The composition of the essential oils of 16 individual plants of Artemisia herba-alba Asso ssp. valentina (Lam.) Marcl. (at the full bloom stage) growing wild in four different locations from southern Spain were investigated by capillary GC and GC-MS in combination with retention indices. Among the 60 identified constituents (accounting for 80.6-95.0% of the oils), 33 have been reported for the first time in Spanish A. herba-alba oil and 17 of them have not been previously described in A. herba-alba oil. From the analysis of the oil samples, it could be deduced that a noticeable chemical polymorphism typified this taxon. Four groups of essential oils exhibited a single compound with percentages near 30% or higher: davanone, 1,8-cineole, chrysanthenone and cis-chrysanthenol. Two further oil types showed p-cymene and cis-chrysanthenyl acetate as major components in moderate amounts (ca. 20%). All of these types of essential oils have not been previously found in A. herba-alba from Spain and the appearance of such considerable amount of p-cymene is described here for the first time in A. herba-alba. #

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Abstract.-We have studied the geological history of Central America, particularly the Caribbean, in order to discover the impact of other areas on the islands in the Caribbean Sea. The study of the distribution of 675 Melastomataceae species led us to establish the biogeographical ranks of Subregion, Superprovince, Province and Subprovince. We also suggest a biogeographical typology for the Caribbean Islands. In order to discover the relationships between the 16 territories under study, we collected the endemic Melastomataceae taxa occurring in each of them and applied the Jaccard index. Finally, we establish the Caribbean Subregion, with the Western Antilles Superprovince, which in turn includes the Provinces of Florida and Cuba. In this latter, we define two subprovinces, Cuba and Jamaica. The Central-Eastern Antilles Superprovince includes the provinces of Eastern Antilles and Hispaniola. The research involved the implementation of a floristic and distributional study of the Melastomataceae endemic taxa of the Caribbean Islands, particularly on Hispaniola; for this latter, finally the study revealed the existence of two large areas, one siliceous and another of a carbonated character.

We have studied Juniperus oxycedrus L. subsp. badia (H.Gay) Debeaux in the central and southern Iberian Peninsula, where the macrobioclimate ranges from Mediterranean-pluviseasonal-oceanic to Mediterranean-pluviseasonal-continental, and the thermotype from the thermo- to the supramediterranean. The relevés were taken following the Braun-Blanquet phytosociological methodology. A statistical treatment was applied to establish a separation among Juniperus communities. To understand the presence of Juniperus communities in territories dominated by species in the Quercus genus, we applied Thornthwaite’s formula to calculate potential evapotranspiration. The general cluster analysis clearly distinguishes two groups of plant communities and separates the different associations in each group. All the plant communities growing on rocky crests and in extremely steep sloping areas are significantly influenced by the soil. The ombroclimatic index does not explain the presence of plant communities influenced by substrate, so we proposed a new ombroedaphoxeric index which explains the presence of Juniperus communities in territories with a thermotype between the thermo- and supramediterranean. The areas of distribution of Juniperus species are expanding due to the spread of rocky areas; this phenomenon causes an increase in edaphoxerophilous areas and a decrease in climatophilous ones. We propose four new plant associations, with updated structures and floristic compositions. Efficient conservation is possible in both the territories studied (Spain and Portugal) through the implementation of specific cross-border cooperation projects.

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The south of the Iberian Peninsula, with an altitudinal range varying from sea level to 3482 m and annual average rainfall ranging from 206 to 2223 mm, has 516 vascular endemic species or subspecies, that is, an endemicity rate of 13%. This survey deals with parameters such as species richness, originality, life forms and dispersal modes of these plants, in relation to altitudinal and rainfall gradients. Although most of the endemic plants occur between 600 and 1400 m a.s.l. and in the range of 600-1000 mm annual average rainfall, floristic originality (rate of endemic taxa per area unit) increases exponentially with altitude. The biological spectrum of this endemic flora does not follow the usual patterns observed either in local floras in the south of the Iberian Peninsula or in other regions of the Mediterranean Basin. Chamaephytes (46.08%) and hemicryptophytes (31.37%) are very abundant, whereas therophytes (11.96%) and phanerophytes (0.98%) are comparatively rare. There is a statistically significant correlation between life form and both altitudinal and rainfall gradients. Chamaephytes reach their highest density rates within 1400-2000 m a.s.l., but these records tend to decrease as rainfall rates increase. Abundance of hemicryptophytes is directly dependent on rainfall rates and inversely dependent on temperature. The altitudinal distribution pattern of therophytes is opposite to that of hemicryptophytes, but there is no clear correlation as far as rainfall gradient is concerned. Considering both the endemic plants as a whole and each of the life form groups, the relationships between the dispersal modes used and the altitudinal and rainfall gradients are analysed. Up to 44.51% of the endemic plants do not present evident adaptations to promote the dispersion of their diaspores. However, only in the group of therophytes, whose occurrence is positively related to areas of minor altitude, does this difficulty of dispersion play a significant role in the maintenance of stenochory.

Abstract.-The survey deals with juniper groves of Juniperus oxycedrus, i. e. the edaphoxerophilous communities dominated by J. oxycedrus subsp. oxycedrus and J. oxycedrus subsp. lagunae in the centre and south of the Iberian Peninsula. The study of the vegetation has been carried out using the phytosociological method, complemented by a multivariate analysis to statistically process both bibliographical and field relevés. As a result, a new phytosociological alliance (Juniperion oxycedro-lagunae) encompassing four new associations (Pistacio terebinthi-Juniperetum lagunae, Stipo tenacissimae-Juniperetum lagunae, Echinosparto iberici-Juniperetum lagunae and Cytiso eriocarpi-Juniperetum lagunae) and the community of Phlomis purpurea and J. oxycedrus subsp. lagunae is proposed. These juniper groves are plant formations of general interest for the European Union and exhibit interesting endemic flora and vegetation.Key words : edaphoxerophilous communities -juniper groves -multivariate analysis -phytosociology -syntaxonomy.

del Soco and Laguna de Oviedo. With the plant samples taken in the above mentioned sites, we created a synthetic table out of 16 phytosociological tables belonging to 6 original associations and 9 associations obtained from the bibliographical study. With the purpose of obtaining a similarity gradient (matching) between the associations under study, we carried out a statistical analysis (clustering, principal component analysis and Jaccard similarity/dissimilarity analysis). Our phytosociological approach relied on criteria such as biogreography and dynamic-catenal contact. Our sampling analysis has led us to propose the following syntaxa: Machaerio lunati-Rhizophoretum manglis; Rhabdadenio biflorae-Laguncularietum racemosae; Sthalio monospermae-Laguncularietum racemosae; Lonchocarpo pycnifolii-Conocarpetum erecatae; Lonchocarpo sericeiLaguncularietum racemosae; Crataevo tapiae-Conocarpetum erectae. We also propose a new alliance and a change of status: Phyllantho elsiae-Laguncurion racemosae; Dalbergio-Rhizophorion manglis (Borhidi 1991) status novo. The mangrove swamps of Central America are arranged in three vegetation bands corresponding to different plant associations. The analysis of the three sampled area not only revealed the degradation of the vegetation but also the causative factors.