Caterina Angela Dettori

Assessing the potential invasiveness of Cortaderia selloana in Sardinian wetlands through seed germination study

Abstract The present work is focused on the study of abiotic factors that may favour seed germination and the potential invasiveness of Cortaderia selloana, with particular attention to wetlands. Germination tests were conducted at the Sardinian Germplasm Bank (BG‐SAR), testing different temperatures and percentages of NaCl in order to determine the optimal ecological conditions at which germination occurs and the effect of salt on seed germination and viability, as well as on seedling development. Seeds completely germinated at every temperature tested, but the highest germination rate was found at 25°C. Salinity did not prevent seeds from germinating, but it affected germination rate and seedling vigour.

The genetic diversity and spatial genetic structure of the Corso-Sardinian endemic Ferula arrigonii Bocchieri (Apiaceae)

Corsica and Sardinia represent major hotspots of plant diversity in the Mediterranean area and are priority regions for conservation due to their high number of endemic plant species. However, information supporting human decision-making on the conservation of these species is still scarce, especially at the genetic level. In this work, the first assessment is reported of the species-wide spatial genetic structure and diversity of Ferula arrigonii Bocchieri, a Corso-Sardinian endemic located in a few coastal sites and on small islands. Nine populations covering the entire natural range of the species were investigated by means of AFLP (amplified fragment length polymorphism) markers. Results indicate that this species is characterised by high levels of genetic polymorphism (92% polymorphic fragments) and of genetic diversity (H(w) = 0.317) and by relatively low differentiation among populations (F(st) = 0.057). PCoA, Bayesian analysis and neighbour-joining clustering were also employed to investigate the genetic structure of this species. Three genetically distinct groups were detected, although with considerable overlap between populations.

What does the germination ecophysiology of the invasive Acacia saligna (Labill.) Wendl. (Fabaceae) teach us for its management

Acacia saligna is a phanerophyte native to Australia; it was introduced in the 1950s in Sardinia (Italy) for afforestation mainly in coastal areas and at present it is considered naturalized, becoming invasive in sand dune habitats. Seed biology is one of the most important factors contributing to the invasion success of Australian acacias, for this reason the germination ability is an important issue when trying to clarify the invasion dynamics of A. saligna. Germination tests were conducted at the BG-SAR, testing the effect of different temperatures and percentages of NaCl, on seeds belonging to five accessions from four populations of two coastal habitat types. The optimal temperature range for seed germination was 15–20°C; the increase of salt caused a decrease in the final germination percentages. At 1% of NaCl concentration, germination fell at 25–30°C and at 2% it was relatively low (below 40%) and occurred almost only at 15°C. This work represents a contribution to the knowledge of the seed ecology and germination behaviour of the species, providing new data on the interpopulation and interannual variability, and relating them to the invasion dynamics of A. saligna in the coastal Mediterranean habitats.

Discovering the type of seed dormancy and temperature requirements for seed germination of Gentiana lutea L. subsp. lutea (Gentianaceae)

Aims There are a number of mechanisms that regulate germination; among these, seed dormancy, one of the most important, is an adaptative mechanism in plants to promote survival by dispersing germination in space and time until environmental conditions are favourable for germination. The main goals of this study were to determine the temperature requirements for seed dormancy release and germination of Gentiana lutea subsp. lutea, to identify the class and level of seed dormancy and to suggest an optimal germination protocol. Methods Seeds belonging to two different localities were subjected to various pre-treatments, including cold stratification (0 and 5°C), warm stratification (25/10°C) and different combinations of these, and then incubated at a range of constant temperatures (5–25°C) and 25/10°C. Embryo growth during pre-treatments and incubation conditions were assessed at different times by measuring the embryo to seed length ratio (E:S ratio). The final germination percentage (FGP) and the germination rate (t50) were calculated. Important Findings Fleshy mature seeds of G. lutea subsp. lutea have linear underdeveloped embryos. Cold stratification at 0°C was effective in overcoming the physiological dormancy (PD) and promoted embryo growth and subsequent germination. After cold stratification at 0°C, both the root and the shoot emerged readily under a wide range of temperatures. G. lutea subsp. lutea seeds showed an intermediate complex morphophysiological dormancy (MPD). As regards the optimal germination protocol for this taxon, we suggest a period of cold stratification at ca. 0°C followed by seed incubation at 10–20°C. The optimal germination temperatures found for seeds of this taxon, as well as its pre-chilling requirement at 0°C, suggest that it is well adapted to a temperate climate; this behavior highlights an increasing threat from global warming for G. lutea, which could reduce the level of natural emergence in the field, prejudicing also the long-term persistence of the natural populations in Sardinia.

High genetic diversity and presence of genetic structure characterise the Corso-Sardinian endemics Ruta corsica and Ruta lamarmorae (Rutaceae)

Corsica and Sardinia form one of the ten areas with highest biodiversity in the Mediterranean and are considered one of the priority regions for conservation in Europe. In order to preserve the high levels of endemism and biological diversity at different hierarchical levels, knowledge of the evolutionary history and current genetic structure of Corso-Sardinian endemics is instrumental. Microsatellite markers were newly developed and used to study the genetic structure and taxonomic status of Ruta corsica and Ruta lamarmorae, rare endemics of Corsica and Sardinia, respectively, and previously considered a single species. Our analyses identified high levels of genetic variation within each species (P=0.883, He=0.543 for R. corsica; P=0.972, He=0.627 for R. lamarmorae). Intrinsic traits of the species (hermaphroditism, proterandry and polyploidy) and island-dependent factors (i.e. age, origin and history of the islands) might explain the detected high levels of genetic variation. We discovered differentiation between R. corsica and R. lamarmorae, and genetic structure within each species, which are consistent with the observation of low dispersal ability for both species. Our genetic results support the recent taxonomic classification of R. corsica and R. lamarmorae as separate species and suggest that they diverge at only few loci. One R. corsica population (SA) strongly differed from all other studied populations and appeared to be the product of hybridization between the two species in STRUCTURE analyses. Our results provide important insights for the conservation of the two rare endemics. Further genetic analyses are recommended for R. lamarmorae and for population SA (R. corsica).

The genetic structure and diversity of Gentiana lutea subsp. lutea (Gentianaceae) in Sardinia: further insights for its conservation planning

ABSTRACT Knowledge of the levels of genetic diversity and of the spatial genetic structure of plant species is important to ensure their effective management and conservation, especially in the case of endangered species. Gentiana lutea L. subsp. lutea is a long-lived plant which occurs in central and southern European mountains. It has a long-standing history of human exploitation, mainly in the liqueur and in the pharmaceutical industries and it is currently listed in the EU Habitats Directive 92/43/EEC Annex V. Mainly due to a prolonged root harvesting, its current distribution range in Sardinia consists of only a few groups of individuals limited to small areas of the Gennargentu massif (Central-Eastern area of the island). In this study, we investigated the levels of genetic diversity and the genetic structure of the species in Sardinia. We used AFLP (amplified fragment length polymorphism) markers to investigate the genetic variability of 182 samples from 13 subpopulations. A total of 433 fragments were detected, of which 75.5% were polymorphic. The levels of genetic diversity were generally high, but they tended to decrease in smaller subpopulations. Of the genetic variability 88% was found within subpopulations, while the genetic structure among them was fairly weak. In order to ensure the survival of these subpopulations, especially the smaller ones, ex situ and in situ management actions should be planned, such as the long term conservation of its seeds in germplasm repositories and their population reinforcements and monitoring.