George W. Gibbs

Victoria University of Wellington, Wellington, Wellington, New Zealand

Are you George W. Gibbs?

Claim your profile

Publications (12)34.06 Total impact

  • Source
    Andréa E A Stephens · George W Gibbs · Brian H Patrick
    [Show abstract] [Hide abstract]
    ABSTRACT: Three new species from the Pseudocoremia modica complex are described based upon morphological characters. These species are Pseudocoremia foxi from Mt Taranaki, Pseudocoremia hudsoni from the north-east South Island and Pseudocoremia hollyae from the Murchison Mountains of Fiordland. Phylogenetic analysis shows that these species form a paraphyletic group and are in the same clade as P. ombrodes, P. terrena and P. berylia.
    New Zealand Entomologist 02/2007; DOI:10.1080/00779962.2007.9722153 · 0.87 Impact Factor
  • Karen Tutt · Charles H. Daugherty · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Life-history details of the live-bearing Peripatoides novaezealandiae (Hutton) were obtained by measuring and dissecting field collected animals. As in other studies, the sexes were found to have different demographics. Sex-specific weight frequency distributions and regression of weight vs length suggest sex differences in patterns of growth and/or mortality. Mature males were smaller than mature females; females apparently undergo a further period of growth between maturity and the onset of embryo production. The sex ratio of the whole sample was female biased; the sex ratio in the smallest size class was 1:1, and then oscillated from female- to male-, and then back to female-biased as size increased. Embryos were unable to be sexed. The sex ratios in individuals of mature (i.e. mating) size, and of reproductive size, were both 1:1. Females, especially but not exclusively before the onset of embryo production, had widely varying numbers of sperm in their haemolymph, indicating dermal-haemocoelic sperm transfer. These data also suggest that females are able to mate throughout life. Numbers of sperm in spermathecae of females were negatively correlated with body size. Fecundity increased with size in both sexes, somewhat more so in females. Embryo weight was correlated with maternal weight only at the beginning of the embryo's development. Rotting logs containing small populations contained a disproportionate number of large females.
    Journal of Zoology 02/2006; 258(2):257 - 267. DOI:10.1017/S095283690200136X · 1.88 Impact Factor
  • Source
    Andréa E. A. Stephens · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Two new species of Pseudocoremia (tribe Boarmiini) are described, Pseudocoremia amaculata sp. nov. from St Arnaud, Nelson Lakes National Park, and Pseudocoremia dugdalei sp. nov. from the Waitakere Range, Auckland. It is also determined that P. pergrata, which has been synomynised with P. insignita, should be reassigned species status.
    New Zealand Entomologist 12/2003; 26(1). DOI:10.1080/00779962.2003.9722109 · 0.87 Impact Factor
  • Catherine G. Rufaut · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract A population of Hemideina crassidens (the Wellington tree weta) was monitored over a 4-year period after the eradication of Rattus exulans (the Polynesian rat kiore) and Gallirallus australis australis (the South Island weka) from Nukuwaiata (Chetwode Islands), Pelorus Sound, New Zealand. A novel survey technique (entrance scores) was used in combination with a conventional technique (random searches for active weta) to measure changes in weta population parameters after the removal of predation pressure and to investigate impacts of exotic predators on tree weta. Tree weta density did not increase markedly over the 4-year period, but the proportion of active adults did increase. Weta were observed to move into larger and more crowded galleries (refuges), to occupy galleries closer to the ground, and to spend less time sitting in gallery entrances. It was concluded that endemic tree weta are well adapted to withstand some introduced vertebrate predators but are able to live a more “relaxed” lifestyle in the absence of this predation. The most significant change detected was in weta age structure, with adults increasing their proportion of the population.
    Restoration Ecology 02/2003; 11(1):13 - 19. DOI:10.1046/j.1526-100X.2003.00058.x · 1.84 Impact Factor
  • Corinne H. Watts · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: A study of beetle (Coleoptera) communities was conducted in three revegetated sites of different ages (5, 17, and 100 years) and in a remnant coastal habitat dominated by Muehlenbeckia complexa (a liane) on Matiu-Somes Island, Wellington Harbor, New Zealand. The 25-ha island has had a 110-year history as a pastoral agricultural quarantine station. Beetles were surveyed from May 1997 to April 1998 using pitfall traps. We collected a total of 3,430 adult beetles from 78 beetle species belonging to 22 families. Various environmental factors influencing the distribution of beetles in revegetated habitats were investigated. The most important factors were canopy height and canopy density (functions of vegetation age). Overall, results suggest that as habitat/vegetational heterogeneity increases at a site, beetle diversity and abundance also increase. Thus, older replanted sites contained a greater species richness and abundance of beetles than newly replanted sites. Revegetation is, thus, successfully facilitating the establishment and recolonization of the beetle fauna on Matiu-Somes Island.
    Restoration Ecology 04/2002; 10(1):96 - 106. DOI:10.1046/j.1526-100X.2002.10110.x · 1.84 Impact Factor
  • Mary Morgan-Richards · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: A phylogenetic analysis of New Zealand weta from the sub-family Deinacridinae is presented. Eighteen species were studied using 27 genetic characters (allozyme and cytogenetic) and 25 morphological characters. The combined data set produced a phylogenetic hypothesis with twelve well-supported nodes. Despite the great diversity of habitats and life styles exhibited by the eleven Deinacrida White species a well-supported bipartition separates them from the seven Hemideina Walker species. Six of the Hemideina species formed a monophyletic clade, with respect to H. broughi (Buller). Evolution of stridulatory ridges used for sound production in both defence and intraspecific communication appears to have occurred at least twice. Adaptation to the recent New Zealand alpine environment has also had multiple origins. Biogeographic interpretations from the phylogenetic hypothesis are discussed.
    Invertebrate Systematics 02/2001; 15(1):1-12. DOI:10.1071/IT99022 · 2.26 Impact Factor
  • Source
    C. H. Watts · G. W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Previous studies have shown that indigenous beetle diversity reflects indigenous plant diversity in modified and remnant habitats. This study examines the indigenous: introduced relationship at a locality where degraded pasture has been progressively revegetated. Pitfall traps were used to collect beetles from three revegetated sites of different ages (5, 17 and 100 years) and in a coastal Muehlenbeckia habitat on Matiu-Somes Island (25 ha), Wellington Harbour, New Zealand. A total of 78 morphospecies were found over 12 months. The indigenous: introduced status of 74 species were determined; 67 were classified as 'indigenous', and 7 as 'introduced'. A positive trend was found between the proportion of ground-dwelling indigenous beetle species collected and the proportion of indigenous plant species present at a study site. As the revegetated site matured, the proportion of indigenous beetle species increased. We collected 20 (83%), 37 (88%) and 48 (92%) indigenous beetle species from the 5-year scrubland, 17-year shrubland and 100-year forest, respectively.
    New Zealand Journal of Ecology 01/2000; 24(2). · 1.06 Impact Factor
  • George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: The large (4 g) to very large (40 g) stenopelmatid orthopterans of New Zealand are known collectively as weta. A consideration of 20 species of Hemideina, Deinacrida and tusked weta reveals that at one end of a vulnerability gradient are those species which thrive in the presence of key predators (rats), while at the other end are species that have become extinct on the mainland but still survive on predator-free island refuges. Habitat modification does not appear to be a factor in these extinctions. This paper reviews the lifestyles and some important biotic parameters that seem to determine their relative vulnerability along this gradient. When predators are present, the factors leading to extinction are large body size, use of temporary refuges, protective quality of the refuges, time spent on the ground and the effectiveness of their defensive behaviour.
    Journal of Insect Conservation 11/1998; 2(3):161-166. DOI:10.1023/A:1009660200402 · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An underlying assumption of ecological surveys which use rapid inventory techniques is that native invertebrate diversity will be reflected by native plant diversity. This supposition was tested by collecting Coleoptera from seven different habitats, which varied in the proportions of native and introduced plant species found within them. Pitfall traps were used to collect the beetles from a catchment on the South Coast of the lower North Island, New Zealand. A total of 150 beetle ‘species’ were found over a nine-month period. The native/introduced status of 127 of those species were determined; 114 were classified as native, and 13 as introduced. A positive trend was found between the percentage of native beetle species collected, and the percentage of native vegetation in the habitat under study. the sites with the greatest number of plant species (both native and introduced) contained the most beetle species, but modified habitats still showed high beetle diversity and should be considered for conservation purposes in some areas.
    Biological Conservation 02/1998; 83(2-83):209-220. DOI:10.1016/S0006-3207(97)00053-0 · 3.76 Impact Factor
  • Source
    Mary Morgan-Richards · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Scree weta from seventeen locations, covering the complete species range in the South Island of New Zealand, were examined using morphological characters studied by previous workers, as well as allozyme electrophoresis, and cytogenetics. The range of colour we describe does not support the four colour varieties proposed by previous workers for this species. Seven karyotypes are described, with diploid numbers ranging from 2n = 17(X0) to 2n = 22(XX). In contrast, little variation was found at 24 enzyme loci to distinguish different populations of scree weta. The level of allozyme variations suggests that colour and chromosome evolution has been rapid. Geographic structure is evident within both allozyme and chromosome variation but less so with colour variation. The extent of allozyme variation is in agreement with geological evidence that the Southern Alps of New Zealand are less than five million years old.
    Hereditas 04/1996; 125(2‐3):265 - 276. DOI:10.1111/j.1601-5223.1996.00265.x · 1.12 Impact Factor
  • Charles H. Daugherty · George W. Gibbs
    [Show abstract] [Hide abstract]
    ABSTRACT: Eleven populations of the Wellington tree weta, Hemideina crassidens (Blanchard, 1851), were compared with tree weta collected from Stephens Island (H. crassicruris Salmon 1950) and from Mt Holdsworth and Mt Arthur (H. brevaculea Salmon 1950), using 26 allozyme loci. The level of genetic differentiation is consistent with that found between conspecific populations, supporting the trend in the scientific literature to relegate both H. brevaculea and H. crassicruris to synonomy with H. crassidens. On the basis of morphological data indicating differentiation of the Stephens Island population, we conclude that H. crassicruris should be considered a subspecies of H. crassidens but H. brevaculea a synonym. There is an undescribed cryptic species, defined from the level of genetic differentiation, in Hawke's Bay.
    Journal- Royal Society of New Zealand 06/1995; 25(2):301-312. DOI:10.1080/03014223.1995.9517491 · 0.66 Impact Factor
  • Charles H. Daugherty · George W. Gibbs · R.A. Hitchmough
    [Show abstract] [Hide abstract]
    ABSTRACT: The terrestrial New Zealand fauna has developed on an ancient landmass of continental origins that has had an increasingly isolated existence since the late Mesozoic. As a continental remnant, New Zealand harbours survivors of many ancient lineages many of which were once far more widely distributed. But New Zealand's fauna also resembles that of an isolated archipelago: many higher taxa are missing; some have undergone extensive radiations in situ; and levels of endemism approach 100% in many groups. Ecologically, the fauna is characterized by frequent niche shifts, gigantism, and extended life histories with low reproductive rates, factors that make many species vulnerable to human disturbance. Data continue to amass supporting the ecophysiological as well as phylogenetic distinctiveness of the fauna. Described taxonomic diversity, even of terrestrial vertebrates, continues to increase.
    Trends in Ecology & Evolution 12/1993; 8(12):437-42. DOI:10.1016/0169-5347(93)90006-B · 16.20 Impact Factor