Arctic shipping and polar seaways

Climate change in the Arctic triggered a series of discourses about the opening-up of a previously unreachable region. Navigation remains however difficult in the Arctic, transits are still very limited, as sea-ice still is a major constraint. How did the development policies of both the North West Passage and the Northern Sea Route unfold ? What are the recent trends in Arctic shipping ?

Host range and local parasite adaptation

Parasites may be expected to become locally adapted to their hosts. However, while many empirical studies have demonstrated l

Sex differences in mercury contamination of birds: Testing multiple hypotheses with meta-analysis

The sex of a bird can, in principle, affect exposure and accumulation of mercury. One conventional explanation for sex differences in mercury burden suggests female birds should have lower concentrations than conspecific males, because breeding females can depurate methylmercury to their eggs. However, sex differences in body burden of mercury among birds are not consistent. We used meta-analysis to synthesize 123 male-female comparisons of mercury burden from 50 studies. For breeding birds, males had higher concentrations of mercury than did females, supporting egg depuration as a mechanism. However, the percentage of female body mass represented by a clutch did not significantly predict the magnitude of the sex difference in mercury contamination, as predicted. Furthermore, whether species were semialtrical or altrical versus semiprecocial or precocial also did not explain sex differences in mercury burden. Foraging guild of a species did explain near significant variation in sex differences in mercury burden where piscivores and invertivores showed significant sex differences, but sex differences were not detected for carnivores, herbivores, insectivores, and omnivores. The magnitude and direction of sexual size dimorphism did not explain variation in sex differences in mercury burden among breeding birds. We reveal targeted research directions on mechanisms for sex differences in mercury and confirm that sex is important to consider for environmental risk assessments based on breeding birds

Species and sex biases in ectoparasitism of dragonflies by mites

An important problem in understanding the evolution of parasite host range is determining the extent to which parasite fitness varies among host species and the factors affecting that fitness variation. We present a detailed investigation on the patterns of host use and successful parasitism of two dragonfly species by the ectoparasitic water mite, Limnochares americana Lundblad. In our field surveys, we found both species biases and sex biases in parasitism by mites, which appear explained by differences in exposure. Differential habitat use by dragonflies helped explain male biases in parasitism in both host species, but was not useful in explaining species biases in parasitism. Species biases in parasitism may be explained by more subtle variation in habitat use not explored in this study, or perhaps by differences in timing of emergence, as we found for the two dragonfly species. Despite species differences in parasitism in nature, we found that mites attached equally successfully to both dragonfly species during experimental infestations. However, mites failed to engorge more often on the dragonfly species less often used as a host in nature. This host species also was more likely to have dead mites in natural infestations as compared to the other host species, which was more often and more heavily parasitized. Our results are consistent with previous research suggesting parasites are less successful on less often used hosts. Such research has implications for understanding determinants of host range for animal parasites

Data from: Invasion status and phylogenetic relatedness predict cost of heterospecific pollen receipt: implications for native biodiversity decline

Understanding the mechanisms by which invasive species affect native plants is a central challenge. Invasive plants have been shown to reduce pollinator visitation to natives and increase pollen quantity limitation. However, visitation and conspecific pollen delivery are only two components of the pollination process; post-pollination interactions on the stigma (heterospecific pollen [HP] receipt) could intensify pre-pollination responses to invasion. Here we used meta-analysis to test the hypotheses that invasive plants are more detrimental as HP donors than natives ones, and that HP donors that are closely related to the recipients have stronger effects on fruit and seed production compared to distantly related ones. Invasive HP donors reduced fruit and seed production of recipients to a greater degree than native ones, and this was more intense for HP donors closely related to natives. Related donors were more detrimental overall. Synthesis: These results suggest that the total effect of invasive plants on native plant reproductive success could be greater than what is inferred from visitation and conspecific pollen transfer alone. Furthermore, these results indicate that invasive species can reduce reproductive success of native species even if pollinator visitation rates remain unaltered. Thus, we highlight the need to evaluate pre- and post-pollination processes in order to fully understand the potential effects of invasive species on the reproductive success and maintenance of native plant populations