Riccardo Guarino

Floristic Traits and Biogeographic Characterization of the Gennargentu Massif (Sardinia)

Abstract Bacchetta, G., G. Fenu, R. Guarino, G. Mandis, E. Mattana, G. Nieddu & C. Scudu (2013). Floristic traits and biogeographic characterization of the Gennargentu massif (Sardinia). Candollea 68: 209–220. In English, English and French abstracts. A study on the vascular flora of the Gennargentu Massif (Central-Eastern Sardinia) is presented. According to our results, the flora consists of 948 taxa: 686 species, 249 subspecies, 10 varieties and 3 hybrids, belonging to 97 families and 427 genera. Three taxa are new findings for the flora of Italy and eight for that of Sardinia. Life form analysis revealed, in particular, dominance of 35.65% hemicryptophytes, 34.6% therophytes, 12.13% geophytes and 11.6% (nano)-phanerophytes. As concerns chorology, the Mediterranean element is largely prevailing (68.14%), mainly represented by circum-Medit. (29.1%) and Euro-Medit. (23.07%). Endemics are 14.87% of the whole flora (141 taxa), with a large prevalence of Sardo-Corsican (39.01%) and Sardinian taxa (35.46%), i.e. 74.47% of the total. Due to the high number of taxa (9) of Gennargentu exclusive endemics and the geologic and geomorphologic peculiarities, it is here proposed a biogeographic classification for these territories serving to the identification of an auto nomous sector.

A stochastic model of seed dispersal pattern to assess seed predation by ants in annual dry grasslands

A combined field experiment and modelling approach has been used to provide evidence that ants may be responsible for an observed lower patchiness and higher plant diversity in the neighbourhood of ant nests, within Mediterranean dry grasslands belonging to the phytosociological class Tuberarietea guttatae. The hypothesis was that seeds occurring in clumps may have a higher probability to be harvested than seeds having a scattered distribution. In order to test this hypothesis, four analysis steps were performed. First, pattern of seed production and dispersal of four species was recorded; two of them were more abundant next to ant nests (Tuberaria guttata, Euphorbia exigua), whereas the other two were more abundant away from ant nests (Bromus scoparius and Plantago bellardi). Second, a stochastic model was developed to simulate the observed dispersal patterns of each studied species. Third, 10 seed spatial arrangements in accordance to the distribution patterns created by the model were offered to ants and the location of predated seeds was recorded. Finally, the observed pattern of seed predation was matched to models performed by different distributions of probability. Results showed that the probability of being predated decreased as distance among seeds increased. This preference of ants for high concentration of food items holds down the dominant species sufficiently to allow the subordinates to survive, thus increasing diversity near nests. The observed higher frequency of small-seeded, small-sized, or creeping therophytes close to the ant nests can be therefore seen as an example of indirect myrmecophily.

Phytosociological notes on the Lygeum spartum grasslands from Crete

Se han estudiado los albardinares de Lygeum spartum L. de Creta aplicando el metodo fitosociologico. Este tipo de vegetacion esta incluido en el orden Lygeo - Stipetalia tenacissimae (clase Lygeo-Stipetea ) de la que describimos una nueva alianza en el presente trabajo, Scorzonero creticae-Lygeion sparti. Asimismo se describen tres nuevas asociaciones incluidas en dicha alianza: Limonio hyssopifolii-Lygeetum sparti , presente sobre substratos arcillosos halomorficos de Sitia (NE Creta), Erodio crassifolii-Lygeetum sparti , colonizadora de los afloramientos arcillosos, fuertemente erosionados al este de Ierapetra (SE Creta) y Convolvulo oleifolii-Lygeetum sparti , que sustituye a la precedente sobre margas estratificadas mezcladas con conglomerados cerca de Makrigialos. En esta ultima asociacion han sido tambien reconocidas dos subasociaciones nuevas: limonietosum roridi, localizada cerca del mar y fumanetosum laevipedis de territorios situados en el interior. Con el objetivo de evidenciar el grado de similitud de los inventarios, se ha efectuado un analisis numerico multivariable.