Effects of host-plant population size and plant sex on a specialist leaf-miner

• Published in: Acta oecologica (Montrouge) 2011-03, Vol.37 (2), p.58-64
• Main Authors: Bañuelos, María-José, Kollmann, Johannes
• Format: Article
• Language: English
• Subjects: adults; Animal and plant ecology; Animal density; Animal, plant and microbial ecology; animals; biogeography; Biological and medical sciences; correlation; Eggs; females; Fundamental and applied biological sciences. Psychology; Gender-biased leaf mining; General aspects; hatching; herbivores; host plants; Ilex aquifolium; immigration; Immigration behaviour; insects; larvae; leaves; Patch area; Phytomyza ilicis; population density; population size; predation; Specialist herbivores; survival rate; Survival rates
• ISSN: 1146-609X; 1873-6238
• DOI: 10.1016/j.actao.2010.11.007

Animal population density has been related to resource patch size through various hypotheses such as those derived from island biogeography and resource concentration theory. This theoretical framework can be also applied to plant–herbivore interactions, and it can be modified by the sex of the host-plant, and density-dependent relationships. Leaf-miners are specialised herbivores that leave distinct traces on infested leaves in the form of egg scars, mines, signs of predation and emergence holes. This allows the life cycle of the insect to be reconstructed and the success at the different stages to be estimated. The main stages of the leaf-miner Phytomyza ilicis were recorded in eleven populations of the evergreen host Ilex aquifolium in Denmark. Survival rates were calculated and related to population size, sex of the host plant, and egg and mine densities. Host population size was negatively related to leaf-miner prevalence, with larger egg and mine densities in small populations. Percentage of eggs hatching and developing into mines, and percentage of adult flies emerging from mines also differed among host populations, but were not related to population size or host cover. Feeding punctures left by adults were marginally more frequent on male plants, whereas egg scars and mines were more common on females. Overall survival rate from egg stage to adult emergence was higher on female plants. Egg density was negatively correlated with hatching, while mine density was positively correlated with emergence of the larvae. The inverse effects of host population size were not in line with predictions based on island biogeography and resource concentration theory. We discuss how a thorough knowledge of the immigration behaviour of this fly might help to understand the patterns found.