Dactylogyrus olfactorius n. sp. (Monogenea, Dactylogyridae) from the olfactory chamber of the fathead minnow, Pimephales promelas Rafinesque (Cyprinidae).

Dactylogyrus olfactorius n. sp. (Monogenea) is described from the olfactory chamber of the fathead minnow Pimephales promelas Rafinesque in Alberta, Canada. The new species resembles Dactylogyrus bychowskyi Mizelle, 1937, D. bifurcatus Mizelle, 1937 and D. simplexus Mizelle, 1937, all parasites of Pimephales spp. in North America, in overall size and shape of the anchors and hooks, and in having a male copulatory complex with a tapered tubular penis and bifurcate accessory piece. Diagnostically, D. olfactorius n. sp. has relatively small anchors, hooks of anchor length, and a thin, long dorsal bar and no apparent ventral bar nor 4A hooks. Scanning electron microscopy revealed the body tegument of D. olfactorius n. sp. to be microvillous and in shallow annular folds, while that of D. bifurcatus, occurring on host gills of the same fish, was avillous and in gill-like folds dorsally and ventrally. Partial 28S rDNA sequences revealed significant differences between the two species, supporting establishment of D. olfactorius n. sp. and dispelling the possibility of ecophenotypic effects of site of attachment on morphology.

Gene Flow of a Forest-Dependent Bird across a Fragmented Landscape.

Habitat loss and fragmentation can affect the persistence of populations by reducing connectivity and restricting the ability of individuals to disperse across landscapes. Dispersal corridors promote population connectivity and therefore play important roles in maintaining gene flow in natural populations inhabiting fragmented landscapes. In the prairies, forests are restricted to riparian areas along river systems which act as important dispersal corridors for forest dependent species across large expanses of unsuitable grassland habitat. However, natural and anthropogenic barriers within riparian systems have fragmented these forested habitats. In this study, we used microsatellite markers to assess the fine-scale genetic structure of a forest-dependent species, the black-capped chickadee (Poecile atricapillus), along 10 different river systems in Southern Alberta. Using a landscape genetic approach, landscape features (e.g., land cover) were found to have a significant effect on patterns of genetic differentiation. Populations are genetically structured as a result of natural breaks in continuous habitat at small spatial scales, but the artificial barriers we tested do not appear to restrict gene flow. Dispersal between rivers is impeded by grasslands, evident from isolation of nearby populations (~ 50 km apart), but also within river systems by large treeless canyons (>100 km). Significant population genetic differentiation within some rivers corresponded with zones of different cottonwood (riparian poplar) tree species and their hybrids. This study illustrates the importance of considering the impacts of habitat fragmentation at small spatial scales as well as other ecological processes to gain a better understanding of how organisms respond to their environmental connectivity. Here, even in a common and widespread songbird with high dispersal potential, small breaks in continuous habitats strongly influenced the spatial patterns of genetic variation.

Integrating landscape genomics and spatially explicit approaches to detect loci under selection in clinal populations.

Uncovering the genetic basis of adaptation hinges on the ability to detect loci under selection. However, population genomics outlier approaches to detect selected loci may be inappropriate for clinal populations or those with unclear population structure because they require that individuals be clustered into populations. An alternate approach, landscape genomics, uses individual-based approaches to detect loci under selection and reveal potential environmental drivers of selection. We tested four landscape genomics methods on a simulated clinal population to determine their effectiveness at identifying a locus under varying selection strengths along an environmental gradient. We found all methods produced very low type I error rates across all selection strengths, but elevated type II error rates under "weak" selection. We then applied these methods to an AFLP genome scan of an alpine plant, Campanula barbata, and identified five highly supported candidate loci associated with precipitation variables. These loci also showed spatial autocorrelation and cline patterns indicative of selection along a precipitation gradient. Our results suggest that landscape genomics in combination with other spatial analyses provides a powerful approach for identifying loci potentially under selection and explaining spatially complex interactions between species and their environment.