Colonisation of experimentally immersed wood in south eastern Australia: responses of feeding groups to changes in riparian vegetation

We investigated macroinvertebrate abundance and functional feeding groups c olonising experimentally-positioned woody substrates of different species i n streams with three different riparian vegetation types. Native Eucalyptus forest formed a dense closed canopy over our streams; introduced (exotic, alien) pine plantation forest did not fully shade the streams, and grasslan d streams were completely open, although with woody riparian vegetation wel l upstream of our sites. Macroinvertebrate assemblages varied taxonomically and functionally with both wood species and riparian vegetation compositio n. Two specialist feeding groups responded clearly to riparian vegetation: wood gougers were most common in forested streams, and algal grazers in mor e open streams. Gougers colonised native Eucalyptus wood in preference to a lien species. Other feeding groups responses showed complex interactions be tween vegetation and wood type. Our results indicate the importance of samp ling appropriate substrates when assessing questions of this type - if seek ing shifts in functional organisation, the substrates on which the feeding groups of interest occur must be sampled. The composition of the riparian s trip may influence xylophilous communities as much as the structure (i.e. w hether closed or open).