The Pronotum of Worker of Camponotus borellii Emery (Hymenoptera: Formicidae): How Can It Affect Performance of the Head, Work Division, and Development of the Worker Caste?

In polymorphic ants, whose workers display continuous size distribution, each subcaste occupies a phenotypic space, usually with diffuse morphological boundaries. These morphological differences are closely associated to size by allometry although the environment also plays a key role that affects the fitness of the species. In Camponotus borellii Emery, the species selected as a study model, workers exhibit a continuous increase in size; geometric morphometric (GM) was used over four morphological traits: head capsule, clypeus, pronotum, and mesosoma, in order to assess (1) changes in shape, among the worker caste; (2) the influence of allometry on such changes; and (3) pronotum shape in respect to the head so as to infer which factors may influence the polymorphic development of the worker caste. The results indicated that the pronotum is organized into two highly integrated functional modules (neck and shield), corresponding to one developmental module. GM shows a similar pattern to that obtained for linear morphometry, though the worker ratio was different along continuous size distribution due to shape changes in two traits, with are also useful for delimiting modular units: (1) rounded shape of the posterior region of the head in minor workers; (2) shape of the pronotum, especially its anterior region, henceforth, neck, which widens as a consequence of the higher development of its central region, henceforth, shield, in major workers. The relevance of these results is discussed regarding functional morphology (pronotum in relation to the head), work division, and development of the worker caste.

Timeless standards for species delimitation

Recently a new species of bombyliid fly, Marleyimyia xylocopae, was described by Marshall & Evenhuis (2015) based on two photographs taken during fieldwork in the Republic of South Africa. This species has no preserved holotype. The paper generated some buzz, especially among dipterists, because in most cases photographs taken in the field provide insufficient information for properly diagnosing and documenting species of Diptera.

Environmental Determinants of the Distribution and Abundance of the Ants, Lasiophanes picinus and L. valdiviensis, in Argentina

The distribution and abundance variation of the terrestrial ants, Lasiophanes picinus and Lasiophanes valdiviensis Emery (Formicinae: Lasiini), which are endemic in Patagonia (Argentina and Chile), are described and a set of environmental factors are examined to explain the observed patterns. Ants were collected using 450 pitfall traps arranged in 50, 100 m² grid plots each with nine traps within a roughly 150 × 150 km area representative of the subantartic-patagonian transition of Argentina. Five sampling periods each 8-days long were carried out between November 2004 and March 2006. To understand the distributional patterns and their link to environmental variables discriminant analysis was used. Path analysis was performed to test for direct and indirect effects of a set of environmental variables on species abundance variation. L. picinus was more frequently captured and attained higher abundance in the forests, while L. valdiviensis was more frequently captured and more abundant in the scrubs. The maximum daily temperature and mean annual precipitation explained L. picinus distribution (i.e. presence or absence) with an accuracy of 90%. L. valdiviensis distribution was predicted with almost 70% accuracy, taking into account herbal richness. The maximum daily temperature was the only climatic variable that affected ant abundance directly; an increase in temperature led to an increase of L. picinus abundance and a decrease of L. valdiviensis abundance. The amount of resources, as indicated by the percent plant cover, explained the variation of the abundance of both species better than the variety of resources as indicated by plant richness (i.e. models including plant richness had low fit or no fit at all). A direct effect of habitat use by cattle was found, as indicated by the amount of feces in the plots, only when variables related to the amount of resources were replaced by variables with less explanatory power related to the variety of resources. This study provides new data on the ecology of Lasiophanes species in relation to existing hypotheses proposed to explain patterns of abundance variation. Evidence is provided that changes in temperature (i.e. global climate change) may have important consequences on populations of these species.

An optimality criterion to determine areas of endemism

A formal method was developed to determine areas of endemism. The study region is divided into cells, and the number of species that can be considered as endemic is counted for a given set of cells (= area). Thus, the areas with the maximum number of species considered endemic are preferred. This is the first method for the identification of areas of endemism that implements an optimality criterion directly based on considering the aspects of species distribution that are relevant to endemism. The method is implemented in two computer programs, NDM and VNDM, available from the authors.