Severe Insect Pest Impacts on New Zealand Pasture: The Plight of an Ecological Outlier.

New Zealand's intensive pastures, comprised almost entirely introduced Lolium L. and Trifolium L. species, are arguably the most productive grazing-lands in the world. However, these areas are vulnerable to destructive invasive pest species. Of these, three of the most damaging pests are weevils (Coleoptera: Curculionidae) that have relatively recently been controlled by three different introduced parasitoids, all belonging to the genus Microctonus Wesmael (Hymenoptera: Braconidae). Arguably that these introduced parasitoids have been highly effective is probably because they, like many of the exotic pest species, have benefited from enemy release. Parasitism has been so intense that, very unusually, one of the weevils has now evolved resistance to its parthenogenetic parasitoid. This review argues that New Zealand's high exotic pasture pest burden is attributable to a lack of pasture plant and natural enemy diversity that presents little biotic resistance to invasive species. There is a native natural enemy fauna in New Zealand that has evolved over millions of years of geographical isolation. However, these species remain in their indigenous ecosystems and, therefore, play a minimal role in creating biotic resistance in the country's exotic ecosystems. For clear ecological reasons relating to the nature of New Zealand pastures, importation biological control can work extremely well. Conversely, conservation biological control is less likely to be effective than elsewhere.

Epichloë uncinata Infection and Loline Content Protect Festulolium Grasses From Crickets (Orthoptera: Gryllidae).

Experiments with artificial diets demonstrated that black field cricket (Teleogryllus commodus (Walker)) and Lepidogryllus sp. were highly responsive to presence of lolines in their diet-quantities of diet consumed declined exponentially with increasing loline concentration. Amount consumed by black field cricket and Lepidogryllus sp. on diet containing 5,600 µg/g lolines was only 8 and 2% relative to those on loline-free diet, respectively. Additional experiments with Festulolium seeds demonstrated that both cricket species predated heavily on endophyte-free seed but largely avoided Epichloë uncinata-infected seed. By 12 h, black field cricket had destroyed 98.8% of endophyte-free but only 24.8% of E. uncinata-infected, loline-containing seed. By 36 h, Lepidogryllus sp. crickets had destroyed 40% of endophyte-free but had not fed on E. uncinata-infected, loline-containing seed. Glasshouse experiments demonstrated this aversion to lolines greatly reduces the damage potential of black field cricket in E. uncinata-infected Festulolium. When microswards were sown with E. uncinata-infected Festulolium, seedling numbers were reduced 25-26%, and yields 29-40%, by black field crickets relative to microswards sown without insect infestation. This contrasts with 70-78% reduction in seedling numbers and 67-80% reduction in yields in microswards sown to either endophyte-free Festulolium, endophyte-free perennial ryegrass, or Epichloë festucae var. lolii-infected Festulolium. Yields of mature E. uncinata-infected Festulolium plants were not adversely affected by black field crickets, irrespective of the presence of the endophyte-free standard Festulolium sown as a companion. In contrast, yields of endophyte-free Festulolium, endophyte-free perennial ryegrass, and E. festucae var. lolii-infected Festulolium plants were reduced by 56-61% by crickets.

Combining α - and ß -diversity models to fill gaps in our knowledge of biodiversity.

For many taxonomic groups, sparse information on the spatial distribution of biodiversity limits our capacity to answer a variety of theoretical and applied ecological questions. Modelling community-level attributes (α- and ß-diversity) over space can help overcome this shortfall in our knowledge, yet individually, predictions of α- or ß-diversity have their limitations. In this study, we present a novel approach to combining models of α- and ß-diversity, with sparse survey data, to predict the community composition for all sites in a region. We applied our new approach to predict land snail community composition across New Zealand. As we demonstrate, these predictions of metacommunity composition have diverse potential applications, including predicting γ-diversity for any set of sites, identifying target areas for conservation reserves, locating priority areas for future ecological surveys, generating realistic compositional data for metacommunity models and simultaneously predicting the distribution of all species in a taxon consistent with known community diversity patterns.

Phylogeography and ecological niche modelling implicate coastal refugia and trans-alpine dispersal of a New Zealand fungus beetle.

The Last Glacial Maximum (LGM) severely restricted forest ecosystems on New Zealand's South Island, but the extent of LGM distribution for forest species is still poorly understood. We used mitochondrial DNA phylogeography (COI) and ecological niche modelling (ENM) to identify LGM refugia for the mycophagous beetle Agyrtodes labralis (Leiodidae), a forest edge species widely distributed in the South Island. Both the phylogenetic analyses and the ENM indicate that A. labralis refuged in Kaikoura, Nelson, and along much of the South Island's west coast. Phylogeography of this species indicates that recolonization of the largely deforested east and southeast South Island occurred in a west-east direction, with populations moving through the Southern Alps, and that the northern refugia participated little in interglacial population expansion. This contradicts published studies of other New Zealand species, in which recolonization occurs in a north-south fashion from many of the same refugia.

Nomenclatural and type catalogue of Athoracophoridae (Mollusca: Eupulmonata: Succineoidea): a synopsis of the first 185 years of biodiscovery in the South West Pacific region.

Athoracophoridae are succineoidean terrestrial slugs that constitute a distinctive faunal element of the South West Pacific biogeographic region, with representatives in New Guinea, Australia, New Caledonia, Vanuatu and New Zealand. Despite many studies on morphology, taxonomy and phylogenetic relationships since the first species description in 1832, the understanding of the diversity within the family, as reported in published literature, remains poor with regional disparities in collection and systematic effort, in taxonomic concepts, and in adherence to type concepts. The systematics of Athoracophoridae needs to be re-evaluated through a modern, phylogenetic approach to properly document infra-familial evolution and taxon diversity, advance understanding of evolutionary relationships with other Eupulmonata, and to delineate evolutionary units for conservation prioritization. A catalogue of all class-, family-, genus- and species-group names erected for or used to include Athoracophoridae over the 185 year period 1832 to 2017 is provided, as a first step towards a systematic revision. The following nomenclatural changes are made: lectotype designation for Aneitea macdonaldii Gray, 1860; lectotype designation for Janella papillata Hutton, 1879; type species designation for Amphikonophora Suter, 1897; and lectotype designation for Athoracophorus verrucosus Simroth, 1889.

Early impact of endoparasitoid Microctonus hyperodae (Hymenoptera: Braconidae) after its establishment in Listronotus bonariensis (Coleoptera: Curculionidae) populations of northern New Zealand pastures.

The South American curculionid Listronotus bonariensis (Kuschel) is an important pest of pastures in New Zealand. Population census data were gathered for L. bonariensis in northern New Zealand pastures during 1980-1983 in the absence of parasitism and again in 1991-1996 after the introduction and establishment of the braconid parasitoid Microctonus hyperodae Loan as a biological control agent. M. hyperodae achieved high rates of parasitism, with 75-90% of overwintering L. bonariensis parasitized within 3 yr of the parasitoid establishing at a site. Multistratum analysis of variance (ANOVA), with allowance for variation in host plant resource (numbers of Neotyphodium-free grass tillers), indicated reduction in the abundance of L. bonariensis life stages in the early part of life cycle. Although providing evidence for suppression of L. bonariensis, these analyses indicated the regulatory role of M. hyperodae was weak because L. bonariensis populations continued to exhibit marked intergenerational variability in abundance. Analyses of life tables indicated larval + pupal survival contributed most to intergenerational changes in abundance, irrespective of presence or absence of M. hyperodae. However, the density dependence of the stage survivals was modified in the presence of the parasitoid, with loss of density-dependent mortality in overwintering adults and increased density dependence in population natality. Regression analyses indicated dual contribution of parasitism and host plant resource to regulation of population natality and population trend in L. bonariensis. We conclude that M. hyperodae is a useful adjunct to host plant resistance in reducing the economic status of L. bonariensis populations in northern New Zealand pastures.

Agricultural intensification exacerbates spillover effects on soil biogeochemistry in adjacent forest remnants.

Land-use intensification is a central element in proposed strategies to address global food security. One rationale for accepting the negative consequences of land-use intensification for farmland biodiversity is that it could 'spare' further expansion of agriculture into remaining natural habitats. However, in many regions of the world the only natural habitats that can be spared are fragments within landscapes dominated by agriculture. Therefore, land-sparing arguments hinge on land-use intensification having low spillover effects into adjacent protected areas, otherwise net conservation gains will diminish with increasing intensification. We test, for the first time, whether the degree of spillover from farmland into adjacent natural habitats scales in magnitude with increasing land-use intensity. We identified a continuous land-use intensity gradient across pastoral farming systems in New Zealand (based on 13 components of farmer input and soil biogeochemistry variables), and measured cumulative off-site spillover effects of fertilisers and livestock on soil biogeochemistry in 21 adjacent forest remnants. Ten of 11 measured soil properties differed significantly between remnants and intact-forest reference sites, for both fenced and unfenced remnants, at both edge and interior. For seven variables, the magnitude of effects scaled significantly with magnitude of surrounding land-use intensity, through complex interactions with fencing and edge effects. In particular, total C, total N, δ15N, total P and heavy-metal contaminants of phosphate fertilizers (Cd and U) increased significantly within remnants in response to increasing land-use intensity, and these effects were exacerbated in unfenced relative to fenced remnants. This suggests movement of livestock into surrounding natural habitats is a significant component of agricultural spillover, but pervasive changes in soil biogeochemistry still occur through nutrient spillover channels alone, even in fenced remnants set aside for conservation. These results have important implications for the viability of land-sparing as a strategy for balancing landscape-level conservation and production goals in agricultural landscapes.

Biology of slugs (Agriolimacidae and Arionidae: Mollusca) in New Zealand hill country pastures.

Life cycles of the slugs Deroceras reticulatum and Arion intermedius were studied over a 2.5-year period in a sheep-grazed pasture in the Kaimai Range, New Zealand. D. reticulatum approximated a bivoltine phenology, with intervals between consecutive generations ranging from 4 to 7 months and maximum life span from 8 to 12 months. Egg laying occurred in autumn and spring-early summer. Periods of egg hatching were followed by a phase of juvenile growth characterised by linear increase in the logarithm of population mean body weights. This was followed by a phase of reproductive activity. A. intermedius had an annual life cycle. Eggs laid during late summer and autumn hatched during autumn-winter. Immature slugs were characterised by a period of low growth rate during winter followed by a period of rapid growth culminating in reproductive maturity. In both species, the phase of rapid growth rate was associated with enlargement of the hermaphrodite gland. The size of the hermaphrodite gland relative to body weight reached a maximum during the spermatozoon stage, generally coincident with maximum body weight. During the reproductive period of D. reticulatum and A. intermedius the body weight remained relatively stable but the hermaphrodite gland became progressively smaller as the slugs approached the post-reproductive stage. The albumen gland attained maximum weight at the oocyte stage of the hermaphrodite gland, at the onset of reproductive activity. The pasture, strongly dominated by grasses, was heterogenous in slope, vegetation and treading/grazing influences from sheep due to stratification of the habitat into contour tracks, associated with sheep movement around the slope contours, and intertrack areas. High population densities of D. reticulatum were associated with the track edges (kerbs) and the upper intertrack slopes, while densities of A. intermedius were highest for the intertrack slopes. Low densities of both species occurred on the tracks and at sheep campsites. Analysis of cohort life tables indicated that these dispersion patterns were important in the dynamics of the populations. The stage mortality contributing most to the variance in reproductive populations of both species was that between hatching and onset of reproduction; most of the mortality occurred shortly after hatching on south-facing slopes, but tended to occur later in the life cycle on north slopes. For D. reticulatum this mortality was inversely related to initial density and associated, at least in part, with predation by carabids and birds and with treading by sheep. Density relationships, both at whole plot and plot stratum level, indicated that variations in natality had a stabilizing influence on D. reticulatum populations.

Biology of the introduced biocontrol agent Microctonus hyperodae (Hymenoptera: Braconidae) and its host Listronotus bonariensis (Coleoptera: Curculionidae) in northern New Zealand.

The South American weevil Listronotus bonariensis (Kuschel) is an important pest of pastures in New Zealand. As a component of management strategies for this pest, the South American parasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae) was released in northern New Zealand during 1991 as a biological control agent. Over the subsequent 5-6 yr, the reproductive biology of M. hyperodae and its relationship to, and effects on, the reproductive phenology and fitness of L. bonariensis were studied at three sites. M. hyperodae was first recovered in the field in December 1991. Subsequently, the incidence of parasitism in L. bonariensis increased to seasonal maxima of 75-90%. There was variable synchrony between parasitoid generations and the two generations of its host, leading to marked seasonal variation in rates of parasitism and parasitoid abundance. Despite marked inter-year variation, abundance of host adult and egg populations declined in the presence of parasitoids. Parasitized host females had lower ovarian maturity scores, had lower egg loads, and exhibited less investment in wing muscle development than females that had escaped parasitism. There was almost complete elimination of egg maturation in parasitized females and these hosts contributed little to population recruitment. Rate of buildup and seasonal maxima in parasitism, frequency of superparasitism, adult abundances, and wing muscle development in adult L. bonariensis varied among the three sites in a manner that was only partially related to climate differences across the 1.83° gradient of latitude. Site effects were weak to absent in measures of reproductive condition in L. bonariensis females.

Island biology and ecosystem functioning in epiphytic soil communities.

Although island attributes such as size and accessibility to colonizing organisms can influence community structure, the consequences of these for ecosystem functioning are little understood. A study of the suspended soils of spatially discrete epiphytes or treetop "islands" in the canopies of New Zealand rainforest trees revealed that different components of the decomposer community responded either positively or negatively to island size, as well as to the tree species that the islands occurred in. This in turn led to important differences between islands in the rates of ecosystem processes driven by the decomposer biota. This system serves as a model for better understanding how attributes of both real and habitat islands may affect key ecosystem functions through determining the community structure of organisms that drive these functions.