Factors Underlying the Narrow Distribution of the Mediterranean Annual Plant Arenaria provincialis (Caryophyllaceae)

Abstract

The factors responsible for the patterns of niche differentiation and narrow endemism have rarely been investigated in annual Mediterranean plants. This topic was addressed here by performing comparative studies on realized niches, regional occupancy, global biogeographical distribution and seed traits of a set of Arenaria (Caryophyllaceae) species inhabiting southern Provence (SE France), focusing in particular on Arenaria provincialis, a narrow endemic restricted to the hills and modest calcareous mountains around the city of Marseille. Field studies were carried out from 2008 to 2009 at 624 sites in the limestone mountains where Arenaria species are likely to occur. The Arenaria species occurring in southern Provence vary greatly in their patterns of regional occupancy and their biogeographical distribution. Multivariate analysis of the realized niche showed that they have some similar limiting environmental factors in common, but they do not all occupy the same habitats. Studies on the fruits and seeds showed that the endemic A. provincialis has a larger seed than its congeners and a capsule that remains closed and falls from the plant at maturity. This well-differentiated diaspore specific to A. provincialis may be responsible for the limited dispersal capacity of this species. Phylogenetic analyses showed that A. provincialis is not closely related to the other taxa inhabiting southern Provence, but rather to Arenaria occurring in highland areas in the south of France. The restricted pattern of distribution of A. provincialis is probably due to the past isolation event from which it originated and to its limited dispersal capacity, rather than resulting from its ecological niche range.

Molecular phylogenetic analysis ofArenaria(Caryophyllaceae: tribe Arenarieae) and its allies inferred from nuclear DNA internal transcribed spacer and plastid DNA rps16sequences

“…5, box G) 1962) in our analyses and its separation from these sections, or at least part of them, is not supported. The affinity of this species with members of Arenaria was also previously determined by detailed morphological and biogeographical analyses as well as molecular data (Youssef et al, 2011 (1962), the 11 species recognized in A. section Occidentales are mainly distributed in the western Mediterranean. Presence of linear to subulate leaves is the most important morphological characteristic separating the species of this section from the members of the allied A. section Orientales, which encompasses about 20 species with somewhat ovate leaves and an eastern Mediterranean distribution.…”

“…section Rariflorae ( A. subgenus Arenaria sensu McNeill, ) in our analyses and its separation from these sections, or at least part of them, is not supported. The affinity of this species with members of Arenaria was also previously determined by detailed morphological and biogeographical analyses as well as molecular data (Youssef et al ., ). The monotypic A. subgenus Porphyrantha , restricted to the Pyrenees and the Cantabrian Mountains, appears to share a similar fate. Our molecular data clearly place the type species of this subgenus ( A. purpurascens Ramond ex DC.)…”

Ecological niche differentiation in peripheral populations: a comparative analysis of eleven Mediterranean plant species

“…Finally, dispersal limitation and past isolation events may at least partially explain distribution patterns (Givnish 2010, Youssef et al 2011) and may play an important role in population limitation at range edges in the northern Mediterranean. While this study highlights effective changes in ecological conditions in natura and on a very fine-scale, the response of the taxa can be diverse, both in terms of divergence and individual plasticity.…”

Redécouverte et Écologie d´Onopordum algeriense (Munby) Pomel = Carduus algeriensis Munby, endémique stricte en voie d’extinction du secteur algérois

“…On a mis en place un dispositif d´étude d'O. algeriense (Vela & al., 2008 ;Baumel & al., 2009 ;Youssef & al., 2011). Après prospection de terrain, nous avons rencontré deux types de situations ou l´espèce apparait: répartition à forte pente (site 1) et répartition en terrain plat (site 2).…”