Phylogenetic relationships among the Australian Leptophlebiidae genera and selected genera from South America and New Zealand were investigated using a cladistic analysis of 43 morphological characters. The outcomes of this analysis were largely consistent with the higher-level relationships previously proposed by Pescador and Peters (1980). The monophyly of the Meridialaris lineage (comprising Austrophlebioides, Tillyardophlebia, Kirrara, ‘WT sp. 1’ and ‘WT sp. 2’ from Australia, Meridialaris from South America and Deleatidium and Atalophlebioides from New Zealand) was strongly supported, as was the monophyly of the Nousia lineage (Nyungara, Nousia and Koorrnonga). However, Australian genera assigned to the Hapsiphlebia lineage (Atalophlebia, Kalbaybaria, Ulmerophlebia, Jappa and Atalomicria) did not form a monophlyletic group. There was support for a sister-group relationship between the Dactylophlebia and Meridialaris lineages, and for the placement of Garinjuga (Penaphlebia lineage) as the sister-group to a large clade comprising genera of the Nousia, Dactylophlebia and Meridialaris lineages. The phylogenetic analysis provided some clarification of the affinities of Neboissophlebia, Bibulmena, Loamaggalangta and Kaninga. These genera appear to belong to lineages not recognised previously among the Gondwanan Leptophlebiidae.

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Summary Understanding spatial and environmental drivers of undisturbed stream assemblages is important for separating natural and human‐induced changes, but has rarely been attempted for an entire tropical bioregion. We sampled riffle macroinvertebrate assemblages and measured associated biophysical variables in post‐wet and dry seasons from 68 streams of orders 1–5 across the Australian Wet Tropics, a small bioregion (18 497 km2) defined by its warm moist climate and closed‐forest vegetation. As climate and landscape were relatively uniform across the bioregion, we predicted that assemblages would be similar, with turnover (beta diversity) unrelated to distance, and with composition determined mainly by habitat. We identified 93 higher taxa. Density and richness of macroinvertebrates were greatest in the dry season because of habitat contraction and minimal flow disturbance. Richness was greatest in higher order streams. Relative abundance and richness of functional groups showed minor effects of catchment, lithology and stream order, and a positive relationship with altitude for richness of collectors, predators and shredders, and for abundance of shredders. Distance‐based linear modelling showed that among‐assemblage differences were explained by landscape‐scale variables (9.5% of the variation), stream size (13.0%), riparian characteristics (9.6%), water quality (4.6%), substratum (21.1%) and organic resources (22.4%); for models of individual taxa and functional groups, habitat and organic‐resource variables also predominated. Similarities among site assemblages differed little among catchments and there was no relationship between pairwise similarities of catchments and their geographical distances. Nestedness analysis confirmed that samples and catchment groupings were nested subsets of the total set of samples. Across the Australian Wet Tropics, uniformity of assemblages (identified to family or above) conformed to the bioregional classification, probably as a result of the great age of the region. The habitat variables that most influenced macroinvertebrate assemblages support the idea that a suite of biophysical influences is common to stream macroinvertebrate assemblages globally.

Three new species of the mayfly genus Austrophlebioides Campbell and Suter are described from the Wet Tropics bioregion of north-eastern Australia: A . rieki sp. n., A . wooroonooran sp. n. and A . porphyrobranchus sp. n. The three species are similar, and are characterised in the male imago by the presence of a prominent ventral projection on each lobe of the penes and segment one of the claspers narrowing at about one-third length, and in the nymph by the absence of fine setae along the outer margin of the mandible between the median setal tuft and the outer incisor. The generic diagnosis of the nymphal stage is modified slightly to accommodate the three new species.

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