Floral biology, pollination vectors and breeding system of Zieria granulata (Rutaceae), an endangered shrub endemic to eastern Australia
Laura C. Lopresti
A * , Karen D. Sommerville B , Amy-Marie Gilpin C and Todd E. Minchinton A
+ Author Affiliations
- Author Affiliations
A Centre for Sustainable Ecosystem Solutions and School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
B The Australian PlantBank, Australian Institute of Botanical Science, The Royal Botanic Gardens and Domain Trust, Mount Annan, NSW 2567, Australia.
C Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia.
Australian Journal of Botany 71(5) 252-268 https://doi.org/10.1071/BT22055
Submitted: 25 May 2022 Accepted: 2 June 2023 Published: 23 June 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
Context: Understanding the factors that influence viable-seed production is crucial in the conservation of threatened plant species, yet these factors are often poorly understood.
Aims: We investigated the reproductive biology of Zieria granulata C.Moore ex Benth., an endangered Australian endemic with a limited distribution, with the intent of improving conservation and restoration outcomes.
Methods: Components of floral biology, including floral ontogeny and nectar production, were quantified to determine the pollination syndrome and the likely breeding system. Flower-visitor surveys (using both digital video recordings and human observations), a manipulative wind-pollination experiment and hand-pollination experiments were conducted to investigate pollination vectors and confirm the breeding system.
Key results: Z. granulata flowers were small, white, protandrous and produced highly ornamented pollen grains and small quantities of nectar; these characteristics suggest that the species fits the general entomophily syndrome. All floral visitors were arthropod species and of the 72 visitors observed, predominantly from the Dipteran and Hymenopteran families, 18 could be regarded as potential pollinators. Failure of simulated wind gusts (40 km h−1) to transport pollen ≥5 cm indicated that anemophily is unlikely for this species. Autonomous and manipulative selfing did not result in viable seed set, indicating that this is an obligate outcrossing species. However, fruit and viable-seed production was highly variable within and among some other treatments. Pre-dispersal seed predation was recorded at all study sites.
Conclusions: Pre-dispersal seed predation was recorded at all study sites and is a likely factor inhibiting viable-seed production.
Implications: This knowledge will be used to improve seed yield for collections used for ex situ conservation and restoration programs for the endangered Z. granulata.
Keywords: entomophilous, entomophily, Illawarra Zieria, insect–plant mutualism, mating systems, parasitoid, plant–animal interaction, pollination syndrome, seed viability.
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