Ms Maria Duynisveld1, Rhydian Crawford2, Bennie Mildren3, Dr. Paul Manning2

1Unaffiliated, Oyster Cove, Australia, 2Dalhousie University, Halifax, Nova Scotia, Canada, 3University of Tasmania, Hobart, Tasmania, Australia

Biography:

Maria Duynisveld is a Canadian transplant to Tasmania. She received a BSc. (Agr.) from Dalhousie University in Nova Scotia in 2023. Maria is also a farmer and passionate naturalist. This is her first major research project, undertaken in the summer following her graduation. Maria plans to continue in research and is exploring options for a higher degree in Australia.

Abstract:

Cornus canadensis is ecologically important for fruit-eating animal species. Three known insect species internally herbivorize C. canadensis, alongside externally herbivorizing insects. Warming climates influence insect ranges, potentially increasing herbivory in Northern forests. This study explores the impact of insect herbivory on the number of fruits produced by C. canadensis.

We used GBIF-sourced photographs of North American fruiting C. canadensis, comparing fruit production per plant. Plants were categorised by visible herbivory type: external insect herbivory (EIH), internal (mined), both, or neither. We conducted further studies in Nova Scotia, Canada.

We mimicked EIH at two instances during flowering, standardised at 40% of leaf area. Herbivory occurred in the first and third weeks using a subset of plants under identical environmental conditions. Fruit production was compared to a control group.

We conducted a five-week survey of C. canadensis in 0.8 ha of forest. Herbivory intensity and type was recorded weekly during flowering and ripening for 200 plants. Using functional data analysis, we compared fruit production per plant of all observed insect herbivory scenarios.

Surveys showed no significant impact on C. canadensis fruit production by insect herbivory. Manipulation showed first-week leaf area loss eliminated fruit production (p<0.001); third-week loss significantly reduced fruit production (p<0.05). Observational surveys did not replicate these scenarios, indicating rare natural occurrences.

These results indicate insect herbivory of C. canadensis does not have a significant effect on fruit production in nature. This suggests potential Northern increases of herbivorous insect ranges will not negatively impact C. canadensis.