Trade‐offs in primate grooming reciprocation: testing behavioural flexibility and correlated evolution

Primates may trade altruistic behaviours, such as grooming, either for itself or for different rank‐related benefits, such as tolerance or agonistic support. Ecological conditions are expected to affect competition and thus the steepness of dominance hierarchies. This, in turn, may influence the value of the different currencies that primates exchange. Thus, it can be hypothesized that, as the dominance hierarchy becomes steeper, more grooming is directed up the hierarchy (in exchange for tolerance or agonistic support) and less grooming is exchanged for other grooming. We assembled a large database of within‐group grooming distribution in primates (38 social groups belonging to 16 species and eight genera) and tested these hypotheses both within species (i.e. comparing different groups of the same species) and between species (using comparative methods that control for phylogenetic relatedness). We found within‐species evidence that steeper dominance hierarchies were associated with more grooming being directed up the hierarchy, and that a trade‐off occurred between the tendency to groom up the hierarchy and the degree of grooming reciprocation (although, in some analyses, only a nonsignificant trend was observed). By contrast, phylogenetically controlled comparisons between species did not reveal evidence of correlated evolution between the steepness of the dominance hierarchy, the tendency to direct grooming up the hierarchy, and the degree of grooming reciprocation. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 439–446.     

Competition trade-offs in the organisation of a Mediterranean ant assemblage

Abstract.  1. The organisation of an ant assemblage inhabiting an olive orchard in central Italy was analysed and patterns of dominance among ant species were described in order to assess (i) the relationship between thermal dependency and degree of behavioural dominance, and (ii) the relationship between dominance and discovery ability.
2. Activity patterns of the most abundant species on trees were examined in a sample of 120 trees during spring and summer. The degree of behavioural dominance and the ability of different species to discover new food sources were assessed using tuna baiting on a subset of 80 trees.
3. Different ant species showed contrasting patterns of activity. Some species (such as Lasius lasioides , Camponotus lateralis , and Camponotus piceus ) were most active during the warmer part of the day, while others restricted their activity to the cooler hours ( Camponotus aethiops and Plagiolepis pygmaea ). Some species (such as Crematogaster scutellaris ) were active irrespective of the time of day.
4. No clear relationship was observed between temperature of maximal activity and degree of behavioural dominance. There was, however, a positive relationship between behavioural dominance and thermal range of activity. A positive relationship between dominance and ability to find resources, with the most behaviourally dominant and aggressive species being most efficient in finding food items, was also observed.
5. The results support the idea that the temperature–dominance relationship is much more complex in Mediterranean-type habitats than in other ecosystems. Of particular interest is the positive dominance–discovery relationship. This finding contrasts with previous investigations, which reported a negative relationship between dominance and discovery ability and suggested that this pattern plays a role in promoting the coexistence of species in ant communities.     

Functional leaf traits,plant communities and acclimation processes in relation to oxidative stress in trees: a critical overview

Tropospheric ozone exercises pressure on vegetation in combination with other oxidative factors such as strong sunlight, UV‐B radiation, high temperatures and water shortage. The relationship established between these factors and the plants can be either antagonistic (cross‐resistance) or synergistic. Response mechanisms are activated involving physiological, chemical and morphological features. Overall sensitivity (or resistance) is determined by the amount of total oxidative pressure in relation to the plant's physiological plasticity [i.e. its ability (within its own resilience potential) to alter its structure and functions in order to react to the oxidative pressure]. Within different populations of the same species, functional leaf traits (leaf area and thickness, leaf mass per area or specific leaf area, tissue thickness) may vary in relation to the extent that the plant succeeds in acclimating to ambient oxidative pressure. The behaviour of a tree in an oxidative environment can be interpreted by means of leaf structure analysis. Leaves presenting high tissue density (and thus low intercellular space content) display a high degree of acclimation to stressors, react little to environmental changes and are characterized by remarkable longevity. Leaves of this type also have a high photosynthesis capacity per surface unit (due to the N content per surface unit) and a high P_N/G_W (or water use efficiency, WUE). Thus, they are able to support detoxification processes. These morphological traits are to be found in adult plants in late successional stands and, above all, in ambients that have already been subjected to oxidative pressure. However, in early successional species and during the dynamic stages of growth (e.g. in the renewal occurring along forest edges), it is the opposite leaf traits that prevail: low leaf density, high photosynthesis capacity per dry weight unit, low WUE, low leaf longevity. These traits make plants far more reactive to environmental changes (e.g. they exploit the light from sun flecks much more effectively), but enable them to achieve only a low degree of acclimation and a poor ability to support detoxification processes. Whereas adult forests display a high level of ecological resilience and have a relatively good tolerance of ozone, the renewal stages are (at least potentially) more vulnerable. In these environments, ozone can alter the competition among genotypes and favour more resistant ones. Among the sectors most at risk, we must include communities growing at the edge of their ecological range, for whom even a slight increase in oxidative pressure can trigger substantial degenerative processes.     

Application of the unified species concept reveals distinct lineages for disjunct endemics of the Brassica repanda (Brassicaceae) complex

Species delimitation is an important issue in terms of conservation priorities, especially for narrow endemics under threat of extinction. The Alpine endemics Brassica repanda subsp. glabrescens and subsp. baldensis belong to a highly polymorphic species complex, although their disjunct distribution suggests favourable conditions for independent evolution. In the present study, we applied the unified species concept to test whether the endemics form distinct evolutionary lineages, both from one another and also from the remainder of the complex. Compliance with the criteria of monophyly, diagnosability, and genotypic clustering was examined, primarily by making use of amplified fragment length polymorphism data. Both endemics were indicated as monophyletic by phylogenetic analyses, and diagnostic characters were found for both taxa. Population structure analyses showed clear genetic discontinuity for each of the endemics, with little admixture among the clusters. This evidence indicates that the endemics have acquired multiple properties that satisfy each of the species criteria considered. Hence, we suggest the taxonomic recognition of B. baldensis and B. glabrescens as separate species. Comparative population genetics analyses show the lack of marked genetic structuring within either taxon, as well as low levels of heterozygosity. Conclusions on the status of threat and on recommended conservation actions are drawn. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 482–497.     

Geographic variation of body size and reproductive patterns in Continental versus Mediterranean asp vipers, Vipera aspis

The occurrence of variation in body size and reproductive traits of Vipera aspis was assessed by analysing 74 reproductive females of different populations, collected throughout a large part of the distribution range of the taxon, from central‐western France to central Italy. Six populations were analysed, two of plain habitats, in France and Italy, characterized by a Continental climate, whereas the other four derived from two coastal and two inland, hilly Italian habitats, respectively, showing a Mediterranean climate. Females of the French area showed the smallest mean body size, whereas the pre‐ and post‐partum body masses of females from the coolest, central Italic area were significantly higher. Litter size varied among habitats and was significantly correlated with maternal body size. If the snout–vent length feature varied largely among offspring of different habitats (with the longest size occurring in representatives of the coastal, central Italian area), the average of both body mass and total mass of offsprings did not exhibit any clear pattern among populations colonizing different habitats. Nevertheless, relative litter mass was higher in the French continental populations, and lower in the coolest, Mediterranean, Italian ones. It is worth emphasizing the positive correlation between the snout–vent length feature of females and the total litter mass to environmental factors, such as hottest month temperature and total rainfall. The available literature records that female body size affects offspring size and fecundity. If the present study bolsters this correlation, it also rules out any other effect of female body size on the offspring characteristics analysed. Finally, evidence is provided for the role of climatic factors on life‐history traits (e.g. pre‐partum body mass) of asp vipers, although confounding effects pursued, for example, by food availability may occur. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96 , 383–391.     

Drought-driven growth reduction in old beech (Fagus sylvatica L.) forests of the central Apennines, Italy

Productivity of old‐growth beech forests in the Mediterranean Basin was measured by average stem basal area increment (BAI) of dominant trees at two mountain sites in the Italian Apennines. Both forests could be ascribed to the old‐growth stage, but they differed markedly with regard to elevation (1000 vs. 1725 m a.s.l.), soil parent material (volcanic vs. calcareous), mean tree age (less than 200 years vs. 300 years), and stand structure (secondary old‐growth vs. primary old‐growth forest). Drought at the two sites was quantified by the self‐calibrated Palmer Moisture Anomaly Index (Z‐index), and by the self‐calibrating Palmer Drought Severity Index (PDSI) for summer (June through August) and the growing season (May through September). Dendroclimatological analyses revealed a moisture limitation of beech BAI at interannual (water availability measured by Z‐index) and decadal scales (water availability measured by PDSI). Both BAI and water availability increased from 1950 to 1970, and decreased afterwards. Trees were grouped according to their BAI trends in auxological groups (growth‐type chronologies), which confirmed that growth of most trees at both sites declined in recent decades, in agreement with increased drought. Because BAI is not expected to decrease without an external forcing, the patterns we uncovered suggest that long‐term drought stress has reduced the productivity of beech forests in the central Apennines, in agreement with similar trends identified in other Mediterranean mountains, but opposite to growth trends reported for many forests in central Europe.     

European and Mediterranean oaks (Quercus L.; Fagaceae): SEM characterization of the micromorphology of the abaxial leaf surface

This paper examines micromorphological characteristics (trichomes, waxes, stomata) of the abaxial leaf surface of European and Mediterranean oaks. Observations were performed In-scanning electron microscopy, and the purpose of the investigation was to ascertain whether it is possible to distinguish the different species taxonomically using these features. Several species, as well as some subspecific entities and taxa considered doubtful, were taken into consideration. Subgenera appear to be well-defined: e.g. the subgenus Quercus is characterized by waxes arranged in vertical scales, the subgenera Cenis and Sclerophyllodris by smooth waxes. They differ because the former has markedly elliptical stomata, while the latter two have roundish stomata. The different species are also fairly easy to distinguish, and this fact confirms the taxonomical validity of the parameters we have taken into consideration. In some cases subspecific entities and doublful species do not diflcr at all from the related species, but in others they present such marked variations that it is difficult even to classify them with certainty. The most critical taxonomic groups (i.e. those which include a number of specific and subspecific entities often too difficult to distinguish from each other) are the series Quercus robur – Quercus petraea,– Quercus pubescens and the Quercus faginea,– Quercus Insitanica Quercus canariensis group.