Ian M. Henderson

Predicting dry weight of New Zealand aquatic macroinvertebrates from linear dimensions

Abstract Regression equations are presented for the estimation of dry weight from head width and body length for 20 common New Zealand stream‐dwelling macroinvertebrate taxa. Equations for taxa grouped at order level are also provided. A power equation, y = a x b is used to express the relationship between dry weight and body size. For the majority of taxa, dry weight could be estimated with more precision from body length than from head width.

Nontarget Effect of Entomophagous Biocontrol: Shared Parasitism Between Native Lepidopteran Parasitoids and the Biocontrol Agent Trigonospila brevifacies (Diptera: Tachinidae) in Forest Habitats

Abstract The parasitoid guild attacking preimaginal Tortricidae on shrubs and small trees in broadleaf/podocarp forests was studied at six sites in the central North Island. Connectance and quantitative webs were used to interpret the complexities of host parasitoid interactions at a community level and identify competition between native parasitoids and the introduced species Trigonospila brevifacies (Hardy). Trigonospila brevifacies is numerically dominant in the tortricid parasitoid guild. Its host range overlaps with 12 native and one introduced parasitoid species, and it parasitizes more species of Tortricidae than other parasitoids at the North Island forest sites surveyed. Quantification of the parasitoid load on native Lepidoptera indicated that T. brevifacies parasitism comprised between 15.6 and 79.5% of the parasitoid load per species. Only the introduced Australian canefruit pest Eutorna phaulocosma Meyrick (Lepidoptera: Oecophoridae) received a higher proportion of parasitism from T. brevifacies than any of the native Lepidoptera. The number of parasitoid species attacking each preimaginal host stage (except for pupae) of native Lepidoptera was relatively constant. The only pupal parasitoid recorded was the introduced ichneumonid Xanthopimpla rhopaloceros Krieger (Hymenoptera: Ichneumonidae). All native parasitoid species were less abundant than T. brevifacies.

Diadromy and longitudinal patterns of upstream penetration of freshwater fish in Taranaki, New Zealand

Abstract Diadromous fish species dominate the New Zealand freshwater fish fauna and make up 15 of the 17 native fish species found on the Taranaki Ring Plain. Trajectories of occurrence in relation to elevation and distance from the sea are described for 11 diadromous and 2 non‐diadromous species using data from the New Zealand Freshwater Fish Database and data collected over the summer of 1997/ 98. Distinctive distributions were found for most of the species related to their differing migratory strategies and abilities. The species were ranked based on components of these trajectories to compare their penetrative ability. Comparison of the ranking methods used revealed they produced similar results. The ranking of the 11 diadromous species in Taranaki relative to each other revealed similar rankings to those for the same species from the West Coast of the South Island. The non‐migratory native fish, Crans bully (Gobiomorphus basalis), was not found on the western side of the mountain. This distribution is thought to be the result of the local extinction of non‐migratory species in high gradient or unstable streams.

Quantitative panbiogeography: An investigation into concepts and methods

Abstract The development of the minimal spanning tree method of panbiogeographic analysis is outlined and its validity and utility discussed. A rationale for geographic parsimony is suggested and problems with the application of spanning trees, including incongruent track orientation, missing cladistic data, and the significance of minimality, are identified. The concepts of graph theory are used to develop criteria for recognition of nodes and to formulate statistical tests of biogeographic patterns. The algorithms and tests described are illustrated with examples from the biogeography of New Zealand Trichoptera.

Foraging ecology of blue ducks Hymenolaimus malacorhynchos on a New Zealand River : implications for conservation

Abstract We investigated whether blue ducks Hymenolaimus malacorhynchos preferentially capture prey that have themselves become rare or that need to be present for successful re-establishment. Working at the Manganuiateao River in New Zealand, we measured the densities and relative abundances of benthic invertebrates, numbers of prey fragments in faeces of adult ducks, and foraging behaviour of adult ducks. Invertebrate densities on stones ranged from 3741 m−2 to 14,417 m−2. Stone and boulder communities were dominated by cased caddisfly larvae or Chironomidae larvae in most months. Patterns of apparent selectivity varied, but Trichoptera larvae in the family Hydrobiosidae and in the genus Aoteapsyche (Hydropsychidae) ranked highly, and cased caddis larvae consistently ranked low, in the diet. Discriminant function analysis indicated that apparent prey preferences were partly related to whether foraging blue ducks were gleaning from the tops or undersides of rocks in the river. Canonical correlation analysis showed that ingestion of stonefly and mayfly larvae was associated with diving behaviour, but it was not possible to predict the ingestion of other prey from foraging tactics. No single prey category was so highly valued by the blue ducks we studied that it might limit population establishment at new sites.

Seasonality, sex ratios and arrival pattern of some New Zealand caddis (Trichoptera) to Light‐Traps

We report the results of three independent light‐trapping studies of caddis (Trichoptera) at three widely‐separated stream‐side sites in New Zealand. A total of 66 caddis species in 10 families was recorded, as follows: 33 from site K (Kawarau Gorge) in 1990–91, 28 from site T (Turitea Stream) in 1986–87 and 45 from site W (Waitakere Stream/Cascade Stream) in 1967–68. Many of the species were captured in sufficient numbers to estimate their adult flight season. The results show that some species in the families Hydrobiosidae, Hydroptili‐dae and perhaps also Philopotamidae and Chathamiidae are present as adults during every month of the year. Species captured from 7 other families appeared to have a mid‐winter break with no active adults present. For some species there is a marked change in the sex ratio through the flight season from predominantly males early in the season to predominantly females at the end. For four common species at one site, the arrival pattern at the light trap was unimodal. It was h...

Influenza viruses, comets and the science of evolutionary trees.

The study of phylogeny is becoming increasing scientific in that hypotheses can be tested quantitatively. We report a method of estimating the probabilities of obtaining a tree of a given length from nucleic acid sequence data. The method is applied to the hypothesis of Hoyle & Wickramasinghe that the earth is being continually bombarded by influenza (and other) viruses which originate from comets. A quantitative analysis of sequences from the H1 strain of human influenza viruses contradicts three versions of the Hoyle-Wickramasinghe model. One non-evolutionary version of their model has less than one chance in 10(66) of being correct. A version that allowed extraterrestrial evolution has less than one change in 10(6) of being correct. The sequence data is in agreement with the biological (evolutionary) model. The results are discussed from the aspect of the falsifiability of evolutionary theory.

Three new species in the endemic New Zealand genus Alloecentrella (Trichoptera), and a re-evaluation of its family placement

Abstract Three new species of caddis in the endemic New Zealand genus Alloecentrella Wise, 1958 (Trichoptera: Sericostomatoidea) are named and described: A. linearis sp. n., A. cirratus sp. n., and A. incisus sp. n. We report the known distribution of each of the four species in the genus; A. magnicornis and A. incisus appear to be found only in North Island; A. linearis and A. cirratus have been recorded only from South Island. We provide characters to differentiate the larvae (extent of the head carina; the shape of the head capsule in lateral profile) and cases (position of the terminal aperture). We present the results of a phylogenetic analysis of larval, pupal and adult morphological characters which places Alloecentrella in the Helicophidae.

The Effect of Formalin on Rumen Surface Area in Red Deer

Previously published studies have related the surface area of rumen wall to diet. The validity of studies that utilize preserved material depends upon the predictability of any change in rumen dimension brought about by preservation. Changes in the surface area of different sections of the rumen wall of red deer (Cervus elaphus) were monitored after immersion in 10% formal saline solution at room temperature for 2, 7 and 14 days. There was a high degree of variability (0–39.5%) in wall‐area reduction. Ignoring such changes when calculating the factor of increase in surface area (FISA), a composite of papillary surface area and density, can result in errors of up to 39.5%. This study questions the validity of using FISA calculations when formalin‐preserved specimens are used in studies of rumen response to diet. Rumen papillary dimensions were not significantly changed by preservation in formalin.

Omasal Anatomy in New Zealand Red and Fallow Deer: An Exploratory Multivariate Analysis

We measured the weight and volume of omasae, and the number, weight and area of omasal laminae from wild fallow (Cervus dama), and wild and farmed red deer (Cervus elaphus) whose diet, as indicated by rumen content, was known. A multivariate analysis yielded two principal components, interpreted as indices of overall omasal size and laminar leafiness. The second component showed significantly greater variance in wild red deer than in farmed red or wild fallow deer. Deer feeding on a mixed diet of browse and grasses may have greater variability of omasal form than those feeding on grass alone. A relationship is derived by which the laminar area can be estimated from counts of laminae in different size classes.