Different Distribution Patterns of Hoverflies (Diptera: Syrphidae) and Bees (Hymenoptera: Anthophila) Along Altitudinal Gradients in Dolomiti Bellunesi National Park (Italy)

Abstract

Hoverflies (Diptera: Syrphidae) and bees (Hymenoptera: Anthophila) are two key taxa for plant pollination. In the present research, the altitudinal distribution of these taxa was studied along two gradients (elevation range: 780–2130 m) in the Dolomiti Bellunesi National Park (Northeastern Italy). Pan traps were used as a sampling device to collect both hoverflies and bees. Other than altitude, the effect of landscape complexity and plant diversity were considered as potential predictors of hoverfly and bee richness and abundance along the two gradients. A total of 68 species of hoverflies and 67 of bees were collected during one sampling year, confirming the efficacy of pan traps as a sampling device to study these taxa. Altitude was the main variable affecting both hoverfly and bee distribution. The two taxa show different distribution patterns: hoverflies have a unimodal distribution (richness and abundance) with peak at middle altitude (1500 m), while bees have a monotonic decline (richness and abundance) with increasing altitude. Both hoverfly and bee populations change with the increasing altitude, but the change in hoverflies is more pronounced than in bees. Species turnover dominates the β-diversity both for hoverflies and bees; therefore, the hoverfly and bee communities at higher altitudes are not subsamples of species at lower altitude but are characterized by different species. This poses important conservation consequences. Some rare species, typical of an alpine habitat were recorded; the present research represents important baseline data to plan a monitoring scheme aimed at evaluating the effect of climate change on pollinators in these fragile habitats.

High species turnover and unique plant–pollinator interactions make a hyperdiverse mountain

“…At high altitudes, hoverflies replace small solitary bees due to their better adaptation to harsh alpine conditions (McCabe & Cobb, 2021; McCabe, Colella, et al, 2019; Sommaggio et al, 2022). A recent review, indicated temperature as the main driver of this bee‐to‐fly transition, showing that below 4.9°C, the pollinator communities were fly dominated, while above 5.7°C were bee dominated (McCabe & Cobb, 2021); yet, other factors like the tree canopy cover or precipitation may also play a role (McCabe, Cobb, et al, 2019; McCabe, Colella, et al, 2019).…”

“…At high altitudes, hoverflies replace small solitary bees due to their better adaptation to harsh alpine conditions (McCabe & Cobb, 2021;McCabe, Colella, et al, 2019;Sommaggio et al, 2022).…”

“…All in all, the prospect for high dissimilarity in pollinator species and their interactions, would imply unique pollination systems existing along the altitudinal gradient of Mt. Olympus and thus pose important implications for designing future ecosystem conservation schemes (Cuartas‐Hernández & Gómez‐Murillo, 2015; Luna et al, 2020; Sommaggio et al, 2022).…”

Changes in Population Densities and Species Richness of Pollinators in the Carpathian Basin during the Last 50 Years (Hymenoptera, Diptera, Lepidoptera)

“…This value in our region is 87%, which is logical since the deep Carpathian Basin is more exposed to Mediterranean effects than the Atlantic Netherlands. According to Sommagio et al [113], in addition to the catastrophic decline in the number of hoverflies, mountainous regions are able to provide shelter for them, but this is not true for bumblebees. They observed that the two taxa showed different distribution patterns: hoverflies had a unimodal distribution (richness and abundance) with a peak at middle altitude (1500 m), while bees had a monotonic decline with increasing altitude.…”

Understanding the Dynamics of Sex-Specific Responses Driven by Grassland Management: Using Syrphids as a Model Insect Group

“…To ensure comprehensive data collection, we carefully considered several factors when choosing our study sites. Primarily, we focused on capturing a uniform range of elevations within the alpine grassland to capture the full spectrum of syrphid diversity patterns in study sites [37]. This approach allowed us to account for potential variations in syrphid communities driven by different grassland types at the same elevation (~989 m).…”