Population structure of Squatina guggenheim (Squatiniformes,Squatinidae) from the south‐western Atlantic Ocean

Population genetic analyses based on both mitochondrial cytochrome b and the internal transcribed spacer 2 of recombinant (r)DNA genes were implemented to examine hypotheses of population differentiation in the angular angel shark Squatina guggenheim, one of the four most‐widespread endemic species inhabiting coastal ecosystems in the south‐western Atlantic Ocean. A total of 82 individuals of S. guggenheim from 10 sampling sites throughout the Río de la Plata mouth, its maritime front, the outer shelf at the subtropical confluence and the coastal areas of the south‐west Atlantic Ocean, were included. The analysis of molecular variance (AMOVA) based on the second internal transcribed spacer (its‐2) region supports that the samples from the outer shelf represent an isolated group from other sites. Historical gene flow in a coalescent‐based approach revealed significant immigration and emigration asymmetry between sampling sites. Based on the low level of genetic diversity, the existence of a long‐term population decline or a past recent population expansion following a population bottleneck could be proposed in S. guggenheim. This demographic differentiation suggests a degree of vulnerability to overexploitation in this endemic and endangered south‐west Atlantic Ocean shark, given its longevity and low reproductive potential.     

Phylogeographical patterns in Coenosia attenuata (Diptera: Muscidae): a widespread predator of insect species associated with greenhouse crops

The tiger‐fly Coenosia attenuata is a globally widespread predatory fly which is not only associated with greenhouse crops, but also occurs in open fields. It is a potential control agent against some of the more common pests in these crops. Assessing the genetic structure and gene flow patterns may be important for planning crop protection strategies and for understanding the historical processes that led to the present distribution of genetic lineages within this species. In the present study, the phylogeographical patterns of this species, based on mitochondrial cytochrome oxidase I and nuclear white and elongation factor‐1α genes, are described, revealing relatively low genetic diversity and weak genetic structure associated with a recent and sudden population expansion of the species. The geographical distribution of mitochondrial haplotypes indicates the Mediterranean as the most likely region of origin of the species. Some dispersal patterns of the species are also revaled, including at least three independent colonizations of North and South America: one from Middle East to North America with a strong bottleneck event, another from Europe to South America (Chile), with both likely to be a result of unintentional introduction, and a third one of still undetermined origin to South America (Ecuador). © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 308–326.