ABSTRACT
Unravelling the history of range shifts is key for understanding past, current and future species distributions. Anthropogenic transport of species alters natural dispersal patterns and directly affects population connectivity. Studies have suggested that high levels of anthropogenic transport homogenize patterns of genetic differentiation and blur colonization pathways. However, empirical evidence of these effects remains elusive. We compared two range-shifting species (Microcosmus squamiger and Ciona robusta) to examine how anthropogenic transport affects our ability to reconstruct colonization pathways using genomic data. We first investigated shipping networks from the 18th century onwards, cross-referencing these with regions where the species have records to infer how each species has potentially been affected by different levels of anthropogenic transport. We then genotyped thousands of single-nucleotide polymorphisms from 280 M. squamiger and 190 C. robusta individuals collected across their extensive species' ranges and reconstructed colonization pathways. Differing levels of anthropogenic transport did not preclude the elucidation of population structure, though specific inferences of colonization pathways were difficult to discern in some of the considered scenario sets. We conclude that genomic data in combination with information of underlying introduction drivers provide key insights into the historic spread of range-shifting species. This article is part of the theme issue 'Species' ranges in the face of changing environments (part I)'.
Subject(s)
Ciona intestinalis , Genomics , Animals , HumansABSTRACT
The rate of biological invasions has strongly increased during the last decades, mostly due to the accelerated spread of species by increasing global trade and transport. Here, we combine the network of global cargo ship movements with port environmental conditions and biogeography to quantify the probability of new primary invasions through the release of ballast water. We find that invasion risks vary widely between coastal ecosystems and classify marine ecoregions according to their total invasion risk and the diversity of their invasion sources. Thereby, we identify high-risk invasion routes, hot spots of bioinvasion and major source regions from which bioinvasion is likely to occur. Our predictions agree with observations in the field and reveal that the invasion probability is highest for intermediate geographic distances between donor and recipient ports. Our findings suggest that network-based invasion models may serve as a basis for the development of effective, targeted bioinvasion management strategies.
Subject(s)
Ecosystem , Introduced Species , Models, Theoretical , Ships , Aquatic Organisms , Models, Biological , Probability , Risk Assessment/methods , Seasons , UncertaintyABSTRACT
In a randomized, double-blind cross-over study in 10 patients with intermittent claudication, 2 concentrations (6% and 10%) of a hydroxyethyl starch (HES) solution of mean molecular weight 200,000 and of substitution degree 0.62 were compared to a 10% low-molecular-weight dextran solution of mean molecular weight 400,000. In addition to several hemorheological parameters, the behavior of the tissue oxygen pressure directly in the ischemic lower leg muscles of patients with chronic arterial occlusive vascular disease (stage IIb) was examined. 500 ml of the solutions described above were infused over a period of 30 min. Parameters such as tissue oxygen pressure and flow properties of blood were determined before infusion, immediately upon terminating infusion and 30, 60, 90, 120 and 180 min thereafter. A reduction of hematocrit values and of whole blood viscosity was observed, which was most pronounced with the 10% solutions. The plasma viscosity increased significantly with both the 10% dextran solution as well as with the 10% HES solution. This behavior was less pronounced with the 6% solution. Measurement of the erythrocyte aggregation yielded an increase in values after infusion which was more significant for the 10% than for the 6% HES solution. The tissue oxygen pressure, as a measure of the tissue oxygen supply, remained more or less constant during hypervolemic hemodilution, despite reduced hematocrit values in the dextran group and in the 10% HES group.(ABSTRACT TRUNCATED AT 250 WORDS)
