North Island Populations Research Articles

A review of the status of New ZealandLeiopelmaspecies (Anura: Leiopelmatidae), including a summary of demographic studies in Coromandel and on Maud Island

Abstract Six species of Leiopelma frog endemic to New Zealand have been described, but three are extinct. Field surveys have extended the known contemporary ranges of L. archeyi and L. hochstetteri, though sub‐fossils reveal that both L. hochstetteri and L. archeyi/hamiltoni were formerly more widespread in New Zealand than they are now. A new North Island population of terrestrial Leiopelma resembling L. archeyi has recently been found. Introduced predators and food competitors, especially Rattus, have probably had a major detrimental impact on Leiopelma. No extant species is immediately at risk of extinction, but L. hamiltoni on Stephens and Maud Islands is very restricted in range and/or numbers. Leiopelma reaches high densities (up to 8 frogs/ m2) in suitable rock‐strewn habitats and can be relatively long‐lived (L. archeyi 17+ years, L. hamiltoni 23+ years). Population levels of L. archeyi have fluctuated in a Coromandel study plot sampled approximately annually over 1982–93, but on Maud Island L. ha...

Genetic and cytogenetic diversity in Hochstetter's frog,Leiopelma hochstetteri,and its importance for conservation management

Abstract Hochstetter's frog, Leiopelma hoch‐stetteri, is now reduced to a series of isolated populations of variable size and extent. Although the species is not considered endangered, some of these isolates may be threatened or vulnerable. In a genetically and geographically discontinuous species like L. hochstetteri, every population may be an important component of total biogeographic diversity, since each isolate may represent an emergent historical entity. Variation in supernumerary chromosome number between populations and, particularly, the morphology of the sex chromosome, in conjunction with isozyme evidence, enable the identification of important subdivisions within L. hochstetteri. The population on Great Barrier Island is cytogenetically distinct since its members have no univalent, sex‐specific chromosome such as is present in all females from the North Island. Frogs from Mt Ranginui in the Rangitoto Range are the most chromosomally and biochemically distinctive of the North Island population...

The evolution of hypervariable sex and supernumerary (B) chromosomes in the relict New Zealand frog, Leiopelma hochstetteri

AbstractChromosomes exhibiting elevated levels of differentiation are termed hypervariable but no proposed mechanisms are sufficient to account for such enhanced evolutionary divergence. Both hypervariable sex and supernumerary (B) chromosomes were investigated in the endemic New Zealand frog, Leiopelma hochstetteri, which is chromosomally polymorphic both within and between populations and has sufficiently elevated variation that different populations can be identified solely by their C‐banded karyotypes. This frog is further distinguished by the univalent, female‐specific W‐chromosome (0W/00 sex determination) uniquely possessed by North Island populations. This sex chromosome exhibited variation in morphology, size, and heterochromatin distribution, sufficient to resolve 11 different types, including isochromosomes. Five of the 12 populations examined also had supernumerary chromosomes that varied in number (up to 15 per individual) and morphology. Specific variations seen among the hypervariable chromosomes could have resulted from heterochromatinisation, chromosome fusions, loss‐of‐function mutations, deletions, and/or duplications. Frogs of the same species from Great Barrier Island, however, had neither supernumeraries nor the female‐specific chromosome. The 0W/00 sex chromosome system must have been derived after the isolation of Great Barrier Island from North Island populations by raised sea levels between 14 000 and 8000 years ago. Furthermore, biochemical divergence between populations is minor and therefore the chromosomal variation seen is comparatively recent in origin. The one characteristic common to all known hypervariable chromosomes is curtailment or lack of recombination. Their accelerated evolution therefore is possible via the mechanism of Muller's ratchet, either alone or in concert with other factors.

Intraspecific variation and interspecific differences in sex pheromones of sibling species inCtenopseustis obliquana complex

The specific status ofCtenopseustis obliquana pheromone-types I, II, and III has been more fully examined. Females of types I and III produce a mixture of (Z)-8- and (Z)-5-tetradecenyl acetates (Z8-14:Ac, Z5-14: Ac). The previously reported different ratios of these two components in females of the two types (type I=80∶20, III=90∶10) have been reinvestigated. The median ratios of each type differed significantly, although there was some overlap in the ranges of these ratios. A field cage trial showed that males of type III are attracted to females of type I, so the observed differences may be ascribed to intraspecific variation. In contrast to females of types I or III, females of type II produce Z5-14∶Ac but no Z8-14∶Ac. The electroantennogram (EAG) profile of antennae of type II males shows a maximum response to Z5-14∶Ac, while the EAG profiles of types I and III show a strong response to Z8-14∶Ac. In wind tunnel tests using mixtures of these two compounds, type II males prefer blends consisting of all or mostly Z5-14: Ac, while type I males showed a preference to a mix of 70% Z8-14∶Ac plus 30% Z5-14∶Ac. We found that type I males are attracted to type I females when offered a choice between type I and type II females in a field cage test and that type II males similarly prefer type II females. Males of types I and II have specialist cells for Z8-14∶Ac and Z5-14∶Ac but differ with respect to relative densities of these cells and to further cell types responsive to other alkenyl acetates. Type IIC. obliquana is considered therefore a sibling species of types I and III. In addition, the amount of Z5-14∶Ac produced by type II females varied geographically. Females from the North Island produced significantly less (median=1.2 ng) Z5-14∶Ac than females from the South Island (median=2.2 ng). Type II populations in the North Island morphologically resembled sympatric type I, rather than type II from the South Island and are designated as type II (North Island). Type II (North Island) populations have so far been found only at Rukuhia (near Hamilton) and from Kerikeri. In contrast, type II populations are sympatric with type III populations over much of the South Island. In a field cage trial, males of types II and II (North Island) were attracted to females of both II and II (North Island). We tentatively ascribe the differences between type II and type II (North Island) to intraspecific variation.

Records ofSticherus flabellatus(R.Sr.) H. St John (Pteridophyta-Gleicheniaceae) from South Island, New Zealand

Abstract Sticherus flabellatus (R.Br.) H. St John in New Zealand occurs not only in numerous localities in the northern part of the North Island but also near Takaka and Stockton, in the South Island. Its occurrence at the South Island sites is documented and discussed in relation to other plants with similar disjunct distributions. Four suggestions are offered to account for the distribution of this species in New Zealand. The one favoured is that North Island and South Island populations have been established independently by long distance dispersal from Australia.

GenusBembidionLatreille (Coleoptera: Carabidae) in New Zealand: A revision

The cosmopolitan genus Bembidion is represented in New Zealand by 20 species, of which 19 are endemic; B. brullei appears to be a recent introduction. On phenetic characters the species fall into 7 subgenera, as follows: Zeplataphus n.subg.—maorinum Bates, dehiscens Broun, charile Bates, granuliferum n.sp., townsendi n.sp., tairuense Bates; Zeactedium Netolitzky—orbiferum Bates, musae Broun; Zeperyphodes n.subg.—callipeplum Bates; Zeperyphus n.subg.—actuarium Broun; Zemetal‐lina n.subg.—chalceipes Bates, solitarium n.sp., anchonoderum Bates, tekapoense Broun, wanakense n.sp., urewerense n.sp., hokitikense Bates, parviceps Bates; Ananotaphus Netolitzky—rotundicolle Bates; Notaphus Stephens—brullei Gemminger & Harold. The North Island population of maorinum is distinct from the typical South Island form in having reduced microscrulpture on the elytra, and is here separated as levatum n.ssp. An apparent geographic isolate of anchonoderum, represented by 2 females from Stewart Island, is provisionally recogni...

Population cytology of the genus Phaulacridium

Samples of Phaulacridium marginale were taken from the North Island of New Zealand, together with further samples from three South Island populations. Seven of the North Island populations were found to be polymorphic for a small telocentric B chromosome. In only one case was the B chromosome significantly associated with an increase chiasma frequency. All three South Island populations contained B chromosomes. Seven of the nine N.I. populations were also polymorphic for extra segments on the centric end of the S11 chromosome. In six of them this polymorphism co-existed with that for B'S. A new polymorphism was encountered in two populations. This was for a large block of heterochromatic material located at the centric end of one of the smaller medium-sized chromosomes which thus becomes acro- rather than telocentric. Tt would appear that the New Zealand grasshopper, Ph. marginale, is able to tolerate many different polymorphisms for extra heterochromatin. However, this ability is perhaps restricted to central populations. In this context, the high level of occurence of these polymorphisms in the North Island could be due to the better climatological conditions existing there compared to most of the South Island.