Colonizations cause diversification of host preferences: a mechanism explaining increased generalization at range boundaries expanding under climate change

International audienceAs species' poleward range limits expand under climate change, generalists are expected to be better colonists than specialists, extending their ranges faster. This effect of specialization on range shifts has been shown, but so has the reverse cause–effect: in a global meta-analysis of butterfly diets, it was range expansions themselves that caused increases in population-level diet breadth. What could drive this unexpected process? We provide a novel behavioral mechanism by showing that, in a butterfly with extensive ecotypic variation, Edith's checkerspot, diet breadths increased after colonization events as diversification of individual host preferences pulled novel hosts into population diets. Subsequently, populations that persisted reverted toward monophagy. We draw together three lines of evidence from long-term studies of 15 independently evolving populations. First, direct observations showed a significant increase in specialization across decades: in recent censuses, eight populations used fewer host genera than in the 1980s while none used more. Second, behavioral preference-testing experiments showed that extinctions and recolonizations at two sites were followed, at first by diversification of heritable preference ranks and increases in diet breadth, and subsequently by homogenization of preferences and contractions of diet breadth. Third, we found a significant negative association in the 1980s between population-level diet breadth and genetic diversity. Populations with fewer mtDNA haplotypes had broader diets, extending to 3–4 host genera, while those with higher haplotype diversity were more specialized. We infer that diet breadth had increased in younger, recently colonized populations. Preference diversification after colonization events, whether caused by (cryptic) host shifts or by release of cryptic genetic variation after population bottlenecks, provides a mechanism for known effects of range shifts on diet specialization. Our results explain how colonizations at expanding range margins have increased population-level diet breadths, and predict that increasing specialization should accompany population persistence as current range edges become range interiors

Cold adaptation across the elevation gradient in an alpine butterfly species complex

International audience1. Temperature acts as a major factor on the timing of activity and behaviour in butterflies, and it might represent a key driver of butterfly diversification along elevation gradients. Under this hypothesis, local adaptation should be found along the elevation gradient, with butterflies from high elevation populations able to remain active at lower ambient temperature than those from low elevation.2. The warming‐up rate and the thoracic temperature at take‐off of 123 individuals of the Alpine butterfly species complex Coenonympha arcania – C. macromma – C. gardetta were recorded in controlled conditions.3. Warming‐up rate increased with elevation in C. arcania: high‐elevation males of C. arcania were able to warm up more quickly compared to low‐elevation ones.4. High‐elevation C. gardetta had a darker underwing pattern than low‐elevation ones. This high‐elevation species was significantly smaller (lower weight and wing surface) than the two other species and had a faster warming‐up rate.5. This study's results suggest that the ability to warm up quickly and to take flight at a high body temperature evolved adaptively in the high‐altitude C. gardetta and that low temperature at high altitude may explain the absence of C. arcania, while the hybrid nature of C. macromma is probably the explanation of its elevation overlap with both the other species and its local replacement of C. gardetta

The ocular disease of Aristodemus and Eurytus 480 BC: diagnostic considerations.

Item does not contain fulltextOBJECTIVE: In the historic description of Herodotus on the battle of Thermopylae at 480 BC two formerly healthy warriors suffer from "ophthalmia". The purpose of this study is to assess the possible aetiologies of this disease. DESIGN: We studied Herodotus' description in translation and offer a differential diagnosis. RESULTS: From the text we deduced that the "ophthalmia" was a condition in two physically fit males with a bilateral decreased or distorted vision, lasting longer than an hour, with an acute or subacute onset in Ancient Greece. The condition ultimately went into remission in one of the two patients, whereas the other subject deceased in combat not long after the onset of the disease, still suffering from the disease. The differential diagnosis consists of (1) anticholinergic syndrome secondary to an intoxication with the berries of the plant Atropa belladonna, (2) automutilation and (3) psychogenic loss of visual acuity. CONCLUSION: It is impossible to assess the ultimate cause of the "opthalmia" after 2500 years, but we suggest the anticholinergic syndrome by intoxication with Atropa belladonna is the most likely.1 april 201

Skipper impoverishment on large West Mediterranean islands (Lepidoptera Hesperioidea): deterministic, historical and stochastic factors

Biogeographical analyses are applied to skipper (Hesperioidea) presence/absence data from the Western Mediterranean mainland and the three largest islands (Sardinia, Corsica and Sicily) in order to identify potential conservation issues. The analyses performed on species, both collectively and individually, indicate that regional species richness and occurrence in the Mediterranean zone are largely predicted by latitude and area but that islands have impoverished faunas. Several species, predicted to be present on these islands from logistic regression of their continental distributions, are actually absent. The number of species predicted to be present from logistic regression analyses for each island, closely matched the number of species predicted to occur in regional-focused multiple regression analysis. This suggests that missing species have been identified. When compared with species that occur in Sicily and Corsica, the missing species are shown to differ for ecological traits, mainly those linked to altitudinal tolerance. No ecological distinctions were disclosed for Sardinian skippers suggesting a mainly stochastic colonisation. These results, and those from an analogous study carried out on Papilionoidea, point to Hesperioidea having (i) overall more impoverished faunas on islands and (ii) being subject to stochastic or historical colonisation events more than Papilionoidea. Species not predicted to occur on islands based on their mainland distributions and ecological traits, are foci for conservation attention. However, as many species becoming extinct on the islands may be irreplaceable, all species, in particular the Sardinian ones, deserve to be conserved