Several methods based on population biology, biogeography, ecology, and genetics have been traditionally used for the identification of units for conservation below the species level. We use a combination of two methods based on population genetic structure estimators and on probabilities of loss of rare alleles to identify the Relevant Genetic Units for Conservation (RGUCs). The aims were to assess the genetic diversity and population structure of the endemic steppe plant Boleum asperum (Brassicaceae), and to determine how many and which populations significantly represent the total genetic diversity and the rarest allelic variation. Despite the high amplified fragment length polymorphism genetic diversity values detected in B. asperum (hT = 0.744), caused probably by its hexaploidy and allogamy, moderate spatial genetic differentiation was detected among populations (< 20%) and geographical ranges (> 13%), suggesting the existence of an ancestral continuous distribution range that was fragmented into separate 'islands' in more recent historical times. Five RGUCs, accounting for the 85.10% of the total genetic variation and representative of the entire geographical distribution of the species, were selected for in situ conservation. Ex situ conservation is proposed to complement the preservation of B. asperum. This method of objective selection of populations may be applied to other candidate taxa for conservation with prior adjustment of the threshold values of diversity required for effective protection of each particular species.

The geology and climate of the western Mediterranean area were strongly modified during the Late Tertiary and the Quaternary. These geological and climatic events are thought to have induced changes in the population histories of plants in the Iberian Peninsula. However, fine-scale genetic spatial architecture across western Mediterranean steppe plant refugia has rarely been investigated. A population genetic analysis of amplified fragment length polymorphism variation was conducted on present-day, relict populations of Ferula loscosii (Apiaceae). This species exhibits high individual/population numbers in the middle Ebro river valley and, according to the hypothesis of an abundant-centre distribution, these northern populations might represent a long-standing/ancestral distribution centre. However, our results suggest that the decimated southern and central Iberian populations are more variable and structured than the northeastern ones, representing the likely vestiges of an ancestral distribution centre of the species. Phylogeographical analysis suggests that F. loscosii likely originated in southern Spain and then migrated towards the central and northeastern ranges, further supporting a Late Miocene southern-bound Mediterranean migratory way for its oriental steppe ancestors. In addition, different glacial-induced conditions affected the southern and northern steppe Iberian refugia during the Quaternary. The contrasting genetic homogeneity of the Ebro valley range populations compared to the southern Iberian ones possibly reflects more severe bottlenecks and subsequent genetic drift experienced by populations of the northern Iberia refugium during the Pleistocene, followed by successful postglacial expansion from only a few founder plants.

No abstract

Allozyme data support the hypothesis of an allotetraploid origin of Vella pseudocytisus subsp. paui that could be representative of other taxa of the core Vellinae group. AFLP data distinguished three geographically distinct groups with no genetic interaction among them. Allotetraploidy and outcrossing reproduction have probably contributed to maintenance of high levels of genetic variability of the populations, whereas habitat fragmentation may have enhanced the high genetic isolation observed among groups. In-situ microgenetic reserves and a selective sampling of germplasm stocks for ex-situ conservation of this taxon are proposed.

Epipetrum Phil. has long been considered one of the five narrow genera of Dioscoreaceae, comprising only three species endemic to Chile (Knuth 1924 ; Burkill 1960). Specimens of the most common species of this genus, collected by Bertero (1829) from Central Chile, were first described as Luzuriaga cordata Bertero, although the plant does not show any morphological affinities with the members of this unrelated genus of Philesiaceae. This misinterpretation was noticed by Colla (1836) who redescribed the species as Dioscorea humilis Colla, creating a nomenclatural conflict that has been recently clarified (Viruel et al. 2009). Dioscorea humilis was later transferred to a new genus, Epipetrum [ E. humile (Colla) Phil.] by Philippi (1862) after the rupicolous habitat of the plant. According to Philippi (1862 , 1864), the separation of this new genus from Dioscorea L. was justified by the absence of winged seeds. This remarkable trait is also shared with three other small genera of the yam family: the Mediterranean-Macaronesian Tamus L., which posseses a baccate fruit rather than a capsule (as in almost all other Dioscorea s. l. species), the Pyrenean Borderea Miégeville, and the Mexican Nanarepenta Matuda (Matuda 1961 ; Téllez-Valdés and Dávila-Aranda 1998), African Dioscorea gilletii Milne-Redh. (Milne-Redhead 1963), Caribbean Rajania L., and some other Dioscorea species with samaroid fruits. The combination of unwinged seeds produced in three-angled capsules, and a dwarf trailing habit shared with Borderea , led Pax (1887) to place E. humile within Borderea [ B. humilis (Bertero ex Colla) Pax], a classification later criticised based on morphological and biogeographical studies of Dioscoreaceae (Reiche 1908 ; Burkill 1960). None of the preceding nomenclatural combinations took into account the original and validly published specific epithet of this plant as L. cordata , and thus this epithet became substituted in the literature by the currently accepted one (humile), forcing the rejection of cordata to promote nomenclatural stability (Viruel et al. 2009). Despite the low taxonomic diversity within Epipetrum , the boundaries among some of its taxa are not completely clear.