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Type: Thesis
Title: The Evolution of Diet Width in Lasioglossum (Chilalictus) (Halictidae, Apoidea), in Association with Speciation and Sensory Morphology
Author: Akankunda, Trace
Issue Date: 2020
School/Discipline: School of Agriculture, Food and Wine
Abstract: Bees are highly dependent on flowers as a source of food, from which they collect oil, nectar or pollen. While most bees rely on multiple plants for nectar, some species specialize on specific pollen hosts while other are generalists. Robertson (1925) was the first to document this observation and he coined the terms monolecty, oligolecty and polylecty to categorise bees based on their pollen host breadth. Since then, several researchers of pollination systems have debated the definitions and biological relevance of these categories. The most significant advancement in this debate comes from the work of Cane and Sipes (2006) who subdivided the categories of diet width further and revised the lexicon used for classifying bees based on their diet width. While their revised classification system remains contentious, it provides a useful framework for representing the various levels of pollen host specialization and generalization observed in bees. Of particular interest in this study, is the category of broadly polylectic bees because despite their economic, ecological and evolutionary significance, as far as we know, no work has been done to understand the factors driving or maintaining the evolution of broad polylecty in bees. Flower visitation records of bees suggest that broad polylecty is rare across the families of bees and is predominantly observed in two families: Apidae and Halictidae. In order to develop a hypothesis on the factors influencing the evolution of broadly polylectic behaviour in bees, I reviewed literature on the evolution of pollen host breadth in bees and phytophagy in herbivorous insects. As in herbivores, the evolution of diet width in bees is bidirectional towards oligolecty and polylecty depending on different ecological factors operating within a given microhabitat. However, the selection of pollen hosts appears to be constrained by neurological, physiological or morphological factors in both oligolectic and polylectic species. Given that broadly polylectic behaviour appears to be taxonomically conserved, I hypothesize that genetic constraints limit the evolution of polylecty to broad polylecty in most bee taxa and that these constraints can be deduced by comparing morphological, neurological and digestive physiological differences between polylectic and broadly polylectic species. To test this hypothesis, I studied the evolution of broad polylecty in a native Australian subgenus of Lasioglossum (Chilalictus). In accordance with observations from the literature, broad polylecty is rare in this subgenus and I found that it has evolved independently at least four times. However, in examining the differences between broadly polylectic species and species in lower pollen host breadth categories, I found no evidence of morphological adaptations for broad polylecty in the peripheral olfactory sensory organs of L. (Chilalictus) species. Possible directions of further research on the factors influencing the evolution of broad polylecty in bees are explored.
Advisor: Hogendoorn, Katja
Lopez, Carlos Rodriguez
Leijs, Remko
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2020
Keywords: evolution
broad polylecty
multilocus barcoding
molecular phylogenetics
olfactory sensory morphology
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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