Antonia Cristaudo

Phylogeographic patterns, genetic affinities and morphological differentiation between Epipactis helleborine and related lineages in a Mediterranean glacial refugium

BACKGROUND AND AIMS In the Mediterranean basin, the Italian peninsula has been suggested to be one of the most important glacial refugia for temperate tree species. The orchid genus Epipactis is widely represented in the Italian peninsula by widespread species and several endemic, localized taxa, including selfing and outcrossing taxa. Here the phylogenetic and phylogeographic relationships in a group of closely related taxa in Epipactis are investigated with the aim of understanding the role of this refugial area for cladogenesis and speciation in herbaceous species, such as terrestrial orchids. METHODS Ribosomal DNA (rDNA) was employed to assess phylogenetic relationships, and plastid sequence variation in the rbcL-accD spacer was used to reveal phylogeographic patterns among plastid haplotypes using a parsimony network. KEY RESULTS Low genetic variation and shared ribotypes were detected in rDNA, whereas high levels of sequence variation and a strong phylogeographic structure were found in the examined plastid region. The parsimony plastid haplotype network identified two main haplotype groups, one including E. atrorubens/microphylla/muelleri/leptochila and the other including all accessions of E. helleborine and several localized and endemic taxa, with a combination of widespread and rare haplotypes detected across the Italian peninsula. A greater genetic divergence separated the Italian and other European accessions of E. helleborine. CONCLUSIONS Phylogenetic and phylogeographic patterns support a working hypothesis in which the Italian peninsula has only recently been colonized by Epipactis, probably during the most recent phase of the Quaternary age and, nevertheless, it acted as a remarkable centre of diversification for this orchid lineage. Changes in pollination strategy and recurrent shifts in mating system (from allogamy to autogamy) could have represented the mechanism promoting this rapid diversification and the observed high taxonomic complexity detected in the E. helleborine species complex.

Germination response of four pasture species to temperature, light, and post-harvest period

Abstract The purpose of this research was to explore the effect of temperature, light, and post-harvest period, and their interactions, on seed germination ecology of four common pasture species in the Mediterranean environment. Mature seeds of Diplotaxis erucoides, Hirschfeldia incana, Hyoseris scabra (Mediterranean distribution) and Sonchus oleraceus (cosmopolitan distribution) were subjected to seven constant temperatures (10–40°C, at intervals of 5°C) under continuous darkness, or a 12 h/12 h light/dark photoperiod at 30, 150 and 270 days after harvest (DAH). Cumulative germination and germination speed were determined. In all the tested species, except S. oleraceus, light significantly enhanced germination. S. oleraceus seeds maintained germination values over 90%, in a wide range of temperatures (10–35°C), in the dark as well as in light. Seeds of H. incana germinated well soon after seed dispersal. In D. erucoides and H. scabra, germination increased with storage period, while in S. oleraceus there was no effect of seed age. In all the species, moreover, no germination was recorded at 40°C. Temperature, light, and post- harvest requirement may be regarded as an adaptation strategy to ensure optimal conditions for seedling development and survival in Mediterranean species, while the species with a cosmopolitan distribution germinates under almost all tested conditions.

Germination ecology of three Plantago L. (Plantaginaceae) species living in a saline environment

ABSTRACT The factors influencing the germination of Plantago coronopus L., Plantago crassifolia Forsskål and Plantago macrorrhiza Poiret, three species typical of saline environments, were analysed. Results show that the temperatures favouring germination lie between 10° and 25°C, and that the three species have an initial period of absolute dormancy at temperatures from 10 to 25°C as regards P. coronopus, and above 15°C for P. crassifolia and P. macrorrhiza. The length of the dormancy period increases as the temperature rises. Saline solutions greatly inhibit germination of P. coronopus, and to a lesser extent that of P. crassifolia and P. macrorrhiza: none of the species germinates in 0.2 M NaCl solutions. These data suggest that the presence of these species in saline environments depends less upon their tolerance to salt with respect to germination as on particular control mechanisms which permit them to carry out their life cycle when the ecological conditions are favourable

Germinative response of redroot pigweed (Amaranthus retroflexus L.) to environmental conditions: Is there a seasonal pattern?

Experiments on redroot pigweed (Amaranthus retroflexus L.) were conducted to investigate whether the germinative response to environmental conditions is affected by the time of seed set. Seeds were collected in the same field (Sicily, Southern Italy) in May, July and October; each lot was dry-stored from 15 to 400 days after harvest (DAH) and submitted to germination assays from 15 to 40°C, both in continuous darkness (D) and in alternate light/darkness regime (L/D). For the three lots, over 15 DAH, the response to temperature and light regime was strongly affected by harvesting time. Seeds set in May, negatively affected by L/D, showed a high germination capability (>80%) at 95 DAH from 25 to 40°C. Seeds set in July were favoured by L/D and required at least 170 DAH to reach 80% germination capability. Seeds set in October were also favoured by L/D and gave a good germination capability only at 300 and 400 DAH. These results prove that seed germination behaviour in redroot pigweed is not independent of the time of the year in which seeds are produced and is due to both the environmental conditions experienced by the mother plant during seed maturation and those experienced by seeds after seed set.

Species–area relationships and minimum area in citrus grove weed communities

Field surveys were carried out in the Catania plain (eastern Sicily, Italy) on winter–spring weed communities in citrus groves, an economical and traditional crop of the Mediterranean area. The aim of this study was to define species–area relationships and to derive information on the minimum sampling area in citrus groves, taking into consideration the ecological, botanical and agronomical implications. Weed flora was composed of 63 taxa belonging to 25 botanical families (42% of taxa included in the families Poaceae, Asteraceae and Brassicaceae). The dominance of therophytes and species with a wide distribution was related to the high degree of artificiality induced by human pressure. The species richness per survey was rather low, ranging from 8 to 22 species, in a surface area of 256 m2. Species–area analyses showed that the minimum sampling area that fully expressed the specific characteristics of plant communities in these citrus groves ranged from 33 to 56 m2. As a result, this methodology can be an appropriate decision support system for sustainable weed management strategies, with a more rational use of herbicides.