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Abstract Premise Many tropical plants are bat‐pollinated, but these mammals often carry copious, multispecific pollen loads making bat‐pollinated plants susceptible to heterospecific pollen deposition and reproductive interference. We investigated pollen transfer between sympatric bat‐pollinated Burmeistera species and their response to heterospecific pollen deposition from each other. Methods We quantified conspecific and heterospecific pollen deposition for two populations of B. ceratocarpa , a recipient species in heterospecific pollen transfer interactions, that co‐occur with different donor relatives ( B. borjensis and B. glabrata ). We then used a cross‐pollination scheme using pollen mixtures to assess the species' responses to heterospecific pollen deposition in terms of fruit abortion and seed production. Results Burmeistera ceratocarpa received significantly more heterospecific pollen from its relatives at both sites than its own pollen was deposited on its relatives. However, heterospecific pollen deposition only affected seed production by B. borjensis and B. glabrata , but not by B. ceratocarpa , suggesting that early acting post‐pollination barriers buffer the latter against reproductive interference. Crosses between sympatric and allopatric populations suggest that the study species are fully isolated in sympatry, while isolation between allopatric populations is strong but incomplete. Conclusions We did not observe evidence of reproductive interference among our study species, because either heterospecific pollen deposition did not affect their seed production ( B. ceratocarpa ) or they receive heterospecific pollen only rarely ( B. borjensis and B. glabrata ). Frequent heterospecific pollen deposition might favor the evolution of barriers against foreign pollen (as in B. ceratocarpa ) that alleviate the competitive costs of sharing low fidelity pollinators with co‐occurring species. 

Three species of Burmeistera discovered during fieldwork in Ecuador are described here. Burmeistera velutina and Burmeistera catulum are unusual in being nearly completely covered in indumentum, short and velvety in the former and remarkably long (up to 4 mm) and silky in the latter. Burmeistera jostii possesses bright red corollas, rare in a genus typically characterized by dull green flowers, and yellow to tan strigose hairs. We provide a discussion of each species’ etymology, phenology, and ecology, a list of all specimens examined, and distribution maps and photos. 

Six species of Burmeistera H. Karst. & Triana are described as new from Ecuador: B. chrysothrix Mashburn & Muchhala, B. crocodila Mashburn & Muchhala, B. erosa Mashburn, B. lingulata Mashburn & Muchhala, B. sierrazulensis Mashburn & Muchhala, and B. valdiviana Mashburn. These discoveries bring the total number of Burmeistera species in Ecuador to ca. 47. Descriptions are given for each species, as well as diagnoses to differentiate them from other Burmeistera. Also provided is a discussion of each species’ etymology, phenology, and ecology, a list of all specimens examined, and distribution maps and photos, when available. 

Understanding how pollen moves between species is critical to understanding speciation, diversification, and evolution of flowering plants. For co-flowering species that share pollinators, competition through interspecific pollen transfer (IPT) can profoundly impact floral evolution, decreasing female fitness via heterospecific pollen deposition on stigmas and male fitness via pollen misplacement during visits to heterospecific flowers. The pollination literature demonstrates that such reproductive interference frequently selects for reproductive character displacement in floral traits linked to pollinator attraction, pollen placement, and mating systems and has also revealed that IPT between given pairs of species is typically asymmetric. More recent work is starting to elucidate its importance to the speciation process, clarifying the link between IPT and current and historical patterns of hybridization, the evolution of phenotypic novelty through adaptive introgression, and the rise of reproductive isolation. Our review aims to stimulate further research on IPT as a ubiquitous mechanism that plays a central role in angiosperm diversification. 

A new taxon belonging to the genus Burmeistera (Campanulaceae, Lobelioideae) is described from El Quimi Biological Reserve in Morona Santiago Province, southeast Ecuador. Burmeistera quimiensis is characterized by its red-violet stems and veins, spiral phyllotaxy, bullate, ascending leaves with a revolute margin, puberulous abaxial leaf surface, cupuliform hypanthia, and thick-walled white to red-violet fruits with reflexed pedicels. Photos of the new species are given, as well as a distribution map of known collection localities, and its relationships with other species are discussed. 

Closely related plant species with overlapping ranges often experience competition for pollination services. Such competition can select for divergence in floral traits that attract pollinators or determine pollen placement. While most species inCentropogon(Campanulaceae: Lobelioideae) have flowers that suggest adaptation to bat or hummingbird pollination, actual pollinators are rarely documented, and a few species have a mix of traits from both pollination syndromes. We studied the pollination biology of a “mixed‐syndrome” species and its co‐occurring congeners to examine the relationship between floral traits and visitation patterns forCentropogon.

Fieldwork at two sites in Bolivian cloud forests involved filming floral visitors, quantifying pollen transfer, and measuring floral traits. Stamen exsertion, which determines pollen placement, was measured from herbarium specimens across the geographic range of these species to test for character displacement.

Results show a generalization gradient, from primarily bat pollination in white‐floweredCentropogon incanus, to bat pollination with secondary hummingbird pollination in the cream‐floweredC. brittonianus, to equal reliance on both pollinators in the red‐flowered, mixed‐syndromeC. mandonis. Pollen transfer between these species is further reduced by differences in stamen exsertion that are accentuated in zones of sympatry, a pattern consistent with character displacement.

Our results demonstrate that key differences in floral color and shape mediate a gradient of specialization in BolivianCentropogon. Interspecific pollen transfer is further reduced by potential character displacement of a key trait. Broadly, our results have implications for understanding the hyper‐diversity of Andean cloud forests, in which multiple species of the same genus frequently co‐occur.