Degree Of Geographic Overlap Research Articles

Fine‐scale social and genetic structure of common bottlenose dolphins (Tursiops truncatus) in the Barataria Basin, Louisiana, USA

Abstract The Barataria Bay Estuarine System (BBES) Stock of common bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico has been a focus of extensive research as a result of the Barataria Basin, Louisiana being one of the most heavily oiled estuaries following the Deepwater Horizon oil spill. The goal of this study was to build upon previous research to better understand social and genetic structure of BBES dolphins. Photo‐identification data from 2010–2019 were analysed with SOCPROG to identify dolphin social clusters. Genetic analyses were conducted on samples obtained during remote biopsy surveys and health assessments (2010–2018) to assess if identified social clusters were congruent with genetic clustering results, and to evaluate relatedness and gene flow within and between social and genetic clusters. Spatial analyses of the cumulative photo‐identification sighting histories from each cluster were also used to determine their geographic range and degree of overlap within the Barataria Basin. Social analyses identified four distinct clusters with some degree of geographic overlap and similar utilization distributions as the three identified genetic clusters. Dolphins in the Barataria Basin were confirmed to be genetically differentiated from those in adjacent coastal waters. In general, genetic analyses differentiate distinct dolphin communities established through long‐term (generational) preferential breeding behaviour. In contrast, social associations can be more fluid over the short‐term, may change in response to habitat or predator/prey changes, and strong associations can be formed between a mix of related and unrelated individuals. The combination of genetic and social methodologies is valuable for developing a better understanding of complex dolphin social interactions and provides unique insights into dolphin behaviour that can be important for developing effective management strategies.

The correspondence between environmental similarity and geographical sympatry in Uromastyx species

Abstract Estimating the realized and potential distribution of species has become a very active field of research with capacity to propose likely speciation mechanisms. Here, environmental variables and point locality data derived from several sources were used to examine the concordance between geographical distributions and environmental niches derived from occurrences for eleven species of the genus Uromastyx (Reptilia, Agamidae). Our results indicate that the degree of geographical overlap is definitively and statistically lower than the degree of environmental similarity. This reinforces the hypothesis that speciation process within the genus Uromastyx will be mainly based on geographical isolation. However, the environmental divergence among some groups of species cannot be excluded; high environmental distances can be obtained for some related species and the environmental gradient represented by two unique climatic variables allows discriminating some species among which an ecological or environmental segregation would be a plausible explanation.

Bioclimatic approach to assessing the potential impact of climate change on two flea beetle (Coleoptera: Chrysomelidae) species in Canada

AbstractBoth the striped flea beetle, Phyllotreta striolata (Fabricius), and crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), are invasive alien species to North America. In western Canada, they are the most significant insect pests of cruciferous (Brassicaceae) crops. Climate is the one of the most dominant factors regulating the geographic distribution and population density of most insect species. Recent bioclimatic simulation models of the two flea beetle species fostered a better understanding of how the two species responded to selected climate variables. They demonstrated that selected climate variables increased population densities and geographic range of the two species. General circulation model inputs were applied in this study to assess the impact of a changing climate on the response of P. cruciferae and P. striolata populations. Model output, using the climate change scenarios, predicted that both P. cruciferae and P. striolata populations will shift north in future climates and the degree of geographic overlap between these two species will be greater than for current climate. This suggests that the two species could potentially cause economic losses over an expanded area in the future.

Spatial turnover in host-plant availability drives host-associated divergence in a South African leafhopper (Cephalelus uncinatus)

BackgroundThe evolution of reproductive isolation between herbivorous insect populations is often initiated by shifts to novel host-plants, a process that underlies some of the best examples of ecological speciation. However, it is not well understood why host-shifts occur. Arguably the most common hypothesis is that host-shifts occur in response to competition, while a less frequently invoked hypothesis is that herbivores adapt locally to geographic differences in potential host-plant communities. Here we investigate whether geographic variation in host-plant availability is likely to have driven host-shifts in restio leafhoppers. We studied local adaptation of a camouflaged restio leafhopper species, Cephalelus uncinatus, to host-plants in the Restionaceae (restios); a family of plants with exceptional diversity in the anomalously species-rich Cape Floristic Region (CFR). To determine whether C. uncinatus experiences heterogeneous host communities across its range, we first quantified the degree of geographic overlap between C. uncinatus and each of its associated host-plant species. Then we quantified trait divergence (host preference, body size and colour) for three pairs of C. uncinatus populations found on different host-plant species differing in their degree of spatial overlap. Spectral reflectance was modelled in bird visual space to investigate whether body colour divergence in C. uncinatus corresponds to leaf sheath colour differences between restio species as perceived by potential predators.ResultsWe demonstrate that C. uncinatus is forced to use different restio species in different regions because of turnover in available host species across its range. Comparisons between geographically separated populations were consistent with local adaptation: restio leafhoppers had preferences for local host-plants over alternative host-plants and matched local plants better in terms of size and colour.ConclusionsSpatial turnover in host-plant availability has likely facilitated host-shifts in C. uncinatus. Spatial turnover in host-plant availability may be an important driver of insect diversification in the CFR and globally.

Geographical distribution of pelagic decapod shrimp in the Atlantic Ocean.

Ninety-one species of pelagic decapod shrimp were identified in 938 midwater-trawl collections taken between 1963 and 1974 from the North and South Atlantic. Distributional maps are provided for the most frequently occurring species. Nighttime abundance of most species was greatest within the upper 200 m. Degree of geographical overlap was estimated using the geometric mean of the proportion of joint occurrences with a value ≥ 0.5 deemed significant. Geographical distributions tended to be unique, and only 31 species had values ≥ 0.5 with one or more other species. Species within genera and within phylogenetic subgroups of Sergia were generally parapatric or partially overlapping in distribution. Five geographical groupings of co-occurring species across genera were identified: Subpolar-Temperate, Southern Hemisphere, Central, Tropical, Eastern Tropical and Western Tropical. The two species of the Southern Hemisphere group are circumpolar at temperate latitudes. The 12 species of the Central group occurred throughout the subtropical and tropical North and South Atlantic. The eight species of the Tropical group occurred broadly across the equatorial Atlantic and Caribbean with ranges usually extending into the Gulf of Mexico and northward in the Gulf Stream. The two species of the Western Tropical group occurred most often in the western tropics, but there were scattered occurrences at subtropical latitudes. The four species of the Eastern Tropical group were endemic to the Mauritanian Upwelling and the Angola-Benguela Frontal zones off western Africa. Two of the three species in the Subpolar-Temperate group had bipolar distributions, and all three occurred in the Mediterranean and in the Mauritanian Upwelling zone. Most Central, Tropical and Western Tropical species were present in the in the Gulf of Mexico. The 10 species from the Mediterranean were a mixture of Subpolar-Temperate, Central and benthopelagic species. Patterns of distribution in Atlantic pelagic decapods closely parallel those of other pelagic taxa, but myctophid fishes from the same collections appear to partition subtropical regions more finely.

Identificação das espécies brasileiras de Akodon (Rodentia: Cricetidae: Sigmodontinae) através da microestrutura dos pelos

No Brasil há 10 espécies de Akodon Meyen, 1833 e a maioria apresenta algum grau de sobreposição geográfica havendo inclusive registros de simpatia. A identificação das espécies é difícil e pode ser feita pela análise da estrutura morfológica de pelos. Assim, para a identificação da microestrutura de pelos de nove espécies brasileiras de Akodon, foram utilizados pelos-guardas primários de amostras de coleções zoológicas. Foi adotado o método de análise das escamas cuticulares e da medula. O padrão de cutícula para todas as espécies foi folidáceo estreito. Já para a medula foram reconhecidos três padrões básicos como multisseriada alveolar, multisseriada listrada e misto de alveolar e listrada. Akodon cursor é a única espécie com predomínio de quatro fileiras sendo que exemplares 2n = 14 e 2n = 15 apresentam medula alveolar e o 2n = 16, medula listrada e células longilíneas. Para Akodon paranaensis e A. lindberghi a medula se alterna entre três e quatro fileiras. As demais espécies apresentam três fileiras. Akodon mystax apresenta um maior espaçamento entre as células. Akodon reigi possui o setor intermediário com fileiras ovaladas e bem ligadas e Akodon toba tem as células da fileira central variando com uma e duas células alveolares pequenas. No padrão listrado, Akodon montensis apresenta espaço intercelular mais estreito em relação à espessura da célula. No padrão misto, Akodon azarae apresenta células com contorno evidente, já Akodon serrensis as células apresentam formato irregular. Assim, o uso da microestrutura dos pelos como ferramenta para a identificação das espécies de Akodon mostrou-se perfeitamente viável.

Phylogenetics and predictive distribution modeling provide insights into the geographic divergence of Eriosyce subgen. Neoporteria (Cactaceae)

The classification of Eriosyce subgenus Neoporteria (“subsection” in the sense of Kattermann) and the role of allopatry/sympatry in the diversification of the group were studied by use of cladistic and predictive distribution modeling methods. We reconstructed the phylogenetic relationships of subgenus Neoporteria by analyzing 38 morphological characters and DNA sequences from two chloroplast regions of 21 taxa from the Chilean subsections of Eriosyce using a Bayesian and maximum likelihood phylogenetic framework. Also, we attempted to find out if the divergence between the sister taxa in the Neoporteria group had been caused by allopatric or sympatric mechanisms. The morphology-based analysis placed E. chilensis basal within the Neoporteria clade and suggested a further broadening of the group by including E. taltalensis var. taltalensis, formerly considered a member of subsection Horridocactus. However, the combined DNA data placed E. sociabilis and E. taltalensis var. taltalensis within the Horridocactus clade, and placed E. chilensis with E. subgibbosa var. litoralis. The broad concept of E. subgibbosa sensu Kattermann (comprising seven infraspecific taxa), was rejected by our combined molecular results. Finally, our results corroborated changes in subsection Neoporteria proposed by various authors and suggested further modifications within Neoporteria. The analyses of the degree of geographic overlap of the predicted distributions indicated null overlap between the sister taxa, and one probable hybrid origin of E. chilensis, indicating that evolutionary divergence is mainly caused by an allopatric process associated with climatic tolerance.