Simulating an invasion: unsealed water storage (rainwater tanks) and urban block design facilitate the spread of the dengue fever mosquito,Aedes aegypti,in Brisbane,Australia

Aedes aegypti (Linnaeus) was once highly prevalent across eastern Australia, resulting in epidemics of dengue fever. Drought conditions have led to a rapid rise in semi-permanent, urban water storage containers called rainwater tanks known to be critical larval habitat for the species. The presence of these larval habitats has increased the risk of establishment of highly urbanised, invasive mosquito vectors such as Ae. aegypti. Here we use a spatially explicit network model to examine the role that unsealed rainwater tanks may play in population connectivity of an Ae. aegypti invasion in suburbs of Brisbane, a major Australian city. We characterise movement between rainwater tanks as a diffusion-like process, limited by a maximum distance of movement, average life expectancy, and a probability that Ae. aegypti will cross wide open spaces such as roads. The simulation model was run against a number of scenarios that examined population spread through the rainwater tank network based on non-compliance rates of tanks (unsealed or sealed) and road grids. We show that Ae. aegypti tank infestation and population spread was greatest in areas of high tank density and road lengths were shortest e.g. cul-de-sacs. Rainwater tank non-compliance rates of over 30% show increased connectivity when compared to less than 10%, suggesting rainwater tanks non-compliance should be maintained under this level to minimize the spread of an invading Ae. aegypti population. These results presented as risk maps of Ae. aegypti spread across Brisbane, can assist health and government authorities on where to optimally target rainwater tank surveillance and educational activities.

     

Estrous cycle-dependent changes in the expression of aromatic hydrocarbon receptor (AHR) and AHR-nuclear translocator (ARNT) mRNAs in the rat ovary and liver

The aromatic hydrocarbon receptor (AHR) and AHR nuclear translocator protein (ARNT) mediate the toxic effects of a wide variety of halogenated and polycyclic aromatic hydrocarbons. While it can be assumed that AHR has an endogenous function, its role in reproduction is currently undefined. The present study seeks to examine the regulation of AHR and ARNT mRNAs in liver and ovarian tissues across the rat estrous cycle. Message for hepatic AHR was increased significantly on the morning of proestrus, and decreased dramatically by the evening of proestrus; while hepatic ARNT mRNA was significantly decreased between diestrus and the morning of proestrus, and between the evening of proestrus and the morning of estrus. Ovarian AHR mRNA was unchanged from diestrus to proestrus, and was decreased on the evening of proestrus. Changes in the expression of ARNT mRNA mirrored changes in the liver. To assess interaction between the AHR- and estrogen-receptor (ER)-signaling pathways and to test the hypothesis that estrogen regulates AHR mRNA, 25-day-old female rats were injected with either 17beta-estradiol, the ER antagonist ICI 182 780, or with vehicle, and hepatic AHR mRNA was measured. Treatment with estrogen or the estrogen antagonist did not alter the abundance of AHR mRNA in the liver. These data suggest that while estrogen may not be the key regulator of AHR mRNA expression, a factor associated with the rat reproductive cycle may be important in regulating the expression of both the AHR and ARNT genes in the ovary and liver.     

Genetic and morphological differentiation in Populus nigra L.: isolation by colonization or isolation by adaptation?

Identifying processes underlying the genetic and morphological differences among populations is a central question of evolutionary biology. Forest trees typically contain high levels of neutral genetic variation, and genetic differences are often correlated with geographic distance between populations [isolation by distance (IBD)] or are due to historic vicariance events [isolation by colonization (IBC)]. In contrast, morphological differences are largely due to local adaptation. Here, we examined genetic (microsatellite) and morphological (from a common garden experiment) variation in Populus nigra L., European black poplar, collected from 13 sites across western Europe and grown in a common garden in Belgium. Significant genetic differentiation was observed, with populations from France displaying greater admixture than the distinct Spanish and central European gene pools, consistent with previously described glacial refugia (IBC). Many quantitative traits displayed a bimodal distribution, approximately corresponding to small‐leaf and large‐leaf ecotypes. Examination of nine climatic variables revealed the sampling locations to have diverse climates, and although the correlation between morphological and climatic differences was significant, the pattern was not consistent with strict local adaptation. Partial Mantel tests based on multivariate summary statistics identified significant residual correlation in comparisons of small‐leaf to large‐leaf ecotypes, and within the small‐leaf samples, but not within large‐leaf ecotypes, indicating that variation within the small‐leaf morphotype in particular may be adaptive. Some small‐leaf populations experience climates very similar to those in large‐leaf sites. We conclude that adaptive differentiation and persistent IBC acted in combination to produce the genetic and morphological patterns observed in P. nigra.     

The Ichnogenus Undichna, With Examples From The Permian Of The Falkland Islands

Abundant, well-preserved and variable species of Undichna are described from the Permian of the Falkland Islands. The environment is considered to be non-marine and the traces are associated with turbidite and rhythmite deposits. There are strong similarities between the Undichna and other ichnogenera of the Falkland Islands and those of the Eastern Cape Province of South Africa, thus strengthening the view that the missing eastern end of the Permian Karoo Basin is present in the Falklands. Undichna binaU. insolentia occur associated within glacially influenced rhythmite and turbidite facies of a non-marine basin in the Cantera Formation, Camilla Creek, East Falkland. U. quina isp. nov. occurs on Sea Lion Island and is associated with thin (mm–cm scale) graded interbeds between thicker amalgamated sandstones in a sequence deposited by density currents derived from a delta feeding the same non-marine basin. The elements that comprise Undichna traces are (1) single sinusoidal grooves, (2) paired sinusoidal grooves, (3) broad shallow grooves, (4) repeated arcuate imprints, (5) irregular grooves, (6) striated brush-like imprints. A distinct, repeated morphology is only produced by a constant activity of the tracemaker (generally a fish). Irregular activity (e.g. acceleration, sharp turns) or current action produces non-constant morphology, lacking the defining regularity of the ichnogenus Undichna. Such irregular forms can frequently be identified as a modified expression of a described ichnospecies, but morphologically do not fall within the definition of the ichnospecies. It is suggested that rather than create new names they should be referred to as 'cf. Undichna isp.' (irregular form).     

Formation and composition of a graded estuarine shell bed

The surface bed of a mudflat in the Ythan Estuary, Aberdeenshire, consists of mud and sandy mud overlying broken-shell material, the whole bed being graded. Production of shell fragments by bird predation and their subsequent incorporation in the bed due to the activities of a burrowing fauna are considered. The graded bed represents a stable situation in the mudflat area. Diagenesis of shells within the bed varies with species, Mytillus being prone to disintegration into fine needles of carbonate.     

Mark-release-recapture of male Aedes aegypti (Diptera: Culicidae): Use of rhodamine B to estimate movement,mating and population parameters in preparation for an incompatible male program

Rapid advances in biological and digital support systems are revolutionizing the population control of invasive disease vectors such as Aedes aegypti. Methods such as the sterile and incompatible insect techniques (SIT/IIT) rely on modified males to seek out and successfully mate with females, and in doing so outcompete the wild male population for mates. Currently, these interventions most frequently infer mating success through area-wide population surveillance and estimates of mating competitiveness are rare. Furthermore, little is known about male Ae. aegypti behaviour and biology in field settings. In preparation for a large, community scale IIT program, we undertook a series of mark- release-recapture experiments using rhodamine B to mark male Ae. aegypti sperm and measure mating interactions with females. We also developed a Spatial and Temporally Evolving Isotropic Kernel (STEIK) framework to assist researchers to estimate the movement of individuals through space and time. Results showed that ~40% of wild females captured daily were unmated, suggesting interventions will need to release males multiple times per week to be effective at suppressing Ae. aegypti populations. Males moved rapidly through the landscape, particularly when released during the night. Although males moved further than what is typically observed in females of the species, survival was considerably lower. These unique insights improve our understanding of mating interactions in wild Ae. aegypti populations and lay the foundation for robust suppression strategies in the future.