The effect of lake acidification was evaluated, in the field, in terms of its impact on both the structural and functional composition of the macrozoobenthic community. The littoral macrozoobenthic community and water chemistry of 45 Canadian Shield lakes was sampled. The water chemistry variables sampled included pH, total dissolved calcium, conductivity, and dissolved organic acid (measured as colour). Partial canonical correlation analysis and partial regression analysis were used to identify those components of the macrozoobenthic community that most directly reflected pH variability. This was done by first removing from the data that portion of the variability attributable to total dissolved calcium, conductivity, and dissolved organic acids. In addition, the spatial structure in the data was removed by identifying the geographic coordinates of the sampling sites. / In general, the results presented here are not consistent with previous studies where the response of the macrozoobenthic community was related to pH without consideration of confounding covariables. Snails, leeches, mayflies and crayfish have all been cited for their sensitivity to acidification. The present study found these taxa to reflect, not pH variability, but rather attributes of water hardness. Similar results were found for both total zoobenthic biomass and functional feeding group abundance.

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

No description available.

Spatial heterogeneity of the environment, as measured by floral diversity, composition and structure, is known to influence the distribution and diversity of invertebrates. Heterogeneity brought about by anthropogenic disturbance may be a threat to invertebrate diversity. This thesis investigates the impacts of vegetation heterogeneity at a range of scales on the diversity of invertebrate populations in modified high-altitude indigenous grasslands on the Rock and Pillar Range, Central Otago. Invertebrates were sampled in and on the edges of snow tussock fragments to assess whether species richness increased systematically with fragment area. Invertebrate composition was poorly related to fragment area, plant composition and environmental variables. Taxon richness, abundance and/or diversity for three invertebrate groups increased as fragment area decreased, perhaps reflecting an influx of species from the surrounding matrix. For snow tussock leaf invertebrates in autumn, richness and abundance were at least two times lower in tussocks exposed to the wind than those in the centre of fragments, suggesting selection of habitat may be based on microclimatic characteristics. Invertebrates were sampled from the bases of tussocks after they were clipped to simulate three levels of vertebrate grazing. Invertebrate community composition differed between sites and sampling dates but was unaffected by clipping treatment. At the higher altitude site invertebrate abundance was 1.45 times greater and Shannon-Wiener diversity (H�) 1.22 times lower than at the lower altitude site. The latter sampling date had higher abundance (2.12 times) and taxon richness (1.14 times) than the earlier date. Pitfall-trapped invertebrates in cushionfield, herbfield and snow tussock differed in community composition and often by taxon richness, abundance and diversity. Across habitats, plant composition, plant diversity and some environmental variables were correlated with invertebrate variables, but could not be separated from vegetation type. The invertebrates collected in the course of the study are listed. Four Phyla, eight Classes, 24 orders and over 300 taxa were recorded. Almost all taxa are endemic and many have limited distributions and/or are undescribed. A species list is provided with collection altitude, method and habitat type. Invertebrate assemblages from sites differing in altitude, vegetation type and level of habitat modification on the Rock and Pillar Range are compared. Sites differed in species composition and rank orders of abundance and richness. At lower elevations, invertebrate richness was at least 25% less, and standardised trap abundance at least 44% less, than that at the highest elevation. Richness and abundance of exotic invertebrates decreased with increasing altitude. This thesis highlights several points concerning the study of grassland invertebrates and heterogeneity on the Rock and Pillar Range. First, there are differences in invertebrate assemblages at a range of scales. Conserving invertebrate diversity will therefore require altitudinal sequences and different habitat types, including disturbed areas. At high elevations, tussock habitat may be disproportionately important due to its relative rarity. Second, the effects of disturbance on invertebrates were only visible at large spatial scales. Third, there is a paucity of research on New Zealand invertebrates, especially in regard to terrestrial disturbance, which has resulted in a shortfall of biological, distributional, taxonomic and ecological knowledge.

Cold seep ecosystems in the deep sea are fuelled by chemosynthetic processes based on methane emission to the sediment surface from gas hydrate disassociation, methanogenesis or thermogenic processes. While cold seep ecosystems have been studied in the last three decades worldwide, little is known about New Zealand’s cold seep habitats and associated fauna. A joint German-New Zealand cruise to the Hikurangi Margin in early 2007 enabled biological and sediment sampling to investigate the biological and sedimentological relationships and variability of seeps and their faunal diversity. Multi-disciplinary approaches were employed that included Xray radiography, stratigraphic descriptions, lebensspuren traces analysis, sediment grain size analysis, determination of total organic content, carbonate content and its stable isotopic composition, and analysis of benthic invertebrate assemblages of seep habitats. The results of this study revealed three distinctive habitats and associated fauna based on the sediment characteristics and faunal type. Habitat 1 includes all sites pertaining to Omakere Ridge, a seep-related habitat comprised of layers of very poorly sorted, sandy silt, shell hash and bands of methane-derived authigenic aragonitic carbonate nodules with low total organic content (TOC). Due to the characteristics of the sediments and death assemblages of molluscs, it is inferred that Habitat 1 methane seepage is actively diffusive, waning or dormant. Habitat 2 describes sites that are either non-seep or relic and applies to those at Bear’s Paw and Kaka. Habitat 2 constituted of shell hash overlain with very poorly sandy silt, and low carbonates content and low to medium TOC. Habitat 3 describes non-seep related habitats, and includes all sites of the Wairarapa region and one reference site from Kaka also falls into this category. Sediments for Habitat 3 constituted poorly sorted silt with high TOC and low carbonate content which can be explained by their close proximity to land and converging sea currents. The mineral components of the background siliciclastic sediments for all sites studied originated in the Tertiary mudstone of the East Coast Basin. The characteristics of seep habitats of the Hikurangi Margin were comparable to that of the Northern Hemisphere modern seep counterparts, although the abundance and distributions of seep fauna were low. Results from this research have enhanced our understanding on the spatial and variability of methane fluxes and their affects on the duration of cold seep ecosystems, especially for New Zealand. However, more such studies are essential to increase our understanding of seep sediments and explain disturbance-sediment-benthic invertebrate interactions.

Cold seep ecosystems in the deep sea are fuelled by chemosynthetic processes based on methane emission to the sediment surface from gas hydrate disassociation, methanogenesis or thermogenic processes. While cold seep ecosystems have been studied in the last three decades worldwide, little is known about New Zealand’s cold seep habitats and associated fauna. A joint German-New Zealand cruise to the Hikurangi Margin in early 2007 enabled biological and sediment sampling to investigate the biological and sedimentological relationships and variability of seeps and their faunal diversity. Multi-disciplinary approaches were employed that included Xray radiography, stratigraphic descriptions, lebensspuren traces analysis, sediment grain size analysis, determination of total organic content, carbonate content and its stable isotopic composition, and analysis of benthic invertebrate assemblages of seep habitats. The results of this study revealed three distinctive habitats and associated fauna based on the sediment characteristics and faunal type. Habitat 1 includes all sites pertaining to Omakere Ridge, a seep-related habitat comprised of layers of very poorly sorted, sandy silt, shell hash and bands of methane-derived authigenic aragonitic carbonate nodules with low total organic content (TOC). Due to the characteristics of the sediments and death assemblages of molluscs, it is inferred that Habitat 1 methane seepage is actively diffusive, waning or dormant. Habitat 2 describes sites that are either non-seep or relic and applies to those at Bear’s Paw and Kaka. Habitat 2 constituted of shell hash overlain with very poorly sandy silt, and low carbonates content and low to medium TOC. Habitat 3 describes non-seep related habitats, and includes all sites of the Wairarapa region and one reference site from Kaka also falls into this category. Sediments for Habitat 3 constituted poorly sorted silt with high TOC and low carbonate content which can be explained by their close proximity to land and converging sea currents. The mineral components of the background siliciclastic sediments for all sites studied originated in the Tertiary mudstone of the East Coast Basin. The characteristics of seep habitats of the Hikurangi Margin were comparable to that of the Northern Hemisphere modern seep counterparts, although the abundance and distributions of seep fauna were low. Results from this research have enhanced our understanding on the spatial and variability of methane fluxes and their affects on the duration of cold seep ecosystems, especially for New Zealand. However, more such studies are essential to increase our understanding of seep sediments and explain disturbance-sediment-benthic invertebrate interactions.

Compared to natural forests, fast-growing plantations of exotic species such as Pinus radiata are often perceived as marginal habitat or unsuitable habitat for most native species. By studying Coleoptera (beetles) in a variety of landscape elements (pasture, native forest and different aged Pinus radiata stands) in a highly modified and fragmented landscape in New Zealand I aimed to determine the value of exotic plantation forests for native biodiversity, and how these species are affected by different sized clearfell harvest areas. Pitfall trap sampling of beetles showed that plantation forest stands can provide suitable complimentary habitat to native forest for many species. Rarefied species richness of Carabidae, Scarabaeidae and Scolytinae was not significantly different between habitats, however, habitat types differed significantly in their beetle community composition. Comparing different production habitats, Pinus radiata stands had a beetle community composition most similar to native forest. However, a small minority of species, e.g., Dichrochile maura, were restricted to native forest habitat highlighting the importance of retaining indigenous ecosystems within plantations. Unlike human modified habitats, native forests did not provide suitable habitat for exotic species. Clearfell harvesting is controversial and its impact on biodiversity is a key constraint for many forest certification programs, such as that administered by the Forest Stewardship Council (FSC). Despite this, no replicated manipulative experimental studies of the impact of different sized clearfell harvest areas on biodiversity have been undertaken at scales relevant to the New Zealand forest industry. One potential model of the impact of different clearfell harvest sizes is the concept of a threshold size. A threshold scenario may occur where clearfell harvest impacts increase at a rate disproportionate to the change in clearfell size over a small range of harvest areas, but impacts remain relatively unchanged either side of the threshold zone. I sampled Coleoptera in experimentally created 0.01, 0.05, 0.5, 5.0, 50 and 500 ha clearfells within Pinus radiata plantations in the central North Island of New Zealand. The wide range of clearfell harvest sizes, including some very small areas, such as 0.01 ha was instigated in an attempt to document potential clearfell harvest size thresholds. Rarefied native beetle species richness was higher in harvest areas compared to adjacent mature plantation stands. The beetle species richness in 5 ha and 500 ha harvest areas was significantly greater species than that in small 0.01 - 0.5 ha harvest areas. Although, the high beetle diversity recorded in 500 ha clearfells should be treated with caution due to confounding spatial autocorrelation. The degree of change in beetle community composition increased with increasing clearfell harvest area. Beetle assemblages in large harvest areas were less similar to their paired adjacent mature forest than smaller harvest areas. Although, constrained multivariate ordination techniques did show a short-term change in beetle species composition between recently clearfelled harvest areas of as little as 0.05 ha and adjacent mature P. radiata stands. The colonisation by open-habitat disturbance-adapted species was a key driver of this change, some species dispersed into clearfelled stands in significant densities within days post-harvest. Overall, there were no distinct short-term trends to the change in species richness as a function of increasing harvest area that would suggest an ecological impact threshold response. If short-term outcomes of clearfell harvesting are ameliorated by successful recolonisation, the long-term spatial arrangement of different aged stands becomes more important for the maintenance of biodiversity at the landscape level than short-term consequences of harvesting. By sampling selected beetle taxa in 1, 2, 4, 8, 16 and 26 year-old stands, I found that the abundance of seven out of eight of the species selected for analysis recovered to levels similar to those in adjacent mature forest within the timeframe of a single harvest rotation. Individual species utilised different aged stands, indicating different life-history strategies. For example, open-habitat, disturbance-adapted species such as Cicindela tuberculata and Sitona discoideus were prominent in young stands, and forest species such as Pycnomerus sophorae and Paracatops phyllobius were highly abundant in older stands. These alternative life-history strategies highlight the benefits of maintaining a mixture of different aged stands to increase biodiversity at the landscape level. This thesis fills an important gap in our knowledge of biodiversity in production landscapes. I show that plantation forests have value as complimentary habitat to native forest and they make an important contribution to the maintenance of biodiversity at the landscape level. Although clearfell harvesting is a severe disturbance to the forest ecosystem, the long-term recovery of beetle populations suggests that harvesting is not the key limiting factor to the enhancement of biodiversity in the plantation forests studied. This unusual situation is possibly the result of prior land-use history, as many plantations were established on degraded pastoral land, and harvest-sensitive species are unlikely to have survived this initial land-use change. As such, the severity of the long-term impacts of clearfell harvesting on biodiversity are likely to be context specific and will vary accordingly. The importance of spatial heterogeneity of habitat elements, including different aged plantation stands and native forest remnants, needs to be investigated in more detail to determine what limits biodiversity in this plantation landscape. Key points to consider are the proximity to, and proportion of, native forest cover in the landscape and the degree of connectivity among native remnants. It is these landscape-level attributes that may determine biodiversity at a regional scale, and more emphasis should be placed on landscape scale factors and there interaction with stand specific forest management practices. For example, the spatial mosaic of harvesting areas may need to be of a finer-scale when there are fewer native remnants within the landscape.

The potential relationship between riparian arachnids and aquatic insect productivity was assessed in forest streams throughout the central South Island of New Zealand. Initially, a survey was conducted of thirty seven, first-third order forest streams. Streams were selected to represent a range of benthic invertebrate standing crops (as a surrogate measure of "productivity") from Banks Peninsula streams with relatively high benthic invertebrate densities to acid mine drainage streams near Reefton that were almost devoid of aquatic life. At each site benthic invertebrate densities and biomass were measured in riffle habitats and adjacent gravel bars were sampled for terrestrial invertebrates. At a sub-set of 16 sites, a 20 metre longitudinal web-building spider survey was conducted along each bank of the stream. As an additional component, a 20 metre transect starting at the stream margin and running perpendicularly into the forest was used to survey the density of web-building spiders with increasing distance from the stream. Results from the survey of in-situ stream insect biomass and gravel bar invertebrates showed a strong relationship between aquatic insect biomass and the biomass of riparian arachnids (R2 = 0.42, P < 0.001) having accounted for potentially confounding factors such as stream size, elevation, substrate and disturbance. The 20 metre longitudinal survey showed that streams with the highest in-situ insect biomass had significantly higher densities of web-building spiders along their banks (R2 = 0.28, P < 0.05), having accounted for potential confounding variables of elevation, habitat architecture and stream and channel width. The stream to forest survey showed a strong exponential decay in web-building spider densities with increasing distance from the stream (R2 = 0.96, P < 0.0001). Regardless of stream productivity web-building spiders were most abundant at the stream margins and rapidly declined to very low densities 20 metres from the stream. In order to further test the relationship between riparian web-building spider densities and stream insect productivity, a stream fertilization experiment was conducted on six first-second order streams in the Maimai experimental catchment, Reefton. Three streams were enriched by the addition of a fertiliser solution mainly consisting of sodium nitrate for seven months, and the other three streams were used as controls. Water chemistry, benthic invertebrate communities, emerging aquatic adults, and the densities of web-building spiders along the stream corridor and in the forest were monitored in three seasons (spring, summer and autumn) over the course of the nutrient-addition. By the end of the experiment, conductivity was significantly higher in nutrient-addition streams than in the control streams (F = 80.5, P < 0.001), but chlorophyll concentrations showed no significant differences between treatments. Both benthic mayfly densities (F = 6.15, P < 0.05) and the biomass of adult aquatic dipterans (Chironomidae, Simuliidae) (F = 9.25, P < 0.01) were significantly higher in nutrient-addition streams in the last sampling round. Spiders recorded from intercept traps indicated that by the end of the experiment spider activity was significantly higher within 2.5 metres of the nutrient-addition streams (F = 5.70, P < 0.01). However, seasonal densities of web-building spiders along the stream margin and in the forest decreased with no significant differences observed between nutrient-addition and control streams. The results from these studies indicate that adult insects emerging from streams represent an important source of prey that could influence the biomass and abundance of riparian arachnids. Additionally, the results imply that stream productivity and size could mediate the strength of the interaction between riparian and stream habitats. Moreover, feedback mechanisms present in both systems could have implications for such interactions. The elevated densities of web-building spiders observed at the stream margin led to the proposal of the "Highway Robber" hypothesis. This hypothesis suggests that such higher densities of spiders are the result of increased insect activity along the stream corridor: the emergence of adult aquatic insects was predicted to vary less over temporal and spatial scales than that of terrestrial insects due to the poorly synchronized life histories in many New Zealand stream insects. I conclude by suggesting that there are numerous anthropocentric perturbations such as loss of heterogeneity, introduced species, pollution and habitat degradation that could undermine and decouple the intimate linkages between aquatic and terrestrial ecosystems.

Thesis (M.S.)--Ohio University, August, 2006. / Title from PDF t.p. Includes bibliographical references.