1. Diet composition of two syntopic species of Messor seed-harvester ants (M. wasmanni Krausse and M. minor André) was evaluated during different periods over the year (May, July, October), by analysing food type (plant parts and species) and food size (weight, length, width). Morphological traits of foragers (head width and femur length) considered important features promoting diet partitioning were measured.2. We used two robust randomisation algorithms (RA2 and RA3), adopted in niche overlap studies, to check for random vs non random utilisation of resources at intraand interspecific level for the different periods.3. Analyses showed high levels of overlap in the diet of the two species and no evidence of interspecific competition during most of the activity season. In particular, there was an aggregated use of resources in summer, whilst niche partitioning and evidence of competition when resources decreased in autumn. Intraspecifically, no evidence of competition was found. 4. Results suggest two different mechanisms for minimising competition: when food resources are abundant (summer), ants collected the same plant species but selected different sizes; when food resource is scarce (autumn), ants foraged on different plants.5. The importance of different factors (morphological, behavioural, ecological) possibly affecting competition and coexistence are discussed.

Physiological tolerance of species to temperature, moisture or chemicalphysical properties of the soil could be important in determining the distribution and abundance of ant nests. In the present study we investigated the possible differences in the nesting site microhabitat characteristics of two syntopic species of harvester ants of the genus Messor living in a Mediterranean homogeneous grassland area belonging to a single phytosociological association known as "Vulpio ligusticae-Dasypyretum villosi". We tested to see whether the activity of the colonies of the two species directly altered the microhabitat characteristics of the nesting sites. Microhabitat characteristics were assessed quantifying several abiotic factors (light, temperature, soil moisture, soil pH, nitrogen) by means of the Ellenberg Bioindication Model. The model represents a simple way of interpreting the vegetation pattern in terms of ecological factors from the perspective of the plants and can be considered an effective and promising approach to link animal and plant ecology. Our data showed significant differences in the nesting site microhabitat characteristics partially due to a different capacity of the two species to alter nesting site proprieties. Possible differences in the physiological tolerance of these species to moisture gradients could be crucial in determining the distribution and abundance of their nests.

Different aspects of the foraging strategies of two harvester ant species, Messor wasmanni and M. minor, were investigated in a Mediterranean dry grassland area. Baits were used to evaluate the existence of a trade-off between resource discovery and domination as well as the effect of three variables (air temperature, relative humidity and distance) on the trade-off. Baits were also utilized to explore random vs non random use of time by colonies. Random vs non random utilization of space was instead evaluated by mapping the daily foraging area of colonies in a grid of 900 plots of 1 m2 each. Results revealed that species coexistence is not preferentially supported by a trade-off in resource utilization with no overall effect of the examined variables. The foraging activity of the two species widely overlapped whilst a clear competition for space occurred. The observed space partitioning could represent an advantageous strategy for the coexistence of the two ant species. © 2014 Springer Science+Business Media New York

The present study used a multi-set indicator approach to evaluate environmental quality in complex ecosystem. The simultaneous analysis of information deriving from different ecosystem scales and/or taxonomic groups was used to achieve a better understanding of the interconnected above-and below-ground ecosystem components. Three indicator sets were utilized in eight sampling sites representative of the main habitats of a Mediterranean area in Central Italy, the Castelporziano Presidential Estate:(1) plant indicators derived from Ellenberg and Hemeroby models; (2) fauna indicators from soil microarthropods; and (3) humus forms and soil parameters from direct measurements. Principal component analysis and Spearman correlation test were performed on the data indicators/parameters matrix to evaluate the agreement of the multi-set in describing environmental quality. Results highlighted significant correlations among the different indicators/ parameters. In particular, vascular plants and soil microarthropods represent two independent gradients in assessing ecosystem functioning, whilst humus forms provided similar information on habitat characteristics.

The population size (estimated by POPAN method) and potential interspecific competition and spatial distribution in relation to vegetation features were studied in two sympatric and syntopic rodent species, Apodemus sylvaticus and Apodemus flavicollis. The study was performed by capture-mark-recapture study within a trap grid, at two adjacent forest sites in Mediterranean central Italy. We found that the population sizes of the two rodent species were comparatively lower than those recorded in conspecifics from other central Italian areas, and that the potential for interspecific competition was low at both sites, as revealed by the lack of negative correlations between the relative abundances of the two species after Monte Carlo analyses. The number of captures of both rodent species was not correlated to either the number of trees in each grid cell or the sum of tree diameters. The general implications of the obtained results are discussed