Habitat requirements affect genetic variation in three species of mayfly (Ephemeroptera, Baetidae) from South Africa

Description of a new montane freshwater crab (Arthropoda, Malacostraca, Decapoda, Potamonautidae) from the Eastern Cape, South Africa

A new species of freshwater crab, Potamonautesamatholesp. nov., is described from the Winterberg-Amathole mountain range in the Eastern Cape Province, South Africa. Morphologically, P.amathole Peer & Gouws, sp. nov. most closely resembles P.tuerkayi but can be distinguished by key morphological characters including the variation in the shape of the subterminal segment of gonopod 2 between both species. Genetically, P.amathole Peer & Gouws, sp. nov. is placed within the clade of small-bodied, mountain-dwelling crabs including P.parvispina, P.parvicorpus, P.brincki, P.tuerkayi, P.baziya, and P.depressus. The new species is found in slow-moving mountain streams and pools at high altitudes. The continued discovery and description of new freshwater crab species reinforces the need for ongoing research, especially in under-sampled regions.

Assessing population genetic structure of three New Zealand stream insects using mitochondrial and nuclear DNA markers

Assessing genetic differentiation among natural populations can aid understanding of dispersal patterns and connectivity among habitats. Several molecular markers have become increasingly popular in determining population genetic structure for this purpose. Here, we compared the resolution of mitochondrial cytochrome c oxidase subunit I (COI) and nuclear single nucleotide polymorphism (SNP) markers for detecting population structure among stream insects at small spatial scales. Individuals of three endemic taxa - Coloburiscus humeralis (Ephemeroptera), Zelandobius confusus (Plecoptera), and Hydropsyche fimbriata (Trichoptera) - were collected from forested streams that flow across open pasture in the North Island of New Zealand. Both COI and SNP data indicated limited population structure across the study area, and small differences observed among these species were likely related to their putative dispersal abilities. For example, fine-scale genetic differentiation between and among neighbouring stream populations for H. fimbriata suggests that gene flow, and hence dispersal, may be more limited for this species relative to the others. Based on the generally similar results provided by both types of markers, we suggest that either COI or SNP markers can provide suitable initial estimates of fine-scale population genetic differentiation in stream insects.

Location and Species Matters: Variable Influence of the Environment on the Gene Flow of Imperiled, Native and Invasive Cottontails

The environment plays an important role in the movement of individuals and their associated genes among populations, which facilitates gene flow. Gene flow can help maintain the genetic diversity both within and between populations and counter the negative impact of genetic drift, which can decrease the fitness of individuals. Sympatric species can have different habitat preferences, and thus can exhibit different patterns of genetic variability and population structure. The specialist-generalist variation hypothesis (SGVH) predicts that specialists will have lower genetic diversity, lower effective population sizes (Ne), and less gene flow among populations. In this study, we used spatially explicit, individual-based comparative approaches to test SGVH predictions in two sympatric cottontail species and identify environmental variables that influence their gene flow. New England cottontail (Sylvilagus transitionalis) is the only native cottontail in the Northeast US, an early successional habitat specialist, and a species of conservation concern. Eastern cottontail (S. floridanus) is an invasive species in the Northeast US and a habitat generalist. We characterized each species' genomic variation by developing double-digest Restriction-site Associated DNA sequence single nucleotide polymorphism markers, quantified their habitat with Geographic Information System environmental variables, and conducted our analyses at multiple scales. Surprisingly, both species had similar levels of genetic diversity and eastern cottontail's Ne was only higher than New England cottontail in one of three subregions. At a regional level, the population clusters of New England cottontail were more distinct than eastern cottontail, but the subregional levels showed more geographic areas of restricted gene flow for eastern cottontail than New England cottontail. In general, the environmental variables had the predicted effect on each species' gene flow. However, the most important environmental variable varied by subregion and species, which shows that location and species matter. Our results provide partial support for the SGVH and the identification of environmental variables that facilitate or impede gene flow can be used to help inform management decisions to conserve New England cottontail.