Graham Stone

Dr. Graham Stone

  • D.Phil Oxford University 1990: Behavioural and physiological thermoregulation in solitary bees.
  • Post-Doc, 1990-1993 Imperial College at Silwood Park with Profs. Mick Crawley and John Lawton on the population biology of invading insects.
  • 1993-1998 Departmental Lecturer in Invertebrate Zoology, Oxford University.
  • 1998- Lecturer in Animal Ecology, ICAPB.

Research interests

I have a schizoid interest in two parts of the general field of insect-plant interactions.

Population biology of oak feeding gallwasps. Gallwasps induce a wide diversity of highly complex galls on oak trees, and show high specificity to particular plant organs and oak taxa. With Dr. James Cook (Imperial College at Silwood Park) and Ph.D. student Antonis Rokas (ICAPB) I am using DNA sequence phylogenies to examine patterns of evolution in these traits. On a shorter evolutionary timescale, with Ph.D. student Rachel Atkinson (ICAPB) I am looking at the genetic consequences of post-glacial range expansion in a range of gallwasp species. We are particularly interested in identifying colonisation routes, and examining the importance of glacial refugia in southern Europe as centres of genetic diversity. Our studies concern particularly species in the genera Andricus, Biorhiza and Cynips, and make use of allozyme and microsatellite markers.

Pollination biology of acacias. The thousand or so species of acacia are important woody plants throughout the southern hemisphere, particularly in seasonally arid habitats. In many regions, seasonal rainfall prompts mass flowering by several acacia species at the same time (co-flowering). The general "pom-pom" structure of acacia flowers means that acacias share many pollinating insects and raises the question of how co-flowering acacias avoid interspecific pollen transfer. While pollen is rarely a limiting resource, pollen from the wrong species can be a serious cost by blocking the limited receptive surface of the stigma. Work in Tanzania and Kenya with Dr. Pat Willmer (St. Andrews University) is revealing that while acacia species may flower at the same time, species in fact have characteristic and distinct daily times of pollen release, spread through the day between dawn and dusk. Shared pollinators visit one species after the other through the day, reducing interspecific pollen flow. We are now looking at whether daily times of pollen release are species specific, or show regional variation in response to the diversity of other acacia species.

An additional component of the acacia work is the interaction between acacia pollinators and the ant-guards present on certain acacia species. While such ant guards provide a valuable service in repelling herbivores from caterpillars to giraffes, they could interfere with pollination by driving away useful pollinating insects. We have shown that acacia flowers possess ant-repellents that keep ant-guards away for the crucial pollination period. We are now looking at the specificity and source of such ant repellents.