Search

Carpoglyphus wardleorum n. sp. (Astigmatina: Carpoglyphidae) is described from males and females collected from sooty mould fungi on the bark of black beech, Nothofagus solandri, at Ashley Gorge, Canterbury, New Zealand. [ABSTRACT FROM AUTHOR]

1. The degree of infestation by New Zealand sooty beech scale insects ( Ultracoelostoma assimile, Homoptera: Margarodidae) varies dramatically among adjacent southern beech trees ( Nothofagus spp., Fagaceae), but has previously been assumed to be uniformly or randomly distributed within individual host trees. In this study, a full-census survey was conducted from ground level to canopy level on 14 naturally occurring, canopy-dominant red beech ( Nothofagus fusca) trees (size range 38.7–107.6 cm diameter at breast height) to determine the degree of within-tree heterogeneity in herbivore density. 2. The within-tree distribution of the sooty beech scale was vertically stratified and highly heterogeneous, with the greatest densities occurring on bark surfaces in the canopy rather than on the trunk, and on the lower rather than upper sides of the branches. The spatial distribution was strongly negatively correlated with trunk and branch diameter, and increasing bark thickness (as a function of diameter) provides a plausible explanation for differences in the establishment and population density of sooty beech scale insects with trunk and branch size. Furthermore, there was a significant change in the spatial distribution of scale insect populations on trunks and branches of trees of increasing diameter at breast height. This indicates a strong temporal component to the spatial dynamics of the sooty beech scale insect driven by changing host phenology. Future studies on phytophagous insects infesting large host trees need to consider more explicitly changes in population dynamics through space and time. 3. Because of the high degree of within-tree heterogeneity in population density, the total population size of scale insects on an individual tree could not be predicted from any measure of population density low on the trunk. However, the dry weight biomass of sooty mould fungi growing on the ground beneath infested trees was a remarkably accurate predictor of the total population size of scale insects. The use of sooty mould fungi as a relative measure of population size could be incorporated into studies of other honeydew-producing hemipterans, since the growth of sooty mould is a distinctive feature synonymous with high concentrations of honeydew production worldwide. [ABSTRACT FROM AUTHOR]

1. Intraspecific competition can be an important factor influencing the individual fitness of organisms. This study reports density-dependent effects on the fecundity of the beech scale insect ( Ultracoelostoma assimile, Hemiptera: Margarodidae) on naturally occurring, canopy-dominant red beech ( Nothofagus fusca, Fagaceae) trees in New Zealand. For the first time an increasing intensity of intraspecific competition at increasing spatial scales within individual host trees is demonstrated. 2. Beech scale insect ‘tests’ containing adult female scale insects and eggs were collected from the trunks of 10 red beech trees [17.7–48.5 cm in diameter at breast height (1.4 m), d.b.h.] with varying densities of scale insect infestation. The relationship between individual female fecundity and scale insect density at three spatial scales: local (within 5 cm), lower trunk (below 2 m above ground level), and whole tree, was tested. 3. Beech scale insect fecundity was density dependent, with total female egg load decreasing with increasing scale insect density. The strength of the density-dependent effect increased with increasing spatial scale, suggesting that scale insects are creating a tree-wide drain on the quality of phloem sap, rather than depleting nutrients from localised, high-density areas within trees. These results indicate that at high densities, the New Zealand beech scale insect can have a negative effect on the nutritional quality of the phloem of red beech, thus negatively affecting conspecifics elsewhere on individual host trees. The increasing intensity of the effect with increasing spatial scale within individual trees emphasises the importance of measuring density-dependent effects at the appropriate spatial scale. [ABSTRACT FROM AUTHOR]