Régine Verlaque

Ploidy level and origin of the European invasive weed Senecio inaequidens (Asteraceae)

Native to South-Africa, species of the Senecio inaequidens complex are presently invasive in Europe, Australia and South-America. Previously, different ploidy levels have been found in these different areas, with only tetraploid individuals reported in Europe, and only diploids in South-Africa and Australia. In the present study chromosome counts and flow cytometry were used to survey DNA ploidy levels in a large sample of 66 native and 21 European invasive populations. One Mexican individual was also added to the study. We found only tetraploid individuals occurring in Europe, whereas both ploidy levels, diploid and tetraploid, were found in South-Africa. Moreover, based on genome size, we suggest that two largely allopatric varieties of diploids exist in South-Africa. The Mexican individual was diploid. We suggest that European tetraploid individuals come from South-Africa and hypothesize that a hybridization event between the two DNA types of diploids occurred in the Lesotho area. The taxonomic difficulties surrounding species of theS. inaequidens complex are briefly discussed.

Valeur prédictive des types biologiques pour la conservation de la flore méditerranéenne.

The validity of Raunkiaers biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.Abstract The validity of Raunkiaer’s biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.The validity of Raunkiaer’s biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.

Plant species diversity and polyploidy in islands of natural vegetation isolated in extensive cultivated lands

Natural polyploidy is often related to a longer life span, vegetative reproduction and higher competitive ability. In this paper, we test the possibility that these characteristics may favour the survival of polyploid taxa under conditions of long-term habitat fragmentation. In islands of natural vegetation isolated in extensive vineyards located in the South of France and in a large neighbouring area of natural vegetation, plant species richness and the relative abundance of polyploid taxa were assessed according to island size, isolation and vegetation structure. High species richness was observed, with numerous species restricted to the islands, suggesting that these may constitute refugia. However, species richness was not related to island size or to degree of isolation except for the flora of the woody areas. A very positive effect of area fragmentation on plant richness was observed, which is probably attributable to relatively low species overlap among the islands. Particularly high species richness was observed in open areas, provided that these were not extensively colonized by shrubs which seem to be responsible for local extinction of many annual taxa. Polyploids, which comprised mostly perennial herbs and woody species, were predominant in all the islands and in the large reference area. In open habitats invaded by shrubby species, a higher relative frequency of polyploids was observed in islands than in the reference area. Moreover, polyploid taxa were present in a larger number of islands than the diploid taxa, which were often restricted to a single island, suggesting that, after a long period of isolation, the polyploids may still have a lower probability of extinction. Evidence was obtained from vegetation structure analysis that diploid and polyploid annual herbs were restricted to open habitats and were both eliminated by shrubby species. Conversely, the diploid perennial herbs were also significantly affected by shrub colonization whereas the polyploids were mostly present in shrubby areas. This suggests that the higher competitive ability of polyploid perennial herbs may constitute a critical factor responsible for their wider distribution over the islands. We report the implications of our findings on conservation strategies, more particularly for a Mediterranean flora.

Pollen morphology of Zelkova sicula (Ulmaceae), a recently discovered relic species of the European Tertiary flora: description, chromosomal relevance, and palaeobotanical significance

Pollen morphological characteristics of Zelkova sicula Di Pasquale, Garfi et Quezel and Z. carpinifolia (Pallas) Koch (Ulmaceae) are described. Z. sicula is a shrub species which was recently discovered on southeastern Sicily. Z. carpinifolia is the Zelkova species to which some European Tertiary to Quaternary leaf fossils have been attributed in recent studies. The new results were compared with the pollen morphological characteristics of some other Ulmaceae species such as Z. abelicea (Lamark) Boissier, Z. serrata (Thunberg) Makino, Ulmus glabra Hudson, U. laevis Pallas, U. minor Miller, and U. procera Salisbury. It was observed that Z. sicula usually possesses 5 to 6 pores, whereas the other Zelkova species normally have fewer than 5 pores. Higher frequencies of tetrads, a Y-mark on the proximal face, and a smoother exine sculpture (compared with other Zelkova species) were noted for pollen of Z. sicula. The equatorial diameter of Z. sicula was larger than every other Ulmaceae species, with a smaller PE ratio. Some of these differences can be explained by the triploid nature of Z. sicula, which is quite exceptional for Ulmaceae. Given these remarkable characteristics, it should be possible to recognise Z. sicula pollen grains in fossil pollen assemblages. It is thus anticipated that a more comprehensive pollen analytical study will lead to a revision of the Mediterranean phytogeographical history of the genus Zelkova.

On a broad-leaved form of the seagrass Posidonia oceanica (Posidoniaceae) from Algiers (Algeria)

Abstract The discovery in the Algiers (Algeria) region of a population of Posidonia showing distinct individualisation with reference to the classic description of the species Posidonia oceanica (L.) Delile would appear to confirm that this species, endemic to the Mediterranean, is less homogeneous than had previously been thought. The Algerian population at La Marsa differs from the typical taxon (based on observations on the French coasts) in leaf breadth, its greater number of longitudinal vascular bundles, its distinctive karyotype and certain specific anatomical features. It would, however, be premature at this stage to come to any definite conclusions with regard to its systematic position and rank.

Unexpected morphological and karyological changes in invasive Carpobrotus (Aizoaceae) in Provence (S-E France) compared to native South African species.

Hybridization processes can lead to evolutionary changes, particularly in co-introduced congeneric plant species, such as Carpobrotus spp. which are recognized as invasive in Mediterranean climate regions. Morphological and karyological comparisons have therefore been made between native Carpobrotus edulis and C. acinaciformis in South Africa and their invasive counterparts in Provence (C. edulis and C. aff. acinaciformis). Morphological data exhibited the most significant differences in invasive C. aff. acinaciformis that forms a new phenotypic variant. Unexpected chromosomal restructuring has been highlighted for both taxa in Provence, with in particular a clear decrease in asymmetry, an increase in the intraspecific variability, and an interspecific convergence of karyotypes. These changes suggest a drift that has facilitated various crosses, and has been amplified through hybridization/introgression. Furthermore, several morphological and karyological transgressive characters have been found in the two invasive taxa. These results stress the important role and the rapidity of karyological changes in invasive processes.

Genetic Differentiation Between and Among Refugia

1. Since the Last Glacial Maximum, the distribution of terrestrial plant and animal taxa in Europe has shifted from their refugia, Northwards in latitude and upwards in altitude. 2. The populations from refugia, mainly the mountain massifs of S Europe (Pyrenees and Alps, and also the Carpathian and Balkan Mountains), harbor a higher genetic diversity than the populations of N Europe. 3. The isolation by distance effect between populations tends to decrease with the increasing distance from the glacial refugia. 4. In areas of admixture from colonization originating in different refugia the heterozygosity may be higher than near the refugia. 5. Numerous thermophilous species have survived in their Mediterranean refugia at low altitude (particularly in islands). 6. Diploid populations or taxa often remained restricted at mid and high altitudes in S Europe, while their polyploid relatives spread in the lowlands. 7. For cold-adapted species, the refugia are mainly located in the S European mountains, and sometimes in N Eurasia, such as in Andoya island or in Taymyr peninsula. 8. The relict populations retaining a high allelic diversity and the endemic diploid taxa are now key elements in the long term conservation.

Étude cytotaxinomique de quelquesDipsacaceae d'Iran

Chromosome numbers for 28 Iranian populations ofDipsacaceae, corresponding to 14 taxa, are presented. New are those forScabiosa aff.olivieri var.pinnatisecta, S. persica, Pterocephalus canus, P. kurdicus, Dipsacus strigosus, Cephalaria dichaetophora, C. hirsuta, C. microcephala, C. subindivisa andC. aff.sublanata. Except forC. syriaca (x = 5) andC. dichaetophora (x = 7 : new basic chromosome number forCephalaria), all species examined are characterized by the basic chromosome number (x = 9). Instances of aneusomaty, B-chromosomes, aneuploidy, dysploidy, and polyploidy have also been found.

Biologie et écologie du gaillet nain (Galium minutulum Jordan, Rubiaceae) sur les îles d'Hyères (Var, France); implications pour la conservation de l'espèce

Abstract Several biological and ecological characteristics of Galium minutulum Jordan, a rare steno—mediterranean annual species, were investigated on some populations of the Hyères islands, which are located in the north—eastern limit of the species distribution. The objectives of this study were to better document distribution, autecology and the form of rarity of this species in Provence and to propose accordingly some elements for a sustainable management of that vulnerable taxa. Galium minutulum exhibits a noteworthy polymorphism and an important ecological plasticity, which were both mostly explained by the existence of two allopatric cytotypes. Tetraploid individuals, small—sized and spindly, are located in the core—areas of the biggest islands (Porquerolles, Port-Cros, Le Levant), at the edges of the sclerophyllous matorrals or the thermophilous holm- oak forest. Hexaploids, more robust, grow on the coastal habitats directly exposed to sea sprays, notably on the smallest islands (Bagaud, Grand Ribaud). Many factors such as meiosis abnormalities, reduction of germination capacity of the tetraploid cytotype, frequent infestations of a pathogene fungus (blight), and the sensitive locations near the tracks and paths, generate several threats on this species and contribute to its rarity.