Scaccabarozzi, Daniela (2019) Pollination Ecology and Pollination Evolutionary Processes with Relevance in Ecosystem Restoration – Pollination Biology of Diuris: Testing for Batesian Mimicry in Southwestern Australia. [Tesi di dottorato]

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Mimicry is based on the interaction between a mimic, a model and a receiver. While there is increasing recognition of Batesian floral mimicry in plants, there are few confirmed cases where mimicry involves more than one model species. The Australian orchid genus Diuris has been long hypothesised to engage in guild mimicry of a range of co-occurring pea plants (Faboideae). Some clades of Diuris are superficially similar in both colour and shape to those of a guild of yellow and brown pea plants (Faboideae). Here, we test for pollination via mimicry of pea plants in Diuris (Orchidaceae). Additionally, we test for further ecological interactions (non-model plants, pollination limitation, habitat size and plant frequency) in order to assess the reproductive success of the orchids. For addressing these hypothesis we select two study species, occurring in different habitat: Diuris brumalis (Jarrah forest) and Diuris magnifica (Banksia woodland), the latter occurring in fragmented habitat. We test for floral mimicry criteria in both of the species. In order to frame the pollination ecology of the putative model plants, we verify the type of pollinator interactions (generalised vs specialized) occurring in four communities of pea plants in the southwestern Australian Floristic Region (SWAFR). D. brumalis, D. magnifica and the pea plants showed strong flower similarity and were likely to be perceived as the same by pollinators, native bees (Trichocolletes; Colletidae). However, in D. brumalis the orchid reproductive success increased with the local abundance of the model species (Daviesia spp.), while in D. magnifica the reproductive success wasn’t in relation to the putative models. Alternatively, D. magnifica reproductive success was influenced by a non-model pea plant (Hardenbergia) which is locally abundant and widespread in all the study sites. Additionally, habitat size and orchid plant frequency influenced the orchid reproductive success. Pea plant species were visited by between one and four genera of native bees, indicating variation in levels of specialisation of the pollination systems of Faboideae. Several pea plant species showed specialised interactions with bee genera attracted. Unexpectedly, some pea plant species frequently attracted beetles that may play an important role in pollination. Evidence for mimicry of multiple models suggests that D. brumalis and D. magnifica may be engaged in guild mimicry system. Interestingly, D. brumalis and D. magnifica belongs to a complex of species with similar floral traits, suggesting that this represents a useful system for investigating speciation in lineages that employ mimicry of food plants. Furthermore, the study on pollination of Faboideae species of SWAFR, offers a pivotal research for next investigations on pollinator webs and syndromes of Australian pea plants scarcely documented until now.

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