Gianluigi Bacchetta

Phylogenetic Analysis Informed by Geological History Supports Multiple, Sequential Invasions of the Mediterranean Basin by the Angiosperm Family Araceae

Despite the remarkable species richness of the Mediterranean flora and its well-known geological history, few studies have investigated its temporal and spatial origins. Most importantly, the relative contribution of geological processes and long-distance dispersal to the composition of contemporary Mediterranean biotas remains largely unknown. We used phylogenetic analyses of sequences from six chloroplast DNA markers, Bayesian dating methods, and ancestral area reconstructions, in combination with paleogeographic, paleoclimatic, and ecological evidence, to elucidate the time frame and biogeographic events associated with the diversification of Araceae in the Mediterranean Basin. We focused on the origin of four species, Ambrosina bassii, Biarum dispar, Helicodiceros muscivorus, Arum pictum, subendemic or endemic to Corsica, Sardinia, and the Balearic Archipelago. The results support two main invasions of the Mediterranean Basin by the Araceae, one from an area connecting North America and Eurasia in the Late Cretaceous and one from the Anatolian microplate in western Asia during the Late Eocene, thus confirming the proposed heterogeneous origins of the Mediterranean flora. The subendemic Ambrosina bassii and Biarum dispar likely diverged sympatrically from their widespread Mediterranean sister clades in the Early-Middle Eocene and Early-Middle Miocene, respectively. Combined evidence corroborates a relictual origin for the endemic Helicodiceros muscivorus and Arum pictum, the former apparently representing the first documented case of vicariance driven by the initial splitting of the Hercynian belt in the Early Oligocene. A recurrent theme emerging from our analyses is that land connections and interruptions, caused by repeated cycles of marine transgressions-regressions between the Tethys and Paratethys, favored geodispersalist expansion of biotic ranges from western Asia into the western Mediterranean Basin and subsequent allopatric speciation at different points in time from the Late Eocene to the Late Oligocene.

A new method to set conservation priorities in biodiversity hotspots

Abstract Prioritization of endemic, threatened species and the habitats where they live is a crucial point of conservation actions, particularly in areas with rich endemic floras. In this study, we have developed a new procedure to define the conservation priorities among endemic plants and habitats by evaluating eight criteria. Five criteria deal with the geographic and ecological range of the evaluated species, whereas the other three refer to threats. After the evaluation of each criterion, we combined the partial scores to obtain a priority index (PI). Finally, we characterized the EU habitat categories of conservation concern on the basis of the average PI value of the plants living in each habitat. We tested the method on a list of 260 endemic plants from a biodiversity hotspot (Sardinia) that had an average PI of 3.66 ± 0.16. Even if the habitat categories that are most rich in endemic plants were rocky habitats, and coastal/halophytic habitats, the most endangered habitat was coastal sand dunes (PI = 6.75 ± 1.15). The method herein presented is complementary with the application of IUCN criteria. This integrated approach is a concrete solution that adapts IUCN criteria and categories to local contexts.

Environmental Factors Influencing Coastal Vegetation Pattern: New Insights from the Mediterranean Basin

Coastal dune ecosystems show strongly dynamic interactions between abiotic and biotic factors. The relationship between plant communities and environmental factors has been previously studied in oceanic dune systems, but few studies have been conducted along Mediterranean coasts. In this study we analyze the relative contribution of environmental factors associated with two of the main drivers of vegetation zonation: soil and wind. We chose two representative coastal dune systems in the western Mediterranean Basin subject to low levels of human disturbance. Within 54 plots we recorded floristic and environmental data. Vegetation zonation and relationships with environmental variables were investigated through unconstrained and constrained ordinations, correlation, and variance partitioning. Environmental factors shift along the gradient from coastal to inland dunes, concomitantly with the pattern of community types from annual beach communities to shrub-covered fixed dunes. This general gradient is similar both in the Mediterranean and in the oceanic coastal ecosystems, with the same factors that show similar trends along the dune profile. However, our results highlight some peculiarities of the Mediterranean dune systems in relation to the amount of variation explained by environmental factors. While most studies conducted in oceanic ecosystems find that wind-related parameters may control the vegetation zonation, in our study areas we observed a minor importance of the wind-related variables when compared to soil properties. In particular, organic matter and grain-size variability were found to be closely correlated with the distribution of plant communities along the gradient.

Morphological characterisation of Vitis vinifera L. seeds by image analysis and comparison with archaeological remains

In archaeobotanical studies, the taxonomic classification of diaspores has usually been done by simple morphological observation and visual comparison with ex situ collections of seeds, although the use of biometric indices has often proved to be a powerful approach in the taxonomic studies of the genus Vitis as well as for the species attribution of archaeological remains. Using image analysis techniques, seeds from two Sardinian archaeological sites, the pre-Nuragic and Nuragic complex of Sa Osa in central-western Sardinia, attested as the oldest Sardinian archaeological site with remains of Vitis seeds, and the Isola di Coltellazzo in southwest Sardinia, were selected and characterized on the basis of morphological features and Elliptic Fourier Descriptors. Moreover, seeds of five modern populations of V. vinifera ssp. sylvestris collected from southwest Sardinia and the seeds of 41 cultivars of V. vinifera ssp. vinifera mainly from southern and central-western Sardinia were also analysed by computer image analysis. The obtained data were used to implement a database of biometric parameters and to compare the unknown archaeological seeds with the characterized recent seeds, using Linear Discriminant Analysis. The similarity of the archaeological seeds to V. vinifera ssp. vinifera cultivars rather than to V. vinifera ssp. sylvestris populations could allow it to be stated that, between the Middle and Final Bronze Age, varieties very close to modern V. vinifera ssp. vinifera were already being used to produce wine and/or to be preserved for foodstuffs. Moreover, the better matching of the archaeological seeds to white grapes rather than black grape cultivars could indicate the origins of the traditional cultivation of white grapes in these regions of Sardinia.

Relationships between coastal sand dune properties and plant community distribution: The case of Is Arenas (Sardinia)

Abstract Coastal dune environments are selective ecosystems characterized by a close interaction between abiotic and biotic factors in a dynamic balance. The present study focused on the psammophilous geosigmetum, the most affected by the interactions between physical processes and biological and anthropic processes. The main purpose was to study the relationships between the abiotic properties of the dune and the presence of the various plant communities, combining morpho-sedimentological, geopedological, and geobotanical data. The study was carried out on the well-preserved dune system of Is Arenas (CW Sardinia) which is one of the most important in the Mediterranean area. The analyses revealed differences at the morphodynamic, sedimentological, and geopedological levels. The micro-topography of the dunes affects the values of the main abiotic variables, and determines the presence of various microhabitats of great heterogeneity. This work shows that thedata on the geomorphological dynamics and the chemical–physical processes, correlated with the geobotanical analyses, might make it possible to identify the ecosystemic processes, and thereby plan adequate management and conservation strategies for this coastal dune system.

A field experiment on the use of Pistacia lentiscus L. and Scrophularia canina L. subsp. bicolor (Sibth. et Sm.) Greuter for the phytoremediation of abandoned mining areas

Abstract A two-year study has been conducted in an abandoned Pb/Zn mining site, with the aim of investigating the feasibility of phytoremediation using two native Mediterranean plants (Pistacia lentiscus and Scrophularia bicolor) and of assessing the performance of amendments able to reduce the toxic effects of heavy metals. The amendments used were compost, chemical fertilizer, and zeolites, used singly or in combination. Depending on the amendments applied, the two species showed different mortality rates in the different plots, but all produced an increase in P. lentiscus survival, while S. bicolor survival improved only when amended with zeolite or zeolite + fertilizer. Scrophularia bicolor proved to be a more efficient accumulator than P. lentiscus, especially for Pb uptake. Pistacia lentiscus accumulated metals mostly in the roots. The effect of amendments was to generally reduce the bioavailable metal fraction, especially lead, in the plots amended with compost. Pistacia lentiscus proved to be the most suitable species for phytostabilization and environmental restoration, both for its resistance to metals and high phytomass production. The experiments demonstrate that the use of compost not only encourages this kind of revegetation in degraded areas, but is also an economical option that uses a by-product of solid municipal waste treatment.

Spatial genetic structure of Aquilegia taxa endemic to the island of Sardinia

BACKGROUND AND AIMS The Mediterranean Basin is one of the most important regions for the Earths plant biodiversity; however, the scarcity of studies on fine scale patterns of genetic variation in this region is striking. Here, an assessment is made of the spatial genetic structure of all known locations of the three Sardinian endemic species of Aquilegia in order to determine the relative roles of gene flow and genetic drift as underlying evolutionary forces canalizing the divergence of Sardinian Aquilegia taxa, and to see if the spatial genetic structure found fits the current taxonomic differentiation of these taxa. METHODS DNA from 89 individuals from all known locations of Aquilegia across Sardinia was analysed by means of amplified fragment length polymorphism (AFLP) markers. Both principal co-ordinates analysis (PCoA) and Bayesian clustering analyses were used to determine the spatial genetic structure irrespective of any taxonomic affiliation. Historical effects of gene flow and genetic drift were assessed by checking for the existence of isolation-by-distance patterns. KEY RESULTS STRUCTURE and PCoA analyses revealed a pattern of genetic variation geographically structured into four spatial genetic groups. No migration-drift equilibrium was detected for Aquilegia in Sardinia, when analysed either as a whole or in individual groups. The scenario approached a Case III pattern sensu Hutchinson and Templeton, which is associated with extreme isolation conditions where genetic drift has historically played a dominant role over gene flow. CONCLUSIONS The pattern of genetic variation of Sardinian taxa of Aquilegia indicates that genetic drift has been historically more influential than gene flow on population structure of Sardinian species of Aquilegia. Limited seed dispersal and divergent selection imposed by habitat conditions have been probably the main causes reinforcing post-Pleistocene geographical isolation of Aquilegia populations. The spatial genetic structure found here is not fully compatible with current taxonomic affiliations of Sardinian Aquilegia taxa. This is probably a consequence of the uncoupling between morphological and genetic patterns of differentiation frequently found in recently radiated taxa.

Distribution, status and conservation of a Critically Endangered, extremely narrow endemic: Lamyropsis microcephala (Asteraceae) in Sardinia

The aims of this work were to verify the distribution and population size of Lamyropsis microcephala (Asteraceae), characterize its habitat, assess its conservation status and initiate conservation measures for this Critically Endangered species. Distribution was determined by field surveys and mapping. To estimate population size and density 81 permanent monitoring plots were randomly established. Ex situ conservation measures were activated by harvesting and appropriate storage of seed. We confirmed the presence of L. microcephala at two previously known sites and found it in two previously unknown localities. The areas in which the species occur vary from 200 to 240,000 m 2 , at altitudes of 1,450–1,820 m, on slopes of 15–45° with aspects from north to west. The estimated number of ramets per population varied from c. 2,000 to c. 2,000,000, with a mean density of 8.29 ± SD 14.3 to 10.33 ± SD 10.05 ramets m -2 . Our findings confirmed the Critically Endangered status of this species, although with different criteria. This study is an example of an integrated approach for the conservation of an extremely narrow endemic plant species and may be useful for other little-known threatened species for which urgent conservation measures are needed.

Adaptation to habitat in Aquilegia species endemic to Sardinia (Italy): Seed dispersal, germination and persistence in the soil

Abstract The autecology of the Sardinian endemics Aquilegia barbaricina Arrigoni et Nardi and A. nugorensis Arrigoni et Nardi were investigated. Peaks of anthesis and seed dispersal were recorded for five populations occurring in two distinct habitats, one riparian and one rupicolous. Germination tests were carried out on seed lots belonging to each population by sowing seeds at 10, 15, 20, 25 and 25/15°C. In addition, seeds were incubated for 2 months at either 25°C (summer), 5°C (winter) or 25°C for 2 months plus 2 months at 5°C (summer followed by winter–SW), and then moved to the germination temperatures. Embryo measurements were taken during pre-treatments and germination. Experimental seed burials were carried out for two populations of each species. Both species dispersed in summer. The population of A. nugorensis occurring on rocky outcrops differed in phenology from both the other A. nugorensis population from riparian vegetation and from A. barbaricina. Both species showed morphophysiological seed dormancy, with <50% germination under laboratory conditions. All riparian populations germinated only after the SW pre-treatment, while the rupicolous population germinated at 25°C, without any pre-treatment. Low germination percentages were observed in the experimental seed burials, suggesting the ability for both species to form a persistent soil seed bank.

The Endemic Vascular Flora of Supramontes (Sardinia), a Priority Plant Conservation Area

Abstract FENU, G., E. MATTANA, A. CONGIU & G. BACCHETTA (2010). The endemic vascular flora of Supramontes (Sardinia), a priority plant conservation area. Candollea 65: 347–358. In English, English and French abstracts. The main aim of this work is to present a checklist of the endemic vascular flora of the Supramontes region (Central Eastern Sardinia) in order to classify this area in the Sardinian biogeographic subprovince and to better assess its conservation priorities. It is one of the most interesting regions of the Island and spreads for 335 km2 from the inland limestone massif to the Orosei gulf. This work was based on bibliographic and herbarium studies, integrated by several field surveys carried out from 2004 to 2009. In this study 138 endemic taxa, belonging to 98 genera and 42 families, have been found, with 92 of which being species, 40 subspecies, 5 varieties and 1 hybrid. The analysis of biologic and chorologic data highlighted the peculiarities of this territory. Due to the relatively high number of Supramontes exclusive endemics and to the geologic and geomorphologic peculiarities, it is here proposed a biogeographic classification for these territories and the identification of an autonomous biogeographic sector divided in two distinct subsectors. According to the recent conservation policies at local level, we propose the definition of micro hotspots for this sector, which hold ca. the 40% of the endemic flora of Sardinia, and the concept of nano hotspots for three narrows areas with an exceptional concentration of endemic species, which represent less than 1% of the whole sector surface and whose in situ protection may allow conserving of more than 80% of the vascular endemic flora of this sector.