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Rilevanza ecologica delle briofite degli stagni temporanei della Sardegna Congresso della Società Botanica Italiana
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The bryophyte flora of the Asinara Island (northwest Sardinia, Italy)
No full textSeventy-four taxa (59 mosses, 13 hepatics, and 2 anthocerotes) are reported from the National Park of Asinara island, an islet situated at the north west of Sardinia. Besides general comments on phytogeographic and ecological aspects of this catalogue, some taxa, Riccia sommieri, Tortula israelis, Scleropodium cespitans, Enthostodon muhlenbergii are commented
Bryophyte flora of some temporary pools of Sardinia and Corsica
No full textA comparative study of the bryophytes in some Sardinian and Corsican wetlands of major naturalistic value, such as the "padule of Suartone" (SE Corsica) and "pauli of the Giara of Gesturi" (C Sardinia), was carried out. In Europe, these habitats ( Mediterranean temporary pond) are indicated as priority natural habitats under the Habitats Directive 92/43/EEC. In the Sardinian pauli, 56 taxa (50 Bryophyta and six Marchantiophyta) were found, while in the Corsican padule, 30 taxa (21 Bryophyta and nine Marchantiophyta) are reported. Among the bryophytes collected in the padule, the discovery of Scleropodium cespitans, Riccia perennis and Campylopus introflexus is of particular phytogeographic interest. Data are here reported together with information on the phytogeography and ecology of the recorded species
Analysis of bryophyte’s spores in Mediterranean temporary ponds
No full textThe persistence and abundance of most of the species in an area are the result of a dynamic balance between the duration of the habitat and the ability of species to colonize such environments through the production and dispersion of spores. This study presents a preliminary analysis of bryophyte’s spores from the pauli of the Giara of Gesturi (C Sardinia). The Giare (average altitude 550 m a.s.l.) are basaltic plateaus that rise unexpectedly from the plain of the country, as huge natural fortresses. Several authors have studied the population dynamics of some bryophytes confined to fragmented and temporary habitat (1, 2, 3) and, in particular, studies conducted by Herben & Söderström (4) show that the most important factor that regulates the survival of the species is the ability to form new colonies on substrates fragmented. The aim of this study is to determine what are the species that show a better fitness for survival and adaptation in Mediterranean temporary ponds, in order to evaluate the conservation status. In Europe, Mediterranean temporary ponds are indicated as priority natural habitats under the Habitats Directive 92/43/EEC (5): in those habitats bryophytes are recognized to have an important ecological function. Thirthy soil samples were collected in November (rainy season) in three ponds until the depths of 7 cm. The samples were taken and subdivided in seven portions, which were collected for obtaining an ex situ germination of spores, at the Botanical Garden of University of Cagliari. The results showed the capacity of some genus and two species to germinate in ex-situ conditions: Bryum sp., Pohlia sp., Tortula sp., Fossombronia sp., Riccia canaliculata Hoffm. and Archidium alternifolium (Hedw.) Mitt. It is possible to observe as these bryophytes are the most recurring in the study area, showing a better fitness for survival and adaptation to these environments.
1) W.S.C. Gurney and R.M. Nisbet (1978) American naturalist, 112, 1075-1090.
2) J. Roughgarden and Y. Iwasa (1986) Theoret. Popul. Biol., 29, 235-61.
3) L. Fahrig and J. Paloheimo (1988) Theoret. Popul. Biol., 34, 194-213.
4) T. Herben and L. Söderström (1992) Biological conservation, 59, 121-126.
5) Directive 92/43/CEE. (1992) Journal officiel de Communautés europénnes L 206:7
Increased divergence in floral morphology strongly reduces gene flow in sympatric sexually deceptive orchids with the same pollinator
No full textIn sexually deceptive orchids, pollinator specificity is the main factor responsible for species isolation. The two sexually deceptive orchids Ophrys chestermanii and Ophrys normanii occur sympatrically on Sardinia and attract the same pollinator, males of Bombus vestalis, by producing the same odour bouquets. Since gene flow between these two species has been shown to be almost absent, their genetic distinctness seems to be preserved by other forms of reproductive barrier than pollinator specificity. The aim of this study is to investigate the nature and strength of these isolation barriers which apparently halt gene flow between these two orchids that share the same pollinator.
Morphological measurements, combined with observations of cross-pseudocopulations, revealed that, in sympatry, the longer caudicles of O. normanii and the smaller and differently shaped stigmatic cavity in O. chestermanii are the main factors preventing gene flow between these two sympatric species. In contrast, other pre- or post-mating barriers seem to be weak or absent, as the two species have overlapping flowering time and we were able to rear hybrid offspring from interspecific manual crosses. At the same time, genetic analysis of orchid plantlets collected at sympatric sites detected the presence of only two putative hybrid individuals. Thus, the probability of natural cross-pollination between O. normanii and O. chestermanii seems to be strongly limited by divergence in their floral morphology. For some traits, this divergence was found increased between sympatric populations
DNA barcoding to analyse taxonomically complex groups in plants: the case of Thymus (Lamiaceae)
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