The Impact of Colonization History and Fish Predation on Larval Odonates (Odonata: Anisoptera) in a Central New Jersey Farm Pond

Abstract

Larval odonates were manipulated in a small farm pond in central New Jersey to study the effects of colonization history and fish predation on species composition. Species exhibited a wide range of breeding phenologies. Temporal separation may have an affect on the larval assemblage by reducing interactions between species. Abundances of metamorphs were negatively correlated with species-specific final instar body length suggesting the other, size dependent interactions such as vertebrate predation may also affect the dragonfly guild. Experiments with screen enclosures which differed in (1) time of placement and (2) presence or absence of fish predators studied the effects of breeding phenology and predation on larval odonates. Timing of pen placement did not significantly affect the abundances of larval odonates. Two species with extremely different life histories were able to coexist in large numbers in the natural community. The abundance of a late fall breeding species in early treatment pens implied that identifying priority effects may involve more than simply equating them with species which breed early in the year. Fish predation had a significant impact on production and species composition. While fish reduced the abundance of larger odonate species, they enchanced the abundance of small odonates in the experimental enclosures. The dragonfly assemblage in this study appears to be controlled more by the actions of vertebrate predators rather than by the seasonal segregation of species-specific life histories.