Taxonomical notes on the Sicilian populations of Asperula gussonei (Rubiaceae): A. peloritana sp. nov

Brullo, C., Brullo, S., Giusso del Galdo, G.P. & Scuderi, L. 2009. Taxonomical notes on the Sicilian populations of Asperula gussonei (Rubiaceae): A. peloritana sp. nov. Anales Jard. Bot. Madrid 66(1): 000-000. Taxonomical investigation on Asperula gussonei, a rare Sicilian endemism, allowed us to verify that the Madonie population is well differentiated from the Mt. Scuderi one. These two populations are here treated as distinct species: A. gussonei Boiss. from Madonie and A. peloritana sp. nov. from Mt. Scuderi. The main morphological and ecological differences between the two species are pointed out. Their iconographies and relationships with the allied species are given too.


Introduction
The aim of this work is the taxonomical survey of Asperula gussonei Boiss., a species circumscribed to some mountain stands of Sicily.It was firstly identified by Gussone (1827) as A. nitida, species described by Sibthorp & Smith (1806) on Greek material.Afterward, Gussone (1843) attributed these populations to A. suberosa Sibth.& Sm., highlighting that the Sicilian plant is very different from A. nitida.Later, Boissier (1849) considered the specimens referred by Gussone to A. suberosa as a distinct species, named A. gussonei.As concern the distribution in Sicily of this species, it was collected for the first time by Gussone (1827Gussone ( , 1843) ) on some mountains of the Madonie massif (Scalone, Quacella, Mufara) and on the Peloritani Range (Mount Scuderi), where it occurs so far.According to literature, herbarium investigations and field surveys, this species grows exclusively on the Madonie and Mt.Scuderi, where it is represented by small and few-numbered populations.An in-depth macro-and micro-morphological analysis on living material coming from these localities allowed to verify that the Mt.Scuderi population is very different from that one occurring in the Madonie.The main differences regard the vegetative and reproductive structures such as the leaves, inflorescences, flowers and fruits.As a consequence of this, it was necessary to deal with the lectotypification of A. gussonei.In particular, basing on the protologue of Gussone (1843) and Boissier (1849), the morphological features listed are the same of those observed in the specimens coming from the Madonie.Therefore, we choose as lectotype one of the syntypes preserved in the Gussone Herbarium (NAP-GUSS), in particular the specimen collected by himself at Mt. Scalone (Madonie), while the population of Mt.Scuderi is here described as a species new to science, named Asperula peloritana.

Material and methods
The morphological study was carried out on living plants coming from Madonie and Mt.Scuderi, as well as on herbarium material (CAT, FI, G and NAP).The micro-morphology of the mericarp outer coat was studied on dried material with the aid of a scanning electron microscope (SEM) Leica Cambridge LEO 420.The preparation of the seeds for SEM observation was done according to the protocol of Huttunen & Laine (1983).
Distribution.On the basis of literature data and herbarium investigations, Asperula gussonei is localized on some mountain stands of the Madonie (Mt. Mufara, Mt. Scalone, Mt. Quacella, and Mt. Pomieri) where it is represented by few-numbered, scattered populations at an altitude of 1400-2000 m (Fig. 4).
Phenology.Flowering July to August.Conservation status.According to Conti & al. (1997), Asperula gussonei is considered a plant at low risk of extinction (LR), probably because it grows on rupestrian stands which are habitats usually less affected by human activities.Due to its rarity and few number of individuals, it should be better to consider this species as vulnerable (VU).
Etymology.The specific epithet refers to "Peloritani", the mountain range of north-eastern Sicily where the species occurs.
Distribution.This species is exclusive of the northern slopes of Mt.Scuderi (1253 m a.s.l.), a quite isolated peak of the Peloritani range (Fig. 4).In this area, it is represented by a population with several individuals (more than 300).
Habitat.Asperula peloritana grows on rocky sites characterized by Palaeozoic impure marble outcrops on north-facing, rather steep slopes (Fig. 6).It  Phenology.flowering May to early July.Conservation status.For its restricted localization (ca.15 ha) and for the intensive grazing (horses, cows and sheep) affecting the area at issue, Asperula peloritana requires the adoption of protective measures.In fact, for this serious threat and for the low number of individuals, we propose to include this species in the "Regional List of the Threatened Species" as critically endangered (CR).Based on the criteria adopted by IUCN (2001IUCN ( , 2003IUCN ( , 2005)), it is proposed its inclusion in the following category: CR B1ab(ii, iii)+2ab(i, ii, iii).
Taxonomic remarks.For some morphological features, such as the leaf dimorphism, long internodes, hairy corolla, ovary and mericarp turbeculate-papillose, Asperula peloritana shows close relationships with A. suberosa Sibth.& Smith, rare endemism of Mt.Athos in N Greece (see Schonbeck-Temesy & Ehrendorfer, 1991).Therefore, these two species can be considered as endemo-vicariants, probably originated from the long geographical isolation of the Peloritani populations.
To conclude, on the basis of some morphological features and ecology, Asperula gussonei and A. peloritana belong to a group of species occurring in the mountain belt of many Mediterranean territories.On the whole, this group is represented by typical orophytes with a compact pulvinate habit localized on rocky places, and having normally a punctiform or very circumscribed distribution.In particular, they are In order to emphasize the main morphological differences among the Sicilian and the closely related species, a comparative table is given too (Table 1).These species can be considered as paleoendemisms, likely arising from a common ancestor as a consequence of the speciation processes favoured by the geographical isolation.As concerns A. gussonei and A. peloritana, their remarkable morphological differences, such as their mericarp outer coat (Fig. 3), allow to hypothesize a different origin for the two species.In particular, they are probably linked to the existence of paleo-geographical land connections with the Balkan region as concern A. peloritana, and with the Sardo-Maghrebian territories with regard to A. gussonei.

Table 1 .
Comparative scheme of the morphological characters of Asperula gussonei, A. peloritana and allied species.