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.
The descriptions of males of the two described species of Ramiheithrus (R. virgatus Neboiss and R. kocinus Neboiss) are expanded using additional material. The female, pupa and larva of Ramiheithrus virgatus are described for the first time for the genus. Preliminary genetic barcoding analysis suggests the presence of additional undescribed species that are only known as larvae. The unusual larval habitat is described and issues relating to this are discussed.
The female, larva, and pupa of Antipodoecia Mosely from Australia are described, males re-examined and briefly described. Similarities with other trichopteran families are discussed. Based on morphological synapomorphies of males, females, pupae, and larvae, we infer that the genera Antipodoecia, Anomalopsyche, and Contulma share an immediate common ancestor, although relationships among these genera remain unresolved. Consequently, the Neotropical family Anomalopsychidae is a junior synonym of Antipodoeciidae from Australia.
-Larvae of Condocerus aphiS, Notoperata tenax, Symphitoneuria wheeleri, Triplectides niveipennis, and Triplectides en thesis are described for the first time. The female of Triplectides niveipennis is also described for the first time. Variation in larvae and adults of Triplectides niveipennis is discussed, together with unusual characters in the larvae requiring redefinition of the genus. Minor changes to the generic descriptions of Condocerus, Notoperata and Symphitoneuria are also made.
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