In 1980 the variegated leafhopper (VLH), Erythroneura variabilis, invaded California's San Joaquin Valley, and has since rapidly increased in numbers to become a major pest in vineyards. Correlated with the invasion by VLH are declining populations of congeneric grape leafhopper (GLH), E. elegantula. This paper explores interspecific competition and shared parasitism as possible reasons for this decline in GLH. Although interspecific competition between VLH and GLH was evident in field—cage experiments, its effects were equivalent to instraspecific competition. Instead of simple direct competition explaining the replacement of GLH by the invading VLH, the key appears to be parasitoid that is shared by two leafhoppers. In particular, the native GLH experiences higher attack rates from the shared parasitoid (Angarus epos) than does the invading VLH. This differential parasitism apparently shifts the competitive balance from one of equality to a strong disadvantage for the native relative to the invader. This is the first study, to our knowledge, to document the importance of parasitoid—mediated indirect effects in an invasion.

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It has been hypothesized that most morphological evolution occurs by allometric differentiation. Because rodents encapsulate a phenomenal amount of taxonomic diversity and, among several clades, contrasting levels of morphological diversity, they represent an excellent subject to address the question: how variable are allometric patterns during evolution? We investigated the influence of phylogenetic relations and ecological factors on the results of the first quantification of allometric disparity among rodents by exploring allometric space, a multivariate morphospace here derived from, and encapsulating all, the ontogenetic trajectories of 34 rodent species from two parallel phylogenetic radiations. Disparity was quantified using angles between ontogenetic trajectories for different species and clades. We found an overlapping occupation of allometric space by muroid and hystricognath species, revealing both clades possess similar abilities to evolve in different directions of phenotypic space, and anatomical diversity does not act to constrain the labile nature of allometric patterning. Morphological features to enable efficient processing of food serve to group rodents in allometric space, reflecting the importance of convergent morphology, rather than shared evolutionary history, in the generation of allometric patterns. Our results indicate that the conserved level of morphological integration found among primates cannot simply be extended to all mammals.

Previous attempts to sex juvenile skeletons have focused on the application of qualitative or semi-quantitative techniques. This study applies a variety of geometric morphometric methods, including eigenshape analysis, to this problem. Six metric criteria for the ilia were tested with the aim of investigating previous ideas concerning sexually diagnostic characters. This study uses 25 ilia from juveniles of known age and sex from Christ Church, Spitalfields, London. Ninety-six percent of juvenile ilia were correctly identified as male or female using the shape of the greater sciatic notch. Identification accuracy is shown to improve with age for several criteria. Males were identified to a higher accuracy than females. Application of geometric techniques improves the understanding of the relationship between age, sex, and shape and the clarity with which these relationships can be quantified. Archaeological and forensic relevance of the results are discussed with recommendations for future application.