Suzette Puech

Utility of rDNA ITS sequences in the systematics ofTeucrium sectionPolium (Lamiaceae)

A phylogenetic study based on sequence data from the complete internal transcribed spacer region (ITS) of nuclear ribosomal DNA for sect.Polium of the genusTeucrium shows both intersectional congruence and intrasectional incongruence with traditional morphological classifications. We attribute this incongruence largely to problems related to the polyploid complex studied. SectionPolium includes many poorly differentiated taxa of probable recent origin through hybridization followed by polyploidization. Both on the basis of parsimony and distance (Neighbor-Joining method) analyses,T. dunense andT. thymifolium are the species that diverge most from the sampled taxa. However, unlikeT. thymifolium, the morphology ofT. dunense is not much differentiated in relation to the other taxa. Both species are, nonetheless, the only sampled species to occupy isolated, exclusive environments and which may have undergone rapid evolution by a bottleneck effect.Teucrium dunense is found only on dunes along the Spanish and French coasts andT. thymifolium, a chasmophytic species with limited endemism, is found solely on limestone and dolomite cliffs in the low mountains in south-eastern Spain. A hypothesis is presented to explain the discrepancy between the observed comparatively large amount of ITS sequence divergence and the low morphological differentiation inT. dunense.

Geographical Variation and Successive Adaptive Radiations of Yellow-Flowered Teucrium (Labiatae) in the Mediterranean Region

Study of the geographical variation of yellow-floweredTeucrium sect.Polium species using morphological, chemical, and cytological analyses shows that the group of North African taxa is both differentiated from the European group and homogeneous with it. It displays stable vegetative and floral characters that are common to all the taxa. The essential differences concern the indumentum structure and the habit of the plants. The diversity of environments has enhanced the expression of successive radiations of the group. The first doubtless originated in the Betic-Rif zone and in particular in the southeastern part of the Iberian Peninsula. These radiations probably first gave the groupT. aureum, now endemic in the Ibero-Provençal mountains. The species then became better differentiated in North Africa. Differentiation took place in the mountain ranges (Rif, Atlas, and Hoggar) and some Mediterranean islands (off the eastern coast of Tunisia) for the current species with narrow endemism and in desert regions (steppes and the Sahara) for those with wider endemism.

Le Poliumoside, Marqueur Chimique de la section Polium du Genre Teucrium (Labiatae): L'exception du Teucrium mideltense, Espéce Endémique du Maroc

Abstract In a chemical study on the distribution of caffeic acid esters and flavonoids in Teucrium section Polium (Labiatae) in Morocco, poliumoside, the chemical marker for this section, was found to be present in a stable manner in all the species tested, thus confirming its value as a taxonomic marker. It contrasts with other caffeic acid esters which display considerable variation related to environmental conditions to the extent of disappearing or appearing during culture. T. midefense , an endemic species in Morocco, is an exception with regard to poliumoside. The molecule was absent in ell populations of this taxon. The result is backed up by the paradoxical nature of the species, as its reproductive characters are typical of sub section Polium and its vegetative characters—and especially these of the indumentum—are distinctly marginal with regard to sub-section Polium to which it nevertheless belongs.

CYTOGENETICS AND ADAPTATION TO INCREASINGLY ARID ENVIRONMENTS : THE EXAMPLE OF PLANTAGO ALBICANS L. (PLANTAGINACEAE)

Abstract Analysis of the productivity, germination and karyograms of new populations of P . albicans in Tunisia clearly confirms that germination strategies are correlated with an increasing aridity gradient and hexaploid or tetraploid and diploid cytotypes. Germination is synchronous for the seeds of the hexaploid populations in a semi-arid bioclimate with cool or temperate winters in the north and in the hills of the Dorsale region of Tunisia as in the hills of northern Morocco. The germination of tetraploids and diploids in a semi-arid or Saharan bioclimate with mild or cool winters in central and southern Tunisia, as in southern Morocco, takes place in successive waves. These remain true-to-type for several years before losing viability. In contrast, seeds from experimental cultivated plants, at least under the conditions used, lost their adaptation to the original biotope and germinated actively as soon as they were placed in favourable conditions. These results might form proof of the impact of the ecological conditions encountered by the seeds during maturation on their future germination potential. The distribution of chemical compounds confirmed the distinction between diploids and tetraploids in arid zones on the one hand and hexaploids in moist regions on the other. Nevertheless, the disappearance of poliumoside in experimental vegetative specimens, whatever their robustness, remains unexplained.

La variabilité chimique de l'huile essentielle chez Teucrium puechiae greuter et burdet sur le littoral languedocien (France)

Abstract The composition of the essential oil of Teucrium puechiae Greuter and Burdet ( Lamiaceae ), shows no essential oil plasticity and, on the other hand, a very low chemical polymorphism. This small intrapopulational qualitative variability is probably the rsult of an adaptation to the environmental variation in Languedoc (French Mediterranean coast). However, the mode and growth rate, connected to the perturbations in dune ecology, have an effect the quality of the essential oil. The natural selection seems to act upon the quantitative proportional aspect of the essential oil in seedling and young plants, by favouring the precocious elaboration of sesquterpenes (terminal products).