Evaluation of Plant Diversity in the Steppes of White Wormwood of the Region of Saida (Western Algeria)

This work is an evaluation of the plant diversity of the white Wormwood formations (Artemisia herba-alba Asso.) in the steppes rangelands of the south-eastern zone of Sa?da (municipality of Maamora, Western Algeria). For this purpose, twenty-one phytoecological statements are carried out on three sample stations: an exclosure station where the white Wormwood is well developed and two other stations not protected where in one, the white Wormwood is moderately degraded and in the other one, it is strongly degraded. The factorial correspondences analysis (FCA) and the ascending hierarchical clustering (AHC) carried out on the floristic and edaphic parameters measured on these stations led to a hierarchy of the ecological factors determining the diversity of the studied plant formations with white Wormwood. The vegetation studied is marked by the dominance of the therophytes, particularly in the third station (very degraded station), while the exclosure station is essentially characterized by a high recovery rate and an important phytomass.

Inventory and Analysis of Phytodiversity along an Altitudinal Gradient in the Southern Slope of the Mount of Tessala (Western Algeria)

Our work consists in inventorying and analyzing the phytodiversity along an altitudinal gradient of the southern slope of the mount of Tessala (north-western Algeria). For this purpose, we choose seven stations, inside each one of them floristic statements are realized. The inventory carries out on the whole of the stations made it possible to draw up a floristic list represented by 103 species, distributed on 39 botanical families dominated by Asteraceae, Poaceae, Lamiaceae and Brasicasseae. The biological spectrum of these species reveals the predominance of the hemicryptophytes and the therophytes, and on the physiognomical level, the vegetation of our stations allows distinguishing from the tree, shrubby, bushy and herbaceous formations. The processing data obtained by the factorial analysis of correspondences (AFC) and by ascending hierarchical classification (CHA) emphasize the existence of two groups of stations. A first group of stations are located in altitude, less degraded, more diversified and where in particular the phanerophyts dominate. A second group of stations are located in low altitude, little diversified and where the degradation of vegetable cover is important, resulting in the installation of the hemicryptophyts and the therophyts.

Phylogenetic inferences in Prunus （Rosaceae） using chloroplast ndhF and nuclear ribosomal ITS sequences

Sequences of the chloroplast ndhF gene and the nuclear ribosomal ITS regions are employed to recon-struct the phylogeny of Prunus (Rosaceae), and evaluate the classification schemes of this genus. The two data sets are congruent in that the genera Prunus s.l. and Maddenia form a monophyletic group, with Maddenia nested within Prunus. However, the ndhF data set is incongruent with the ITS data supporting two major groups within Prunus: one consisting of subgenera Laurocerasus (including Pygeum) and Padus as well as the genus Maddenia and another of subgenera Amygdalus, Cerasus, and Prunus. The ITS data, on the other hand, support a clade composed of subgenera Amygdalus and Prunus and Prunus sect. Microcerasus in addition to a paraphyletic grade of subgenera Laurocerasus and Padus (and the genus Maddenia) taxa. In general, the subgeneric classifications of Prunus s.l. are not supported. The ITS and ndhF phylogenies differ mainly in interspecific relationships and the relative position of the Padus/Laurocerasus group. Both ITS and ndhF data sets suggest that the formerly recog-nized genus Pygeum is polyphyletic and that the distinction of the subgenera Padus and Laurocerasus is not supported. The biogeographic interactions of the temperate and tropical members in the Padus/Laurocera- sus/Maddenia alliance including Pygeum are shown to be highly dynamic and complex.