Thermal refugia and the survival of species in changing environments: new evidence from a nationally extinct freshwater fish.

Variation in global climate during the Quaternary has helped shape current species distributions. The stenohaline fish fauna of the British Isles is generally thought to have colonised eastern England via a landbridge following the last glacial maximum. This theory is investigated using the nationally extinct burbot, Lota lota, as a model species. Samples were collected from 15 museum specimens of known English provenance and analysed for differences in the mitochondrial DNA control region. The DNA analysis produced eight sequences of 270 base pairs, with one sample reaching 420 base pairs in length. Genetic analysis suggests the extinct English population of the burbot was a distinct lineage, differing from those previously described from across the species’ global distribution. Despite this, network analysis suggests that the English lineage is closely related to populations in western Europe, supporting colonisation via a postglacial landbridge. The rate of genetic divergence suggests that the timing of L. lota's colonisation of English rivers was prior to the last glacial maximum. Lota lota appears to have survived the last glacial maximum in refugia within the British Isles. This study adds to the evidence for a British freshwater refugia and furthers our understanding of the colonisation history of British freshwater fishes. These results also provide valuable information for conservation strategies for L. lota indicating the western European clade as most genetically appropriate for potential future reintroductions to English rivers.     

Influence of roadways on patterns of mortality and flight behavior of adult dragonflies near wetland areas

The relatively low population size and long adult lifespan of dragonflies (Odonata, Anisoptera) makes them one of the few non-vertebrate groups likely to be impacted by direct roadway mortality. We studied adult dragonfly mortality and behavior associated with roadways for a number of species. Daily mortality rates for dragonflies were estimated from standardized surveys along predetermined lengths of roads. Relative abundance and flight behavior around and across roadways, a potentially important mortality factor, was determined from timed roadside observations. Observed flight behavior provided no evidence that roads act as significant barriers to dispersal for adult dragonflies. Estimated mean number killed ranged from 2 to 35 dragonflies/km/day. Species varied greatly in their susceptibility to motor vehicles. Two species (Plathemis lydia and Libellula luctuosa) made up more than 70% of the dead dragonflies collected, but only represented 14% and 31% of live dragonflies observed, respectively. The relatively low flight heights of these two species over roads (typically under 2 m) may explain their susceptibility; however, another common species (Tramea lacerata) also exhibited low flight height but did not experience high mortality, possibly because of its increased flight agility. Large numbers of adult dragonflies were killed over the entire flight season by motor vehicle collisions, exhibiting the need for assessing the long-term impact of roadway mortality on dragonfly population dynamics.     

Effect of cyclophosphamide immunosuppression on the immunity of turkeys to viral rhinotracheitis.

Turkey poults, free of antibodies to turkey rhinotracheitis (TRT) virus were treated with cyclophosphamide on days 1, 2 and 3 after hatching and vaccinated by eyedrop when 10 days old with a Vero cell-attenuated preparation of TRT virus. No ELISA antibodies to TRT virus developed in the sera of these poults but they were as resistant to virulent virus challenge 21 days later as vaccinated groups which were not cyclophosphamide-treated but produced humoral antibodies. Following challenge with virulent virus at 31 days old cyclophosphamide-treated unvaccinated poults developed a more severe clinical response than untreated birds and had higher virus titres in tracheal swabs. The findings show that the respiratory tract of turkeys may be resistant to TRT despite the absence of ELISA antibodies in the serum.