Biology subjects

Leonhardt, S. D.

Publications and source records attributed to Leonhardt, S. D..

3 recordsLinked to original sources

bioRxiv2026

No need for fat: Nutritional preferences affect pollen foraging networks in alpine pollinator communities

Most flowering plant species rely on insect pollinators for successful cross-pollination. While floral color, scent, and morphology help attract visitors, the primary motivation for visiting a flower is the nutritional reward - nectar and, especially, pollen. Pollen provides a complete set of macro- and micronutrients essential for adult and larval provisioning in many insect flower visitors. However, pollen nutrient composition (i.e., quality) varies widely among plant species, and different visitors may have distinct nutritional requirements. Whether these differences are linked to the selection of plants visited remains poorly understood. In this study, we investigated whether the nutrient composition of pollen is linked to the visitation patterns of two main alpine pollinator groups: bumblebees and hoverflies. We observed flower visits in the field and identified the origin of pollen collected by bumblebees and hoverflies via metabarcoding. In addition, we analyzed the nutrient profiles of alpine flowering plants from the same habitat, including amino acids, fatty acids, and sterols. We hypothesized that both bumblebees and hoverflies (i) differ in the plant spectrum they were observed on/collected from and visited for pollen collection, (ii) and that preferred nutrient profiles differ between the two pollinator groups. We additionally expected (iii) that, in the studied alpine plant communities, the nutrient composition of pollen of plant species collected by flower visitors is more strongly associated with pollinator identity than with plant phylogeny due to competition for pollinators. Our results revealed that alpine bumblebees and hoverflies were more similar in their pollen hosts and nutritional preferences than expected, but, for both groups, the network based on observed flower visits differed significantly from that based on pollen collection. Pollen fatty acids and amino acids content was positively correlated, and both bumblebees and hoverflies preferred pollen with low fatty and amino acid content. Pollen sterols did not differ between plants collected by pollinators and non-collected plants. Neither fatty acid, amino acid, nor sterol composition was linked to plant phylogeny. Our findings suggest that not only amino acid content, but also fatty acid content, plays a key role in shaping pollen-collection patterns of flower visitors in alpine ecosystems.

animal behavior and cognition↗

bioRxiv2025

Improving allometric models to estimate the proboscis length of tropical bees

The proboscis length of bees is a key morphological trait shaping communities, pollination networks, and likely their responses to habitat loss. Despite its importance, it is rarely considered in ecological studies because of logistic limitations in obtaining accurate measurements across many different species. In two previous studies, the proboscis length of temperate bee species was estimated based on body size and bee family. However, bee taxa partially occurring in the tropics might deviate from this allometric relationship due to different functional constraints. Thus, we tested if equations developed for temperate bees can accurately predict the proboscis length in Meliponini, Euglossini (both Apidae), and Augochlorini (Halictidae), three ubiquitous and highly important tribes of tropical bees. We measured the intertegular distance (as a proxy of body size measurement) and the proboscis length of 892 specimens of 105 tropical species. We used these measurements to evaluate the previous model and found that its estimations lacked accuracy when applied to tropical bees, particularly to Meliponini and Euglossini. We developed new allometric equations estimating the proboscis length based on the intertegular distance, using (sub-) genera as an additional predictive variable to refine the estimations. We tested our approach by creating a test model for Meliponini, trained with only 80 % of the data, and evaluated this model using the remaining 20 %, resulting in a high accuracy of estimates. Our results shed additional light on the nature of the proboscis length-body size allometric relationship in tropical bees and provide a tool for future studies on the functional ecology of bees and their interactions with plants.

zoology↗

bioRxiv2025

Stratification along tropical forest succession enhances pollinator diversity via functionally unique canopies

Vertical stratification is a prominent driver of biodiversity in forests. As the proportion of successional forests increases worldwide and canopies are lost at a fast pace, it is crucial to understand the role of stratification as a driver of community recovery and ecological processes during succession, particularly for important plant mutualist groups essential for forest recovery. Within a well-resolved chronosequence in the northwestern Ecuadorian rainforest, we compiled an extensive database of over 20,000 diurnal and nocturnal pollinators and 2,000 interactions with plants and examined the interacting effects of recovery age and stratification on pollinator community and interaction network reassembly. In late successional and old-growth forests, stratification was a stronger predictor of pollinator abundance, alpha-diversity, functional richness and beta-diversity than forest legacy. While most groups were strongly associated with canopies (moths, social bees, and nocturnal bees), orchid bees exhibited an inverse pattern, also presenting the strongest functional response to stratification and recovery status. Within the entire chronosequence (0-38 years of recovery, plus old-growth forests), recovery status and stratification, alongside landscape features, acted synergistically as predictors of pollinator community parameters. Although structurally stable across the chronosequence and between strata, Interaction networks were richer and most distinct in canopies, while the highest pollinator and interaction diversity were found in old-growth canopies. In successional forests, networks were only comparable in size to active disturbances and early recovery with both strata combined, whereas complete networks in old-growth forests were more than twice as large as those in other recovery statuses. Our study underlines the importance of stratification in leveraging pollinator diversity during forest succession. By serving as havens for canopy-adapted species, tropical canopies may thus help safeguard pollination processes in disturbed landscapes.

ecology↗