La flora del Fiume Cavata. Guida pratica alla conoscenza delle piante acquatiche

Raramente le piante riscuotono l’interesse dell’escursionista e ancor più le piante acquatiche che si presentano spesso molto simili fra di loro e di difficile osservazione nel corpo idrico. Questa guida fotografica vuole essere di aiuto al riconoscimento delle piante che popolano i fiumi dell’Agro Pontino. L’escursionista, in canoa o a piedi lungo l’argine, potrà dare un nome agli alberi e alle “erbe” acquatiche. La guida è incentrata sul fiume Cavata, ricco di storia naturale e umana, ma risulta utile anche per gli altri fiumi e canali del territorio. Con la speranza che la conoscenza di questi particolari organismi vegetali possa risvegliare in noi un maggior rispetto per l’ambiente, gli autori augurano al “viandante fluviale” una piacevole e fresca escursione

Bryophytes of Alpine and Apennine mountain streams: floristic features and ecological notes

Floristic and ecological features of aquatic bryophytes, and main abiotic factors, were studied in 23 mountain streams located in the Western Alps and Central Apennines (Italy). At 46 stations, a total of 36 taxa were collected. Most species showed both low occurrence (≤ 2 records) and low cover respect to sampled area (&lt; 4%). However, in over 50% of stations, bryophyte communities with at least three species and cover over 10% were recorded. Platyhypnidium riparioides, Fontinalis antipyretica subsp. antipyretica and Hygrohypnum luridum were the most common and abundant species. Other species, more rarely recorded, have limited distribution in the Mediterranean region (Blindia caespiticia) and Italy (Hygrohypnum duriusculum). Some species show specific ecological preferences. In particular, Hygrohypnum luridum and Palustriella falcata are mostly linked to turbulent and cold waters (11.0-16.0°C), neutro-alkaline (7.3-8.4), with low conductivity (&lt; 160 μS) and phosphates (&lt; 0.01 mg/l) values. Brachythecium rivulare, Platyhypnidium riparioides and Fontinalis antipyretica subsp. antipyretica occur abundantly in less turbulent and less cold (15.3-18.2°C) waters, shaded, alkaline (8.3-8.6), with moderate conductivity (330- 440 μS), and higher values of phosphates (0.06-0.09 mg/l). This study provides new floristic and ecological data on bryophyte communities occurring in mountain streams. It can also represent a useful contribution for biomonitoring activities of these habitats, often understudied floristically, where bryophytes are a significant part of the aquatic macroflora.</p

Morphological study of Lemna minuta Kunth, an alien species often mistaken for the native L. minor L. (Araceae)

Lemna minuta Kunth and Lemna minor L. are two small aquatic floating plants easily mistakable for similar morphology. The need to distinguish with certainty these two species is a relevant issue, not only from a floristic viewpoint, but also for establishing management plans in wetlands where L. minuta is an invasive alien species as in Europe. The vein number and frond length are considered by most authors as the main morphological characters discriminating the two species. However, in this study the use of these two characters has not been effective for the determination of 43 specimens out of 248 living specimens of Lemna collected from 15 different wetlands of the Central Italy. Statistical analyses of the dataset made it possible to better define the variability of the morphological characters of these two species and to identify additional diagnostic characters to use for improving the morphological discrimination between them. Among these characters, width, apex and shape of the frond, were the most helpful. Decision Trees were elaborated for differentiating L. minor from L. minuta with greater efficiency both in the laboratory and in the field. The increase in percentage of correct determination of Lemna specimens through measurement and parallel utilization of the emerged morphological characters will facilitate the botanists' activities, but also will have practical implications, such as the ability to contribute better to the decision-making system in drawing up plans for plant biodiversity protection and/or eradication of the alien species

Lemna valdiviana Phil. (Araceae) as a potential invasive species in Italy and Europe: taxonomic studies and first observations on its ecology and distribution.

Lemna valdiviana Phil. and L. minuta Kunth are native species of the Americas. At present L. minuta colonizes in Europa and Asia, where it is often considered an invasive alien species. Recent floristic surveys in the Agro Pontino area (Lazio region, central Italy) allowed to find a population referring to L. valdiviana, supported by the recent gathering in Sardegna region. With the aim to identify correctly the two species, we carried out a morphometric study based on measurements of both qualitative and quantitative characters, made on herbarium and living specimens collected from America and Europe. The univariate and multivariate analyses clearly support the attribution of the population from Lazio to L. valdiviana. This gathering is the first record of this species for the Italian peninsula. Moreover, the checking of Herbaria allowed us to find the older specimen of L. minuta collected in Europe (around 1877). At present L. valdiviana is to be considered as a casual alien species in Agro Pontino, but the rapid colonization of the aquatic environments by Lemna species by means of vegetative reproduction allows us to recognize it as a potential invasive species

Ecological comparison between duckweeds in Central Italy: the invasive Lemna minuta vs the native L. minor

The American duckweed Lemna minuta shows an invasive behaviour in Europe, causing weed problems in aquatic habitats there. Few studies addressed this species’ ecological requirements for a suitable establishment in a site. In this paper, L. minuta populations were analysed through feld surveys so as (1) to defne the autoecology of this duckweed as regards the main environmental factors characterizing invaded habitats, and (2) to identify possible overlaps/differences in ecological requirements between the alien L. minuta and the common native L. minor, with which it is often associated and in direct competition. The occurrence/abundance of the two species and environmental data were collected from 41 wetlands in central Italy. Currently, L. minuta is more common and abundant than L. minor in the study-area, despite its recent arrival there (2007). The two species have a partially overlapped autoecology. However, L. minuta differs from L. minor since it occurs in waters which are less alkaline, slightly less warm, and richer in nitrates. It shows tolerance for environmental conditions which are limiting for most of macrophytes, including L. minor, such as high shading and low water oxygenation. This enables L. minuta to increase its invasion potentiality and thus to enlarge its distribution area

Colonization dynamics of the alien macrophyte Lemna minuta Kunth: a case study from a semi-natural pond in Appia Antica Regional Park (Rome, Italy)

Most studies describing biomass production of Lemna’ species (duckweeds) underline high growth rates of these species under controlled conditions. L. minuta’s growth, as well as its colonizing capability under natural conditions, has never been investigated, despite this species being the most widespread and invasive alien duckweed in Europe. In this study, the colonization dynamics of L. minuta were analysed through a 5 month field-experiment carried out in a semi-natural pond of 26.3 m in the city of Rome. Variations in plant coverage (m ), biomass pro- duced (g) and Relative Growth Rate (RGR, day of three main phases: (1) an initial phase (40 days), in which L. minuta grows moderately by covering just under 15 % of the pond surface; (2) an exponential phase (45 days), in which the duckweed grows intensively, until it completely covers the entire pond surface with a monolayer floating population; (3) an apparently stationary phase perpetuated in time, in which, instead, the species continues to grow in biomass, giving rise to a dense multilayer population 2.5 cm thick. L. minuta was able to colonize the entire pond surface in a few months of experiment, increasing its total bio- mass over 600 times respect to that initial. This underlines the species’ high biomass production in natural condi- tions. The RGR of L. minuta estimated at the end of the experiment amounts to 0.041 day (0.046 day , 0.006 day 0.126 day conditions for the native congeneric L. minor, showing a higher colonization capability of the alien species respect to the native ones. The characterization of the growth dynamics in field of the alien L. minuta provides information that could be useful for a better planning of management programs of natural wetlands invaded by this alien species, also with respect to its invasion control. Our findings suggest that in lentic environments, it is necessary to remove the species 2 2 –1 ), show that L. minuta has an growth of exponential type, consisting –1 –1 –1 , as average, minimum and maximum RGR, respectively) more than double of that calculated in similar –1 every 30 – 40 days for controlling this duckweed and prevent its future outbreaks locally. However, the complete removal of an entire L. minuta population from a natural site can result difficult and demanding but, combining a physical control of L. minuta with a subsequent biological one, it could make more effective the eradication action of the species from a site

Bryophytes of Alpine and Apennine mountain streams: floristic features and ecological notes

Floristic and ecological features of aquatic bryophytes, and main abiotic factors, were studied in 23 mountain streams located in the Western Alps and Central Apennines (Italy). At 46 stations, a total of 36 taxa were collected. Most species showed both low occurrence (<= 2 records) and low cover respect to sampled area (< 4%). However, in over 50% of stations, bryophyte communities with at least three species and cover over 10% were recorded. Platyhypnidium riparioides, Fontinalis antipyretica subsp. antipyretica and Hygrohypnum luridum were the most common and abundant species. Other species, more rarely recorded, have limited distribution in the Mediterranean region (Blindia caespiticia) and Italy (Hygrohypnum duriusculum). Some species show specific ecological preferences. In particular, Hygrohypnum luridum and Palustriella falcata are mostly linked to turbulent and cold waters (11.0-16.0 degrees C), neutro-alkaline (7.3-8.4), with low conductivity (< 160 mu S) and phosphates (< 0.01 mg/l) values. Brachythecium rivulare, Platyhypnidium riparioides and Fontinalis antipyretica subsp. antipyretica occur abundantly in less turbulent and less cold (15.3-18.2 degrees C) waters, shaded, alkaline (8.3-8.6), with moderate conductivity (330440 mu S), and higher values of phosphates (0.06-0.09 mg/l). This study provides new floristic and ecological data on bryophyte communities occurring in mountain streams. It can also represent a useful contribution for biomonitoring activities of these habitats, often understudied floristically, where bryophytes are a significant part of the aquatic macroflora

Riding invasion waves: Spatial and temporal patterns of the invasive Lemna minuta from its arrival to its spread across Europe

In Europe, the duckweed Lemna minuta is an invasive alien that can cause severe abiotic-biotic alterations of lentic aquatic ecosystems. Its invasion history across Europe was spatio-temporally reconstructed from its various introductions to its present distribution by analyzing georeferenced historical records obtained from different sources (bibliography, national-international digital databases). Fuzzy clustering, a form of classification in which an element belongs to different clusters according to a degree of belonging, was used to identify the most important temporal invasion events (pulsations). Geographical representation of these pulsations in invasion maps simplified the detection of the main dynamics of L. minuta movements across Europe. Based on the analyses of the historical data, five main invasion pulsations were identified (1965, 1982, 1991, 2000, 2010). Invasions in Europe began along the Atlantic coasts around the 1950s–1960s. Around the 1980s, L. minuta spread extensively across the United Kingdom and Central Europe. After this, it started to invade Southern and also Eastern Europe, mainly stabilizing around the 2000s. In the last decade, L. minuta consolidated its occurrence in Western and Central Europe, while it continues to colonize new Mediterranean and Eastern European regions. This analysis type is effective in determining spatial-temporal dynamics of invasive alien plants using georeferenced historical data and it also offers insight into the behavior of a biological invader by identifying the main invasion routes and areas most susceptible to future invasion. This latter information can be useful for development of management strategies for preventing invasions and conserving aquatic ecosystems potentially under threat