The rapid spread of invasive Eurasian Collared Doves Streptopelia decaocto in the continental USA follows human‐altered habitats

Understanding factors related to the range expansion trajectory of a successful invasive species may provide insights into environmental variables that favour additional expansion or guide monitoring and survey efforts for this and other invasive species. We examined the relationship of presence and abundance of Eurasian Collared Doves Streptopelia decaocto to environmental factors using recent data from the North American Breeding Bird Survey to understand factors influencing its expansion into the continental USA. A zero‐inflated Poisson (ZIP) model was used to account for excess zero observations because this species was not observed on the majority of survey routes, despite its large geographical range. Model fit was improved when we included environmental covariates as compared with the null model, which only included distance from the route where this species was first observed. Probability of zero count was positively related to the distance from the first route and road density and was inversely related to minimum temperature and distance to coast. Abundance of the species was positively related to road density and was inversely related to annual precipitation and distance to coast. Random intercept by land‐cover type also improved model fit. Model fit was improved with the ZIP model over the standard Poisson model, suggesting that presence and abundance of this species are characterized by different environmental factors. However, overall low accuracy of model‐predicted presence/absence and abundance with the independent validation dataset may indicate either that there are other explanatory factors or that there is great uncertainty in the species’ colonization process. Our large‐scale study provides additional evidence that the range expansion of this species tends to follow human‐altered landscapes such as road and agricultural areas as well as responding to general geographical features such as coastlines or thermal clines. Such patterns may hold true for other invasive species and may provide guidelines for monitoring and assessment activities in other invasive taxa.     

Multiple refugia and barriers explain the phylogeography of the Valais shrew,Sorex antinorii (Mammalia: Soricomorpha)

The aim of the present study was to investigate the genetic structure of the Valais shrew (Sorex antinorii) by a combined phylogeographical and landscape genetic approach, and thereby to infer the locations of glacial refugia and establish the influence of geographical barriers. We sequenced part of the mitochondrial cytochrome b (cyt b) gene of 179 individuals of S. antinorii sampled across the entire species' range. Six specimens attributed to S. arunchi were included in the analysis. The phylogeographical pattern was assessed by Bayesian molecular phylogenetic reconstruction, population genetic analyses, and a species distribution modelling (SDM)‐based hindcasting approach. We also used landscape genetics (including isolation‐by‐resistance) to infer the determinants of current intra‐specific genetic structure. The phylogeographical analysis revealed shallow divergence among haplotypes and no clear substructure within S. antinorii. The starlike structure of the median‐joining network is consistent with population expansion from a single refugium, probably located in the Apennines. Long branches observed on the same network also suggest that another refugium may have existed in the north‐eastern part of Italy. This result is consistent with SDM, which also suggests several habitable areas for S. antinorii in the Italian peninsula during the LGM. Therefore S. antinorii appears to have occupied disconnected glacial refugia in the Italian peninsula, supporting previous data for other species showing multiple refugia within southern refugial areas. By coupling genetic analyses and SDM, we were able to infer how past climatic suitability contributed to genetic divergence of populations. The genetic differentiation shown in the present study does not support the specific status of S. arunchi. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 864–880.     

Osmoregulation in Crocodilians

Recent crocodilians live primarily in freshwater habitats. Howevertwo species (Crocodylus acutus and C. porosus) are estuarinespecialists; two others (C. niloticus and C. johnstoni) thatare primarily found in fresh water, have estuarine populations.Routes of uptake of water and sodium include drinking, feedingand associated incidental drinking, and integumental and buccaldiffusion. Routes of loss include faeces-cloacal fluid, lingualsalt glands, integumental and buccal diffusion, and respiratoryloss. The least understood route of salt and water exchangeis that of the oral and buccal epithelia, which are much morepermeable to water and sodium than the general integument. Thefreshwater alligator (Alligator mississippiensis) osmoregulatesin a manner typical for an amphibious reptile. Body sodium turnoveris low and the general integument is quite low in permeabilityto sodium. Water turnover is more rapid (in terms of molar exchange)but still relatively low for an aquatic reptile. Most waterexchange occurs across the integument and buccal epithelia.The presence of lingual salt glands in freshwater crocodiliansremains enigmatic, as does the failure of these exocrine glandsin estuarine species to respond to saline loading. Secretiondoes occur after injection of the parasympathetic stimulantmethacholine chloride. The "salt water crocodile" (C. porosus)possesses a suite of osmoregulatory adaptations similar to thosefound in other estuarine reptiles. Water and sodium balanceare maintained primarily by an extremely low general permeabilityto sodium, by economies in water loss, and by excretion of excesssodium by the lingual salt glands. Further work is needed toexamine newly hatched C. porosus, and the possibility of ontogeneticchange in lingual gland function in C. acutus. The importanceof incidental drinking of sea water during feeding (recentlydiscovered in turtles) needs to be evaluated in crocodilians.The use of osmoregulatory data in interpretation of the evolutionaryhistory of the genus Crocodylus needs to be viewed with caution.The hypothesis that all species of Crocodylus originated fromthe transoceanic migration of a saline-tolerant form may notbe the most parsimonious explanation.