Floral visitation in two high-elevation rock outcrop communities

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Carson A. Ellis (Creator)
Institution
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Advisor
Beverly Collins

Abstract: In the southern Appalachian Mountains, sparsely distributed rock outcrop communities harbor a significant number of rare and endemic plants. Unique communities of plants are found on rock outcrops of differing bedrock, distinguished in this study as Montane Redcedar (MRC) outcrops, occurring over mafic bedrock, and Non-Montane-Redcedar (NMRC) outcrops, occurring over felsic bedrock. Many plants in these communities have pollination mutualisms with insects. To assess plant-pollinator relationships in these unique communities, this study asks: 1) Are flowering plant and floral visitor communities on MRC and NMRC rock outcrops distinct? 2) Do diversity and richness of floral resource communities vary seasonally on MRC or NMRC rock outcrops? 3) Does floral visitor activity and diversity vary seasonally on MRC or NMRC rock outcrops? 4) Is there evidence for specialization in flower-visitor relationships on MRC or NMRC rock outcrops? 5) Do floral resources or floral visitors function as keystones within seasonal networks on MRC and NMRC rock outcrops? and, 6) Does the topology of rock outcrop visitation networks vary by outcrop type and/or by season? I evaluated floral resources and floral visitation in continuous two-week blocks, between April and October, on three MRC rock outcrop communities and three NMRC rock outcrop communities in the Highlands-Cashiers Plateau in North Carolina. Over the full season flowering plant (FRB) species composition differed between MRC and NMRC outcrops, while floral visitor (FV) communities were more similar and shared the same dominant insect orders (Hymenoptera, Coleoptera, and Diptera). Diversity and richness of FV and FRB communities was consistent across spring, summer, and fall on both MRC and NMRC outcrops, while turnover patterns in flowering plant communities on both outcrop types indicated that species composition was seasonally distinct. Abundance of floral visitors and dominant floral visitor orders also demonstrated seasonal patterns: FV abundance was greatest in spring and fall in NMRC communities, but greatest in the summer in MRC communities, and the dominant FV orders differed by season and outcrop type. Floral visitation networks generated from spring, summer, and fall interactions between FRB and FV on MRC and NMRC outcrops indicated that networks were, overall, generalist, but interactions between flowers and floral visitors on rock outcrops were unique both across seasons and between outcrop types. Five families of FV were identified as central to these networks (Apidae, Syrphidae, Halictidae, Formicidae, and Chrysomelidae), and select floral visitor families demonstrated high floral fidelity to single plant species during specific seasons. Overall, both seasonality and outcrop type influence diversity, composition, and plant-pollinator interactions in rock outcrop communities, and results recommend that land managers treat MRC and NMRC outcrops, and their spring, summer, and fall floral visitor and floral resource communities, as distinct and of equivalent importance to overall rock outcrop diversity. While generalist interactions suggest lower susceptibility to temporal mismatches between plants and pollinators with climate change, some species and families were identified as playing unique roles within the network: short-term specialization may have important implications for pollination, and species central to the network are likely integral to the maintenance of network structure.

Additional Information

Publication
Thesis
Language: English
Date: 2022
Keywords
Conservation, Networks, Phenology, Pollination, Rock outcrops
Subjects
Plant phenology
Outcrops (Geology)
Pollinators

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