Pollinator and floral odor specificity among four synchronopatric species of Ceropegia (Apocynaceae) suggests ethological isolation that prevents reproductive interference

Abstract

Possession of flowers that trap fly pollinators is a conservative trait within the genus Ceropegia, in which pollination systems can be generalized or highly specialized. However, little is known about the role of plant–pollinator interactions in the maintenance of species boundaries. This study examined the degree of plant–pollinator specialization and identified the parameters responsible for specificity among four co-occurring Ceropegia species with overlapping flowering times. All investigated plant species were functionally specialized on pollination by Chloropidae and/or Milichiidae flies and each Ceropegia species was, in turn, ecologically highly specialized on only two pollinating fly morphospecies, though one plant species appeared more generalist. Species-specific fly attraction was due to the differences between plant species in floral scents, floral morphology, colour patterns, and presence of other functional structures, e.g., vibratile trichomes, which were shown to contribute to pollinator attraction in one study species. The combination of these olfactory and visual cues differentially influenced pollinator preferences and thus hindered heterospecific visitation. Furthermore, a pollinator exchange experiment also highlighted that species integrity is maintained through efficient ethological isolation (pollinator attraction). The mechanical isolation mediated by the fit between floral morphology and size and/or shape of fly pollinators appears less pronounced here, but whether or not the morphological match between male (pollinium) and female (guide rails) reproductive organs can impede hybridization remains to be investigated.

Specialized pollination by cecidomyiid flies and associated floral traits in Vincetoxicum sangyojarniae (Apocynaceae, Asclepiadoideae)

“…The fact that the corpuscular groove is usually attached to a maxillary palpus emphasizes the essential role of this organ of the insect in the detection of nectar sources, as found in other Diptera ( e.g ., Syed & Leal 2007 and references therein; Kidyoo et al . 2022). Also, it seems that whilst searching for nectar, the insect bends its maxillary palpi so that the dorsal side of the second segment slips into the corpuscular groove.…”

Comparative Analysis of the Mitochondrial Genomes of Chloropidae and Their Implications for the Phylogeny of the Family

“…[ 7 , 8 ]. Some species are known pollinators of Genoplesium (Orchidaceae) [ 9 ], Aristolochia (Aristolochiaceae) [ 10 ], Phoradendron (Santalaceae) [ 11 ], and Ceropegia (Apocynaceae) [ 12 ]. Many chloropid species are saprophagous, meaning that they live in decaying plant tissues or animal carcasses [ 13 ], and they play an important role in the decomposition of vegetable matter [ 8 ].…”

“…Nartshuk [ 22 , 23 ] treated Rhodesiellinae as a subfamily, which was followed by Cherian [ 24 ], Nartshuk [ 1 ], Nartshuk and Andersson [ 15 ], and Riccardi and Amorim [ 2 ], resulting in the recognition of Chloropidae comprising four subfamilies. Andersson [ 12 , 25 ] initially intended to reconstruct the phylogeny of the family. Due to high diversification and relatively recent evolution of chloropids, Andersson identified a considerable challenge in conducting a cladistic analysis of the family based on morphology.…”

Screening Universal Stress-Response Terpenoids and Their Biosynthetic Genes via Volatile and Transcriptomic Profiling in Citrus

“…1−6 Many studies have shown that the emission of volatile terpenoids helps improve the adaptive ability of plants during their evolution 7,8 and helps plants defend themselves against pathogens 9 and herbivores, 10 attract pollinators and repel insects. 11 With respect to individual compounds, Cypripedium subtropicum releases trans-β-farnesene and β-pinene to attract hoverflies for pollination. 12 Selinene is an essential precursor promoting fungal pathogen resistance 13 in Zea mays.…”

“…Biotic and abiotic stressors are commonly encountered challenges in commercial plant cultivation and affect plant growth and product quality to varying degrees. Many studies have inferred that stress affects plant-pest-natural enemy, plant-insect, and plant–plant interactions through its influence on volatile emissions. − Many studies have shown that the emission of volatile terpenoids helps improve the adaptive ability of plants during their evolution , and helps plants defend themselves against pathogens and herbivores, attract pollinators and repel insects . With respect to individual compounds, Cypripedium subtropicum releases trans -β-farnesene and β-pinene to attract hoverflies for pollination .…”