24 March, 2024

Assessing pollinator assembly and potential across species ranges in the genus Triodanis (Campanulaceae)

Triodanis bee

By Tillotson-Chavez et al.

Flowering plants and the insects that they rely on for pollination continue to be an important topic of study in ecology. Pressures such as habitat destruction can disrupt these important relationships. The impacts of these pressures on plant-pollinator relationships are still understudied for many native plants. Even when pollinators visit flowers, successful transfer of compatible, intraspecific pollen is not always guaranteed, especially when habitat is degraded or destroyed. However, plants have evolved various methods to ensure pollination, such as flowers that are completely self fertile and never open, ensuring that they can reproduce without pollinators. This strategy is “cheaper” than producing resource expensive open flowers with petals and rewards (i.e., nectar) that are attractive to pollinators. The maintenance of these different strategies in a population and how human pressures may influence these reproductive strategies remain questions of interest. We used the native plant species Triodanis, or Venus’ Looking Glass, as a system to investigate these questions. Because these weedy annual plants have both flowers open to pollination (chasmogamous) and  flowers that are completely closed and self-pollinating (cleistogamous)this is an excellent system to investigate  how reproductive strategies influence pollinator relationships.

We specifically examined if variability in production between these two types of flowers impacted the quantity, quality, and diversity of insect pollinators present for species and populations in multiple species in the genus Triodanis. We sampled across the Midwestern US and Texas in different habitats, including those that were very human disturbed and developed (eg., sidewalks, along parking lots, etc), as well as maintained natural areas such as those similar to the Tallgrass Prairie National Preserve. Overall, small solitary native bee species, bee flies, and syrphid or flower fly species were collected across this wide sampling. During feeding or pollen collection, pollinators did not differentiate between the flowers of Triodanis species that occurred together which elucidates a previously undescribed mechanism for hybridization between these species. Overall, pollinator communities (bees and flies) were less diverse and abundant in areas of greater habitat degradation. However, variation in reproductive strategy (proportion of open to closed flowers) did not impact the identity or abundance of pollinators for Triodanis. Our work builds on the sparse natural history of Triodanis and its associated pollinators and emphasizes the importance of habitat quality in maintaining pollinator diversity. Further, we establish a framework for understanding possible relationships between variation in reproductive strategy (i.e., allocation to open flowers) and pollinator community. Future work will examine the plant fitness implications of variation in habitat quality as a driver of pollinator community diversity.

Read the scientific publication in JPE

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