Pollinator-mediated isolation promotes coexistence of closely related food-deceptive orchids.

Identifying the factors that contribute to reproductive isolation among closely-related species is key for understanding the diversification of lineages. In this study, we investigate the strength of premating and postmating reproductive isolation barriers between Disa ferruginea and Disa gladioliflora, a pair of closely-related species, often found co-flowering in sympatry. Both species are non-rewarding and rely on mimicry of different rewarding model flowers for attraction of pollinators.

Structural anther mimics improve reproductive success through dishonest signaling that enhances both attraction and the morphological fit of pollinators with flowers.

Numerous studies have identified traits associated with anther mimicry; however, the processes underlying floral deception remain poorly documented for these structures. We studied the importance of pollinator attraction and mechanical fit of anther mimics in Tritonia laxifolia (Iridaceae) and their relative contributions to reproductive success. To determine anther mimics role in attraction, we offered bees' binary choices to flowers painted with UV-absorbent and UV-reflecting paints.

Character displacement drives floral variation in Pelargonium (Geraniaceae) communities.

Interactions between plant community members are an underexplored driver of angiosperm floral variation. We investigate character displacement as a potential contributor to floral variation in Pelargonium communities. Pelargoniums all place pollen on the ventral sides of their pollinators, potentially leading to interspecific pollen transfer (IPT) in sympatry.

Local adaptation: Mechanical fit between floral ecotypes of Nerine humilis (Amaryllidaceae) and pollinator communities.

Geographic variation in floral morphology is often assumed to reflect geographic variation in pollinator communities and associated divergence in selective pressures. We studied populations of Nerine humilis (Amaryllidaceae) to assess whether geographic variation in floral form is the result of local adaptation to different pollinator communities. We first tested for associations between floral traits and visitor communities, and found that populations with similar floral morphologies were visited by similar insect communities.

Matching floral and pollinator traits through guild convergence and pollinator ecotype formation.

Background And Aims: Pollinator landscapes, as determined by pollinator morphology/behaviour, can vary inter- or intraspecifically, imposing divergent selective pressures and leading to geographically divergent floral ecotypes. Assemblages of plants pollinated by the same pollinator (pollinator guilds) should exhibit convergence of floral traits because they are exposed to similar selective pressures. Both convergence and the formation of pollination ecotypes should lead to matching of traits among plants and their pollinators.

Flower colour adaptation in a mimetic orchid.

Although the tremendous variability in floral colour among angiosperms is often attributed to divergent selection by pollinators, it is usually difficult to preclude the possibility that floral colour shifts were driven by non-pollinator processes. Here, we examine the adaptive significance of flower colour in Disa ferruginea, a non-rewarding orchid that is thought to attract its butterfly pollinator by mimicking the flowers of sympatric nectar-producing species. Disa ferruginea has red flowers in the western part of its range and orange flowers in the eastern part--a colour shift that we hypothesized to be the outcome of selection for resemblance to different local nectar-producing plants.