The use of demersal trawling discards as a food source for two scavenging seabird species:a case study of an eastern Mediterranean oligotrophic marine ecosystem

Background: The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Medi?terranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.Methods: On?board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli's Shearwater(Calonectris diomedea) and the Yellow?legged Gull(Larus michahellis).Results: A total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli's Shearwaters and 1210 were Yellow?legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; how?ever, they appeared to avoid poisonous species and/or large?sized fish. Yellow?legged Gulls displayed kleptoparasitic behaviour on Scopoli's Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.Conclusions: Considering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understand?ing of the potential impacts of the discards reform bill on seabirds.

No treeline shift despite climate change over the last 70 years

Background:The recent rise in temperature and shifting precipitation regimes threaten ecosystems around the globe to different degrees.Treelines are expected to respond to climate warming by shifting to higher elevations,but it is unclear whether they can track temperature changes.Here,we integrated high-resolution aerial imagery with local climatic and topographic characteristics to study the treeline dynamic from 1945 to 2015 on the semiarid Mediterranean island of Crete,Greece.Results:During the study period,the mean annual temperature at the treeline increased by 0.81℃,while the average precipitation decreased by 170 mm.The treeline is characterized by a diffuse form,with trees growing on steep limestone slopes(>50°)and shallow soils.Moreover,the treeline elevation decreases with increasing distance from the coast and with aspect(south>north).Yet,we found no shift in the treeline over the past 70 years,despite an increase in temperature in all four study sites.However,the treeline elevation correlated strongly with topographic exposure to wind(R^(2)=0.74,p<0.001).Therefore,the temporal lag in treeline response to warming could be explained by a combination of topographic and microclimatic factors,such as the absence of a shelter effect and a decrease in moisture.Conclusion:Although there was no treeline shift over the last 70 years,climate change has already started shifting the treeline altitudinal optimum.Consequently,the lack of climate-mediated migration at the treeline should raise concerns about the threats posed by warming,such as drought damages,and wildfire,especially in the Mediterranean region.Therefore,conservation management should discuss options and needs to support adaptive management.

Genomic and mitochondrial evidence of ancient isolations and extreme introgression in the four-lined snake

Comparing mitochondrial and genomic phylogenies is an essential tool for investigating speciation processes,because each genome carries different inheritance properties and evolutionary characteristics.Furthermore,mitonuclear discordance may arise from ecological adaptation,historic isolation,population size changes,and sex-biased dispersal.Closely related taxa are expected to experience gene flow;however,this may not be true for insular populations or populations isolated in refugia.The four-lined snake Elaphe quatuorlineata has a fragmented distribution,separating populations of the Italian and Balkan Peninsulas,whereas several insular Aegean populations of significantly smaller body size(Cyclades island group and Skyros Island,Greece)are currently considered distinct subspecies.We constructed the species-tree phylogeny of this species utilizing genome-wide single nucleotide polymorphisms and a gene-tree based on complete cytochrome b sequences,aiming to detect convergence and discrepancies between biparentally and maternally inherited genomes.Population structuring,phylogenetic patterns and migration events among geographically defined lineages supported our hypothesis of isolation in multiple sub-refugia.Where biogeographical barriers did not restrict subsequent dispersal,extensive genetic exchange occurred between mainland Balkan populations.This process has led to the mitochondrial sweep of an ancestral mitolineage that survived only in peripheral(East Greece)and insular populations(North Cyclades and Skyros).The Central Cyclades represent an ancient lineage for both molecular markers that emerged almost 3.3 Mya.Considering their distinct morphology,insular E.quatuorlineata populations should be the future focus of an extensive sampling,especially since the mitonuclear discordance observed in this species could be related to ecological adaptations,such as the island-dwarfism phenomenon.