Changes in the structure and composition of the ‘Mexical’ scrubland bee community along an elevational gradient

Abstract

‘Mexical’ scrubland is a sclerophyllous evergreen Mediterranean-like vegetation occurring in the leeward slopes of the main Mexican mountain ranges, under tropical climate. This biome occupies an elevational range approximately from 1900 to 2600 meters above sea level, which frequently is the upper-most part of the mountains range. This puts it at risk of extinction in a scenario of global warming in which an upward retraction of this type of vegetation is expected. The Mexical remains one of the least studied ecosystems in Mexico. For instance, nothing is known about pollinator fauna of this vegetation. Our main objective is to make a first insight into the taxonomic identity of the bee fauna that inhabits this biome, and to study how it is distributed along the elevational gradient that it occupies. Our results highlight that elevation gradient negatively affects bee species richness and that this relationship is strongly mediated by temperature. Bee abundance had no significant pattern along elevational gradient, but shows a significant relationship with flower density. Interestingly, and contrary to previous works, we obtained a different pattern for bee richness and bee abundance. Bee community composition changed strongly along elevation gradient, mainly in relation to temperature and flower density. In a global warming scenario, as temperatures increases, species with cold preferences, occupying the highest part of the elevation gradient, are likely to suffer negative consequences (even extinction risk), if they are not flexible enough to adjust their physiology and/or some life-story traits to warmer conditions. Species occupying mid and lower elevations are likely to extend their range of elevational distribution towards higher ranges. This will foreseeably cause a new composition of species and a new scenario of interactions, the adjustment of which still leaves many unknowns to solve.

Variation in Plant–Pollinator Network Structure along the Elevational Gradient of the San Francisco Peaks, Arizona

“…Further, decreasing temperatures at the higher elevations of the Mexical scrublands supported declines in bee species richness, with mean annual temperature as the best predictor of declines [1]. Cooler temperatures can affect the physiological and foraging capabilities of insects, which can lead to overall environmental filtering on bee or other insect communities along altitudinal gradients [1,16,72,73]. Average pollinator species richness also followed a significant hump-shaped pattern, but average plant species richness was not significantly different between the mixed conifer and spruce fir life zones.…”

“…One recent study [16] found significant decreases of plant and insect species at higher elevations of Jonaskop Mountain, South Africa, and similarly, research in the Andes of Mendoza, Argentina [31], showed that the number of pollinator species decreased by over 33% from a lower to higher elevation zone. Further, decreasing temperatures at the higher elevations of the Mexical scrublands supported declines in bee species richness, with mean annual temperature as the best predictor of declines [1]. Cooler temperatures can affect the physiological and foraging capabilities of insects, which can lead to overall environmental filtering on bee or other insect communities along altitudinal gradients [1,16,72,73].…”

“…Insects, especially bees, are critical for pollination services worldwide [1][2][3]. Many fly species replace bees as the dominant pollinators at high elevation communities due to their ability to maintain functionality in cooler conditions [3][4][5].…”

Niche divergence at the intraspecific level in an endemic rare peony (Paeonia rockii): A phylogenetic, climatic and environmental survey

“…Simulation results from three high-resolution GCMs (BCC-CSM1.1, BCC-CSM2-MR and MIROC5) show that the centers of the suitable areas are predicted to tend to displacement toward high latitudes and elevations, under the emissions scenarios for the 2050s and 2070s ( Figure 8 and S10 ). The elevation of species distribution is largely driven by the temperature gradients, so as the climate warms, species ranges shift to higher altitudes ( Lenoir et al., 2008 ; Osorio-Canadas et al., 2021 ). Indeed, numerous studies have demonstrated that climate change has altered the distribution patterns of species, where many species have moved to higher latitudes or higher altitudes ( Parmesan and Yohe, 2003 ; Colwell et al., 2008 ).…”

Smaller, more diverse and on the way to the top: Rapid community shifts of montane wild bees within an extraordinary hot decade

“…Another commonly used approach to predict the fate of species communities under climate change is to look at current community patterns along spatial temperature gradients, using this comparison as the so‐called space‐for‐time substitutions. Wild bee community assessments along spatial temperature gradients indeed detected more species and higher abundance under higher temperatures (Arroyo et al, 1985; Classen et al, 2015; Mayr et al, 2020; Osorio‐Canadas et al, 2021; Perillo et al, 2017). There is also evidence that the mean body size of wild bee communities varies with climate, increasing in cool highlands and decreasing in warmer lowlands (Hoiss et al, 2012; Peters, Peisker, et al, 2016).…”