Oral Presentation Australian Society for Limnology Congress 2013

Linking distribution, morphology and reproductive maturity of adult caddisflies with flight activity in the riparian zone (#51)

Joshua J Grubb 1 , Jill Lancaster 2 , Richard Marchant 1
  1. Museum Victoria, Melbourne, VIC, Australia
  2. Resource Management and Geography, Melbourne University, Melbourne, VIC, Australia

Although adult aquatic insects represent an important link between aquatic and terrestrial environments, especially in the riparian zone, their biology is not well-understood. The aim of this study was to characterise the distribution of adult caddisflies in the riparian zone and test whether flight distance from the stream differed between species, sexes, female reproductive status, and with wing morphology. To describe caddisfly distribution in the riparian zone, we set up light traps at various distances (0-45 m) from the Cumberland River, SW Victoria. For six species encompassing a range of body sizes, wing morphology was described by wing aspect ratio; female reproductive maturity was characterized by stage of ovarian development and presence/absence of eggs. Contrary to predictions, 50-80% of males and 30-60% of females caught were found throughout the riparian zone, and wing aspect ratio was not correlated with median flight distance. Immature females of some species indicated a relatively long-lived adult stage and tended to be found near the river. Most females were mature and the proportion of mature and spent females was similar over all distances. These results suggest that the riparian zone is an important habitat for adult caddisflies and a broad zone may be necessary to support diverse assemblages. Distribution patterns in the riparian zone may be more strongly linked to adult behaviours, such as mate searching or food acquisition, than to sex, reproductive status or wing morphology.