Bumblebee community homogenization after uphill shifts in montane areas of northern Spain

Abstract

Widespread alterations in species distribution and abundance as a result of global environmental change include upwards and polewards shifts driven by local extinctions in the south or at lower elevations and colonizations of newly available habitat elements in the north or at higher elevations. Although cumulative changes on patterns of community composition are also expected, studies following a community-level approach are still scarce. Here, we estimate changes in abundance and distribution of bumblebee (Bombus spp.) species over two decades along an elevational gradient to test whether these changes entailed concomitant alterations on patterns of community composition. Bumblebee species showed an overall trend to shift uphill their upper- or lower-elevational boundaries, resulting in narrower elevational ranges from one period to another, coincident with a regional warming of ca. 0.9 °C. Changes in elevational ranges were, however, mainly related to retractions of the lower limit of species distribution, rather than to variations in their upper elevational limit. Species turnover was associated with colonization and extinction events and also with variability in the relative abundance of short-, medium- and long-tongued species along the elevational gradient. Extinctions were especially relevant at medium elevations, while only communities at higher elevations had a positive net outcome between colonization and extinction events. The combination of these effects resulted in the homogenization of bumblebee assemblages, especially between medium and upper elevations. The changes reported in our study strongly match with predictions of global change driving elevational shifts in species distribution and provide the first evidence of elevational changes in bumblebees at both species and community level.

Climatic Risk and Distribution Atlas of European Bumblebees

“…Several alternative factors such as herbicides or helminthicides impacting other organism groups could also be a factor in bumblebee decline (Lumaret, 1986;Madsen et al, 1990;Colin & Belzunces, 1992;Vandame & Belzunces, 1998;Hayes et al, 2002;Mussen et al, 2004;Simon-Delso et al, 2014). At least one other factor is regarded as strongly affecting the bumblebee fauna: the changing climate Ploquin et al, 2013;Herrera et al, 2014). However, throughout the present work, it should be kept in mind that it is very likely that none of the factors potentially explaining bumblebee decline is the unique or even the main trigger of current bumblebee regression.…”

“…Year after year, the local bumblebee fauna can change (including local species extinctions) due to variations in local climatic factors such as heat waves and droughts . However, this seems to drive the species not only along a random climatic hazard as proposed by Ranta & Vepsäläinen (1981) but also to a temporal and spatial gradient of changes (Ploquin et al, 2013;Herrera et al, 2014).…”

“…This random cycle of "sudden extermination -fast recovery" is considered as a key process of local species diversity, by maintaining all species under a competition level (Pekkarinen, 1984;Rasmont, 1989). Recent contributions noticed that bumblebees are indeed sensitive to extreme climatic events Ploquin et al, 2013;Herrera et al, 2014;Rasmont & Iserbyt, 2014). Year after year, the local bumblebee fauna can change (including local species extinctions) due to variations in local climatic factors such as heat waves and droughts .…”

Short communication: First data on the prevalence and distribution of pathogens in bumblebees (Bombus terrestris and Bombus pascuorum) from Spain

“…Alternatively, protozoa virulence in B. terrestris may be lower compared to B. pascuorum (Goulson et al, 2012). Moreover, B. terrestris emerges early in the spring, whereas B. pascuorum emerges later (Ornosa & OrtizSánchez, 2004;Ploquin et al, 2013). We conclude that this ecological difference between host species might affect the success of the parasite's biological cycle and consequently infection prevalence.…”

Are pollinators and seed predators selective agents on flower color in Gentiana lutea?

“…Also color variation might be maintained in the population by a number of reasons. The pollinator community changed over the past decades at the Cantabrian range (Ploquin et al 2013). Temporal changes in the community composition may change the direction and magnitude of selective pressures (Eckhart 1992;Frey 2004;Price et al 2005), contributing to flower color variation.…”