The ecological benefits of larger colony size may promote polygyny in ants.

How polygyny evolved in social insect societies is a long-standing question. This phenomenon, which is functionally similar to communal breeding in vertebrates, occurs when several queens come together in the same nest to lay eggs that are raised by workers. As a consequence, polygyny drastically reduces genetic relatedness among nestmates. It has been suggested that the short-term benefits procured by group living may outweigh the costs of sharing the same nesting site and thus contribute to organisms rearing unrelated individuals. However, tests of this hypothesis are still limited. To examine the evolutionary emergence of polygyny, we reviewed the literature to build a data set containing life-history traits for 149 Palearctic ant species and combined this data set with a reconstructed phylogeny. We show that monogyny is the ancestral state and that polygyny has evolved secondarily and independently throughout the phylogenetic tree. The occurrence of polygyny is significantly correlated with larger colony size, dependent colony founding and ecological dominance. Although polydomy (when a colony simultaneously uses several connected nests) tends to occur more frequently in polygynous species, this trend is not significant when phylogenetic history is accounted for. Overall, our results indicate that polygyny may have evolved in ants in spite of the reduction in nestmate relatedness because large colony size provides immediate ecological advantages, such as the more efficient use of temporal food resources. We suggest that the competitive context of ant communities may have provided the conditions necessary for the evolution of polygyny in some clades.

Ant community structure in citrus orchards in the mediterranean basin: impoverishment as a consequence of habitat homogeneity.

This study analyzes the structure and composition of ant communities in citrus orchards in Catalonia (northeast Spain) and compares them with the ant fauna found in natural communities of the region. In the citrus orchards considered in this study, the most abundant species were Lasius niger and Pheidole pallidula, which are behaviorally dominant species. Two other dominant species, Linepithema humile and Tetramorium caespitum, were also abundant, although only in one orchard. Species richness and diversity in the studied orchards were low compared with natural communities: although in orchards, there were few species and low diversity values, in natural communities, the number of species was higher and diversity also increased. This reduction of species richness and diversity was not modified by edge effects: only light and local differences were found between the inner part of the orchards and the orchard margins, and differences among orchards were greater than differences between inner parts and edges. The activity peaks of the different ant species actively foraging on these citrus orchards were distributed throughout the whole activity period of ants. Overall, the composition of ant communities present in the citrus orchards of this study was extremely poor. This agrees with the fact that monocultures are ecosystems associated with an inevitable loss of biodiversity and abundance of insect populations.

Geographic variations in seed dispersal by ants: are plant and seed traits decisive?

The effect of local ant species on the dispersal success of a myrmecochorous plant, Helleborus foetidus, was analyzed in two populations of the Iberian Peninsula (Caurel and Cazorla, respectively). The contribution of the various local ant species to dispersal was very unequal. While 5 and 19 ant taxa visited the plants of Caurel and Cazorla, respectively, most removal activity (67 and 80%) was performed by two species only (Formica lugubris and Camponotus cruentatus, respectively). Visits by dispersers were also unequally distributed between neighboring plants. While some plants were always visited during the period of seed release, others were never visited. A regression model indicated that this pattern might be explained by two plant traits: ants preferred to visit plants that released more seeds and whose elaiosomes were richer in oleic acid. Although it has long been known that this compound triggers removal by ants, it is the first demonstration that quantitative variations in elaiosome traits contribute to variation in dispersal success. Finally, other variables being equal, morphological traits (seed size, elaiosome size, and elaiosome/seed size ratio) did not affect ant behavior. Although myrmecochory has long been considered a diffuse interaction, our results support the idea that, at local scale, a limited number of ant species may be decisive to its evolution.

Exploitative strategies of the invasive Argentine ant (Linepithema humile) and native ant species in a southern Spanish pine forest.

The Argentine ant, Linepithema humile (Mayr, 1868), is displacing native ant species in Doñana National Park (Spain). This paper discusses the results of experiments aimed at analyzing exploitation competition between the invading species and other ant species in a park community. The Argentine ant was found to implement several strategies favoring its success in exploitation competition: mass recruitment, use of various microhabitats (on the ground and in trees), and activity over a wide range of temperatures. Although these strategies were not exclusive to L. humile, their joint use, together with the large number of workers forming each "unicolony," conferred a clear advantage for resource exploitation. Some native species were more severely affected than others by the presence of L. humile in terms of both abundance and behavior. The worst affected species were those whose ecological characteristics were similar to those of the Argentine ant, e.g., Pheidole pallidula (Nylander, 1849); the species least affected was Cataglyphis floricola Tinaut, 1993, possibly because of its subordinate and thermophilous nature (little overlap of daily activity rhythms with the exotic species).

The geographic mosaic in predispersal interactions and selection on Helleborus foetidus (Ranunculaceae).

We examine the hierarchical geographic structure of the interaction between a plant, Helleborus foetidus, and its floral herbivores and pollinators (interactors). Six populations from three distant regions of the Iberian Peninsula were used to examine intra- and inter-regional variation in plant traits, interactors and plant fecundity, and to compare, through selection gradient and path analyses, which traits were under selection, and which interactors were responsible for differential selection. Geographic and temporal congruency in interactor-mediated selection was further tested using a recent analytical approach based on multi-group comparison in Structural Equation Models. Most plant traits, interactors and fecundity differed among regions but not between populations. Similarly, the identity of the traits under selection, the selection gradients (strength and/or the direction of the selection) and the path coefficients (identifying the ecological basis for selection) varied inter- but not intra-regionally. Results show a selection mosaic at the broad scale and, for some traits, a link of differential selection to trait differentiation.

Indirect effects of alternative food resources in an ant-plant interaction.

The seeds of many plant species present a food body that is consumed by animal dispersers. In theory, if the animals are polyphagous, the availability of alternative food resource other than the diaspore itself may influence its dispersal and survival. We used the myrmecochore Helleborus foetidus L. (Ranunculaceae), the seeds of which are attached to a lipid-rich elaiosome that is attractive to ants, as a model system to investigate (1) whether alternative foods that are present along with the plant affect ant foraging behavior and diaspore removal and (2) whether food availability in an ant nest affects seed predation and germination. In a field experiment, artificial diaspore depots were offered together with either sugar, insect corpses, seed, or no food (control). Contrary to the prediction that ants would rather concentrate their foraging effort on the highly rewarding alternative foods only, many workers, attracted by the sugar, switched to the hellebore diaspores, which significantly enhanced removal rate. Results obtained in the laboratory further indicated that the larvae of Aphaenogaster iberica (a major seed disperser) predated more on the H. foetidus embryos when no alternative food was available. This, in turn, slightly reduced seed germination. Overall, these results shed light, for the first time, on the potential indirect effects of alternative resources on the fate of diaspores adapted for ant dispersal.

Geographical variation in autonomous self-pollination levels unrelated to pollinator service in Helleborus foetidus (Ranunculaceae).

Autonomous self-pollination may be considered as a mechanism enhancing plant reproductive success when plant access to pollen sources may limit seed production. We have studied the relationship between geographical patterns of variation in pollinator service to Helleborus foetidus and self-pollination ability in three widely spaced regions in the Iberian Peninsula. As could be expected from its early flowering period, pollinator visitation rates to both plants and flowers of H. foetidus were very low at all sites. Pollinator composition remained consistent among regions, but there was significant variation among regions in pollinator service. Despite the low visitation rates, fruit set did not appear to be pollen limited in any of the study areas, which may be explained by the long duration of flowers (up to 20 d). When pollinators were excluded experimentally, fruit set decreased significantly, but substantial levels of self-pollination occurred at all regions. Autonomous self-pollination levels were lowest in the two regions with lowest pollinator service and highest in the region with highest pollinator service. This disagreement between our results and the expectations derived from the reproductive assurance hypothesis may reflect a nonequilibrium situation of the northern H. foetidus populations in relation to their current pollinating environment.

Orientation and navigation during adult transport between nests in the ant Cataglypis iberica.

Cataglyphis iberica is a polydomous ant species in which adult transports between nests are frequently observed. When pairs of workers were captured and released at the same location, the transporters (Ts) field directly towards their destination nest and reached it in most of the cases. The transportees (Te), on the other hand, fled in the opposite direction and only a third of them eventually reached their nest of departure. Additional experiments suggest that this result may be explained by the fact that the Ts ants have a memory of the compass direction of the nest they are heading to and that they adjust their course by using a sequence of memorised landmarks. As regards to the Te, the reversal of their direction of transport seems to be based essentially on celestial cues.

[Improving the quality of clinical interview teaching: evaluation of an intervention with medical students]. / Mejorando la calidad de la enseñanza de entrevista clínica: evaluación de una intervención en estudiantes de medicina.

BACKGROUND: Quality of clinical interview is a key issue both for patient satisfaction and for diagnostic efficiency. Its adequacy relates to better clinical diagnosis treatment plans and patient compliance. AIM: To measure the quality of interviews performed by medical students in three Chilean medical schools before receiving specific training on the subject and to compare the scores obtained after introductory courses on interview. MATERIAL AND METHODS: The interviews were videotaped and then evaluated using an objective scale, that measures 33 skills grouped in six areas: opening, problem exploration, non verbal facilitation, interpersonal patient reaction and closing. The students were assigned to an experimental group that received an interactive workshop with role-plays, vignettes and videotape feedback, and to a non intervention group that received the usual bedside training on medical interviews. RESULTS: Both groups shared the same skill level before the training, with better scores on nonverbal, patient reaction and problem exploration, and worse ones on closing and interpersonal skills. Comparing pre and post-test results, the overall score improved in the experimental group (from 33.2 to 38.3, p = 0.002) and worsened among non intervened students. There were statistically significant changes for opening (p < 0.002), problem exploration (p < 0.05), non verbal facilitation (p < 0.0001) and closing (p < 0.0001). CONCLUSIONS: It is important to train students not only in specific knowledge contents but in the process of interview. This training should encourage the development of empathy and closing skills.

Patterns of diversity and composition of Mediterranean ground ant communities tracking spatial and temporal variability in the thermal environment.

The present study analyzed ant community structure and the factors affecting it in the Spanish Mediterranean area. The aim of this study was to test whether temperature controls the composition and diversity of the ground ant fauna and the spatial and temporal distribution of dominance groups along adjacent communities. The main descriptors of community structure (except perharps species richness) were found to vary along the gradient of vegetation cover: increased vegetation cover resulted in an increase in the relative abundance of the most common species, which led to a significant decrease in species evenness, together with a reduction in total ant density on the ground. In open habitats, dominant and subordinate species were abundant during different periods of the day, and this led to an increase in species evenness. In areas with high vegetation cover, dominants benefited from the lower temperatures by lengthening their periods of activity. This resulted in a decrease in the abundance of subordinate species, and in lower evenness. Seasonal patterns in community structure tracked temperature fluctuations and varied between habitat types. Evenness was similar in the two habitat types in spring, but increased in grasslands and decreased in shrublands/forests in summer. Species richness did not vary between seasons or habitat types. The relative abundance of dominance groups in the two types of habitats showed a different pattern between seasons. In grasslands, subordinates increased and dominants decreased their relative abundance from spring to summer, while in shrublands/forests, the opposite pattern was found. The overall conclusion from this study is that ground ant communities in open areas are primarily regulated by temperature variations, while in shrublands and forests, dominant species are more abundant, and competitive interactions appear to be the major structuring force.

Social closure, aggressive behavior, and cuticular hydrocarbon profiles in the polydomous antCataglyphis iberica (hymenoptera, Formicidae).

Nestmate recognition was studied in the polydomous antCataglyphis iberica (Formicinae) in the laboratory. The study examined six colonies collected from two different populations 600 km apart in the Iberian peninsula (Barcelona and Murcia). Introduction of an alien worker into an allocolonial arena always ended in death to the intruder, demonstrating that in this species societies are extremely closed. Dyadic encounters composed of individuals from different colonies in a neutral arena confirmed the existence of high aggression between allocolonial individuals. We also investigated variability in the composition of the major cuticular hydrocarbons between the colonies used in the behaviorial tests. There were marked quantitative differences between the profiles of ants from the two populations, suggesting that the populations are completely segregated. Cuticular profiles within a population tended to be more similar, but were nevertheless colony specific. The degree of colony closure inC. iberica seemed to be independent of geographic distance since aggression between the colonies was always at its maximum, irrespective of their population origin.

Induction of choriogenesis by 20-hydroxyecdysone in the German cockroach.

Experiments in vitro have shown that 20-hydroxyecdysone (at a concentration of 0.2 and 2 microM and after 12 and 24 hr of incubation) is able to induce the precocious deposition of chorion materials by the follicular epithelium of young oocytes of the cockroach Blattella germanica. Since previous studies had shown that 20-hydroxyecdysone levels in B. germanica ovaries increase with oocyte maturation to reach a peak just before oviposition, we therefore hypothesize that ovarian ecdysteroids trigger Choriogenesis in this species through an autocrine action.