The Community Ecology, Behaviour and Biology of New Zealand Carrion Flies

Abstract

True flies (Diptera) are amongst the most diverse groups that inhabit our planet. Despite this, most Diptera species remain unstudied, and in New Zealand are poorly known. This thesis investigates several aspects of the community ecology and behaviour of carrion and forest associated Diptera. Carrion is a nutrient-rich and ephemeral resource that sustains a large diversity of organisms, both directly and indirectly, of which Diptera form a dominant component. Diptera are known to form diverse communities around carrion and experience high levels of both intra- and interspecies competition for access to this resource for feeding and oviposition. Differences in seasonality, voltinism (amount of breeding cycles), and developmental rate of individual flies is thought to facilitate the coexistence of the many species that inhabit the highly competitive environments of carrion and dung resources. I sampled the Diptera community at several forest sites throughout the Waitakere Ranges in Auckland, New Zealand using carrion-baited traps in different sub-habitats. The diversity, community composition, and relative abundances of individual Diptera species were described in relation to environmental variables. Habitat and season were both found to have a significant and interactive effect on carrion-attracted fly species assemblages. All dipteran communities differed in accordance to season, habitat and trap methodology. The other aim of my project was to examine the aggressive, courtship and mating behaviours of the previously unstudied Diptera species, Scordalus femorata (Helosciomyzidae) and investigate variation in structures associated with these behaviours. Analysis of field data, combined with laboratory experiments were used to characterise and describe the mating system of this species. Static allometry was used to determine if various structures exhibit scaling relationships typical of those under sexual selection in male and female S. femorata. Our findings here were the first to describe any of the behaviours of S. femorata and indicated ritualised displays in both aggression and courtship. Prolonged copulation was also observed in this species and combined with female-biased allometries suggests sexual coevolution. Allometric relationships and sexual size dimorphism also suggest an intense level of competition and sexual selection in males of this species. Our research suggests that S. femorata could be a useful model organism for the study of sexual selection, behaviour and the evolution of associated morphologies. Together, the findings of this thesis are distinctive in that they investigate and document patterns of carrion-fly community ecology, behaviour and the evolution of traits in the light of sexual selection. This information lays the foundation for which further research into the ecology, behaviour and life-histories of New Zealand Diptera can be undertaken.