice‐free land in this area. This study fills a significant gap in our knowledge of the age of the contemporary Antarctic terrestrial biota. Adding to previous inferences on the other Antarctic vascular plant species (the grass Deschampsia antarctica), we suggest that both angiosperm species are likely to have arrived on a recent (late‐Pleistocene) time‐scale. While most major groups of Antarctic terrestrial biota include examples of much longer‐term Antarctic persistence, the vascular flora stands out as the first identified terrestrial group that appears to be of recent origin.
Species recognition in freshwater snails of the genus Heleobia Stimpson, 1865 in the Loa River basin is a difficult task to perform because these snails are similar in shell morphology. In this complex hydrological network, the genus comprises two endemic species, but the taxonomic status of other previously undescribed sympatric and allopatric populations is uncertain. Here we examined DNA sequences from cytochrome c oxidase subunit I (COI) gene and morphological data to investigate species boundaries along the system. Phylogenetic trees were inferred using maximum parsimony, neighbour joining, maximum likelihood and Bayesian inference methods based on samples ranging from the outlet of the Loa River on the Pacific coast to more than 4,200 m altitude in the Andes. Although not always well supported, four clades were consistently recovered in the phylogenies, one corresponding to Heleobia loaensis (Biese, 1947), another to Heleobia opachensis (Biese, 1947), and two more additional cryptic lineages. Additionally, a fifth cluster of sequences not recovered in these analyses was inferred in the BEAST analysis. Outline-based geometric morphometrics of the shell was useful to differentiate a single lineage sustaining that typological discrimination in Heleobia is challenging. Our results also indicate that all lineages diverged by independent non-adaptive allopatric processes during the Middle Pleistocene
The chiton genus Tonicia is composed of 12 species, 11 of which are found in the eastern Pacific, but the taxonomic status and geographical distribution of these species have long been controversial. In this study, we compare eastern Pacific Tonicia species using molecular systematics. The molecular markers cytochrome oxidase c subunit I (COI), 16S and 18S ribosomal RNA were used to estimate the phylogenetic relationships and divergence times among species. Species delimitations were inferred using a Bayesian generalized mixed Yule coalescent (bGMYC) and a Bayesian Poisson tree processes (bPTP) approach. We assigned southeastern Pacific specimens to nine recognized species based on their morphology, but these were resolved into only six species in our molecular phylogeny, suggesting that three of the recognized morpho species need to be synonymized. The bGMYC and bPTP analyses indicate the existence of six total coalescent groups interpreted as seven species in our gene tree results. Likewise, pairwise genetic distances, phylogenetic estimates and coalescent approaches support only seven lineages when considering specimens that match the nine currently recognized southeastern Pacific Tonicia species. We suggest that the colouration and morphological characters used to identify Tonicia species must be re-examined in depth.
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