Introduction

Lepidopteran fauna of the Sila Massif was explored by several authors which highlighted the great interest of this mountainous area always providing surprises to lepidopterists. For example, the recently described Nothocasis rosariae Scalercio, Infusino & Hausmann, 2016 (Geometridae) has here its locus typicus (SCALERCIO et al., 2016). Among Macrolepidoptera, one species is endemic of this massif, Itame messapiaria Sohn-Rethel, 1929 (Geometridae), and a number of species has relict populations here, some of which reported in Italy with certitude only for the Alps and for the Sila Massif only, namely Brenthis ino (Rottemburg, 1775) (Nymphalidae), Acossus terebra ([Denis & Schiffermüller], 1775) (Cossidae), Dichagyris signifera ([Denis & Schiffermüller], 1775) (Noctuidae). Furthermore, Zygaena nevadensis Rambur, 1858 (Zygaenidae) and Eupithecia conterminata (Lienig, 1846) (Geometridae) are known with certitude in Italy only from the Sila Massif (EFETOV et al., 2011; INFUSINO & SCALERCIO, 2015). Although its great biogeographic importance, very few data concerning abundance and community composition of Lepidoptera inhabiting the Sila Massif are available (SCALERCIO et al., 2008; INFUSINO et al., 2017a), and none of these is specifically devoted to the fauna of black alder forests (Alnus glutinosa (L.) Gaertn.).

These forests extend along the watercourses not following an altitudinal zonation and in wild condition they set up swamped riparian woods. Conditioned by the presence of water, they are vulnerable both by agricultural activities, whose subsistence is conditioned by large water catchments by the streams, and by climate change. During the 20th century, in fact, a decrease in precipitation of up to 20% was observed in some parts of southern Europe (EEA, 2008) with a consequent increase in local drought events. Another threat is deforestation both for the conversion of grazing woods and for the demand for timber. This last activity in the first half of 20th century involved all the forests, causing deep changes in the Sila landscapes (IOVINO & MENGUZZATO, 2000; CIANCIO et al., 2005).

In the Sila Massif black alder forests (Alnus glutinosa (L.) Gaertn.) develop along wáter courses as a result of human pressure, especially within landscape with strong human impact. In the most natural contexts, they develop on more large patches forming small, compact woodlots which often are in continuity with beech and pine forests. The first type plays the important role as ecological corridor among forest patches, increasing long-distance movements of habitat-restricted species (HADDAD, 1999).

Black alder forests are classified in the Euphorbio-Alnetum glutinosae association of the phytosociological alliance Salici purpureae-Populetae nigrae and they are among the priority habitats (Annex I) of Directive 92/43 / CEE - Habitat code 91E0: Alluvial forests with Alnus glutinosa (L.) Gaertn. and Fraxinus excelsior L. (Alno-Padion, Alnion incanae, Salicion albae).

Lepidoptera have often been used as ecological indicators, and in forested habitats it is preferable to use moths because more abundant in forested environments (USHER & KEILLER, 1998; SUMMERVILLE et al., 2004, 2009), instead of diurnal Lepidoptera who typically live in ecotonal environments or meadows. Moreover, moths play a key role in several food chains, and their communities rapidly react to environmental changes in response to climate (WILSON et al., 2005) and landscape attributes (SCALERCIO et al., 2012) by modifying species composition. In this paper we studied diurnal and nocturnal Macrolepidoptera, usually studied separately because of the difference in the sampling methods, in order to depict the entire Macrolepidoptera community.

The aim of this study was to explore for the first time the lepidopterological fauna inhabiting black alder forests submitted to different levels of human impact. This forest is extremely vulnerable in Mediterranean areas as there the effects of ongoing climatic changes on hygrophilous ecosystems are expected to be stronger than in the rest of the European continent (EEA, 2008).

Material and methods

STUDY AREA

The Sila Massif shows the characters of a vast continental esplanade with soft ridges (CRISCI et al., 2013), with an average altitude of 1200 m a.s.l. The highest reliefs are Mount Botte Donato (1928 m a.s.l) and Mount Gariglione (1764 m a.s.l). The climate is temperate-cold. The average annual temperature is 9ºC with strong temperature ranges, with peaks of over 30ºC in summer and -20ºC in winter. The rainfall is always high, between 1200-1600 mm/year, concentrated mainly between September and May, often snowy between December and March (CIANCIO, 1971). The survey areas (Figure 1) concerned the black alder forests chosen in different localities (Figure 2).

Diurnal Lepidoptera were sampled along transects contiguous to linear black alder forests only (Table 1), whilst nocturnal Lepidoptera were sampled in both linear and compact woodlots (Table 2).

Moths were sampled monthly from March to November 2017 by using UV-Led light traps (further details in INFUSINO et al., 2017b). In each site we positioned one trap during nights favourable to the moth activity (i.e. low wind intensity, no full moon interference, no or very low rainfall, temperatures near the average of the period).

Diurnal Lepidoptera were sampled from April to September 2017, once every two weeks, for a total of 9 sampling sessions. The method used was the semi-quantitative transect (POLLARD & YATES, 1993) 500 meters long and 5 meters width, carried out in the central hours of the day, in conditions of clear sky and no wind.

Collected specimens were identified according to the available literature and preserved in the collection of the Council for Agricultural Research and Economics, Research Centre for Forestry and Wood (CREA-FL), Rende (Cosenza), Italy. Most difficult species were dissected for a correct identification. Nomenclature follow the most recent version of Fauna Europaea (KARSHOLT & NIEUKERKEN, 2013). Species are listed in alphabetical order within any family.

Results

A total of 402 species and 9,140 individuals, belonging to 20 families, was collected of which 2,942 individuals and 117 species during diurnal samplings, 6,198 individuals and 306 species during nocturnal samplings. In the faunistic list reported after the reference list, for any species we reported the number of individuals collected in each site, the total abundance and the phenology indicated as the month of sampling in Roman numbers followed, only for diurnal Lepidoptera, by an Arabian number as exponent indicating the decade of sampling.

NOCTURNAL LEPIDOPTERA

Individual sites showed a richness varying from 86 species found in the site most impacted by human activities (SL_On4), to 157 found in the best preserved black alder forest (SL_On2) (Table 3).

Many species (132) were collected at least in 4 sites showing a relative homogeneity of species assemblages, as confirmed by the low number (from 0 to 8) and the low abundance (no more than 8 individuals) of exclusive species (Table 3). The 3 most abundant species compose the 32.8% of the entire sample. The most abundant species was Orthosia incerta (Noctuidae) (n=332), followed by Eilema lurideola (Erebidae) (n=308) and Eilema complana (Erebidae) (n=246). Represented by more than 100 individuals were also Hoplodrina octogenaria, Lycia hirtaria, Agrotis cinerea, and Luperina testacea. These species, with Pachetra sagittigera (n=86), are present in all sampled sites. 28 species are needed to reach the 52.5% of individuals, whilst the remaining 279 species, with less than the 1% of occurrence each, represented the 47.5% of total abundance (Figure 3).

Phenological changes in moth community were very significant as only few species were among the most abundant in more than one sample and none of them seemed to be bivoltine. At the beginning of the spring, species belonging to the genus Orthosia, mainly O. incerta and O. gothica, and Endromis versicolora characterized the species assemblage accompanied by Lycia hirtaria and Cerastis rubricosa as the season proceeded (Figure 4). Also few overwintering adults of Dasypolia templi were detected. Significant changes occurred in May, when few individuals of L. hirtaria are still on flight and the assemblage was dominated by Agrotis cinerea, Pachetra sagittigera and Athetis pallustris. From June to September four species, namely Campaea margaritaria, Peribatodes rhomboidaria and Hypena proboscidalis, were constantly among the most abundant, accompanied by different species as the season proceeded (Figure. 4). During the summer there was a strong turnover of dominant species, most of which trophically linked to herbaceous plants. Late-summer assemblage was mainly characterized by Luperina species, among which the most abundant was L. dumerilii, accompanied by Tholera decimalis and Episema glaucina. From October to November changes were less pronounced as Agrochola macilenta and Epirrita christyi were similarly abundant, whilst Allophyes corsica characterized the first period of the season and Poecilocampa alpina the last one.

DIURNAL LEPIDOPTERA

Three sites showed a richness varying from 71 to 85 species. As for the moths, the site most impacted by human activities (SL_On4_d) showed the lowest richness (S=55) (Table 4). Many species (59) were collected at least in 3 sites confirming the homogeneity of species assemblages observed also in nocturnal Lepidoptera. Exclusive species are very few (from 6 to 9) and showed low abundance (no more than 8 individuals) (Table 4). The 8 most abundant species compose the 44.6% of the entire sample. The most abundant species was Maniola jurtina (Nymphalidae) (n=241), followed by Polyommatus icarus (Lycaenidae) (n=226). Further six species are represented by more than 120 individuals and all of these were observed at least in 3 sites. The species of conservation concern Zerynthia cassandra and Parnassius mnemosyne were absent in the overgrazed site SL_On4_d, and Phengaris arion was only recorded from SL_On1_d. The 75% of individuals belonged to 26 species only, whilst the remaining 91 species, with less than the 1% of occurrence each, represented the 25% of total abundance (Figure 5).

During early spring most abundant species were Pieris napi and Lycaena phlaeas, the only ones collected during the whole study period, accompanied by Erynnis tages that typically flight in spring (Figure 6). From May to June the widespread Coenonympha pamphilus and Polyommatus icarus characterized the assemblages together with Euclidia glyphica and Parnassius mnemosyne.

The beginning of the summer is characterized for the increased abundance of Maniola jurtina and Plebejus argus, accompanied by Ochlodes venatus and Thymelicus lineola as the season proceeded.

In the middle of the summer, Adscita alpina and Argynnis paphia attained their máximum abundance followed by Hipparchia hermione and Lycaena tityrus in late summer.

Discussion

To the best of our knowledge, this paper seems to be one of the few available in literature based on both diurnal and nocturnal Macrolepidoptera inhabiting a given habitat. The main obstacle to the monitoring of Lepidoptera with a such different behavior is the different sampling method that in most case determined great difficulties for recorders. Furthermore, nocturnal Lepidoptera can be identified in laboratory, but diurnal ones must be identified in the field with the exception of rare specimens that need the dissection of genitalia for their identification. The sampling design we applied allowed us to collect for the first time in Italy quantitative data on the populations of diurnal Heterocera such us Zygaenidae, and diurnal species of moths such as Euclydia mi, E. glyphica, or Cleta filacearia, among the others.

Quantitative data concerning the composition of Macroheterocera communities of deciduous trees are available in Calabria for Acer sp., Fagus sylvatica, and Castanea sativa Mill. forests (GRECO et al., 2018a, 2019; INFUSINO & SCALERCIO, 2018). Main differences among these communities and those sampled in Alnus glutinosa (L.) Gaertn. forests concerned the relative abundance of shared species due to feeding preferences of their larvae and to the altitudinal gradient. For example, Campaea margaritaria was found as a common species in all deciduous forests as larvae are polyphagous on several trees (SKOU & SIHVONEN, 2015), but it was relatively less common in the alder forest as Alnus sp. is likely not among preferred foodplants of their larvae. On the other hand, the distribution of Eilema lurideola, less common in chestnut forests, seems to be influenced mainly by the altitudinal gradient.

As expected, moth communities sampled along linear forests inhabit a greater number of species having preferences for open habitat such as the abundant Agrotis cinerea and the very rare Cleta filacearia. Several forest species strongly reduced their abundance in linear-shaped forests, showing preferences for alder forest patches contiguous to other forest types. In definitive, the continuity of the forest cover seems to greatly contribute to reduce the border-effect on the composition of communities.

The absence of exclusive species among the most abundant ones doesn’t reduce the importance of this forest type from a conservation point of view. In fact, we found there many species of great biogeographic and/or conservation interest known to be present in the Sila Massif such as Dychagiris signifera, Acossus terebra, Plusidia cheiranthi, and Zygaena nevadensis among Heterocera, and Zerynthia cassandra, Parnassius mnemosyne, Brenthis ino and Phengaris arion among Rhopalocera. Furthermore, the finding of Eupithecia trisignaria in alder forests only (GRECO et al., 2018b) strongly improve its importance for the conservation of biodiversity at least at regional scale. This paper also contributed to the knowledge of the biodiversity inhabiting two Special Area of Conservation (SAC) included in the Natura 2000 network of Calabria region. In fact, two sampled sites (SL_On1, SL_On2) were within the SAC Cozzo del Principe (code: IT9310079) and one (SL_On3) was within the SAC Arnocampo (code: SL_On3). According to our results, these areas appear to be the best preserved from human impact as the former inhabits all the Rhopalocera included in the Habitat Directive that we found (Zerynthia cassandra, Parnassius mnemosyne and Phengaris arion) and the latter inhabits the only population of Eupithecia trisignaria found in southern Italy.

Acknowledgments

We are deeply indebted with Marco Infusino for his help during field trips. The work was financially supported by the Sila National Park (Project Il Barcoding delle farfalle nel Parco Nazionale della Sila: aree umide).

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Notas de autor

francescoluigi.leonetti@virgilio.it