Cagiotti M.R., Ranfa A., Marinangeli F., Maovaz M.

Department of Plant Biology, Environment section. Borgo XX giugno, 74 - 06100 Perugia
Italy
cagdipvg@unipg.it

A list is given of the species which for many years have been present in urban and suburban areas in Umbria, in particular in the area of Perugia and Lake Trasimeno. These species were introduced deliberately or naturally, and are currently cultivated in gardens, parks, avenues and walkways, and also in marginal urban and suburban areas. They often create problems because of their capacity to spread and invade. Sometimes very large specimens of some species damage sewer networks, boundary walls, and even ancient city walls. Roadside species can cause accidents linked to particular environmental situations such as heavy rain or wind. Moreover they often trigger allergic reactions, caused by the large quantity of specimens in a given area. Sometimes they are more vulnerable to attack by parasites, in that they have fAster metabolisms than native species. There are also cases linked to the damaging effects of invasive species on cultivated crops.

List of species per area:
Robinia pseudoacacia L., Senecio inaequidens DC., Hypericum calycinum L., Acer negundo L., Syringa vulgaris L., Prunus laurocerasus L., Amorpha fruticosa L., Parthenocissus quinquefolia (L.) Planchon, Helianthus tuberosus L., Portulaca oleracea L., Wisteria sinensis (Sims) Sweet.
Some of the above species have reached a high degree of naturality, others are now beginning to reveal tendencies to occupy marginal ecological niches, while others have only recently been observed as spontaneous species, flowers in gardens and city parks. There are many remarkable cases of coevolutive adaptation in urban and suburban cenosic; some of them are adopting truly invasive characteristics due to their large numbers in a given area.

Perugia the city and the province: Sophora japonica L., Paulownia tomentosa Steud., Broussonetia papyrifera L'Hérit, Ailanthus altissima Swingle, Cupressus arizonica Greene, Maclura pomifera Schneid., Gleditsia triacanthos L., Agave americana L., Salpichroa origanifolia (Lam.) Baillon, Dichondra micrantha Urban, Portulaca oleracea L.
Most of the above species are arboreal and are ornamental plants for gardens, public and private parks in environments with a submediterranean climate, capable of resisting sudden climatic variations, either of excessive rainfall or  periods of excessive hot or cold temperatures. They have adopted various survival strategies and almost all of them have naturalised, except Cupressus arizonica and Sophora japonica. They often show significant signs of coevolutive adaptation.

Trasimeno: Abutilon theophrasti Medicus, Oenothera L. sp., Ceratostgima plumbaginioides Bunge, Elaeagnus angustifolia L., Datura stramonium L., Lantana camara L., Opuntia ficus-indica L., Yucca aloifolia L.
These species are found in antropic areas, on the margins of agricultural crops, but some of them tend to have crop fields even if only on marginal strips of land. They prefer conditions good water availability, together with high temperatures, allowing them to survive and spread.

Middle Tiber valley: Ambrosia gigantea, Sicyos angulatus L., Bambusa Schreber. sp., Arundinaria Richard sp.

Plants belonging to these species take advantage of  extremely favourable geopedological and bioclimatic conditions; they grow in sandy soils, with adequate water availability.

Ignazio Camarda

Dept. of Botany and Plant Ecology
University of Sassari
Via Muroni, 25 - 07100 - Sassari
Italy
camarda@ssmain.uniss.it

The presence of exotic species in Sardinia goes back to the very old times and now many of them are very common in several different places as woods, coastal regions, cultivated areas, rice-fields, along the roads (Chiappini, 1963; Bocchieri 1978; 1990, Camarda, 1982, 1983, 1998; Viegi 1993; Lanza, Camarda and Natali, 1995). Their impact on the landscape, in spite of being quite low in the past, it's increasing more and more in the last time.
Pinus pinea, Castanea sativa, Corylus avellana, Prunus avium, Amygdalus communis, Olea europaea, Vitis vinifera, Juglans regia, and probably Ceratonia siliqua also, are introduced and characterise the countryside. It consists of entities diffused above all during roman period and they also represent an important source as food for human alimentation (Cherchi-Paba F., 1974-77; Perra, 1993). Only Ceratonia siliqua and Olea europaea spread spontaneously, as native species. The other ones, in general, are substituted by local flora and vegetation in a more or less long period of time.
After America discovery another group of exotic species made more abundant Sardinian flora, but only some of them as, e.g., Opuntia ficus-indica, Agave americana and Nicotiana glauca must been considered as fully part of the landscape.
Between ligneous species coming from other regions of the world Acacia cyanophylla s.l. and Ailanthus altissima are the only ones that seem able to propagate, contrary to Alnus cordata, Casuarina equisetifolia, Cupressus sempervirens, C. arizonica, C. macrocarpa, Eucalyptus sp.pl., Fagus sylvatica, Pinus nigra, Pinus canariensis, Pinus radiata, Myoporum tetrandra, Pittospyrum tobira, Sarothamnus scoparius, introduced for afforestation.
Pinus halepensis and Pinus pinea, are the conifers which show a low capacity of spreading. The exotic species more utilised for afforestation in Sardinia are P. nigra, P. radiata, P. canariensis, Cedrus atlantica, while broad-leaved are Acacia cyanophylla, Eucalyptus camaldulensis and E. globulus.
Conifers wood have a strong impact on local flora and spontaneous vegetation, both because the vegetation is totally destroyed during the soil tillage for the plantation, and because the high density of plants. The disappearance of native species on large surfaces impoverish the biodiversity. When the cover of tree is reduced it is possible the restoration of natural vegetation.
Eucalyptus camaldulensis is an heliofilous species, that constitutes clear woodlands, but the competition of imposing root-system and the accumulation of organic matter undecayed on the soil, in addition to the presence of Acacia cyanophylla, both developing by seeds and by suckers from roots, impedes the development of native flora. In every cases changes of landscape bring to an immediate influence on natural habitats, decreasing biodiversity of biocenosis.

References
Bocchieri E. et al., 1978 - Solanum cornutum Lam. e Solanum elaeagnifolium  Cav., nuove avventizie per la Sardegna.  Inf. Bot. Ital., 10: 226-249.
Bocchieri E., 1990 - Segnalazioni floristiche italiane: 621. DC. Inf. Bot. Ital., 22:323-331.
Camarda I., 1982 - Segnalazioni floristiche italiane: 145-150. Inf. Bot. Ital., 14: 281-282.
Camarda I., 1983 - Segnalazioni floristiche italiane: 216-218. Inf. Bot. Ital., 15: 76-78.
Cherchi-Paba F., 1974-77 - Evoluzione storica del'attività industriale, agricola, caccia e pesca in Sardegna. Voll. 1-4.  Ed. Fossataro, Cagliari.
Chiappini M., 1963 - Artemisia verlotorum Lamotte: avventizia infestante che costituisce parte integrante della flora sarda. Studi Sassaresi, Sez., III,  Ann. Fac. Agr. Univ. Sassari, 11:3-13.
Lanza B., Camarda I., Natali A., 1995 - Solanum  sisymbrifolium Lamarck, an alien new to Sardinia. Boll. Mus. Reg. Sc. Nat. Torino, 13 (1): 289-295.
Perra M., 1993 - La Sardegna nelle fonti classiche dal VI sec. a.C. al VI sec. d.C. S'Alvure ed., Oristano.
Viegi L., 1993 - Contributo alla conoscenza della biologia delle infesanti delle colture della Sardegna nord-occidentale. I. Censimento delle specie esotiche della Sardegna. Boll. Soc. Sarda Sci. Nat., 29: 116-234.
 

Campelo, F., Marchante, H. and Freitas, H.

Department of Botany. Faculty of Sciences and Technology. University of Coimbra. 3049 Coimbra.
Portugal
Phone: +351 39 822897
Fax: +351 39 820780
fcampelo@hotmail.com

Coastal areas are particularly vulnerable to natural and anthropogenic disturbances, especially dune systems. The fragmentation of natural vegetation, due to anthropogenic pressure, associated with biological invasion represents a serious threat to the conservation of native species in sand dunes.
Carpobrotus edulis (Aizoaceae) is native from South Africa. This perennial succulent was introduced in Portugal for dune stabilisation and erosion control. The fleshy fruits of C. edulis are edible and the native fauna may constitute a strong dispersion mean. Once stabilised this plant shows a high vegetative reproduction rate and growth is not affected by herbivory or competition. This exotic species was greatly dispersed throughout Portuguese sand dunes, affecting the natural succession and ecological processes by changing species composition.
It is our aim is to understand the extension of the invasion of Carpobrotus edulis in the sandy coast of Portugal, the way it competes with native species and how serious are the ecological consequences of this invasion.

Key words: plant invasion, Carpobrotus edulis, biodiversity, sand dunes.

Giulia Ceccherelli and Nicola Sechi

Dipartimento di Botanica ed Ecologia Vegetale, Università di Sassari, via Muroni 25 - 07100 Sassari
Italy
ceccherelli@botanica.uniss.it

The introduction of non-native plants has become an increasing problem in many different ecosystems. Introduced species have interested ecologists because of their effects which are often detrimental to the biodiversity of their new environment. Non-indigenous seaweed species, for instance, have been claimed to reduce the distribution of native seagrasses by competitively displacing them. Marine rhizophytic algae, such as Caulerpae species, show to be highly invasive especially where they are non-native.
The introduced green algae Caulerpa racemosa (Forsskål) J. Agardh and Caulerpa taxifolia (Vahl) J. Agardh have been shown to fast-spread and colonize many types of substrata in the Mediterranean. In fact they are found on sand, cobbles, on algal mats and seagrass habitats such as Cymodocea nodosa (Ucria) Aschers. and Posidonia oceanica (L.) Delile.
In this paper we present results obtained in two different experimental studies that have investigated separately the effect of the removal of Caulerpa racemosa and Caulerpa taxifolia on Cymodocea nodosa. Both experiments were carried out in the field, lasted for 18 months and had, as response variables, density, length of the seagrass canopy and density of flowers.
Results obtained indicated that in areas where C. racemosa and C. taxifolia were present the shoot density of C. nodosa was lower than in controls, suggesting a negative effect of both introduced algae on the native seagrass. However, the number of both male and female flowers in removal treatment are significantly higher where algae were present than in the removal areas.

Celesti Grapow L., Di Marzio P., Blasi C.

Dipartimento di Biologia Vegetale, Università "La Sapienza", P.le Aldo Moro, 5 - 00185 Roma
Italy
Tel.: 06-49912845
Fax: 06-49912642
acosta@uniroma1.it

Urban floras generally comprise a high proportion of alien species. In this study the flora of several Italian cities is analysed in order to evaluate the relative importance  of alien and native species. Both experimental data and data gathered from literature are considered. The proportion of aliens in the Italian urban flora is generally lower than that found in Central European cities. This trend particularly characterises the Mediterranean Region where the apophytes (indigenous species expanding into man-made habitats) are the most successful  group of spontaneous urban flora. Besides, in Mediterranean cities, alien plants are almost totally confined to man-made habitats and do not generally invade semi-natural vegetation. These results may be explained by the minor importance of the urban heath island effect in the distribution pattern of the species in the Mediterranean area. Another possible reason may be found in the pre-adaptation of many Mediterranean plant species to human disturbance which strongly characterises urban habitats.
 

Lois Child (1), Max Wade (2) and Sean Hathaway (3)

(1) Environmental Sciences, Department of Chemistry, Loughborough University, Loughborough, LE11 3TU. United Kingdom. L.E.Child@lboro.ac.uk
(2) Department of Environmental Sciences, University of Hertfordshire, Hatfield, AL10 9AB.
United Kingdom
(2) Nature Conservation Section, Planning Department, City and County of Swansea, Guildhall, Swansea, Wales, SA1 4PH.  United Kingdom

Since the export of Fallopia japonica (Houtt.) Ronse Decraene from Japan in the mid nineteenth century as an ornamental species, this rhizomatous perennial plant has rapidly extended its distribution in its introduced range.  The control of the plant in both urban and rural environments is now a significant problem in Europe, the northern states of the USA, Canada and New Zealand. Human activity is mainly responsible for its spread, particularly in urban environments through movement of soil containing plant fragments.
The Planning Department of the City and County of Swansea, a local authority in South Wales, UK, has attempted to manage the invasion of F. japonica in the area of their jurisdiction by establishing a strategic management plan.
A comprehensive ground survey created an accurate picture of the distribution of the plant within an area of approximately 400 km2. These data were transferred to a Geographical Information System (GIS) enabling rapid manipulation and the establishment of links between e.g. planning policy, land ownership and the presence of F. japonica. Three priorities have been identified in formulating a management strategy (i) to prevent further spread of the plant; (ii) to protect vulnerable areas from becoming infested; (iii) to target control at priority areas on the basis of, for example, high nature conservation value, aesthetics and nuisance. The opportunities and constraints involved in controlling F. japonica in an urban environment are explored from a local authority perspective. Some problems encountered in using GIS for this type of exercise are discussed.
Results of the survey show that the area covered by F. japonica is 100 ha which represents 0.25% of the total area surveyed. In relation to the strategic management of the plant within the city, the use of GIS has enabled the Council to identify alert areas where plans for re-development within the city affect infested sites and to place restrictions on the movement of infested soil. A Knotweed Officer has also been appointed.

Lois Child (1) and Max Wade (2)

(1) Environmental Sciences, Department of Chemistry, Loughborough University, Loughborough, LE11 3TU, United Kingdom. L.E.Child@lboro.ac.uk
(2)Department of Environmental Sciences, University of Hertfordshire, Hatfield, AL10 9AB
United Kingdom
 

The group of Asiatic knotweeds in the genus Fallopia, incuding F. japonica, F. sachalinensis, F. japonica var. compacta and the hybrid F. x bohemica, are now well distributed throughout their introduced ranges worldwide. The relative invasion potential of these Asiatic knotweeds was investigated by exploring their rates of vegetative regeneration from fresh stem and rhizome material in a series of greenhouse trials. Stems were subjected to two conditions, either buried in a soil medium or placed in water, rhizomes were buried in a soil medium. Stem material from F. japonica plants regenerated more rapidly than stems from hybrid plants under both aquatic and terrestrial conditions. Buried hybrid stems gave higher regeneration rates than hybrid stems in water treatments. For all treatments, F.  japonica and F. x bohemica stem material gave higher regeneration success rates than either F. sachalinensis or F. japonica var compacta. The hybrid F. x bohemica showed a regeneration potential comparable to that of F. japonica with a greater than 50% rate of successful regeneration from 3.9 g of fresh rhizome material. Rhizome material taken from male-fertile hybrid plants showed a greater regeneration potential than material from female hybrid plants in terms of time to shoot emergence, shoot height and percentage success rate.  The invasion potential of rhizome material from F. sachalinensis and F. japonica var. compacta plants was not as great with lower regeneration success rates and larger amounts of material being required for regeneration success. Assuming that the means of dispersal are similar for each of these species, the potential for a secondary invasion of F. x bohemica is indicated.

Gerry Clabby, Bruce Osborne, Mark Manto, Gary Lanigan, Chris Kavanagh and Tommy Gallagher

Botany Dept.
University College Dublin
Belfield, Dublin 4
Ireland
Gerry.Clabby@ucd.ie

Attempts at understanding the key features that contributes to the success of introduced plants have focused on species that have a major impact on exixting communities. In the main, however, this approach has failed to identify those characteristics that make some plants successful invaders and others not. An alternative approach is the examination of plants that, although introduced, have not become invasive, although they may have potential to become invasive in the future. We have applied this latter approach to a study on Mycelis muralis (L.) Dumort, the wall lettuce. This species has almost certainly been introduced into Ireland and now occupies a number of predominantly shaded sites although, unusually, it reaches its greatest abundance in the Burren, an exposed limestone area. However, M. muralis is never a majorcomponent of the vegetation in any habitat in which it is present, consistent with its occurence throughout its range. Competition experiments with Geum urbanum have indicated that the performance of this species in shade may be poor at low calcium supply and this may limit its spread outside calcareous understory environments. The origin of the open pavement population is thought to be relatively recent (~ 60 years) and, based on RAPD analysis, is genetically distinct from the woodland populations. These differences are not, however, related to a number of physiological attributes. This indicates that increases in the range of habitats occupied by introduced species may not be simply predictable on the basis of their overall ecology or physiology.

Colasante M., Corazzi G., Mortellaro R.

Dipartimento di Biologia  Vegetale, Università " La Sapienza", Roma
Italy
Colasante@uniroma1.it

Generally, the families Cyperaceae, Iridaceae and Commelinaceae are considered ornamental plants, but, when they interfere with man's activities, they become weeds. As all the plants can become weeds as function of time and place, in Italy, some species of Cyperaceae, Iridaceae and Commelinaceae are weeds among crop plants.
Here, are our preliminary observations on some species of these three mentioned families, their presence in Italian crops, their general strategy for dispersal.
The species of the genus Cyperus L., C. esculentus L. (Ter Borg et al., 1998), C. glomeratus L., and C. rotundus L. that can be found wild in damp soils, but in the case of their spreading into monoculture crops, in vineyards, and even in asphalt in the city roads, they must be considered invasive.
In the family Iridaceae, even though we are used to observe the large diffusion of ornamental rhizomatous Irises out of the  areas designed to them (this can be bothering sometime for the man's activities or desirable in soils subject to landslides), actually we can consider invasive the species of another genus of Iridaceae, the genus Gladiolus L. Indeed, G. italicus Miller and G. byzantinus Miller can become invasive of wheat crops.
In agronomy and agriculture practices, many species of these families show strong similarity in habit to that of the crops, especially wheat, in which they live.
The appearance of leaves, for example, of a lot of species of Cyperus, is very close to that of young plants of Triticum and other cultivated Poaceae. The same can be easily observed in the leaves of the genus Gladiolus L., at least before the blooming of the plant. So, for many farmers, it is very difficult promptly to distinguish these invasive plants from the crop.
Another important characteristics of these plants which underlines their strong potentiality of diffusion linked to their wide ecological adaptability, is represented by their life form. Many Cyperaceae (Cyperus, Carex) produce a hypogeous modified stem, often very long with usual spatial high development (Munzik, 1970).
Commelinaceae, such as Murdannia sp. pl., are the most cases perennial herbaceous creeping plants, growing in tropical places (in Italy, we can find M. keisak (Hassk.) Handel-Mazz. as invasive in rice monocultures, near Vercelli); they  normally produce adventitious roots at the nodes of vegetative stems, at more or less regular distance one by one, so the population appears in thick tufts. This is very important for their diffusion, because when the same stem is broken by accident, it can easily give origin to another plant completely independent from the original, able to produce other plants in the same vegetative way.
In addition, as both Cyperaceae and Commelinaceae have sexual reproduction, the number of individuals in each population can increase rapidly in this way and can be well advantaged by their biological form in vegetative reproduction. On the contrary, Gladiolus species, because of their biological cycle and, consequently, for their reproductive strategy, cannot produce adventitious roots or stolons, having just a bulb-tuber (Mathew and Swindells, 1996), so they use sexual reproduction as an invasive strategy and their distribution is less abundant that of the other mentioned genera.
The basal biosystematic investigation as from morphological characters and distribution  data shows immediately that G. italicus, even if it is of doubtful origin, because it is  over all Italy, becomes more noxious economically than G. byzantinus, that is characteristic only of the Central-Southern Italy.
Consequently, a systematic study of the above mentioned genera can help in the case of mechanical or biological control of  cereal crops.
In this preliminary study, we show the importance of convergence of characters between the invasive with "autoctone" species, the relation between their life cycle and their strategy of diffusion  and some systematic data that point out also the misidentification (Pignatti, 1982) of the above mentioned Murdannia keisak with Commelina communis L., even the colour of flower in the last species is pale blue and not white-pink, and rarely with Tradescantia virginiana L., often cultivated ornamental species that escape in fields near houses and gardens to become invasive.

References
Behrendt S., Hanf M., 1982 - Le infestanti graminacee delle grandi colture. 153-155. BASF.
Mathew B., Swindells P., 1996 - Le piante bulbose. 12-13. Zanichelli. Bologna.
Munzik T.J., 1970 - Weed biology and control. McGraw-Hill Book Company. 29-40. N.Y.
Pignatti S., 1982 - Flora díItalia. 3: 449. Edagricole. Bologna.
Ter Borg S. J., Schippers P., Van Groenendael J.M., Rotteveel A.J.W., 1998 - Cyperus esculentus (yellow nutsedge) in N.W. Europe: invasion on a local, regional and global scale (in Plant invasions, ed. by U. Starfinger et al.). Backhuys Publisher, Leiden.

Colasante M., Corazzi G., Cima M.

Dipartimento di Biologia  Vegetale, Università " La Sapienza", Roma
Italy
Colasante@uniroma1.it

In Italy, red annual papavers (poppies) are taxonomically complex weeds, which are widespread in different wild, cultivated and ruderal sites. Since they are very invasive it is difficult to eliminate them from crops. Several studies have been carried out to resolve the many problems linked to their high potentiality for diffusion in crops ( Munzik 1970, Hanf 1980,Viggiani 1990), but the solution is difficult without a clear understanding of the characters related to their life forms, reproduction and ecological strategy.
A recent investigation assessed the systematics (Kadereit 1988) of the genus Papaver L. sect. Rhoeadium Spach and led to the separation of a new species "Ïntrasection" and eliminated others already instituted. However, this study was carried out mainly on herbarium specimens, not always taking relative populations into account, and with an arbitrary rejection of some samples.
We quote from Kadereit (1988) a paragraph which elucidates the difficult interpretation of P. rhoeas: " On the one hand, Elkan (1839) and Kunze (1887) accommodated all taxa known at their time in two (P. rhoeas L. and P. dubium L.) or one (P. rhoeas) species respectively. On the other hand, a large number of new species were described by Fedde (1909), often from single herbarium specimens only or including obvious monstrosities, and by Timbal-Lagrave (1870, 1892), Jordan (1861, 1864) and Wein (1911 a, 1911c), who worked on a regional scale. This approach has led to the acceptance of 16 species with 9 subspecies and three varieties. "
The systematics of the problematical species P. rhoeas and its allies is established mainly on morphological elements. Our approach to this "Papaver group" therefore involves a macro and micro-morphological investigation of natural populations to establish which one of the previous discordant revisions and systematic interpretations could be considered valid.
Our investigation started with examination of bibliographic data, then examination of herbarium specimens, collection of new samples (both living and dry), comparison of these with the Linnean samples, observations made in the field, and laboratory analysis. The results showed an inconsistency of the present systematic position of the poppies based only on morphological study of samples either of unknown origin or from different areas and mainly from herbarium specimens. The importance of a study of populations and their range of variation in delimiting the P. rhoeas entity, seems to have been often neglected. Our preliminary analysis has demonstrated high variability and provided new and interesting systematic data.
All the populations examined (mainly among crops, in abandoned fields and either near or within cities mainly from Lazio, Abruzzi and Campania) were highly polymorphic as well as rich in individuals; also they had a high diversity of individuals in a very small population (1m x 1m). They were polymorphic for the following characters: large or reduced lamina of leaves, branched or unbranched stem, solitary or many flowers, more or less elliptical to subspherical capsules, coloured or bicoloured spots on petals, number of stigma rays, some heteromorphic pairs in the karyotypes (2n=14), new plants obtained from the seeds of poppies of known characters.
Investigation of seeds by S.E.M. revealed other characteristics: the seeds presented a low level of intra-individual (same capsule) variation, but some inter-individual variation in each population, mainly in distribution of testa cells and in the wall. On the basis of the available data we agree with Kadereit on the complexity of P. rhoeas and the difficulty of separation of the species by the seeds. However, we found in each population more or less the same range of seed variation referred by Kadereit to many of the species that this author instituted and recognized  (1988), with the big difference that we could refer them only to each population of P. rhoeas s. l.. On the whole we remain perplexed both about some of the solutions adopted, and on the systematics of the section by Kadereit.
We conclude that, although we need more data to interpret the systematic entity of this taxon and consequently to address the biological problems, our opinion is closer to that of Kuntz (1887) than Kadereit (1988), but with two main differences. Our results from karyotype analysis also show evidence of high genetic potential and possible phenotypic plasticity linked to the constant possibility of annual recombination by meiosis that increases variation and consequently populational polymorphism. The hypothesis of a possible hybrid origin of this complex weed from autoctones and oriental species, is partly upheld by the introduction of poppies to many fields in Italy through crop seeds from different countries. Studies on experimental hybrids ( Wein 1911a, 1911c) and cytogenetic, observations on natural hybrids have given some data (McNaughton and Harper 1960a 1960b), but the origin of the many different individuals of each population is still uncertain.

References
Altamura L., Cima F., Colasante M., 1991 - Variabilità intraspecifica in Papaver rhoeas L. Giorn. Bot. Ital., 125, N. 3: 382.
Colasante M., Altamura L., Cima F., 1989 - Osservazioni sul polimorfismo di Papaver rhoeas L. Giorn. Bot. Ital., 123, Suppl.1. : 113.
Cima F., Colasante M., Del Caldo L., 1992 ñ Su Papaver rhoeas L. s.l. : analisi della morfologia di semi al S.E.M. ed osservazioni relative.  Giorn. Bot. Ital.,126, n. 2: 285.
Elkan L. ,1839 - Tentamen Monographiae Generis Papaver. Berlin.
Fedde  F., 1909 - Papaveraceae novae vel notabiles. Bull. Herb. Boissier, Sèr.5, 2: 165 -171 and 438 - 448.
Hanf M., 1980 - Le erbe infestanti e le loro plantule. 285 - 287. Edagricole. Bologna.
Jordan  A., 1861 - Diagnoses d'espèces Nouvelles ou Mèconnues. Ann. Soc. Linn. Lyon 7: 456-468.
Jordan  A.,1864  - Diagnoses d'espèces Nouvelles ou Mèconnues 1. Paris.
Kadereit J.W. ,1988 - A revision of Papaver L. section Rhoeadium Spach. Notes R. B. G. Edinb., 45 (2):225-286.
Kuntz  O., 1887 ñ-Plantae Orientalis-Rossicae. Acta Horti Petrop. 10: 137-262.
Mcnaughton I. H. And Harper J. L., 1960a - The comparative biology of closely related species living in the same area. 1. External breeding-barriers between Papave species. New Phytol. 59: 15-26.
Mcnaughton I. H. And Harper J. L., 1960b - 2. Aberrant morphology and a virus-like syndrome in hybrids between Papaver rhoeas L. and P. dubium L. New Phytol. 59: 27- 41.
Munzik T.J., 1970 - Weed biology and control. McGraw-Hill Book Company. 29-40. N.Y.
Timbal-Lagrave P. M. E., 1870 ñ PrÈcis des herborisations. Bull. Soc. Hist. Nat. Toulouse 4 : 156-165.
Timbal-Lagrave P. M. E., 1892 - Florule des Corbiéres. Rev.Bot. Bull. Mens. 10: 33-39.
Viggiani P., 1990 - Erbe spontanee ed infestanti: tecniche di riconoscimento (dicotiledoni). 172-173. Edagricole. Bologna.
Wein K.,1911a - Papaver rhoeas x strigosum (x P. feddeanum) K. Wein, nov. hybr. Repert. Spec. Nov. Regni Veg. 9:172.
Wein K, 1911c ñ Beitrage zur Kenntnis der deutschen Mohnarten. . Repert. Spec. Nov. Regni Veg. 9: 225-229 and 241-244.
 

Colasante M. (1), Lucchese E (2), Noris M. (1)

(1) Dipartimento di Biologia Vegetale, Università "La Sapienza" Roma
Italy
Colasante@uniroma1.it
(2) Facolta' di Agraria, Universita' del Molise, Campobasso
Italy

In Italy, Stellaria media (L.) Vill. can be found in every site, often also where it is unwelcome. The  more or less procumbent arrangement of the first part of the stem, divided in nodes and internodes, makes easier the diffusion in wild areas, inside the cities, in abandoned fields, but  also in crops. During the year, the long flowering time of this taxon leads to the maturation of many seeds that increase the potentiality of diffusion of S.m. and the chromosome rearrangement, so it has been treated as invasive by  many Authors (Mann and Barnes 1950, Hanf 1980, Viggiani 1990) and some attempts with chemical and biological control have been operated to eliminate it from  crops, not always successfully.
S. media is a taxon yet in discussion because of its doubtful origin, high polymorphism, over a broad diffusion  area and  uncertain systematics (Colasante and Lucchese, 1995).
The main taxonomic problems concern: a) a lot of forms that have been described, b) the different denomination and systematic rank that have been assigned to these forms, c) the relation with the putative ancestors: S. neglecta Weihe and S. pallida (Dumort.) PirË. Actually, there is the interpretation of Beguinot ( 1910a, 1910b, 1920) that separated many species  and forms, while that of Greuter et al. (1984) separates three species S.pallida, S. neglecta and S. media aggr., the last subdivided in the subspp. media, cupaniana and  postii, the second subspecies synonymyzed with the third. We have investigated specimens of three European herbaria: Patras (UPA), Geneve (G), and Rome (RO) regarding the taxa S. media subsp. media, S. m. subsp. cupaniana  (Jourd. and Four.) Nym., S. m. subsp. postii Holmb., but the specimens presented many misdeterminations. In addition, the herbarium data stray from the reality verified in the wild areas, because of the high polymorphism of this taxon. The analysis of some wild Italian populations (in Lazio, Molise and Sardinia) showed higher inter and intra-populational (rare intraindividual) polymorphism in relation to broader spread areas of the populations. In fact, we noted a correlation between the variations of the characters and the number of the individuals into each population.
We analysed macro and micromorphological characters of each individual within and  between different populations to compare the taxon S. m. and the contiguous taxa, at different levels, also using scanning electron microscopy. The usual character of strip of hairs along the stem, to indentify the species and subspecies of the mentioned taxa (Whitehead and Sinha, 1967), appeared very variable within the populations in number, thickness and distribution, so that it did not appeare of valid diagnostic use in the species and in the subspecies. The form and the nature of the hairs (simple or glandular) have not been significant enough to separate in taxa specific and subspecific because of their irregular distribution.  The comparison of the seeds, often a very conservative character, by S.E.M., showed testa cells arranged in an external denticulate group and the other cells with variable winding wall (Godeau 1973). The total arrangement presented intraspecific variation in S.m., but also pointed out some difficulty of separation between the seeds of S.m.. (and its subspecies media and cupaniana, syn.postii), S. pallida and S. neglecta because of  the many intermediate seed forms found in S.m. (Colasante and Lucchese, 1995), supporting the hypothesis of allopolyploid origin of S. m. and the possible ancestors in the last two mentioned Stellaria (Peterson, 1933, 1935, 1936; Negodi, 1936). In addition, the many intermediate forms between these and the probable amphidiploid natural hybrid, put in evidence the difficulty of separation between the above mentioned critical taxa also at subspecific level. On the basis of the slight diagnostic characters, the institution of some subspecies geographically distinct, as cupaniana and postii, appears unjustifiable in accordance with other A. l.c., but also the same institution of the subspecies, in our opinion seems to be rejected  as in our examination of some Italian populations we found together individuals that were referable to the subspp. media and cupaniana together with some intermediate forms.

References
Beguinot A., 1910 - Ricerche intorno al polimorfismo della Stellaria media (L) Cyr. Parte I. Bibliografia Sistematica. N. Giorn. Bot. Ital., 17: 299-326.
Beguinot A., 1910 - Ricerche intorno al polimorfismo della Stellaria media (L.) Cyr. Parte 11. Illustrazione sistematica. N. Giorn. Bot. Ital., 17: 348-390.
Beguinot A., 1920 - Ricerche intorno al polimorfismo della Stellaria media (L.) Cyr. Parte 111. Il polimorfismo nel ciclo di Stellaria media e le leggi che lo governano. Fasc. 1: 1-149. Padova.
Colasante M., Lucchese F., 1995 - Stellaria  media (L.) Vill. s.l. (Caryophyllaceae): variabilita inter ed intrapopolazionale. Boll. Soc. Sarda di Sci. Nat. 30: 297-308.
Godeau M.M., 1973 - Stellaria media (L) Vili., S. neglecta Weihe, S. pallida (Dum.) Pirè: observation des tèguments sèminaux au microscope èlectronique à balayage. C. R. Acad. Se. Paris, t. 277, ser. D., n. 21: 2381-2384.
Greuter W., Burdet H.M., Long G. (Ed.), 1984 - Med-Check list.1: 286-287.
Hanf M., 1980 - Le erbe infestanti e le loro plantule. 207. Edagricole. Bologna.
Mann H.H., Barnes T.W., 1950 - The competition between barley and certain weeds under
controlled conditions. 4. Competition with Stellaria media. Ann. Appl. Biol., 37: 139-148.
Negodi G., 1936 - Contributo alla cariologia di Stellaria media (L.) Cir. N. Giorn. Bot. Ital., 43: 1-9.
Peterson D., 1933 - Stellaria media L. x Stellaria neglecta Weihe. Bot. Not., 1933: 500-504.
Peterson D., 1935 - Some chromosome numbers in the genus Stellaria. Bot. Not., 1935: 409-410.
Peterson D., 1936 - Stellaria - Studien. Zur ZytologÌe, Genetik, Oekologie und Systematik der Gattung Stellaria, insbesondere der media - Gruppe. Bot. Not., 1936: 281- -419.
Scholte G.A.M., 1978 - Biosystematic studies in the collective species Stellaria media (L.) Vill. (I), (II). Proceedings, 81 (4): 442-456 and 457-465.
Sinha R.P., Whitehead F.II., 1965 - Meiotic studies of British populations of Stellaria media (L) Vill., S. neglecta Weihe and S. pallida (Dumort.) Pirè. New Phytol., 64: 343-345.
Viggiani P., 1990 - Erbe spontanee ed infestanti: tecniche di riconoscimento (dicotiledoni). 144. Edagricole.  Bologna.
Whitehead F. H., Sinha R.P., 1967 - Taxonomy and taximetrics of Stellaria media (L) VilL, S. neglecta Weihe and S. pallida (Dumort.) Pirè. New Phytol., 66: 769-784.

Colombo Speroni, Federico and Marta L. de Viana

Cátedra de Ecología, Universidad Nacional de Salta, Bs.As. 177 (4400), Salta, Argentina
Fax: 0054-87- 4921364
Ecologia@Ciunsa.edu.ar -

Gleditsia triacanthos L. (Fabaceae) is original from the central-east E.E.U.U, and has invaded the mountain forest of San Lorenzo (Salta, Argentina) in association with anthropogenic disturbances. This work is part of a mayor research and is focused in some community features related to the invasion process as well as the impact of G. triacanthos on the local diversity. We analyzed species richness, relative abundance, similarity, DBH and diversity in three successional stages: colonized, mixed and climax. The three situations were different in the environmental and vegetational characteristics. The invasion of G. triacanthos was associated to the colonization of gaps formed for cattle grazing. We didn't found individuals of the introduced species in the climax stage. G. triacanthos is the most abundant species in the mixed stage but we also found abundant recruitment of native species. The diversity of trees was similar between mixed and climax stages. The diversity of the study area was higher due to the introduction of new species in the community and the disturbance regime. The results are discussed taken into account the importance of different successional stages in the invasion process, the regeneration of the native forest, the intrinsic features of the invasive species and the impact of the invasion on the local tree species diversity.

Corbetta F., Capriotti O., Ciaschetti G., Frattaroli A., Pirone G.

Dipartimento di Scienze Ambientali, Università dell'Aquila, Via Vetoio loc. Coppito - 67100 L'Aquila
Italy
corbetta@univaq.it

Vengono riportatio dati a diverso grado di approfondimento relativi alla invasività della Robinia nel bosco di Agognate (NO), nei boschi relitti in territorio di Parona e Clavegna (PV), nei boschi della valle di Aterno (AQ), nei boschi in Lomellina (PV); dell'ailanto nel bosco della Mesola (FE), nell'isola di Montecristo (LI) e nella valle dell'Aterno (AQ); di Amorpha fruticosa nella foresta Panfilia (FE) e nell'oasi di Campotto (FE).
Allo stato attuale delle conoscenze, peraltro ancora incomplete, si nota che il più significativo influsso sul sottobosco è esercitato dalla Robinia.

Anne C. Cully (1), Jack F. Cully (2) , Ronald D. Hiebert (3)

(1) Division of Biology, Kansas State University
U.S.A.
acully@ksu.edu
(2) Kansas Fish and Wildlife Cooperative Research Unit, Kansas State University
U.S.A.
(3) National Park Service, Omaha, Nebraska
U.S.A.

Since European agricultural practices began on the Great Plains, the tall-grass prairie hasœdeclined in area between 82-99%. In addition to decline in area, species numbers in the remainingœprairie may also have declined as a result of habitat fragmentation. Further species loss andœalteration of plant communities may result from the invasion of prairie fragments by non-nativeœplant species.
A study of 24 tall-grass prairie fragments ranging geographically from Minnesotaœand Wisconsin to Oklahoma and Missouri (and ranging in size from 0.5 ha to 12,000 ha) addresses these questions:
1) do numbers of non-native plant species increase as prairie unit sizeœdecreases;
2) do naturally fragmented units (in woodlands) have lower numbers of non-nativeœinvaders than human fragmented units (in agricultural settings) of the same size; and
3) will prairieœfragments clustered in space have more similar non-native species assemblages than like sizeœfragments from more distant locations?
Information from study plots indicates that most of theœprairie plant communities studied have a component of early, or cool season non-native plantœspecies. Non-native plants are a major part of community species composition and abundance inœmany prairie fragments, but the patterns of distribution and abundance of these plants appear toœhave little to do with size of the prairies. Prairies isolated in northern woodland margins had theœlowest numbers and abundance of non-native species, and the highest numbers and abundance of non-natives were found in the northern prairies isolated by agriculture.