Continental Scale Patterns in the Floral Host Breadth of Australian Native Bees

Author: Patricia Slattery

Slattery, Patricia, 2024 Continental Scale Patterns in the Floral Host Breadth of Australian Native Bees, Flinders University, College of Science and Engineering

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As a biogeographically isolated continent, there have been limited dispersal opportunities for biota into Australia in the last 35 million years. Consequently, the Australian biota has evolved a high degree of endemism, with unique adaptations and specialisations. This is reflected well in both our native bees and their visitations to various flora in the landscape. The Australian native bee fauna is distinct at even the global scale, and made up of five families including: Colletidae, Megachilidae, Apidae, Halictidae, and the entirely Australian endemic family, Stenotritidae. The short-tongued colletids are the most species-rich family in Australia but are not common outside of South America and Australia. Conversely, the most species-rich family at the global scale, the long-tongued Apidae, is outnumbered by any one of the major colletid subfamilies in Australia. Therefore, while their endemism and floral visitation habits are a part of what makes our native bees so interesting, what factors could be driving these unusual patterns?

I introduce this thesis with a broad review of the native bee fauna’s varied biogeographic histories, potential drivers of diversity, and discuss their future in the Australian environment. Much of the literature, however, is consistently evaluating species or populations at only the regional scale. Building an understanding of how native bees utilise floral resources at the larger continental scale could inform on potential evolutionary drivers that might have impacted their diversity. This is most feasible to assess in an island-continent such as Australia, where inward and outward dispersals are limited and likely less important than any potential co-evolutionary relationships. Determining the use of floral hosts can highlight any reliance on certain flora (i.e. specialisation), or more generalist visitation habits, which can help inform future practices or management.

Using records that encompass more than 100 years of museum collections from across Australia, we conducted the first continental-scale research into the floral host breadth (visited floral genera) of two major Australian bee families: the Colletidae and the Apidae. These bees make up over half of our native bee fauna and comprise a range of different morphologies and social structures. Colletidae are generally small to tiny, solitary, short-tongued bees, which we would expect to somewhat limit their floral host breadth. Contrastingly, Apidae, enabled by their long tongues and variable sociality, might be able to visit a broader range of floral hosts and have a greater floral host breadth. Our data and analyses rejected these hypotheses, with colletid bees displaying a much greater floral host breadth, even when correcting for differences in sampling effort (i.e., record numbers) and species number. I discuss the preponderance of a hyper-diverse colletid subfamily on one plant family and explore how drivers other than morphological differences might be affecting the floral host breadth of our native bee fauna.

Keywords: Apidae, Colletidae, Pollination, Interaction Networks, Euryglossinae, Hylaeinae, Neopasiphaeinae, Australia

Subject: Biology thesis

Thesis type: Masters
Completed: 2024
School: College of Science and Engineering
Supervisor: Dr Buno Alves Buzatto