Genetic structure, phylogeography and demography of two ground-beetle species endemic to the Tenerife laurel forest (Canary Islands)

The volcanic island of Tenerife (Canary archipelago) was formerly covered at 600-1200 m above sea level on most of its northern side by a cloud forest holding much of the endemic insect fauna. In the most significant surviving patches of this laurel forest at the eastern and western tips of the island occur two forest-specialist, closely related species of Eutrichopus (Coleoptera, Carabidae); here we present data on mitochondrial DNA variation among populations of these species. In total, 116 individuals from 16 localities were sampled and a 638 bp fragment of the cytochrome oxidase subunit II gene was sequenced, obtaining evidence for two distinct evolutionary lineages, in accordance with morphological and biogeographical data. Volcanic events at approximately 0.7 Ma might be responsible for vicariance and the fragmentation of the geographical range of an ancestral species, causing the establishment of two matrilineal lineages. Using nested clade and historical demography analyses we infer past cycles of demographic bottlenecks followed by population expansion, mostly in agreement with the geological time scale of volcanic events. Recent trends, however, refer to fragmentation of the cloud forest due to human intervention.     

Mitochondrial DNA, ecology and morphology: interpreting the phylogeography of the Nesotes (Coleoptera: Tenebrionidae) of Gran Canaria (Canary Islands)

The genus Nesotes (Coleoptera: Tenebrionidae) is represented in the Canary Islands by 19 endemic species, the majority of which are single island endemics. Nesotes conformis and N. fusculus are described on four and three islands, respectively, but each forms a paraphyletic assemblage between Gran Canaria and the other islands. The other described species for Gran Canaria are N. quadratus, N. lindbergi and N. piliger. Thirty-six individuals representing the five species on Gran Canaria have been sequenced for 675 bp of the mitochondrial DNA (mtDNA) cytochrome oxidase II gene. Neighbour-joining analysis of maximum likelihood distances resulted in five distinct mtDNA lineages for N. quadratus, two of which also include mitotypes of N. conformis. Each of the other three species is found on only one mtDNA lineage. We propose from the molecular data that differentiation in a widespread N. quadratus-type ancestor was followed by morphological adaptation to coastal, pine and laurel forest habitats.     

PROmiRNA: a new miRNA promoter recognition method uncovers the complex regulation of intronic miRNAs

The regulation of intragenic miRNAs by their own intronic promoters is one of the open problems of miRNA biogenesis. Here, we describe PROmiRNA, a new approach for miRNA promoter annotation based on a semi-supervised statistical model trained on deepCAGE data and sequence features. We validate our results with existing annotation, PolII occupancy data and read coverage from RNA-seq data. Compared to previous methods PROmiRNA increases the detection rate of intronic promoters by 30%, allowing us to perform a large-scale analysis of their genomic features, as well as elucidate their contribution to tissue-specific regulation. PROmiRNA can be downloaded from http://promirna.molgen.mpg.de.     

The phylogeography of the darkling beetle,Hegeter politus,in the eastern Canary Islands.

We investigated the phylogeography of Hegeter politus, a saprophagous, flightless darkling beetle endemic to the eastern Canary Islands, using a fragment of the mitochondrial COI gene. Distance and parsimony based gene trees of the mitotypes identified revealed a striking association between mitotype clades and sampling locations. The branching order of the clades suggested that the colonization of the islands by Hegeter politus proceeded from the southern part of Fuerteventura in a north-northeast direction to Lanzarote and the smaller islands. Based on this, a colonization scenario compatible with the reported geological ages and volcanisms of the various parts of the islands has been proposed. The high divergence of the beetles collected from the extreme south of Fuerteventura (the Jandía peninsula) from all other samples has led us to propose that they may be from a new species that has not been described previously. The ecological isolation of Jandía from the rest of Fuerteventura by the sand dunes that cover its narrow isthmus in the north, and the existence of many plant and animal endemisms unique to Jandía, lend supportive evidence to our proposal. The similarities between the evolution of island endemics in the Hawaiian and Canary archipelagos have been discussed. We conclude that many endemics in the Canary archipelago, like the Hawaiian Islands, are most likely to have originated from post-colonization differentiation and divergence.