Beetle Community Structure Research Articles

Habitat and Community Patterns of Tropical Australian Hydradephagan Water Beetles (Coleoptera: Dytiscidae, Gyrinidae, Noteridae)

Water beetle communities have been investigated in northern regions of the Northern Hemisphere but similar studies have not been conducted within the tropics. Thus, a study was undertaken to describe patterns of water beetle co‐occurrence in a tropical environment and to compare these with water beetle community structure in temperate regions. Hydradephagan water beetles (Dytiscidae, Noteridae and Gyrinidae) were sampled quantitatively and qualitatively from a variety of habitats in the Atherton Tableland region of tropical Queensland from September 1990 to February 1991. Principal component analysis (PCA), using species occurrence in samples, supported a primary classification of sites as lotic, lentic and closed‐forest lotic. Closed‐forest lotic sites were tightly grouped in the PCA ordination, whereas the lotic and lentic groups of sites were more diffuse. Through analysis of species distributions in the PCA ordination it was inferred that factor 1 corresponded to habitat stability (e.g. permanence, water level fluctuation), especially among lotic sites, whereas factor 2 corresponded to the interrelated variables of water flow, substratum and vegetation. Quantitative samples taken from the shorelines of reservoirs showed that water beetle densities dropped sharply from the dry to the wet times of the year. Also, densities decreased and faunal mix changed with distance from shoreline. Quantitative samples from rice fields and a temporary pond demonstrated that a suite of species were quick to colonise and breed in newly formed habitat. Many of these species breed before other predators such as fish or Odonata become established. the lack of defined communities is due largely to the high mobility of many species which retreat to watered refuges during dry periods and opportunistically colonise new habitat as it is available. This mobile element obscures community boundaries, although characteristic species occur in certain habitat types such as closed‐forest streams, permanent vegetation‐rich ponds and particular regions along habitat continua. Patterns in size and habits of species of permanent habitats, and colonisation patterns of species occurring in temporary habitats, suggest that these represent mechanisms that reduce predation from other aquatic predators.

Carabid Beetles and Agricultural Practices: Influence of Soil Ploughing

ABSTRACT Deep ploughing drastically changes soil structure and is probably one of the most disturbing agricultural practices for soil fauna. The aim of this paper was to investigate the effect of ploughing reduction on the structure and composition of adult carabid beetle communities. Three soil treatments, normal ploughing, light ploughing and no ploughing, were applied in four kinds of crop. Carabid beetles were sampled weekly using pitfall traps. Soil ploughing increases the abundance of the dominant species, Pterostichus melanarius. Species richness significantly depended on the crop type. However, it appears that the less abundant species in deep ploughing became more numerous when reduced tillage or no cultivation was applied.

Spatial and Temporal Co-Occurrence of Competitors in Southern African Dung Beetle Communities

1. Co-occurrence of 11 species of crepuscular-nocturnal medium-sized tunnelling dung beetles from two core functional groups that vary in their rate of dung burial was examined at a range of spatial and temporal scales to identify the likely extent to which competition for dung might affect the structure of beetle communities of subtropical pasture. 2. At the largest scale, clear seasonal co-occurrence and similar habitat preferences (soil type and vegetation associations) were found amongst the species. 3. Medium- and fine-scale distributions of the species were investigated across nine blocks of dung-baited traps dispersed over a 400 ha tract of open cattle pasture, on deep sandy soil in Natal, South Africa. Traps were baited overnight and cleared in the morning in two series of three successive days

The effects of scrub management on the ground beetles of oolitic limestone grassland at Castor Hanglands national nature reserve, Cambridgeshire, UK

The effects of different scrub management regimes on the structure of ground beetle communities in oolitic limestone grassland at Castor Hanglands National Nature Reserved were analysed over the course of one complete season using pitfall trapping. Communities were studied at eight sampling sites comprising four plots cleared sequentially, over four years, from each of two different scrub clearance regimes. The ground beetle communities from these plots were compared with those from four grassland plots each separated by two years in an eight-year cutting rotation of scrub management. Species incidence and catch data were ordinated using detrended correspondence analysis to investigate the effects of the different management regimes on the beetle communities present. Two sites not included in these analyses were also sampled and their relative position in the incidence ordination was predicted from the ground beetle species present and from site environmental data. The implications of these results for the conservation of limestone grassland and the potential for using ground beetle data in monitoring conservation management practice are discussed.

ALLOZYME AND MORPHOLOGICAL DIFFERENTIATION OF MOUNTAIN PINE BEETLES DENDROCTONUS PONDEROSAE HOPKINS (COLEOPTERA: SCOLYTIDAE) ASSOCIATED WITH HOST TREE.

The purpose of this study was to determine whether mountain pine beetles utilizing different host species were differentiated for either morphological or protein variation. Genetic differentiation among host species has been reported for the southern pine beetle, the Douglas-fir beetle, the jeffrey pine beetle, and the mountain pine beetle. However, in these studies, the host trees were sampled at separate sites, and hence geographic variation and variation due to host tree were confounded. The mountain pine beetle occasionally utilizes three host trees (ponderosa pine, lodgepole pine, and limber pine) at single sites in Colorado. Five polymorphic enzyme loci and six morphological characters were used to describe beetles resident in different hosts. Differentiation within a site among host trees was detected at two of five polymorphic proteins, and for both size and morphological shape. The magnitude of genetic differentiation among hosts within a site was approximately equivalent to the magnitude of differentiation among sites. These data suggest that the species of host tree may be an important biotic factor associated with the genetic structure of bark beetle communities. The results are discussed in terms of their potential role in the process of speciation by host race formation.