Vrecko, V. | Search bioRxiv

bioRxiv2026

Pollinator specificity among three co-flowering Mediterranean Aristolochia species pollinated by Diptera

Attracting specific pollinators can be favoured by natural selection to avoid reproductive interference between sympatric plant species. However, the ways in which fine differences in floral traits lead to the attraction of specific pollinators are diverse and unknown in many pollination interactions. We surveyed pollinators on three sympatric Aristolochia species (A. clematitis, A. pistolochia and A. rotunda) pollinated by Diptera to investigate if specific pollination occurs. To decipher if specific pollination may be mediated by different floral odours, we characterized the volatile organic compounds (VOCs) emitted by flowers and highlighted those VOCs electrophysiologically detected by pollinators in A. rotunda and A. pistolochia. Among the most abundant pollinators, Forcipomyia monilicornis was a specific pollinator of A. pistolochia while two Dasyhelea species were specific pollinators of A. clematitis. Forcipomyia aristolochiae and T. ruficeps were non-specific pollinators of A. rotunda, although they were more frequently found in A. rotunda flowers. The floral odours of A. rotunda and A. pistolochia differed significantly from each other and elicited specific electrophysiological responses in their respective pollinators. Although several pollinator species visit more than one Aristolochia species, those pollinators are preferentially found in one Aristolochia species. Selective attraction is likely mediated by specific VOCs.

ecology↗

bioRxiv2025

Seasonal variation in insect assemblages at flowers of Balanites aegyptiaca, an ecologically and socially important tree species in the Ferlo region of Senegal's Great Green Wall corridor

AO_SCPLOWBSTRACTC_SCPLOWInteractions between flowers and flower-visiting insects play central roles in ecosystem functioning. In addition to ensuring pollination, flower-visiting insects are also crucial for numerous other biotic interactions, using floral resources as fuel in their search for prey, hosts, breeding sites, and other resources. Studying insect-flower interactions may thus be strategic to conserve and restore biotic interactions in ecosystems heavily degraded by intensive land use and climate change, such as the arid savannas of the northern Sahel. We aimed to document for the first time the diversity of flower-visiting insects in this region and to examine whether restoration efforts of the Great Green Wall initiative have affected insect abundance and diversity. Using two capture methods, hand netting and pan traps, we inventoried insects visiting flowers of Balanites aegyptiaca. This is the most abundant tree species in the region and is also of economic importance. We sampled three sites in a single locality: a "Restored" site from which livestock are excluded, an "Unrestored" site in intensively grazed rangeland, and a topographical "Depression" site in a grazed area but with high tree density. Each site was sampled at three different periods to examine variation in this extremely harsh and seasonal environment. The open-access flowers of Balanites aegyptiaca are produced in multiple flowering events each year. We found a surprisingly high diversity of insects visiting its flowers, comprising 371 morphospecies from 10 insect orders, with a predominance of Hymenoptera and Diptera. Insect abundance, diversity and species composition differed markedly between seasons. Bees appear to be important pollinators, particularly solitary bees of the family Halictidae, which were abundant in all seasons. Diptera, in particular several families of small flies, were also frequent visitors and were especially abundant and diverse in the wet season. Ants were especially abundant at flowers in the dry season, when few resources other than flowers and flower-visiting insects were likely available to them. Insect abundance and observed diversity differed only little between sites, but estimated total diversity (Chao1 richness) was highest in the Depression site. Insects visiting flowers of B. aegyptiaca included herbivores, decomposers, and parasitoids and predators of diverse arthropods, underlining the role of these floral resources in numerous facets of ecosystem functioning. The floral resources of B. aegyptiaca and other trees, which can flower throughout the year, are likely critical to assure the persistence of numerous insect species. Integrating biotic interactions into ecosystem management is crucial for conservation and restoration in Sahelian ecosystems.

ecology↗