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Visitor profiles for related sympatric Cape plants

thesis
posted on 2023-05-26, 16:45 authored by Nelson, Leanne
Many angiosperms require the pollination services of insects to effectively transfer pollen between conspecifics. Closely-related plants that overlap in their range and utilise the same pollinators may experience interspecific pollen flow which can lead to a reproductive disadvantage and increase the likelihood of hybridisation. Reproductive isolation among plants is achieved either by the structural mechanisms of flowers that preclude entry to or pollination by certain species, or the foraging behaviour of the pollinator fauna when they restrict their visits to one particular species. The fynbos flora in the southwestern Cape of South Africa is characterised by extremely high species diversity among various genera, but the pollination ecology of most of the flora remains poorly known. This flora offers a remarkable opportunity to explore details of the insect flower interaction in communities ofrelated plants. The main objective of this study was to examine the extent of overlap and pollinator sharing in a sample of this assemblage by comparing the diversity and abundance of floral visitors among several related species pairs. Field studies were conducted over summer on the visitor profiles of three pairs of closely-related, sympatric plant species (Erica daphniflora/E. multumbellifera; Lobelia tomentosa/L. erinus; Lobelia neglecta colour polymorphs) at Wildcliff Nature Reserve. Levels of interspecific pollen flow and flower constancy were assessed by observing the sequential movements of all visitors, and their body and wing dimensions were measured to analyse variation in the morphological profile of visitors associated with each plant species and between telated pairs. A range of taxonomically diverse insects (29 species from four orders) were identified as flower visitors - Hymenoptera (primarily apid bees), Diptera, Coleoptera and Lepidoptera and all plants maintained generalist pollination systems. Ordination methods reveal nominal overlap in the visitor profiles for each plant pair and high levels of flower constancy were observed among all insect taxa. A principal components analysis identified wing width as varying independently of other size variables and this is thought to have an influence on pollinator behaviour through its influence on flight control. I discuss these findings in the context of pollinator behaviour, insect and plant morphology and community composition.

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Copyright 2010 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (MAppSc)--University of Tasmania, 2011. Includes bibliographical references

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