Spatial variation in invertebrate communities in New Zealand braided rivers By Duncan Gray and Jon S. Harding
Science for Conservation 302. 43 p.
What's it about? Large braided rivers are a distinctive feature of the landscape in several regions of New Zealand. The invertebrate communities of braided rivers have been described as taxonomically depauperate, but recent research has suggested otherwise. We conducted a field survey of 11 braided rivers, collecting benthic invertebrates from six reaches dispersed down each river, and sampling up to five habitats per reach. We compared the taxonomic richness of these braided, multi-channel rivers with non-braided, single channel rivers, and found that braided rivers actually support very diverse invertebrate assemblages when all floodplain habitats are included in analyses. We then compared biodiversity patterns within braided rivers. A total of 144 taxa and over 100 000 individuals were collected from the 11 braided rivers. Thirty-four percent of taxa were found in ≤ 3 rivers and comprised < 1% of all individuals, whereas 13% of taxa were found in all rivers and constituted 80% of all individuals. Total taxonomic richness ranged from 99 taxa in the Wairau River to 56 taxa in the Waiapu River. Surprisingly, no consistent longitudinal pattern in taxonomic richness or density was found; however, braided reaches were more diverse than headwater and gorge reaches. At the reach scale, 80% of lateral habitats (i.e. springs and ponds) were more diverse than their associated main channel. These findings show that despite high variation between and within rivers, lateral floodplain habitats are important biodiversity hotspots. Therefore, any assessment of the diversity of braided rivers must incorporate sampling across multiple spatial scales and include the full range of habitats present in the floodplain.
The above new publication is now in press and can be downloaded from:
http://www.doc.govt.nz/upload/documents/science-and-technical/sfc302entire.pdf (1228 KB)
