Systematics, phylogenetic relationships and conservation of the taxa ofAnchusa(Boraginaceae) endemic to Sardinia (Italy)

Abstract

Sardinia is a major centre of diversity of Anchusa, but the systematics, phylogenetic relationships and conservation status of the taxa endemic to the island are still poorly known mainly because of their remarkable rarity. We present a study on these endemics based on the results of field research focusing on the distribution, the number and size of the populations, the characteristics of the habitat and the factors of threat. Combined with observations on aspects of reproductive biology, on wild populations and cultivated plants, we evaluate the conservation status of the taxa and propose Red List IUCN categories of vulnerability. Original descriptions, nomenclatural types and karyological data are added. The following Anchusa taxa are endemic to Sardinia: A. capellii, A. crispa ssp. crispa, A. crispa ssp. maritima, A. formosa, A. littorea, A. sardoa and A. montelinasana sp. nov. The latter is described, based on the discovery of a morphologically distinct entity on a mountain in southwest Sardinia. Anchusa littorea was found at a single site after c. 25 years from the last record and 7 years of unsuccessful field research; this species is at the brink of extinction due to the extremely reduced size of the only remaining population. Our complete collection of taxa allowed an analysis of phylogenetic relationships based on DNA sequences from the ITS 1 ribosomal genome. In spite of the low variation, this marker produced Maximum Parsimony and Neighbour-Joining phylograms suggesting that the group is monophyletic and that the split between the two clades of the mountain and coastal endemics has been a key evolutionary event. We assume the three mountain species to be relict schizoendemics ancestral to the coastal taxa, and the Paleozoic siliceous massifs of central and south Sardinia as the centre of origin of the group.

Reproductive biology of the narrow endemic Anchusa littoreaMoris (Boraginaceae), an endangered coastal Mediterranean plant

“…The ANC2 discovery, in a site where this species was not found in previous years (Bacchetta et al, 2008), suggested that the A. littorea population might be adapted to large space shifts, inhabiting similar habitats: a significant migration could have occurred for this plant inside the dune system over the years. Likewise, our results could indicate a migration of the "population core" (in term of maximum seed productivity and population vitality) among patches: the "population core" has moved in the space from ANC1 to ANC2, suggesting that also the "population core" might move inside the dune system over the years.…”

“…Each plant develops one or several cymes, with small tubular flowers distanced at the axil of cauline leaves, often also in the lower part of the stems just above ground level, on pedicels 2-3 mm long deflexed in fruit. Corolla, with tube 4 mm long and limb 4-5 mm, is light blue or white, rotate with rounded lobes; the small mericarps are light gray-brown small, 1.5-2 × 0.5-1 mm, with a lateral beak and a thin basal annulus, with finely tuberculate surface (Bacchetta et al, 2008).…”

“…microforest (Bacchetta et al, 2008;Figure 2). This species grows exclusively within the "Is Arenas" penitentiary area, in a few small and isolated patches within the dunal system, and in particular in 2 main patches, which are ca.…”

Evidence for age-structured depensation effect in fragmented plant populations: The case of the Mediterranean endemic Anchusa sardoa (Boraginaceae)

“…The Corsican-Sardinian system is a main center of diversity for the Anchusa genus, with seven allopatric taxa occurring in either coastal or mountain habitats of the two islands (Bacchetta et al, 2008).…”

“…As a model species we chose A. sardoa, a narrow endemic plant that grows in a limited area where the touristic impact is very high both in habitat loss and in human trampling (Farris et al, 2013). Genetic data showed that this species has low levels of genetic variation due to bottleneck events caused by loss of habitat and natural stochastic factors (Bacchetta et al, 2008;Coppi et al, 2008). Morphological and biological features also make A. sardoa a potential vulnerable species (Farris and Filigheddu, 2008).…”