Orchis longicornuPoiret in Sardinia: genetic, morphological and chorological data

Data are given on the genetic structure, morphology and chorology of the Long-Spurred
orchid,Orchis longicornuPoiret (1789) from Sardinia and the occurrence in this island of the
morphologically similarOrchis morioL. (1753), often recorded for Sardinia, is investigated. The
genetic analysis of 27 enzyme lo ci 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 Nei'sD= 0.01): less than 2% of the overall genetic variation observed is
attributable to differences between populations (GST = 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 withO. moriofrom continental Italy, significant differences in genetic variation were observed: average He= 0.16 in the former, 0.12 in thc latter;(v)the genetic distance found between Sardinian populations and those ofO. moriofrom continental
ltaly is relatively high: average Nei'sD= 0.18, average Rogers'D= 0.22;(vi)highly
significant differences in allele frequencies were found at a number of loci (Mdh-2, Sod-3, Pgm-1,
Gpi-1, Gpi-2) between populations from Sardinia and continental Italy, each giving a probability
of correct identification that varies from 0.90 to 1 (diagnostic loci). These findings provide
evidence thatO. moriois not present in the material genetically analyzed from Sardinia, which
includes a single species, apparently corresponding toO. longicornu. The slight heterogeneity
observed at some loci in the Sardinian population samples can be attributed in some cases (e.g.Mdh-1, Adh, Est-6) to local differences, possibly adaptive; in others (e.g.Pgm-1andGpi-l) to
genetic drift effects. The hypothesis that some alleles (Gpi-1100,Dia107,NADHdh-296) found inO. morioand recorded at low frequency in a few Sardinian populations reflect palaeointrogressive
phenomena (owing to sporadical immigrant individuals ofO. moriohaving diluted their
genes inO. longicornugenome through multiple generations of backcrosses) is not sufficiently
supported by the available data. The genetic data are in agreement with the results from
morphological studies. These involved the examination of about 1500 specimens (both alive and
dried) from all over Sardinia, and their comparison with herbarium specimens ofO. longicornufrompatria typica(Algeria) and ofO. moriofrom continental Italy. The typification ofO.
longicornuis given. The specimens from Sardinia correspond well, on a morphological basis, to
the Algerian ones and therefore were all assigned toO. longicornu. Several characters were
considered, differentiatingO. longicornufromO. morioboth in fresh and dried specimens.
However, some of them, currently used in diagnostic keys, show much overlap between the two
species. This explains the quotations ofO. moriofrom Sardinia, that appear to be misidentifications ofO. longicornu. A description ofO. longicornufrom Sardinia is provided, and its
distribution in the island is defined, on the basis of(i)a critical revision of literature rccords, and(ii)the examination of fresh and dried Sardinian specimens.O. longicornuis shown to be
widespread throughout Sardinia, living in many different habitats from 0 to 1500 m a.s.l.