Landscape genetics of the blotched tiger salamander (Ambystoma tigrinum melanostictum)

The field of landscape genetics has great potential to identify habitat features that influence population genetic structure. To identify landscape correlates of genetic differentiation in a quantitative fashion, we developed a novel approach using geographical information systems analysis. We present data on blotched tiger salamanders (Ambystoma tigrinum melanostictum) from 10 sites across the northern range of Yellowstone National Park in Montana and Wyoming, USA. We used eight microsatellite loci to analyse population genetic structure. We tested whether landscape variables, including topographical distance, elevation, wetland likelihood, cover type and number of river and stream crossings, were correlated with genetic subdivision (F(ST)). We then compared five hypothetical dispersal routes with a straight-line distance model using two approaches: (i) partial Mantel tests using Akaike's information criterion scores to evaluate model robustness and (ii) the BIOENV procedure, which uses a Spearman rank correlation to determine the combination of environmental variables that best fits the genetic data. Overall, gene flow appears highly restricted among sites, with a global F(ST) of 0.24. While there is a significant isolation-by-distance pattern, incorporating landscape variables substantially improved the fit of the model (from an r2 of 0.3 to 0.8) explaining genetic differentiation. It appears that gene flow follows a straight-line topographic route, with river crossings and open shrub habitat correlated with lower F(ST) and thus, decreased differentiation, while distance and elevation difference appear to increase differentiation. This study demonstrates a general approach that can be used to determine the influence of landscape variables on population genetic structure.     

Philopatry, kin clusters, and genetic relatedness in a population of woodrats (Neotoma macrotis)

Studies of highly kin-structured mammal societies have revealedthe importance of natal philopatry in determining the distributionof genetic variation within populations. In comparison, therelationship between philopatry and genetic diversity withinpopulations of moderately kin-structured societies has receivedrelatively little attention. Previous studies of Neotoma macrotishave suggested that females form distinct kin clusters. Eachkin cluster overlaps spatially with the home range(s) of oneor more males that are not related to each other or to the femaleswith which they are spatially associated. To examine interactionsbetween philopatry and genetic structure in this apparentlymoderately kin-structured species, we characterized spatialand genetic relationships among individually marked femalesin a population of N. macrotis from central coastal California.Our field studies revealed that, contrary to expectation, femalesin this population were not strongly philopatric and spatiallyclustered females were not characterized by high levels of geneticrelatedness. Nevertheless, genetic structure was evident withinthe study population; spatial and genetic distances among femaleswere significantly correlated, suggesting that dispersal patternsinfluenced genetic structure even in the absence of marked femalephilopatry. Because females with overlapping spatial distributionswere not typically closely related to one another, opportunitiesfor the evolution of kin-selected social behavior (e.g., cooperativecare of young) appear to be limited in this population.     

Why do kangaroo rats (Dipodomys spectabilis) footdrum at snakes?

We examined alternative hypotheses for the benefits of footdrummingin the presence of snakes by the banner-tailed kangaroo rat,Dipodomys spectabitis, by testing whether the target of thesignal includes conspecifics, the predator or both. Footdrummingrecorded in the field revealed that rats altered their footdrummingsignatures when drumming at snakes. In playback tests, however,neighbors failed to show any measurable change in behavior tobroadcasts of the snake drumming pattern, but mothers footdrummedsignificantly more than nonmothen in the presence of a tetheredsnake. Gopher snakes, Pituophis melanolsucus affinis, respondedto footdrumming vibrations created by a mechanical thumper.Nonhungry snakes avoided footdrumming, while hungry snakes approachedthe seismic footdrumming. Snakes decreased stalking rates asfootdrumming increased, but they spent more time stalking drummingthan nondnimming rats. We conclude that D. spectabilis footdrumsin individual defense and in parental care, rather than to warnadult conspecfics. Footdrumming deters pursuit by informingthe snake that the rat is alert and the chances of predationare low. We find little evidence that footdrumming startles,confuses, or harasses the snake. Hungry gopher snakes, however,may locate prey by eavesdropping on territorial footdrumming     

Phylogeographical structure and regional history of the dusky-footed woodrat, Neotoma fuscipes

The dusky-footed woodrat, Neotoma fuscipes, is a medium-sized rodent that inhabits low elevation woodland habitats along the Pacific coast of North America from Oregon, throughout California and into Baja California. Analyses of mitochondrial sequence variation throughout the distribution reveal substantial phylogeographical structure within N. fuscipes. The major mitochondrial lineages are largely concordant with previously identified morphological subdivisions within the taxon. The geographical distribution of distinct clades suggests that a combination of topographic barriers and the expansion and contraction of suitable habitat during the past 2 million years, especially along particular mountain ranges, have played a major role in the diversification of N. fuscipes. Furthermore, relatively low levels of genetic variation across the northern half of the distribution suggest that dusky-footed woodrats may have only recently expanded into this region.     

Population genetic structure of two ecologically distinct Amazonian spiny rats: separating history and current ecology

Abstract. Population history and current demographic and ecological factors determine the amount of genetic variation within and the degree of differentiation among populations. Differences in the life history and ecology of codistributed species may lead to differences in hierarchical population genetic structure. Here, we compare patterns of genetic diversity and structure of two species of spiny rats in the genus Proechimys from the Rio Jurua of western Amazonian Brazil. Based on the ecological and life-history differences between the two species, we make predictions as to how they might differ in patterns of genetic diversity and structure. We use mitochondrial sequence data from the cytochrome b gene to test these predictions. Although both species maintain nearly the same number of mitochondrial haplotypes across the sampled range, they differ in levels of genetic diversity and geographic structure. Patterns of gene flow are also different between the two species with average M-values of nearly three in P. steerei and less than one in P. simonsi . Our initial predictions are largely upheld by the genetic data and where conflicting hypotheses arise, we suggest further studies that may allow us to distinguish among evolutionary scenarios. Separating the effects of history and ongoing demography on patterns of genetic diversity is challenging. Combining genetic analyses with field studies remains essential to disentangling these complex processes.     

Révision des Amblytylus et essai de mise au point sur les genres Amblytylus Fieber et Megalocoleus Reuter (Heteroptera: Miridae: Phylinae)

Les vingt-deux espèces actuellement répertoriées dans le genre paléarctique Amblytylus Fieber ont été examinées. Le genre est redéfini principalement d’après les caractères des genitalia mâles. Dix espèces sont maintenues dans le genre: A. albidus (Hahn 1834), A. amoenus Wagner 1958, A. arnoldiorum Kerzhner 1977, A. brevicollis Fieber 1858, A. concolor Jakovlev 1877, A. crassicornis Wagner 1964, A. jani Fieber 1858, A. montanus Wagner 1974, A. nasutus (Kirschbaum 1856), A. peitho Linnavuori 1997; toutefois, A. amoenus est considérée comme incertae sedis et A. jani comme nomen dubium. Deux espèces sont transférées dans le genre Megalocoleus Reuter: Megalocoleus delicatus (Perris 1857) n. comb., Megalocoleus tarsalis (Reuter 1894) n. comb. Dix espèces sont mises en synonymie; soit avec une espèce d’Amblytylus: A. similis Wagner 1971 n. syn. de A. albidus (Hahn 1834); A. gregarius Linnavuori 1961 n. syn. de A. brevicollis Fieber 1868; A. vittiger Reuter 1899 n. syn., A. longicornis Wagner 1953 n. syn. et A. eckerleini Wagner 1964 n. syn. de A. concolor Jakovlev 1877; soit avec une espèce de Megalocoleus: A. erectus Wagner 1971 n. syn. de M. longirostris (Fieber 1861); A. glaucicollis Kerzhner 1977 n. syn. de M. exanguis (Herrich-Schaeffer 1835); A. macedonicus Wagner 1956 n. syn. de M. naso (Reuter 1879) n. comb.; A. luridus Hoberlandt 1961 n. syn. et A. scutellaris Horvath 1905 n. syn. de M. delicatus (Perris 1857) n. comb. Un lectotype est désigné pour quatre espèces (Lopus nasutus Kirshbaum, Amblytylus vanduzeei Blatchey, Amblytylus scutellaris Horváth, Capsus delicatus Perris). Une clé d’identification pratique bilingue (français et anglais) basée surtout sur des caractères externes tente de séparer les espèces d’Amblytylus. Une clé révisée des espèces de Megalocoleus est également fournie. Les deux genres Amblytylus et Megalocoleus, très semblables par l’habitus, restent difficiles à définir. Seules les plantes-hôtes - des Poaceae chez les Amblytylus, des Asteraceae chez les Megalocoleus - et dans une moindre mesure la vesica pourvue de deux processus apicaux (Amblytylus) ou d’un seul (Megalocoleus) semble indiquer l’existence de deux groupes d’espèces distincts.     

Revue des espèces attribuées au genre Megalocoleus Reuter, 1890 (Heteroptera: Miridae)

Les vingt-quatre espèces actuellement attribuées au genre Megalocoleus sont réexaminées après étude de tous les types disponibles. Les genitalia mâles et femelles apportent des caractères discriminants beaucoup plus fiables que les caractères externes et sont souvent indispensables pour séparer les espèces. Quelques caractères externes se révèlent néanmoins utiles mais ces derniers sont particulièrement difficiles à apprécier sur les spécimens qui ne sont pas en parfait état. Au terme de cette revue, il apparaît que le genre ne pourra être correctement défini qu’après étude de toutes les espèces décrites dans le genre voisin Amblytylus. Les modifications suivantes peuvent être néanmoins proposées dès à présent:– Réhabilitation d’une espèce, Megalocoleus krueperi (Reuter, 1879) bona species; en conséquence, M. satrapes Horváth, 1907 et M. binotatus (Wagner, 1953), auparavant synonymes de M. lunula, deviennent synonymes de M. krueperi (Reuter, 1879). – Mise en synonymie de 8 espèces: M. hungaricus Wagner, 1944 n. syn. de M. naso (Reuter, 1879); M. ocrensis Wagner, 1972 n. syn. de M. exsanguis (Herrich-Schaeffer, 1835); M. bifidus Wagner, 1973 n. syn. et M. fasciatus Wagner, 1969 n. syn. de M. lunula (Fieber, 1861); M. hirsutus Drapolyuk, 1991 n. syn. de M. signoreti (Reuter, 1879); M. confusus Wagner, 1958 n. syn. et M. pericarti Linnavuori, 1970 n. syn. de M. molliculus (Fallén, 1807). – Exclusion du genre Megalocoleus de quatre espèces; trois sont mises en synonymie: M. femoralis (Reuter, 1879), n. syn. de Tinicephalus hortulanus (Meyer-Dür, 1843), M. fumanae Wagner, 1974 n. syn. de Tinicephalus croceus Wagner 1969, M. servadeii Wagner, 1954 n. syn. d’Amblytylus tarsalis Reuter, 1894; une espèce, M. atricornis devient Tinicephalus atricornis (Wagner, 1965) n. comb. Une clé d’identification pratique (en français et en anglais), basée sur des caractères externes, tente de séparer les 14 espèces de Megalocoleus que le genre compte après cette étude.     

Condition of mule deer during winter: stress and spatial overlap with North American elk

We assessed body condition, diet quality (indexed by fecal nitrogen), and stress levels (using fecal glucocorticoid metabolites) in mule deer Odocoileus hemionus in southeastern Idaho, USA, during a mild (2007) and a harsh winter (2008) to evaluate spatial overlap and potential competition with North American elk Cervus elaphus. We used data from GPS telemetry to construct spatially explicit maps of local population density of elk for January–April. Loss of body condition over winter in yearling and adult female mule deer was not related to elk density but to winter severity. Fecal nitrogen increased as winter progressed in both winters, was significantly lower during 2008 than in 2007, but was not related to local population density of elk. In the mild winter of 2007, a significant positive relationship existed between local population density of elk and fecal glucocorticoid metabolite levels of mule deer, indicating increased physiological stress among mule deer wintering in close proximity to elk. Fecal glucocorticoid metabolite levels in deer were lower in 2008 than in 2007 and exhibited no significant relationship with elk density. Declining fecal glucocorticoid levels through winter may be typical of northern cervids. No difference existed in levels of fecal glucocorticoids between sexes of deer. A reduction in elk populations may not improve diet quality, physiological stress levels, or body condition of mule deer on winter range, especially during severe winters. Consequently, management and conservation of winter habitat are more likely to benefit mule deer than would altering density of elk.     

Phylogenetics of the woodrat genus Neotoma (Rodentia: Muridae): implications for the evolution of phenotypic variation in male external genitalia

Interspecific morphological variation in animal genitalia has long attracted the attention of evolutionary biologists because of the role genital form may play in the generation and/or maintenance of species boundaries. Here we examine the origin and evolution of genital variation in rodents of the muroid genus Neotoma. We test the hypothesis that a relatively rare genital form has evolved only once in Neotoma. We use four mitochondrial and four nuclear markers to evaluate this hypothesis by establishing a phylogenetic framework in which to examine genital evolution. We find intron seven of the beta-fibrinogen gene to be a highly informative nuclear marker for the levels of differentiation that characterize Neotoma with this locus evolving at a rate slower than cytochrome b but faster than 12S. We estimate phylogenetic relationships within Neotoma using both maximum parsimony and maximum likelihood-based Bayesian methods. Our Bayesian and parsimony reconstructions differ in significant ways, but we show that our parsimony analysis may be influenced by long-branch attraction. Furthermore, our estimate of Neotoma phylogeny remains consistent across various data partitioning strategies in the Bayesian analyses. Using ancestral state reconstruction, we find support for the monophyly of taxa that possess the relatively rare genital form. However, we also find support for the independent evolution of the common genital form and discuss possible underlying developmental shifts that may have contributed to our observed patterns of morphological evolution.