Walter Rossi

Orchis longicornu Poiret in Sardinia: genetic, morphological and chorological data

Summary Data are given on the genetic structure, morphology and chorology of the Long-Spurred orchid, Orchis longicornu Poiret (1789) from Sardinia and the occurrence in this island of the morphologically similar Orchis morio L. (1753), often recorded for Sardinia, is investigated. The genetic analysis of 27 enzyme loci in population samples from locations where both species had been recorded showed that: (i) in the population samples from Sardinia the polymorphic loci are in Hardy-Weinberg equilibrium; (ii) these samples are genetically poorly differentiated from each other (average Neis D = 0.01): less than 2% of the overall genetic variation observed is attributable to differences between populations (G ST = 0.015); (iii) a high rate of gene flow was estimated between Sardinian populations: Nm ≈ 4, possibly owing to seed dispersal by wind; (iv) when Sardinian samples are compared with O. morio from continental Italy, significant differences in genetic variation were observed: average He = 0.16 in the ...

Genetic variation and natural hybridization betweenOrchis laxiflora andOrchis palustris (Orchidaceae)

AbstractGenetic divergence between population samples ofOrchis laxiflora and ofO. palustris from various European locations was studied by electrophoretic analysis of 25 enzyme loci. An average genetic distance of DNei = 1.24 was found between the two taxa, with 12 out of 25 loci showing alternative alleles (diagnostic loci). Genetic heterogeneity was observed within bothO. laxiflora andO. palustris, when northern and southeastern populations were compared, being lower in the former taxon (D = 0.06), than in the latter (D = 0.16). Karyologically, 2n = 36 was found for bothO. laxiflora andO. palustris. O. laxiflora andO. palustris produce hybrids, described asO. ×intermedia. Genotype analysis of several sympatric samples showed the presence of hybrid zones, including F1 hybrids and, in low proportions, recombinant classes, putatively assigned to Fn and backcrosses, as well as a few introgressed individuals of both taxa. These data indicate that hybrids are only partially fertile, with a very limited mixing up of the two parental gene pools; this is also shown by the lack of significant lowering of genetic distances when sympatric and allopatric heterospecific samples are compared. Accordingly,O. laxiflora andO. palustris form a syngameon; nevertheless they can be considered as good taxonomic species, with virtually distinct gene pools, which evolve independently. The genetic variability inO. laxiflora andO. palustris is remarkably low (

New species of Laboulbenia from Ecuador, with evidence for host switch in the Laboulbeniales

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New species of Rhachomyces from Ecuador, one of which is dimorphic

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New Laboulbeniales (Ascomycota) parasitic on Staphylinidae from Ecuador

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New or interesting laboulbeniales (ascomycota) from the Mediterranean region

e = 0.02, respectively). In particular, nearly complete absence of polymorphic loci was found inO. palustris from northcentral Europe. Two hypotheses are considered to explain the low genetic variability of this endangered species.