Luigi Mossa

Iridoids from endemic sardinian Linaria species

Linaria arcusangeli contains a new bisiridoid, named arcusangeloside, besides the known antirrhinoside, linarioside, antirrhide, linaride and 5-glucosylantirrhinoside. The new bisiridoid is formed from a non-glycosidic cyclopentanoid which esterified the iridoid glucoside 5-deoxyantirrhinoside, also isolated as a free compound from the plant extract. L. flava subsp. sardoa contains the new bisiridoid, 5-deoxyantirrhinoside, antirrhinoside, linarioside and antirrhide.

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.

QUERCUS ICHNUSAE (FAGACEAE), A NEW SPECIES FROM SARDINIA

ABSTRACT A new species of Quercus, Q. ichnusae, endemic to Sardinia is described and illustrated. Its distribution and relationships with the other deciduous oaks occurring on the island are examined.

Sulla esistenza di due varietà di Ranunculus bullatus L. Osservazioni cariologiche ed ecologiche su materiale della Sardegna

Abstract About the presence of two varieties of Ranunculus bullatus L. Karyological and ecological observations in subjects of Sardinia. — In the present paper ecological and cytotaxonomical observations in two varieties of the Ranunculus bullatus L.: Ranunculus bullatus L. ssp. eu-bullatus Maire var. plantagineus (Jord. et Fourr.) Maire and Ranunculus bullatus L. ssp. eu-bullatus Maire var. supranudus (Jord. et Fourr.) Maire have been carried out. The two entities are indifferent to any rocky substratum and they settle on thin and half-arid muddy-sandy soil. The caryological analysis show the coincidence of the two karyotypes and the attribution of the somatic differences to the natural intraspecific variability. The karyotype formula of each variety is: z=2n=16 = 2L1+2L2+2L32M1+2M2+2M3+2M4+2M2 5.