DIET OF COYPU (mYoCaStor CoYpuS) IN A MEDITERRANEAN COASTAL WETLAND: A POSSIBLE IMPACT ON THREATENED RUSHBEDS?

– We gathered field data to study the impact of the coypu (myocastor coypus), an alien invasive species on the vegetation of a small coastal wetland of central Italy, studying the local diet composition, richness and seasonal turnover around a yearly cycle in the study area where the dominant vegetation includes some habitat types protected by the European Habitat Directive, such as rushbeds. We subdivided plant species in ecological plant categories and verified the hypothesis that coypu prefer feed on aquatic and semiaquatic plants (mainly monocotyledons). In rushbeds we identified 76 available plant species (51 dicotyledons and 25 monocotyledons) with significant seasonal differences. A high turnover in plant availability occurs between winter, the poorest seasons in terms of species richness, and spring, the richest season, following the local abrupt change in water level and the restarting of vegetative period. Around a yearly cycle, we recorded marked differences in plant availability in the four ecological plant categories during winter. Coypu’s diet was composed by a set of 19 plant species (mainly composed by hygrophilous monocotyledons and terrestrial dicotyledons), corresponding to about 25% of the available plant species. We did not observed significant differences among consumed plant categories. Other than monocotyledons, diet included synanthropic dicotyledons largely occurring in the study area and macrophytes associated to Juncetalia maritimi rushbed, a habitat type of European conservation concern (e.g., Carex spp., Juncus spp., bolboschenous maritimus). ALIEN SPECIES PLANT ASSEMBLAGES DIET JunCetalia maritimi HABITAT TYPE CENTRAL ITALY 98 F. MARINI, E. GABRIELLI, L. MONTAUDO, M. vECCHI, R. SANTORO, C. BATTISTI, G. M. CARPANETO Vie milieu, 2013, 63 (2) mainly this species herbivorous (Johnson & Foote 1997), its impact on native vegetation may be of conservation concern, e.g. on Mediterranean salt meadows and rushbeds that are included in the 92/43 “Habitat EU” Directive. In a remnant coastal wetland of Central Italy, the local population of coypu showed a strong demographic increase during the last decade (Marini et al. 2011). Consequently, the Province of Rome, the Agency that manages this protected area, started a study aimed to plan a control program. We studied the coypu’s diet in terms of composition, richness and seasonal turnover of food items around a yearly cycle, subdividing the plant species in ecological plant categories. In particular, we would test the hypothesis that coypus prefer to selectively forage on aquatic and semi-aquatic plants (mainly composed by monocotyledons; Borgnia et al. 2000, Guichon et al. 2003, Wilsey et al. 1991). Since these plant categories represent a large part of Mediterranean rush beds, our results may have implications for the protection of these habitats of European conservation concern and for the start of a control program focused on this rodent. MATERIALS AND METHODS Study area: The study area is located inside the “Palude di Torre Flavia” Natural Monument (hereafter named, TFNM), in Central Italy (41°58’ N; 12°03’ E), a protected wetland on the Tyrrhenian coast (size-area: 40 ha). This site was also designated as Special Protection Area, according to the EU Directive 79/409 (Code IT6030020). TFNM is the remnant of a larger wetland that, in the second half of the 20th Century, was mostly drained and transformed to an agricultural and urbanized landscape. TFNM shows seminatural patchiness with ponds and channels, reedbeds (phragmites australis), rushbeds (Juncus acutus), sedgebeds (Carex hirta and other Cyperaceae), flooded meadows, and low dunes. TFNM is intensely managed for fish farming in a network of channels (800 m/10 ha), mainly located in the reedbed core area (Marini et al. 2011). These channels have been artificially built in the first half of 20th century for fish farming activity. The water supply comes largely from rainfall (Mesomediterranean xeric region; Blasi 1994), while surface flow from surrounding areas is scarce. Water level is seasonally variable, with a clear water stress induced by fishery farm activity in late spring-late summer (Causarano & Battisti 2009, Battisti et al. 2008, zacchei et al. 2011). For data collection, we selected a study area of 10 ha within TFNM, representative for rushbed size area of the whole wetland (Guidi 2006). The study area, characterized by a dominance of monocotyledons (Juncus sp., Carex sp. and bolboschoenus maritimus), is an habitat type of conservation concern (1410 Juncetalia maritimi, EU Habitat type; approximately the 25 % of the study area). Several other habitat types are also present in the study area: i) reed beds with dominance of phragmites australis (ca 15 %), ii), Mediterranean salt meadows (1420 Sarcocornetea fruticosi EU Habitat type; about 5 %), iii) back dunes (2110 Embryonic shifting dunes EU Habitat type and 1210 Annual vegetation of drift lines EU Habitat type; about 5 %), and iv) edge and synanthropic buffer habitats. data collection and analysis: Inside the study area, plant species availability and consumption were monthly sampled from August 2010 to September 2011. Data were clumped in the four seasons: winter (January, February, March), spring (April, May, June), summer (July, August, September), autumn (October, November, December). Since coypu individuals occur everywhere in the rushbed of TFNM we have not possibility of defining a sampling design treatment vs control. Moreover, we cannot realize the fences of enclosures because the study area is very small and any invasive project may act as a disturbance on waterbirds (the TFNM is designated as a Special Protection Area for birds, see above). Plant availability was estimated within a set of sampling plots (1 m2; n = 360). As the study area showed an internal finegrained patchiness without a clear pattern (Guidi 2006), we randomly located our sampling plots. In this study we have generally studied the consumption (including in this process both foraging and collection of nesting materials). The consumption sites (i.e. the sites where the coypu individuals forage and collect materials for nesting) were identified using 8 x 40 and 10 x 50 Nikon binoculars, exploring the consumption and identifying the site where vegetation was regularly consumed (Prigioni et al. 2005, Galende et al. 2013). After the coypu had left the consumption locations we visited them to identify the plants consumed or if in doubt we collected and transported to the laboratory to examine with optical microscopy. Also we examined the consumption locations to detect other important signs of coypu’s presence: faecal pellets, paths, excavations. In each plot we detected the plant species and the parts consumed, subdividing them in roots, rhizomes, stems or leaves, and their vegetative state. When in doubt we have collected and transported to the laboratory a sample of unclassified plants to examine with optical microscopy. Since we have removed only single individual specimens we assume that any significant change in the plant species presence may occur in the plot. Identification of plant species was performed according to Pignatti 1982 and contextbased literature (Buccomino & Leporatti 2009, Guidi 2006). We analyzed only terrestrial and emergent aquatic macrophytes. Plant species were classified into four ecological categories according to whether they were monocotyledons or dicotyledons, and whether they grew in a terrestrial or hygrophilic habitat. Therefore, we defined the following plant categories : hygrophilic monocotyledons (HM), terrestrial monocotyledons (TM), hygrophilic dicotyledons (HD), terrestrial dicotyledons (TD). For each season, we obtained the plant species composition and species richness (i.e. species number and their percent values), evidencing when species were available and when they were consumed both in total and at plant category level. DIET OF COYPU (mYoCaStor CoYpuS) IN A MEDITERRANEAN RUSHBED 99 Vie milieu, 2013, 63 (2) Table I. – List of the plant species, classified in the four plant plant categories available (o) and consumed by coypu (in bold) in each season (L = leaves; S = stems, R = rhizomes). Species Family Summer Autumn Winter Spring Terrestrial monocotyledons (TM) Allium vineale Liliaceae o L o