Reproductive biology of Corymbia citriodora subsp. variegata and effective pollination across its native range in Queensland, Australia

  • CFE Bacles
  • J Brooks
  • DJ Lee
  • PM Schenk
  • AJ Lowe
  • A Kremer

Abstract

The spotted gum species complex represents a group of four eucalypt hardwood taxa that have a native range that spans the east coast of Australia,  with a morphological cline from Victoria to northern  Queensland. Of this group,Corymbia citriodora subsp. variegata (CCV) is widespread in south-eastern Queensland and northern New South Wales. It is currently the most commonly harvested native hardwood in Queensland. However, little basic knowledge of the reproductive  biology of the species is available to inform genetic improvement and resource management programmes. Here we take an integrative approach, using both field and molecular data, to identify ecological factors important to mating patterns in native populations of CCV. Field observation of pollinator visitation and flowering phenology of 20 trees showed that foraging behaviour of pollinator guilds varies depending on flowering phenology and canopy structure. A positive effect of tree mean flowering effort was found on insect visitation, while bat visitation was  predicted by tree height and by the number of trees simultaneously bearing flowers. Moreover, introduced honeybees were observed frequently, performing 73% of detected flower visits. Conversely, nectar-feeding birds and mammals were observed sporadically with lorikeets and honeyeaters each contributing to 11% of visits. Fruit bats, represented solely by the grey-headed flying fox, performed less than 2% of visits. Genotyping at six microsatellite markers in 301 seeds from 17 families sampled from four of Queensland’s native forests showed that CCV displays a mixed-mating system that is mostly outcrossing (tm = 0.899 ± 0.021). Preferential effective pollination from near-neighbours was detected by means of maximum-likelihood paternity analysis with up to 16% of reproduction events resulting from selfing. Forty to 48% of fertilising pollen was also carried from longer distance (>60 m). Marked differences in foraging behaviour and visitation frequency between observed pollinator guilds suggests that the observed dichotomy of effective pollen movement in spotted gums may be due to frequent visit from introduced honeybees favouring geitonogamy and  sporadic visits from honeyeaters and fruit bats  resulting in potential long-distance pollinations.

Southern Forests 2009, 71(2): 125–132

Author Biographies

CFE Bacles
Institut National de la Recherché Agronmique, UMR 1202 Biodiversity, Genes and Communities, 69 Route d’Arcachon, 33612 Cestas Cedex, France; School of Integrative Biology, University of Queensland, Brisbane, QLD 4072, Australia; Current address: School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK
J Brooks
School of Integrative Biology, University of Queensland, Brisbane, QLD 4072, Australia
DJ Lee
The State of Queensland, Department of Primary Industries and Fisheries, Locked Bag 16, Fraser Road, Gympie, QLD 4570, Australia; Faculty of Science, Health and Education, University of the Sunshine Coast, Maroochydore DC, QLD 4558, Australia
PM Schenk
School of Integrative Biology, University of Queensland, Brisbane, QLD 4072, Australia
AJ Lowe
School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia
A Kremer
Institut National de la Recherché Agronmique, UMR 1202 Biodiversity, Genes and Communities, 69 Route d’Arcachon, 33612 Cestas Cedex, France
Section
Articles

Journal Identifiers


eISSN: 2070-2639
print ISSN: 2070-2620