Assessing Pollinator Assembly And Efficacy Across Species Ranges In The Genus Triodanis (Campanulaceae)

Abstract

Plant-insect interactions are a key topic in evolutionary ecology, especially in the face of anthropogenic changes which threaten to disrupt these mutualisms. An in-depth pollinator survey for species in the genus Triodanis is performed here for the first time, with sampling covering four species and spanning a large portion of their geographic ranges (i.e., four U.S. states). All species in the genus exhibit dimorphic cleistogamy with variability in allocation to open (chasmogamous) flowers among populations and taxa. The genus Triodanis, therefore, provides an opportunity for understanding possible associations between pollinator assemblies and variation in species, breeding system, and geography. To assess these relationships, we sampled four species or subspecies of Triodanis at eight field sites in four states. Sampling encompassed a broad area across the Midwestern U.S. and Texas, and across a gradient of anthropogenically disturbed habitats. We found that for species of Triodanis: 1) small bee and fly generalist pollinators showed some floral constancy during feeding bouts but did not differentiate between species, 2) pollinator community was less diverse and abundant in highly degraded habitats, 3) while allocation to open flowers varied among species and populations, we found no association between breeding system (or species) on pollinator identity or abundance. This study represents the first in-depth survey of pollinator visitors of Triodanis and serves as foundational knowledge about the natural history of this group, provides resolution for members of Campanulaceae exhibiting floral traits of generalist hosts, and important documentation of plant-insect interactions in an era of ongoing anthropogenic changes.