Stéphanie Iserbyt

The remarkable diversity of bumblebees (Hymenoptera: Apidae: Bombus) in the Eyne Valley (France, Pyrénées-Orientales)

Abstract Despite its small area (20.18 km2), the Eyne Valley, (France, E. Pyrenees) is known to be a place of great faunistic and floristic diversity. The authors have studied the bumblebee fauna of the valley for six years, gathering more than 5000 detailed observations. They observed 33 species, of the 46 living in continental France. For each species, the distribution and ecological preferences (altitude, vegetation type, CORINE biotopes, floral choices) were recorded. Floral resources may be the most important ecological factor. The altitude, the abundance, the diversity of food plants, and the heterogeneity of habitats seem to explain the survival and the coexistence of this great number of species of bumblebees with various ecological affinities.

The effect of climatic variation on abundance and diversity of bumblebees: a ten years survey in a mountain hotspot

Abstract Even if climates play an evident role in the bumblebees distribution, at the present time, no research has been performed to test whether climatic parameters actually affect their abundance and diversity. For more than one decade (1999–2009), we monitored the bumblebee fauna of a mountain hotspot in the Eastern Pyrenees. We sampled each year, in July, the same hayfield habitat, resulting in the sampling of 28 species. We computed the correlation of the yearly abundance of the main species with several climatic parameters concerning temperature and precipitation. We separated the parameters measured during the bumblebee solitary phase and those measured during their social phase. Bumblebee fauna composition varied significantly over years. In the 13 species considered, the abundance of 9 was correlated with at least one climatic parameter. The lowest abundance of bumblebees was correlated with hot and dry conditions during the month of August the year before sampling (the nuptial time of the founders). The highest overall abundance of bumblebees was observed during the social phase in the rainy months. Across years, climatic parameters seem to have strongly affected the composition of bumblebee fauna. Our results seem to indicate that hot and dry weather represent serious threat for most bumblebee species. The potential effects of Global Warming are discussed: they may cause a severe reduction of the mountain bumblebee diversity.

The Bumblebees Scarcity Syndrome: Are heat waves leading to local extinctions of bumblebees (Hymenoptera: Apidae: Bombus)?

Abstract It is now well known that many bumblebee species are threatened in Europe and in N. America. Various hypotheses have been proposed to explain this regression. Some of the hypothetical factors act at a continental level, as the general restructuration of the agriculture toward the use of synthetic nitrogen fertilisation, in place of leguminous crops. The landscape fragmentation is typically a local factor the fusion of which also leads to large-scale effects. Since 2002, we observed a great number of situations where local droughts and heat waves occurred in France, UK, Scandinavia, Turkey, leading to very strong local reductions of the bumblebee’s fauna. We observed so many local cases in 2007–2009 that we could hypothesise that a merger of these local effects could lead to a new general threat. As they are the most exposed to heat waves, the species with a late (summer) phenology should be the most sensitive to this risk.

Révision des Xylocopinae (Hymenoptera : Apidae) de France et de Belgique

Résumé Cette publication présente les résultats d’une étude de 6.263 spécimens de Xylocopinae récoltés en France métropolitaine (France continentale et Corse) et en Belgique et qui proviennent de récoltes personnelles et de 63 institutions et collections privées. Les Xylocopinae de France sont représentées par 11 espèces du genre Ceratina et 4 espèces du genre Xylocopa. Seules deux de ces espèces sont présentes en Belgique : Xylocopa violacea (L.) et Ceratina cyanea (Kirby). Un nouveau sous-genre pour le genre Ceratina est décrit : Dalyatina n. subg. Il comporte l’espèce méditerranéenne Ceratina parvula Smith présente en France, ainsi que six autres espèces d’Afrique subsaharienne. Pour chaque genre, sous-genre et espèce, les auteurs fournissent une diagnose, une diagnose différentielle, la liste des fleurs visitées, la liste des sites de nidification, la carte de distribution en France métropolitaine, un diagramme phénologique et une clé d’identifi cation des genres, sous-genres et espèces. La systématique, la biogéographie, l’écologie et le sexe ratio des espèces sont présentés et discutés. Les Xylocopinae apparaissent comme très largement polylectiques mais montrent une très nette affinité envers les Lamiaceae, les Asteraceae Cardueae et, pour le genre Xylocopa, envers les Fabaceae. Toutes les espèces présentent une phénologie estivale qui s’étend d’avril à septembre. Le sexe-ratio de la plupart des espèces est biaisé vers les femelles. Aucun mâle de C. parvula, pour 120 femelles, n’a été observé ce qui suggère que, en France du moins, l’espèce pourrait se reproduire par parthénogenèse thélytoque comme c’est le cas de C. dallatorreana Friese. La publication comprend 62 dessins au trait, 18 photos au microscope électronique à balayage, 17 cartes, 14 graphiques de phénologie, une liste de 232 espèces de fleurs visitées par les Xylocopinae, dont 176 observations originales, et 171 références.

La faune des bourdons (Hymenoptera : Apidae) du Parc National des Pyrénées occidentales et des zones adjacentes

Résumé Les bourdons constituent l’un des groupes de pollinisateurs les plus importants dans les écosystèmes montagnards. Cependant, la faune des bourdons du Parc National des Pyrénées occidentales (PNPO) est encore peu connue. Pendant trois ans, la faune des bourdons du Parc National des Pyrénées occidentales a fait l’objet d’une surveillance. Les inventaires effectués en juillet- août 2002, 2003 et 2005 ont permis l’observation de 5889 spécimens de bourdons de 29 espèces. Si l’on tient compte des observations des cinquante dernières années, la diversité spécifique du parc s’élève à 30 espèces de bourdons. Une telle diversité spécifique est remarquable et comparable à celle observée dans d’autres secteurs du massif pyrénéen. La faible différence entre les faunes du Parc et des réserves naturelles d’Eyne et de Nohèdes (Pyrénées-Orientales) rend compte du caractère exceptionnellement diversifié de la faune des bourdons du massif pyrénéen en général.

Long-term changes in the species composition and distribution of Bombini (Apidae) in Cracow since the mid 1850s

Abstract Current distribution of bumblebee species in Cracow was studied in 2000–2003 in 23 atlas squares. The results were compared with historical data available for last 150 years, including published materials and museum collections. A total 28 bumblebee species were recorded throughout that period. Among them, 11 species are currently threatened in the study area. There were stated three tendencies among the studied bumblebee species. After 1850, 10 species were strongly regressing (withdrew from the Cracow area altogether or range contraction); further 11 species were more or less stable in their area; the next 6 species were strongly expanding in Cracow. 6 species were stated as a new for Cracow, including 2 species recorded between 1901–1972 and 4 between 1973–2003. Negative population tendencies by the Bombini in the Cracow area were the result of both natural and anthropogenic factors. Species protection and conservation of the most valuable areas as nature reserves are expected to prevent further decrease of bumblebees in the Cracow area.

High-resolution distribution of bumblebees (Bombus spp.) in a mountain area marked by agricultural decline

Summary Since the 1980s, bumblebee species have declined in Europe, partly because of agricultural intensification. Yet little is known about the potential consequences of agricultural decline on bumblebees. In most mountainous areas, agricultural decline from rural exodus is acute and alters landscapes as much as intensive farming. Our study aims at providing a quantitative assessment of agricultural decline through its impact on landscapes, and at characterising bumblebee assemblages associated with land-use types of mountain regions. The studied area (6.2 km2) belongs to the Eyne’s valley in the French Pyrenees, known to host the exceptional number of 33 bumblebee species of the 45 found in continental France. We compare aerial photographs from 1953 and 2000 to quantify agricultural decline. We cross a bumblebee database (2849 observations) with land-use types interpreted from aerial photographs from 2000. Comparison of land-use maps from 1953 and 2000 reveals a strong progression of woodland and urbanised areas, and a decline of agricultural land (pastures and crops), except for hayfields. Spatial correlations between low altitude agro-pastoral structure and the occurrence of bumblebee species shows that bumblebee specific richness is highest in agro-pastoral land-uses (pastures and hayfields) and in the ski area, and poorest in woodland and urbanised areas. Urbanisation and agricultural decline, through increased woodland areas, could lead to a loss of bumblebee diversity in the future. To preserve high bumblebee richness, it is crucial to design measures to maintain open land habitats and the landscape’s spatial heterogeneity through agro-pastoral practices.