Spatial pattern, patch dynamics and successional change: chironomid assemblages in a Lake Erie coastal wetland

1. Distribution patterns in 1994 and 1995 of chironomid larvae in the sediments of wetlands on Presque Isle, Pennsylvania were used to determine whether relationships exist among species composition and wetland age, position or environmental characteristics. Canonical correspondence analysis was used to relate wetland age, degree of isolation, vegetation abundance and water chemistry to species composition.
2. Of forty-two chironomid taxa collected, Tanytarsus lugens group, Paratanytarsus sp. and Cladotanytarsus mancus group were the most widespread, but Lauterborniella agrayloides , Stictochironomus sp. and Cryptochironomus sp. were locally abundant in several sampling sites.
3. The canonical ordination based on all site characteristics was statistically significant and accounted for 54.9% of the variance in the species data and 69.5% of the variance in the species–environment relationship. The variables that contributed significantly to the ordination model were macrophyte abundance, conductivity and wetland area.
4. Partial canonical ordination based on environmental conditions with wetland age and position effects as covariables showed that environmental conditions explain a significant proportion of the variance in species composition among sites. Neither wetland age nor position variables explain a significant proportion of the variance in species composition.