Upper temperature limits for trout in New Zealand and climate change

The significance of temperature in determining the northernmost limit of trout in New Zealand is discussed, and the river temperature records available suggest that high winter temperatures, rather than high summer temperatures are involved. The predicted climate changes consequent on increased concentrations of atmospheric gases, are used to predict changes in trout distribution. A 1.5 °C increase is likely to result in a contraction of the distribution of brown trout in northern areas, but the effects elsewhere on brown trout would be limited. A 3 °C increase is likely to eliminate both species from borthern latitudes, while heat stress could alter distributions of both species throughout the country. The possibilities of genetic responses to the changes are discussed.     

New Zealand climate in the Neogene and implications for global atmospheric circulation

New Zealand has a good Neogene plant fossil record. During the Miocene it was without high topography and it was highly maritime, meaning that its climate, and the resulting vegetation, would be controlled dominantly by zonal climate conditions. Its vegetation record during this time suggests the climate passed from an ever-wet and cool but frostless phase in the Early Miocene in which Nothofagus subgenus Brassospora was prominent. Then it became seasonally dry, with vegetation in which palms and Eucalyptus were prominent and fires were frequent, and in the mid-Miocene, it developed a dry-climate vegetation dominated by Casuarinaceae. These changes are reflected in a sedimentological change from acidic to alkaline chemistry and the appearance of regular charcoal in the record. The vegetation then changed again to include a prominent herb component including Chenopodiaceae and Asteraceae. Sphagnum became prominent, and Nothofagus returned, but mainly as the subgenus Fuscospora (presently restricted to temperate climates). This is interpreted as a return to a generally wet, but now cold climate, in which outbreaks of cold polar air and frost were frequent. The transient drying out of a small maritime island and the accompanying vegetation/climate sequence could be explained by a higher frequency of the Sub-Tropical High Pressure (STHP) cells (the descending limbs of the Hadley cells) over New Zealand during the Miocene. This may have resulted from an increased frequency of ‘blocking’, a synoptic situation which occurs in the region today. An alternative hypothesis, that the global STHP belt lay at a significantly higher latitude in the early Neogene (perhaps 55°S) than today (about 30°S), is considered less likely because of physical constraints on STHP belt latitude. In either case, the difference between the early Neogene and present situation may have been a response to an increased polar-equatorial temperature gradient. This contrasts with current climate models for the geological past in which the latitude of the High Pressure belt impact is held invariant though geological time.     

Forest pattern,climate and vulcanism in central North Island,New Zealand

Abstract. A quantitative study of relationships between forest pattern and environment in the central North Island, New Zealand, is based on forest composition data from ca. 2000 existing plots distributed throughout the forests of the region. Estimates of mean annual temperature, rainfall, and solar radiation are derived for each plot from mathematical surfaces fitted to climate station data. Estimates of the depth of the last major rhyolitic eruption, (Taupo Pumice, ca. 130 AD) are derived from isopach maps. A classification procedure is used to identify broad compositional groups. Generalised linear models are used to examine relationships between major species and climatic and other physical factors. Significant relationships are identified between the distributions of both plot groups and species, and climate, vulcanism, topography and drainage. Among these factors, temperature and/or solar radiation are indicated as major determinants of the regional forest pattern, with rainfall, topography, and drainage acting at a secondary level. The role of the Taupo Pumice eruption is more difficult to interpret, and its effects seem to have been greatly influenced by topography. Deep extensive deposits of tephra on flat-to-rolling sites close to the eruption centre have probably favoured the current dominance of these sites by more rapidly dispersing conifers. In contrast, on adjacent steep sites where forest destruction was likely to be less severe, slow-dispersing Nothofagus species are largely dominant. Further work is needed to understand the factors favouring conifer dominance of the central basins and the degree to which Nothofagus species might expand their range in the future.     

Species diversity in relation to ultramafic substrate and to altitude in southwestern New Zealand

Altitudinal trends in species diversity were examined on a New Zealand ultramafic mountain, and on nearby normal (schist) substrate. At lower altitudes, diversity is similar on the two substrates. On the ultramafic substrate, species diversity decreased with increasing altitude; on schist substrate the opposite trend was found. This difference was demonstrable in species richness, based on species presence/absence, and in indices of species diversity based on cover data (the ShannonH and the Simpson/Yule — InD). It is suggested that on ultramafics, altitudinal stress and soil conditions lead to a decrease in diversity with altitude. On schist, in contrast, the opening of the canopy with altitude is suggested to be the predominant influence, leading to an increase in diversity with altitude. Nomenclature: Allan, H. H. 1961. Flora of New Zealand, Vol I, Government Printer, Wellington; Mark, A. F. & Adams, N. M. 1986. New Zealand alpine plants. 2nd rev. Reed Methuen, Wellington; Connor, H. E. & Edgar, E. 1987. Name changes in the indigenous New Zealand Flora, 1960–1986 and Nomina Nova IV, 1983–1986, N.Z. Jl Bot. 25: 115–170; except where indicated.     

Genetic Characterization and Transmission Cycles of Cryptosporidium Species Isolated from Humans in New Zealand

Little is known about the genetic characteristics, distribution, and transmission cycles of Cryptosporidium species that cause human disease in New Zealand. To address these questions, 423 fecal specimens containing Cryptosporidium oocysts and obtained from different regions were examined by the PCR-restriction fragment length polymorphism technique. Indeterminant results were resolved by DNA sequence analysis. Two regions supplied the majority of isolates: one rural and one urban. Overall, Cryptosporidium hominis accounted for 47% of the isolates, with the remaining 53% being the C. parvum bovine genotype. A difference, however, was observed between the Cryptosporidium species from rural and urban isolates, with C. hominis dominant in the urban region, whereas the C. parvum bovine genotype was prevalent in rural New Zealand. A shift in transmission cycles was detected between seasons, with an anthroponotic cycle in autumn and a zoonotic cycle in spring. A novel Cryptosporidium sp., which on DNA sequence analysis showed a close relationship with C. canis, was detected in two unrelated children from different regions, illustrating the genetic diversity within this genus.     

Species of the genus Crotonia (Acari: Cryptostigmata) from New Zealand

Five new species of Crotonia from New Zealand ( C. cervicorna, C. cupulata, C. longibulbula, C. tuberculata and C. reticulata ) are described as new, and two species ( C. cophinana (Michael 1908) and C. caudatis (Hammer 1966)) are redescribed. Five species groups of the genus are characterized and a key to the adequately described species of the world is presented.     

Species Radiation of Carabid Beetles (Broscini: Mecodema) in New Zealand

New Zealand biodiversity has often been viewed as Gondwanan in origin and age, but it is increasingly apparent from molecular studies that diversification, and in many cases origination of lineages, postdate the break-up of Gondwanaland. Relatively few studies of New Zealand animal species radiations have as yet been reported, and here we consider the species-rich genus of carabid beetles, Mecodema. Constrained stratigraphic information (emergence of the Chatham Islands) and a substitution rate for Coleoptera were separately used to calibrate Bayesian relaxed molecular clock date estimates for diversification of Mecodema. The inferred timings indicate radiation of these beetles no earlier than the mid-Miocene with most divergences being younger, dating to the Plio-Pleistocene. A shallow age for the radiation along with a complex spatial distribution of these taxa involving many instances of sympatry implicates recent ecological speciation rather than a simplistic allopatric model. This emphasises the youthful and dynamic nature of New Zealand evolution that will be further elucidated with detailed ecological and population genetic analyses.