Assessment of Subalpine Grassland & Heath Sites in Haute- Savoie Using Syrphidae (Diptera)

ASSESSMENT OF SUBALPINE GRASSLAND & HEATH SITES IN HAUTE- SAVOIE USING SYRPHIDAE (DIPTERA)

Martin C.D.Speight & Emmanuel Castella

SYRPH THE NET: THE DATABASE OF EUROPEAN SYRPHIDAE (DIPTERA)

Volume 46

Series Editors: Martin C.D.Speight, Emmanuel Castella, Jean-Pierre Sarthou & Claude Monteil

ASSESSMENT OF SUBALPINE GRASSLAND & HEATH SITES IN HAUTE-SAVOIE USING SYRPHIDAE (DIPTERA)

M.C.D.Speight Research Branch, National Parks and Wildlife Service, 7 Ely Place, Dublin 2, Ireland

E.Castella Laboratoire d'Ecologie et de Biologie Aquatique, Université de Genève, 18 chemin des Clochettes, CH - 1206 GENEVE, SWITZERLAND

Syrph the Net: the database of European Syrphidae (Diptera) Volume 46 Speight, M.C.D., Castella, E., Sarthou, J.-P. and Monteil, C. (eds.) 2005

compilation of this database initially received funding from: contract STEP/CT90/0084 (Science and Technology for Environmental Protection), European Commission

Acquisition of the 2004 Haute-Savoie data received funding from the French “Direction Régionale de l’Environnement” (DIREN Rhône-Alpes).

this publication may be referred to as:

Speight, M.C.D. & Castella, E. (2005) Assessment of subalpine grassland and heath sites in Haute-Savoie using Syrphidae (Diptera). In: Speight, M.C.D., Castella, E., Sarthou, J.-P. and Monteil, C. (eds.) Syrph the Net, the database of European Syrphidae, vol. 46, 37 pp., Syrph the Net publications, Dublin.

ISSN 1393-4546 (Series)

Syrph the Net Publications Dublin 2005 © M.C.D.Speight 2005

Preface

This text is presented as a worked example of a site study. It is an English-language version of "Diagnostic de pelouses et landes sub-alpines, à l'aide des Diptères Syrphidae" (StN vol. 47) and contains the same material, except that Appendices 3 and 4 of the latter have been omitted. Contents

Summary

1. Introduction

2. Materials and Methods

3. Results 3.1. Habitats observed on site 3.2. The syrphids collected by the Malaise trapping programme 3.3. Comparison between predicted and observed species 3.3.1. Anterne 3.3.2. Carlaveyron 3.3.3. Passy 3.4. Species observed but unpredicted

4. Discussion

5. Conclusion

Acknowledgements

References

Appendix 1: results obtained on the Pormenaz site in 2003

Appendix 2: surveillance of invertebrate biodiversity in subalpine/alpine habitats

Summary

1. A study of the Syrphidae (Diptera) of three subalpine grassland/heath sites (Anterne, Carlaveyron, Passy) within Natura 2000 reserves in Haute-Savoie was carried out during the summer of 2004. The objectives were to: a) evaluate these sites using the syrphid data in conjunction with the "Syrph-the- Net" database b) contribute to the process of inventorisation of the syrphids of the nature reserves.

2. The syrphid fauna was sampled using 13 Malaise traps, installed on 6 sub-sites (2 traps per sub-site), from which samples were taken from the end of June to mid- September. A total of 59 syrphid species was collected, representing approximately 20% of the known syrphid fauna of Haute-Savoie (the species list for this département is the longest available for any French département).

3. The expected (i.e. predicted) syrphid fauna is poorly represented on all three sites surveyed and for nearly all habitats observed on those sites.

4. In nearly all cases the expected species with larvae feeding in the tissues of herb layer plants are particularly poorly represented.

5. Poor floral diversity of herb layer plants on the three sites is taken to be the primary cause of the poor representation of expected syrphid species.

6. Due to lack of data from other years and other Haute-Savoie sites unimpacted by heavy livestock grazing in the past, it is uncertain whether the impoverishment of the syrphid fauna is due primarily to the extreme weather conditions experienced in Haute-Savoie during 2003, or to chronic heavy grazing experienced in the more distant past by the sites surveyed.

7. If the remaining syrphid biodiversity of these sites is to be maintained it is recommended that livestock grazing is not re-introduced to them.

8. The impoverished character of the present syrphid fauna of these sites suggests that the management priority is biodiversity restoration, not biodiversity maintenance.

9. If there are grounds for assuming the present poor floral diversity of the herb layer on these sites is due to livestock grazing in the past, rather than to the extreme conditions of the summer of 2003, serious consideration needs to be given to the apparent failure of the sites to recover since grazing ceased.

10. Deliberate re-introduction of selected flowering plants that can be presumed to have been lost from these sites by past livestock grazing pressures could be a useful tool to aid in biodiversity restoration at the Anterne and Passy sites.

1. Introduction

As part of ongoing action, on biodiversity and management of Haute Savoie areas proposed for inclusion in the Natura 2002 network, sites in the Massif Arbe Giffre were selected by the Comité Scientifique des Réserves Naturelles de Haute-Savoie, for survey of their syrphid (Diptera: Syrphidae) fauna during 2004. This study was defined as follows:

"Etude des Diptères Syrphidae des réserves naturelles de Haute-Savoie. Cette étude sera menée sur des placettes de suivi des pelouses subalpines. Elle comprend six sites de suivi qui seront inventoriés de juin à septembre. La capture se fait par l'intermédiaire de pièges passifs.

Les Diptères Syrphidae capturés seront déterminés à l'espèce. Le peuplement de chaque site sera analysé et interprété en fonction des espèces présentes et potentielles. Cette analyse s'appuiera sur la base de données "Syrph the Net, the Database of European Syrphidae".

La liste des espèces par habitat sera établie et l'interprétation des peuplements comprendra l'écologie des espèces, leur sensibilité et les caractéristiques des habitats.

Des propositions de gestion seront faites àAsters.

Les collections d'insectes triés et déterminés dans le cadre de cette convention seront remises au Muséum d'Histoire Naturelle de Genève.

Les prélèvements non triés seront remis au Muséum d'Histoire Naturelle de Genève. La détermination des autres taxons pourra ainsi être accessible aux experts référents."

The Syrphidae are a family of Diptera well represented in Haute Savoie, where more than 260 species are known (Speight & Castella, 2004a). The species exhibit a wide range of different types of life history and between them make use of nearly all natural habitats and most structural components of habitats, from the grass-root zone of the soil to the canopy layer of trees. These and other characteristics make them potentially valuable tools in environmental interpretation/evaluation studies (see Speight, 1986, 2000, 2005, Sarthou & Speight, 2005). This has encouraged databasing of relevant biological information about them, to make them more accessible to analysis (see Speight, 2004; Speight & Castella 2004b; Speight et al, 2004).

In the Alps there are 72 syrphid species known to be associated with unimproved, montane grassland and 106 syrphid species known to be associated with unimproved, alpine grassland (Speight et al, 2004). As shown in Figure 1, 82% and 77%, respectively, of these species are known to occur in Haute-Savoie, so the montane/subalpine grasslands of this part of France could potentially play a significant role in maintenance of the syrphid biodiversity of these habitats, not only in the French Alps, but also in central Europe in general. But the study reported on here appears to be the first carried out specifically on syrphids of montane/subalpine habitats in Haute-Savoie, apart from that of Aubert et al (1976), which was located exactly on the frontier between Haute-Savoie and Valais (Switzerland).

montane, unimproved grassland alpine, unimproved grassland

100 90 80 70 60 50 40 30 20 10 0 France / Alps Haute-Savoie / Alps Haute-Savoie / France

Figure 1: the representation of central European syrphids associated with montane, unimproved grassland and alpine, unimproved grassland in France and Haute-Savoie.

2. Materials and Methods

Malaise traps were installed on the sites selected by the Comité de Gestion (Plate 1), following the general approach to Malaise trap survey for syrphids advocated by Speight et al (2000). Habitats present at each sampling station were noted and recorded photographically. Two, or sometimes three, Malaise traps were installed at each sampling station and sample bottles containing c90% industrial alcohol were attached during June (July at Carlaveyron, where bad weather retarded commencement of the sampling programme). Once in place on the traps, sample bottles were removed and replaced at intervals of two weeks until September (see Table 1). Damage to traps by grazing livestock (sheep) that arrived during August then made continuation of trapping at Carlaveyron impossible, so no sample data are available from that site for September and some of the samples from the second half of August are truncated. In consequence, Anterne and Passy each yielded 24 Malaise trap samples, but Carlaveyron yielded 20, three of them damaged/incomplete. An attempt to obtain data from all three sites by direct collecting (hand net), for comparison with the Malaise trap results, during a period selected as optimal (the second week in July), had to be abandoned due to bad weather - including late snowfall at Carlaveyron. On removal each sample bottle was labelled with individual provenance details.

Site Sampling station Trap June July Aug. Sept. Ist half 2nd half Ist half 2nd half Ist half 2nd half 1st half Anterne Caricion ferruginae A (*) * * * * * * c 1800m B (*) * * * * * * Caricion davallianae A (*) * * * * * * B (*) * * * * * * Passy Seslerion A (*) * * * * * * c2000m B (*) * * * * * * heath with Azaleas A (*) * * * * * * B (*) * * * * * * Carlaveyron siliceous grassland + Carex curvula A * * * * c2200m B * * * * heath /siliceous grassland A * * * * B * * * * C * * * *

Table 1: Malaise trapping programme conducted 2004. Blank areas indicate samples unavailable due to environmental conditions (see text). Asterisks indicate sample collected.. Partial samples (due to climatic conditions) are indicated by asterisks in brackets.

Sample bottles were then topped up with alcohol, where necessary (loss due to evaporation can be significant during a two-week period), and stored until required for sorting. The syrphids were subsequently sorted into separate tubes, each carrying the same provenance details as the parent sample. The sorted material was then determined, a record of the determinations being kept both on paper and electronically. Literature used for determinations was as recommended in Speight (2004). The nomenclature used follows Speight et al, 2004.

Sixt / Anterne Sixt / Anterne Caricion davallianae Caricion ferruginae

Carlaveyron Carlaveyron siliceous grassland + Carex curvula heath /siliceous grassland

Passy Passy Seslerion heath with Azaleas

Plate 1 – The six sites studied in 2004 in the Haute-Savoie nature reserves

Interpretation of the species lists derived from the samples was carried out using the StN database (Speight et al, 2004). The procedure used for generating, from the database, lists of the species predicted to occur in association with a site, habitat or microhabitat is detailed by Speight (2000). This procedure, and its application in biodiversity-related studies, are further elaborated in Speight (2000), Speight and Castella (2001) and Speight et al (2002). The basic procedure is illustrated in Figure 2, taking generation of list of species predicted to occur on a site in Haute-Savoie as an example. The species coded into the database are first filtered using macrohabitat/species association data for the macrohabitats (habitats sensu CORINE/Habitats Directive) observed on-site, so that the species associated with macrohabitats not represented on-site are excluded, and then filtered a second time so that species not known from Haute-Savoie are excluded. Once the list of species predicted to occur on a site has been generated it may then be compared with the list of species observed on that site. In the present report the objective of comparison was to gauge performance levels of the various components of each site, in respect of the ecosystem biodiversity maintenance function (BDMF). The species is taken as the unit of biodiversity and biodiversity maintenance is taken to be maximal when observed and predicted species lists co-incide.

Comparison between predicted and observed lists of species was first conducted at Macrohabitat level, to identify any habitats underperforming in comparison with other habitats present, or in comparison with specified target levels. This phase of the procedure is shown diagrammatically in Figure 3. Because there is no absolute measure of BDMF performance, standard performance measures are shown in Figure 3: if less than 50% of the species expected (i.e. predicted) for a habitat are observed it is regarded as underperforming; if 50-74% are observed its BDMF performance is regarded as reasonable and if 75% or more are observed its BDMF performance is regarded as good/very good. This simple system of BDMF measures was employed in categorising the habitats and microhabitats considered in the present text.

Habitats identified as underperforming were then investigated further, to establish which parts of them (i.e. which microhabitats) could be identified as performing least well. The procedure conducted with the database at microhabitat level is essentially the same as that conducted at macrohabitat level , as indicated by Figure 4, though in considering the results more attention is given to how badly microhabitats are performing, in comparison with one another. Finally, for certain microhabitats identified as underperforming, the traits balance of the predicted and observed faunas was considered, as shown in Figure 5. At this level the comparative performance of different traits was again given particular consideration.

Figure 2: diagrammatic representation of the process of generating a list of the species predicted to occur on a site in Haute-Savoie. The on-site habitats are used to filter out species in the database known only from other habitats and the Haute-Savoie species list is then used to filter-out species not known from Haute-Savoie.

Figure 3: diagrammatic representation of the use of the predicted and observed lists of species for a site, in identification of habitats under-performing in respect of the biodiversity maintenance function (BDMF). Comparison between the predicted and observed lists of species for a habitat demonstrates the percentage of the expected species found. Representation of 50% or more of the expected species is taken as reasonable. A habitat for which less than 50% of the expected species are observed is taken to be under-performing and requiring further investigation.

Figure 4: diagrammatic representation of the use of predicted and observed species lists for a habitat, here called "habitat 1", in identification of microhabitats under-performing in respect of the biodiversity maintenance function.

Figure 5: diagrammatic representation of the use of predicted and observed species lists in identification of traits poorly represented in the fauna of a microhabitat, shown as "microhabitat 1".

3. Results

The results are presented at site level and habitat level. No attempt has been made to consider the individual sample stations or sub-sites in comparison with one another, since the objective is to engender recommendations for management at site level that would accommodate the needs of the habitats observed on each site, wherever on-site those habitats might be located.

3.1.Habitat Survey

The habitats observed on each site were as follows:

Anterne A1: calcareous, montane/subalpine, unimproved grassland (Caricion ferrugineae) with flushes (Caricion davallianae), CORINE 36.41, 36.51, 38.3: sub-site Collet d'Anterne/sub-site Anterne. A2: alpine heath (Rhododendron/Vaccinium) with flushes, CORINE 31.4: sub-site Collet d'Anterne A3: montane/subalpine tall herb communities (Adenostylion), CORINE 37.8: sub-site Collet d'Anterne/sub-site Anterne. A4: alpine Alnus viridis scrub with open, grassy areas, CORINE 31.611: sub-site Anterne.

Carlaveyron C1: acidophilous, alpine, unimproved grassland (Caricion curvulae), CORINE 36.34: sub-site Caricion C2: alpine heath (with Azalea/Vaccinium: "landine"), CORINE 31.4: sub-site Caricion/sub-site Gradient

Passy P1: calcareous, alpine, unimproved grassland (Seslerion), CORINE 36.4: sub-site Seslerion. P2: acidophilous, alpine, unimproved grassland (Nardion strictii)/alpine heath (Loiseleurion) mosaic, CORINE 36.31/ CORINE 31.4: sub-site Azalées. P3: calcareous moraine and scree: sub-site Seslerion/subsite Azalées.

3.2. The Syrphidae collected by the Malaise trapping programme The number of specimens of each syrphid species collected by Malaise trap on the three sites is shown in Table 2. The Malaise trap samples collected a total of 979 individuals, belonging to 59 species - approximately 20% of the Haute-Savoie syrphid fauna. All of the species collected were already known to occur in Haute-Savoie.

Species Anterne Carlaveyron Passy Arctophila bombiforme (Fallen), 1810 3 Baccha elongata (Fabricius), 1775 1 1 Cheilosia derasa Loew, 1857 5 Cheilosia grisella Becker, 1894 1 1 1 Cheilosia impudens Becker, 1894 1 Cheilosia melanura Becker, 1894 1 Cheilosia montana Egger, 1860 1 Cheilosia nivalis Becker, 1894 1 4 Cheilosia rhynchops Egger, 1860 2 Cheilosia scutellata (Fallen), 1817 1 Cheilosia vangaveri Timon-David, 1937 1 1 Cheilosia vicina (Zetterstedt), 1849 7 Chrysotoxum fasciatum (Muller), 1764 4 1 Chrysotoxum fasciolatum (de Geer), 1776 1 Chrysotoxum festivum (L.), 1758 1 Criorhina berberina (Fabricius), 1805 3 1 Dasysyrphus pinastri (DeGeer), 1776 sensu Doczkal, 1996 2 Epistrophella euchroma (Kowarz), 1885 1 Episyrphus balteatus (DeGeer), 1776 51 18 32 Eristalis pertinax (Scopoli), 1763 1 Eristalis similis (Fallen), 1817 23 1 Eristalis tenax (L.), 1758 4 1 3 Eupeodes corollae (Fabricius), 1794 25 17 55 Eupeodes latifasciatus (Macquart), 1829 1 Eupeodes luniger (Meigen), 1822 8 17 12 Eupeodes nielseni (Dusek & Laska), 1976 1 Eupeodes nitens (Zetterstedt), 1843 2 2 Lapposyrphus lapponicus (Zetterstedt), 1838 1 1 1 Melanostoma dubium (Zetterstedt), 1838 27 12 43 Melanostoma mellinum (L.), 1758 14 10 70 Melanostoma scalare (Fabricius), 1794 2 Meligramma cincta (Fallen), 1817 1 9 Meliscaeva auricollis (Meigen), 1822 2 3 Merodon rufus Meigen, 1838 1 Paragus haemorrhous Meigen, 1822 1 Paragus punctulatus Zetterstedt, 1838 3 Parasyrphus lineolus (Zetterstedt), 1843 1 Parasyrphus macularis (Zetterstedt), 1843 2 Parasyrphus vittiger (Zetterstedt), 1843 1 Pipiza noctiluca L, 1758 1 3 Platycheirus albimanus (Fabricius), 1781 3 2 6 Platycheirus angustatus (Zetterstedt), 1843 1 Platycheirus angustipes Goeldlin, 1974 20 Platycheirus clypeatus (Meigen), 1822 3 Platycheirus manicatus (Meigen), 1822 1 1 Platycheirus melanopsis Loew, 1856 2 1 Platycheirus nielseni Vockeroth, 1990 1 Platycheirus splendidus Rotheray, 1998 1 Scaeva pyrastri (L.), 1758 2 15 11 Scaeva selenitica (Meigen), 1822 5 4 24 Sphaerophoria fatarum Goeldlin, 1989 1 4 11 Sphaerophoria interrupta (Fabricius), 1805 6 1 58 Sphaerophoria scripta (L.), 1758 61 23 144 Syrphocheilosia claviventris (Strobl), 1909 1 1 Syrphus ribesii (L.), 1758 11 3 2 Syrphus torvus Osten-Sacken, 1875 1 2 Volucella bombylans (L.), 1758 6 3 Xanthandrus comtus (Harris), 1780 1 5 Xylota jakutorum Bagatshanova, 1980 1 total number of species collected 44 26 35 total number of individuals collected 319 144 516

Table 2: numbers of individuals of each syrphid species collected by Malaise trap on the three sites sampled.

As shown in Table 3, none of the species collected during this Malaise trapping campaign are recognised as threatened at European level, or in France (Speight et al, 2004). A few of them are endemic to Europe, but widely distributed in the continent. None of them would be regarded as European endemics with a restricted range.

Anterne Carlaveyron Passy threatened at European level 0 0 0 threatened in France 0 0 0 restricted European endemic 0 0 0 European endemic 6 3 4

Table 3: the number of observed species on each site in different range and status categories restricted European endemic = a species endemic to Europe and found in a restricted part of Europe, e.g. the Alps; European endemic = a species endemic to Europe, but widely distributed in Europe

3.3.Comparison between predicted and observed species Comparison between predicted and observed site faunas produces three groups of species: Haute-Savoie species predicted but not observed; Haute-Savoie species predicted and observed; Haute-Savoie species observed but not predicted. For the three sites sampled, the number of species in each of these groups is shown in Table 4. This table demonstrates that, overall, less than 50% of the predicted species were observed on each of the sites and the observed species include a high proportion of unpredicted species.

Haute-Savoie species category Anterne Carlaveyron Passy predicted not observed 49 35 43 predicted and observed 23 16 22 % predicted observed 32 31 34 unpredicted 21 10 13 % unpredicted 48 39 37

Table 4: the number of Haute-Savoie species in different occurrence categories on the three sites surveyed.

In Figure 6 the proportion of migrant species in the fauna of each site is shown, comparing the predicted fauna with the observed fauna. The term "migrant" is used here in the sense of Aubert et al (1974) and Gatter and Schmid (1990), to denote highly mobile species known to travel great distances as adults. It is apparent that, at all three sites surveyed, migrants comprise a minority of the predicted site fauna but, in the case of Carlaveyron and Passy, the majority of the observed fauna. Since the observed migrants may originate elsewhere and are none of them likely to survive on these sites through the winter, the implication would be that on the Carlaveyron and Passy sites "indigenous" species (i.e. species resident on the site throughout the year) are only a minority component of the fauna, contrasting strongly with the predicted situation.

In Figure 7 the proportion of the Haute Savoie fauna with one or more generations per annum is shown for different grassland types. The species predicted to occur in

lowland, montane and alpine unimproved grassland are contrasted with one another, showing that, in lowland grassland, species with more than one generation per annum predominate, whereas in alpine grassland univoltine species predominate. Also shown is the component of the observed fauna of the sites surveyed in 2004 (using the combined list from all three sites) that would be predicted to occur in alpine grassland. This figure demonstrates that in the observed fauna of these sites there is, overall, a higher proportion of divoltine and polyvoltine species than would be expected, in the component of the fauna known to be associated with unimproved, alpine grassland. Figure 8 shows the proportional representation of univoltine, divoltine and polyvoltine species among the species missing from the sites surveyed, but predicted to occur with the unimproved, alpine grassland there. It demonstrates the very high representation of univoltine species among the alpine grassland species not observed on the sites

predicted observed

100 90 80 70 60 50 40 30 20 10 0 Anterne Passy Carlaveyron

Figure 6: migrant species as a proportion of the predicted and observed fauna of each site.

1 generation 2 generations >2 generations

100 90 80 70 60 50 40 30 20 10 0 lowland, predicted montane, alpine, predicted alpine, observed predicted

Figure 7: proportional representation of species with different numbers of generations per annum in the predicted fauna of grasslands at different altitudes in Haute-Savoie, and in the observed fauna of the Haute-Savoie sites surveyed.

100 90 80 70 60 50 40 30 20 10 0 1 generation 2 generations >2 generations

Figure 8: voltinism in the predicted, unimproved, alpine grassland species absent from the combined list of species observed on the sites surveyed.

3.3.1.Predicted and observed species of habitats represented on the Anterne site

The proportion of predicted species observed for each habitat represented on the Anterne site is shown in Table 5. This table shows that the species predicted for the montane/subalpine grassland and heath present on the site are less well-represented than the species predicted to occur with the tall-herb and alpine scrub habitats, with alpine scrub the only habitat present for which more than 50% of the predicted species were observed. These figures include known migrants that can occur in the habitats present.

Anterne Habitats % predicted spp observed A1 36 A2 39 A3 44 A4 60

Table 5: proportion of predicted species observed for each habitat represented on the Anterne site, migrants included. A1: calcareous, unimproved, montane/subalpine grassland (Caricion ferrugineae) with flushes (Caricion davallianae); A2: alpine heath (Rhododendron/Vaccinium) with flushes; A3: montane/subalpine tall herb communities (Adenostylion); A4: alpine Alnus viridis scrub with open, grassy areas

Figure 9 shows the proportion of predicted species observed both with and without migrant species included. The most noticeable difference is the decrease in the proportion of predicted species observed for montane/subalpine grassland at Anterne, when migrants are excluded.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 Caric ion Rhododendron / Adenostylion Alnus viridis ferruginae & C. Vaccinium davallianae

Figure 9: proportion of predicted species observed for each habitat represented on the Anterne site, with migrants included or excluded.

Figure 10 looks more closely at the species predicted to occur in montane/subalpine grassland on the Anterne site, by considering species representation at the microhabitat level. This figure shows that in this habitat at Anterne inclusion or exclusion of migrant species does impact on the representation of syrphids whose larvae live on herbs but has no impact on species with larvae that live in the tissues of herb layer plants. At the same time, this figure indicates that species with larvae living in the tissues of herb-layer plants in this habitat are very poorly represented on the

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 tall herbs low herbs in herbs sodden grass root ground zone

Figure 10: Anterne, habitat A1 (calcareous, unimproved, montane/subalpine grassland (Caricion ferrugineae) with flushes (Caricion davallianae)), representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded.

Anterne site, as are species whose would be predicted to occur in water-saturated ground (i.e. the area of the Caricion davallianae flush). Figure 11 shows similar information for alpine/subalpine heath at Anterne. For alpine/subalpine heath the same result is achieved whether migrants are included or excluded, because there are

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 low tall herbs low herbs in herbs sodden grass root shrubs ground zone

Figure 11: Anterne, habitat A2 (alpine heath (Rhododendron/Vaccinium) with flushes), representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded. no migrant species predicted to occur in this habitat. The strong contrast between representation of species with larvae living on and in herb layer plants is exhibited for this habitat as for montane/subalpine grassland. Because subalpine/alpine heath characteristically incorporates dwarf shrubs the representation of species associated with this microhabitat is also shown on this figure, but the predicted species were not observed at Anterne.

Representation of montane/subalpine tall-herb community species associated with different larval microhabitats at Anterne is shown in Figure 12. In this instance species with larvae living within the tissues of herbs, or living free within the grass- root zone, are well-represented, whereas those whose larvae live on herbs are not.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 on tall herbs on low herbs in herbs grass root zone

Figure 12: Anterne, habitat A3 (montane/subalpine tall herb communities (Adenostylion)), representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded.

Representation of alpine Alnus viridis scrub species associated with different larval microhabitats at Anterne is shown in Figure 13. Of the four habitats represented at Anterne A.viridis scrub was the only one for which representation of predicted species

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 shrubs on tall herbs on low herbs in herbs grass root zone

Figure 13: Anterne, habitat A4 (alpine Alnus viridis scrub with open, grassy areas), representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded. reached the 50% level (see Figure 9). This is reflected in the representation of species associated with different microhabitats, although non-migrant species observed, that are associated with shrubs, are represented by less than 50% of the expected species.

The Anterne habitats with the poorest represented faunas (Figure 9) were montane/subalpine grassland (A1) and alpine heath (A2), and in both of these habitats the species with larvae living in the tissues of herb-layer plants were particularly poorly represented.

Some appreciation of the possible role played by each habitat in biodiversity maintenance on the Anterne site can be gained from Table 6, which shows that the grassland may act more as a "reservoir" of species that can occur on other habitats present, but that each of the other habitats tend to support species that are not shared. The part played by the Carex davallianae flush is obscured in this table, since it is regarded as situated partly within the heath and partly within the grassland, but without an identity of its own. The two syrphids Platycheirus clypeatus and P.angustipes would not be predicted to occur on the Anterne site in the absence of this flush, so it, also, can be said to play a specific role in maintenance of the observed syrphid biodiversity of the site.

Non-migrant species habitat association predicted no. habs predicted and observed A1 A2 A3 A4 predicted Cheilosia derasa 1 1 Cheilosia grisella 1 1 2 Cheilosia nivalis 1 1 Cheilosia rhynchops 1 1 Cheilosia vicina 1 1 2 Melanostoma dubium 1 1 2 Melanostoma scalare 1 1 1 3 Platycheirus albimanus 1 1 2 Platycheirus angustipes 1 1 2 Platycheirus clypeatus 1 1 Platycheirus splendidus 1 1 Sphaerophoria fatarum 1 1 2 Sphaerophoria interrupta 1 1 2 Syrphus torvus 1 1 Volucella bombylans 1 1 2

Table 6: non-migrant species predicted to occur on the Anterne site and observed there, showing with which and in how many habitat(s) they would be predicted to occur.

3.3.2. Predicted and observed species of habitats represented on the Carlaveyron site

There is considerable overlap in the Haute-Savoie species predicted to occur in the two habitats present on the Carlaveyron site, namely unimproved, alpine acidophilous grassland (Caricion curvulae) and alpine heath (with Azalea/Vaccinium: "landine"). Moreover, these habitats occur as a mosaic over much of the area. To simplify presentation these habitats have thus been considered together, so the entire site is treated at the same time. As shown in Table 4 less than 50% of the species predicted to occur on the Carlaveyron site were observed there. The corresponding information for selected microhabitats is shown in Figure 14, which shows that a similar situation to that exhibited by the grassland on the Anterne site exists at Carlaveyron. Namely, a very low proportion of the predicted species with larvae living in plant tissues were observed. But Figure 14 also shows that at Carlaveyron migrant species play a more prominent role in determining the character of the site fauna.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 shrubs on tall herbs on low herbs in herbs grass root zone

Figure 14: Carlaveyron, habitats C1/C2, representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded.

3.3.3. Predicted and observed species of habitats represented on the Passy site

The proportion of predicted species observed for each habitat represented on the Passy site is shown in Figure 15. In the case of each habitat less than 50% of the predicted species were observed. None of the species predicted for rock and scree were observed.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 Seslerion w ith Nardion strictii and calcareous moraine temporary streams Loiseleurion and scree

Figure 15: proportion of predicted species observed for each habitat represented on the Passy site, with migrants included or excluded.

Figures 16 and 17 show, for the same microhabitats as figured for the Anterne and Carlaveyron sites, the representation of predicted species in the alpine grassland and heath at Passy. In one feature, namely the poor representation of predicted species

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 on tall herbs on low herbs in herbs grass root zone

Figure 16: Passy, habitat P1 (unimproved, calcareous grassland (Seslerion)) representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded. with larvae living in tissues of herbs, the Passy results are similar to those obtained for grassland and heath habitats at the other sites. The Passy results also resemble those from Carlaveyron in the significant contribution made to the observed site fauna by migrant species. Table 7 gives an indication of the contribution made to syrphid biodiversity on the site by the two main habitats represented, showing that nearly all the non-migrant species observed and predicted for the calcareous grassland there would also be predicted to occur in the acid grassland/heath on the site.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 low shrubs on tall herbs on low herbs in herbs grass root zone

Figure 17: Passy, habitat P2 (unimproved, acidophilous, alpine grassland (Nardion strictii)/alpine heath (Loiseleurion) mosaic), representation on-site of predicted species associated with selected larval microhabitats, with migrants included or excluded.

Non-migrant species hab.assoc.pred. no. habs predicted and observed P1 P2 predicted Cheilosia grisella 1 1 Cheilosia melanura 1 1 2 Cheilosia nivalis 1 1 Cheilosia vangaveri 1 1 2 Chrysotoxum fasciatum 1 1 Melanostoma dubium 1 1 2 Paragus haemorrhous 1 1 Paragus punctulatus 1 1 Platycheirus albimanus 1 1 Platycheirus melanopsis 1 1 Sphaerophoria fatarum 1 1 2 Sphaerophoria interrupta 1 1 2 Syrphocheilosia claviventris 1 1 2 Volucella bombylans 1 1 2

Table 7: non-migrant species predicted to occur on the Passy site and observed there, showing with which and in how many habitat(s) they would be predicted to occur. hab.assoc.pred.= habitat association predicted

3.4. Species observed but unpredicted

As shown in Table 4, the observed syrphid fauna of each of the three sites sampled contained a high proportion of species whose presence would not be predicted on the basis of the habitats present on-site. Among these unpredicted species are a number of recognised migrants, that could have reached the Malaise traps from some quite distant origin, to judge from the work carried out by Aubert et al (1974) on one mountain ridge (Col de Bretolet) between Haute-Savoie and Switzerland. The number of migrant species represented among the unpredicted species collected at each of the three sites sampled in 2004 is shown in Table 8.

site unpredicted species observed all migrant species other species Anterne 21 6 15 Carlaveyron 10 4 6 Passy 13 8 5

Table 8: migrant/non-migrant status of unpredicted species collected on each site

In the case of all three sites one habitat not present on-site but covering very extensive areas in the vicinity, at lower altitudes, is Picea forest. Given the general mobility of adult syrphids it is apposite to consider whether non-migrant, unpredicted species collected in the traps might be derived from those Picea forests. It can be seen from Table 9 that many of these species would be predicted to occur in Picea forest.

site non-migrant,unpredicted species observed all Picea forest species other species Anterne 15 12 3 Carlaveyron 6 5 1 Passy 5 2 3

Table 9: unpredicted species collected, showing the number from each site associated with Picea forest

Another forest type that might be expected to occur in the vicinity of the sites, but also at lower altitude, is humid Fagus forest. But Fagus forest occurs in this way only in the vicinity of the Passy site, the Fagus zone being occupied below the Anterne and Carlaveyron sites by Picea forest. Table 10 shows that two of the remaining unpredicted species collected at Passy would be predicted to occur in association with Fagus forest, but that the solitary remaining unexplained species collected at Carlaveyron would not. One of the otherwise unexplained species from Anterne would be predicted to occur with Fagus forest. But there are taxonomic problems associated with this taxon (see below) and the significance of its occurrence at Anterne cannot easily be decided.

site unpredicted species observed all Fagus forest species other species Anterne 3 (1) (2) Carlaveyron 1 0 1 Passy 3 2 1

Table 10: number of Fagus forest syrphid species among the unpredicted species collected from the three sites, after migrants and Picea forest syrphids have been removed.

The residuum of unexplained species

The unpredicted species whose presence in the samples remains unexplained after exclusion of migrants, Picea forest species and Fagus forest species, are as follows:

Anterne: Cheilosia montana, Eupeodes nielseni, (E.nitens) Carlaveyron: Cheilosia grisella Passy: Platycheirus angustatus

Cheilosia grisella C.grisella is a species known from calcareous, unimproved, alpine grassland, but not from acidophilous alpine grassland. Its occurrence at the Carlaveyron site could be due to its presence in more calcareous grassland somewhere in the vicinity.

Cheilosia montana This species occurs in calcareous, alpine, unimproved grassland rather than montane grassland. Its occurrence at the Anterne site may indicate its presence in the Seslerion grassland that occurs in the vicinity, but which was not sampled.

Eupeodes nielseni E.nielseni is an insect of humid pine forests, including P.cembra and P.mugo in the Alps. Its occurrence at the Anterne site would be explicable if there were stands of either of these trees in the vicinity, but in their absence, and in the absence of P.sylvestris, no obvious explanation can be offered for the presence of this species.

Eupeodes nitens E,nitens is unusual in that it is recognised as occurring in association with both humid Fagus forest and acidophilous, unimproved, alpine grassland. It is not, however, known to be associated with calcareous, unimproved grassland, whether montane or alpine. Of all the unexplained species occurrences engendered by the 2004 data the presence of E.nitens on the Anterne site is perhaps the most interesting, not least because the specimens collected evidence differences from typical material of E.nitens that suggest some other taxon might be involved. Eupeodes is a taxonomically difficult genus in Europe, with various unresolved problems, and it would not be surprising if the (Fagus-associated) E.nitens from lower altitudes proved to be a different species from the one occurring in alpine grassland. Unfortunately, the Anterne site yielded few specimens of "E.nitens". A more substantial series of specimens would be required to resolve the taxonomic issues involved.

Platycheirus angustatus P.angustatus is a low-altitude, wetland species that may also occur in humid grassland. It is not known to occur above the Fagus belt in the Alps. The presence of a female of this species among the material from Passy thus has no obvious explanation and on this site the species could only be categorised as a vagrant from elsewhere.

4. Discussion

The overall representation of expected (i.e. predicted) species in the observed syrphid fauna of each of these three sites is poor - in site evaluation terms at a level that would not generally identify any of them as sites of national importance, let alone international importance. When representation of expected species is examined more closely, at the level of individual habitats on each site, greater heterogeneity is revealed, although grassland habitats consistently show the most poorly developed faunas on each site. When the representation of expected grassland species is examined at microhabitat level it is clear that species whose larvae live in the tissues of herb-layer plants are particularly poorly represented, in all types of grassland and on all sites, a situation reaching its extreme on the Carlaveyron site, where less than 10% of the expected species in this group were observed. The simplest explanation for such a dearth of species would be an unusually impoverished ground flora i.e. a low diversity of flowering plants in the herb layer.

The under-representation of syrphids with plant-feeding larvae in this data set requires further consideration. It is very unlikely to be due to the field campaign being conducted at an inappropriate time of the year, since the predicted flight periods for the species expected to occur fall within the sampling period. It is unlikely to be due to the traps failing to sample a wide enough area, since species from habitats some distance from the traps (e.g. Picea forest) were collected, along with those predicted to occur on the sites sampled. It would be helpful if comparable data sets existed for other subalpine/alpine sites, and from both before and after the exceptional summer of 2003. But, unfortunately, there are no directly comparable data sets. In the study of Aubert et al (1976) a solitary flight interception trap, very similar to a Malaise trap, was operated in alpine grassland at exactly the same location in Col de Bretolet (i.e. it was installed on the same few square metres of ground each year) for a total of 844 trap-days, over a twelve-year period (1962-73). In total, the number of trap days involved in the present study was 900, but all the data are derived from the same year. The Aubert et al (1976) study produced 75% of the species that would be predicted to occur in unimproved alpine grassland in Haute-Savoie, including 63% of the predicted plant-feeding species. Although the Col de Bretolet data provide no basis for concluding that, as coded at present, the database over-predicts plant-feeding species of alpine grassland, neither can the Col de Bretolet data be said to provide any clear indication that the database does not over-predict for such species. The only other data available were gathered using Malaise traps on the Pormenaz site in 2003. But the restricted nature of the Pormenaz data and the fact that survey was carried out during the exceptional summer of 2003 limit data interpretation (see Appendix 1). All that can be said is that species feeding in the tissues of herb layer plants were at least as under-represented in the Pormenaz fauna as among the species observed on the sites surveyed in 2004.

If, as coded at present, the database over-predicts all components of the syrphid fauna of alpine habitats, and this over-prediction is particularly pronounced for plant- feeding species, it would not be easy to distinguish these effects from the effect of sites being in poor condition, particularly in respect of their ground flora. But whether or no the ground flora of alpine/subalpine grasslands is poorly represented on these sites is not in question here - that issue can be decided botanically, by direct examination of the species diversity of the herb-layer plants present. The issue here is

whether the diversity of herb-layer plants on these sites is responsible for the observed under-representation of syrphid species associated with herb-layer plants, or whether this should be interpreted as an artifact of the sampling programme or the methods used to interpret the results.

The data set from the three sites sampled can, itself, be used to investigate this question to some extent, since more than one site and a number of different subalpine/alpine habitats are involved. Predicted species with plant-feeding larvae are not universally under-represented in the habitats represented on these sites. On the Anterne site the tall-herb communities (Adenostylion) exhibited a 60% representation of expected plant-feeding species. Similarly, there is not a universally poor representation of the syrphid fauna of all sub-alpine/alpine habitats on these sites. The alpine scrub habitat, represented by Alnus viridis at Anterne, showed an overall representation of the species predicted to occur with it in excess of 50%. Further, at microhabitat level, the fauna of various habitats sampled on these sites would be categorised as good, or even very good. These points, taken together with the observation that the ground flora of the sites surveyed has apparently been much damaged by long-term sheep grazing (Denis Jordan, pers.comm.) suggest it is reasonable to conclude that the apparent under-representation of syrphids feeding in plant tissues on these sites is real, rather than an artifact. If so, it is both interesting, and of some concern, that the present fauna is still exhibiting such a pronounced effect, since grazing pressure has evidently been much reduced, at least on the Anterne and Passy sites, for much of the last 50 years.

At the Anterne site, despite a reasonable representation of the expected species associated with some microhabitats in the habitats present, there were no species observed that might be regarded as threatened in France, or restricted European endemics. Nonetheless, it is apparent that the habitats represented each contribute to the syrphid biodiversity of the site, in supporting species that would not be expected to occur in the other habitats present. By contrast, the Carlaveyron site has both a more restricted range of habitats represented and considerable overlap between the faunas of the two habitats present. Its observed fauna resembled that of the Anterne site in including no threatened species or restricted European endemics. The more alpine character of the Carlaveyron site is reflected in the presence there of Cheilosia vangaveri and Syrphocheilosia claviventris, species not observed at Anterne. The same is true of Passy, where both of the latter species were observed, accompanied by another primarily alpine syrphid, Paragus punctulatus. Passy resembles the other two sites surveyed, in lacking either threatened species or restricted European endemics among the syrphids observed. Interestingly, the syrphid data suggest that the calcareous grassland at Passy adds little to the fauna of the site, since the observed species predicted to occur in that habitat would be predicted to also occur in the acid grassland/heath present, whereas a number of the observed species predicted to occur in the acid grassland/heath would not be predicted to occur in the calcareous grassland.

Since the predictions made for the fauna of the three sites surveyed were based on the Haute-Savoie species list of Syrphidae, i.e. the Département in which these sites are located, and assuming the same results would not have been obtained everywhere in Haute-Savoie in 2004, the working hypothesis adopted to explain the absence of predicted species from those sites would be that the absent species have been lost

from them, rather than that they were never there. Even if a survey programme involving more traps or more years of sampling might arguably detect some of the missing species, there is no basis for arguing that the marked under-representation of predicted species whose larvae feed in the tissues of herb-layer plants might differentially be reduced in this way. Essentially, this points to a conclusion that the syrphid fauna of these sites has been reduced by chronic heavy-grazing by livestock in the past - in the case of Carlaveyron an unacceptable intensity of grazing may be still continuing - and has not subsequently recovered its potential diversity, unless some external factor can be identified that might also produce the same effects.

The absence of comparative data from either other sub-alpine/alpine sites in Haute- Savoie, or further afield in the Alps, during 2004, means that some uncertainty must remain as to whether the results from the sites sampled were influenced by the exceptional weather conditions to which the Alps were subject in the summer of 2003 (Chuine et al, 2004; Luterbacher et al, 2004). It would seem surprising if those exceptional conditions had no impact on the fauna of sub-alpine/alpine habitats in Haute-Savoie, and many of the syrphids involved are univoltine, i.e. the adults available for survey in 2004 underwent their larval development during 2003. This would also be true for divoltine species collected in the traps up to (and including) July, 2004. The higher than expected proportion of polyvoltine alpine grassland species in the combined list for these sites, as shown in Figure 7, may be indicative of a regional effect as much as an effect local to the three sites surveyed. Certainly, it reflects an absence of many of the univoltine species predicted to occur on these sites, as shown in Figure 8. The strong representation of known migrants among the observed portion of the predicted fauna of these sites may also have a bearing on this issue. While collected on these sites as adults, and potentially capable of completing at least one generation there during the summer months, these migrant species, all of which are polyvoltine, are unlikely to have survived the winter in subalpine/subalpine habitats and are much more likely to have arrived on the sites surveyed from lower- altitude habitats where they developed. So, not only are univoltine species (none of which are migrants) under-represented in the observed fauna of these sites but their observed fauna has a high proportion of highly mobile species potentially originating at lower altitudes.

The generally low numbers of individuals observed in the trap samples, belonging to non-migrant species predicted to occur in the habitats surveyed, may well reflect the extreme environmental conditions of 2003. But it is less easy to see how those conditions might lead to a comparative under-representation of species whose larvae feed in the tissues of herb-layer plants, unless the summer of 2003 led to loss of herb- layer plant species on the sites surveyed and a consequent loss of the plant-feeding syrphids dependent upon them. Whether such a reduction in herb-layer plant diversity occurred on these sites due to the extreme conditions pertaining in the summer of 2003 is beyond the scope of this report, but is presumably open to investigation by botanical survey. All that can be said here is that the present constitution of the syrphid fauna of these three sites suggests that the management requirement there is not so much biodiversity maintenance as biodiversity restoration. If it is established that the diversity of the ground flora was to a significant extent adversely affected by the summer of 2003, it might reasonably be expected to recover (assuming there will not soon be another summer like that of 2003, which may be an unrealistic assumption: see Schär et al, 2004) from in-situ seed stock/propagules. However, this

might have more serious implications for the fauna of syrphids and other insects, since these organisms have no resting stage that can survive adverse conditions, from which to repopulate a site once favourable conditions return. Since the summer of 2003 can be expected to have adversely affected extensive areas of the Alps, not just the sites surveyed, repopulation of these sites by syrphids lost as a consequence of the summer of 2003 might take a considerable length of time. If, on the other hand, the observed impoverishment of the syrphid fauna of these sites is a consequence of long- term heavy grazing in the past, it is already clear that repopulation is taking a long time. It is also unlikely that this situation will change rapidly given that the ground flora apparently remains impoverished.

Survey of the syrphids of these three sites during 2004 had the twin objectives of establishing base-line inventory data for the syrphids and providing management recommendations based on the survey results. Achievement of both of these objectives may have been adversely influenced by the extreme weather conditions to which this part of the Alps was subject during the preceding summer. To understand whether the summer of 2003 or long-term heavy grazing of the sites surveyed was primarily responsible for the reduced syrphid faunas observed might require repeat survey of these sites in a few years time, plus survey of equivalent sites unaffected by heavy grazing. But, whatever may be the cause of the reduced fauna observed, the principal management issue that can be identified is what can, or should, be done to ameliorate the situation, rather than how to maintain the existing fauna. If data become available that demonstrate the reduced fauna observed is probably due to the summer conditions prevailing in 2003 there would seem to be little that could be achieved by site management to rectify the situation - especially if it has to be accepted that those conditions were a manifestation of what has become known as "climatic warming". But, if there are grounds for concluding that chronic heavy grazing of these sites by livestock in the past is the primary reason for their reduced fauna now, certain management options may be worthy of consideration. If biodiversity maintenance, rather than biodiversity restoration, is taken to be the primary objective of management, probably the most important consideration is to ensure that grazing by livestock is not re-introduced to either Anterne or Passy and that grazing by wild ungulates there does not significantly increase. Whether site condition can be maintained at Carlaveyron, in the circumstance that existing grazing pressures by livestock continue there, is a moot point.

In the case of restoration of the Anterne site, the character of its fauna is such that it would seem a valid management option to regard the site as montane, rather than subalpine/alpine. If so, a progressive expansion of tree cover might be anticipated if current grazing intensities are maintained, unless grazing by wild ungulates is currently inhibiting regeneration by woody species. A study of wild ungulate grazing pressure on this site might prove revealing, since even low levels of such grazing can apparently inhibit flowering/seeding by herb layer plants (Hülber et al, 2004) and might conceivably be retarding recovery of the ground flora and its associated fauna, although livestock grazing no longer occurs. The number of Picea forest syrphid species already reaching this site suggests that an increase in tree cover would be accompanied by an increase in on-site biodiversity of forest syrphid species. In the event that existing grazing levels by wild ungulates are deemed irrelevant to recovery of the ground flora it has to be presumed that the failure of recovery of the herb flora, to an extent that enables it to support more than a few of its associated syrphid

species, is indicative of either a lack of local sources of resupply or a lack of landscape permeability, or both. This raises the question of whether it is worthwhile, or feasible, to carry out deliberate re-introduction to the Anterne site, of herb species recognised as typical in Haute-Savoie for the grassland habitat present at Anterne, but currently missing there. While regarded as "sacrilegious" or as "gardening, not management", by some schools of conservation biology, re-introduction has to be recognised as a potentially useful tool in site restoration. Selective re-introduction of characteristic tall herb species to the Anterne site might be expected to evoke a response from nectar-feeding syrphids with predatory larvae (and other flower- feeding insects), even if not from syrphids with plant-feeding larvae, since the former would use the flowers of a wide range of nectar-bearing flowers, but the latter would require the particular plant(s) acting as hosts for their developmental stages. In the event that reintroduction is considered, it is perhaps worthy of mention that, whereas flower-visiting bees and wasps can use the flowers of leguminous plants, most other flower-visiting insects (including the vast majority of syrphid species) cannot and tend, instead, to use the flowers of plants with easily available nectar, such as composites and umbellifers.

The Carlaveyron site is still grazed by livestock, but its syrphid fauna is only marginally poorer than the syrphid fauna of the other two sites. Further, the data set from Carlaveyron is to an unknown extent incomplete, due to livestock damage to the traps. Even so, if heavy grazing in the past has to be recognised as probably the main cause of the reduced syrphid fauna observed at Anterne and Passy today it follows that, for biodiversity restoration at Carlaveyron, the first necessary step would be to reduce grazing pressure there. Until and unless that can be achieved, other site management might be expected to achieve little effect at Carlaveyron.

The Passy site exhibits a reasonable representation of predicted, predatory syrphid species associated with both tall and low-growing herbs, for both habitat types present there. This suggests that any restoration work might appropriately be focused on plant-feeding species, that are contrastingly poorly represented in both habitats. But the plant hosts of many alpine/subalpine syrphid species are uncertain. The observed fauna of the calcareous grassland at Passy is less well developed than that of the acid grassland. If re-introduction of herb species to the calcareous grassland at Anterne were attempted, perhaps a parallel attempt could be made at Passy, to compare effectiveness of the technique at the two sites. The potential requirements of the observed butterfly fauna of the site might usefully be taken into account in selection of plant species to re-introduce.

5. Conclusions

The small numbers of syrphid species collected during course of this study, and the small numbers of individuals collected of those species, gives cause for concern. However, the results presented here do not provide an adequate basis for extrapolation to the syrphid fauna of other sites, because there is no easy way of deciding between local and regional impacts using this data set. But it would be possible to establish whether certain other taxonomic groups exhibit similar tendencies to the Syrphidae on the sites surveyed by similar treatment of other components of the Malaise trap samples collected during the study. This issue requires wider consideration in relation to surveillance of invertebrate biodiversity in general, and is addressed in Appendix 2.

There are grounds for recognising that a progressive decrease in both abundance and diversity of the syrphids of alpine habitats in this part of the Alps has been occurring over the last 15 years (P.Goeldlin de Tiefenau, pers.comm.), probably mediated by climatic change. Any such process can only have been exacerbated by the extreme conditions of the summer of 2003 and would retard recovery of the subalpine/alpine fauna of sites damaged in the past by heavy grazing. Is that the explanation for the impoverished syrphid faunas of the sites surveyed in 2004? If so, perhaps a re-survey of the butterflies would now be timely, since there are butterfly data for these sites from 2002 (Comité Scientifique des Réserves Naturelles de Haute-Savoie, 2002). That survey identified limitations to the fauna of these sites similar to those identified by the syrphid study - absence of threatened species, absence of expected species, small numbers of individuals observed - limitations that might now be more pronounced as a consequence of the summer of 2003. But, assuming the summer of 2003 has not had such a marked effect, and the results of the syrphid study have otherwise been correctly interpreted here, it is probably of more concern that the syrphid fauna of the sites surveyed does not appear to have recovered from heavy grazing in the past. This would imply that there may have been more of a regional impact of past livestock grazing in the Arve Giffre Massif than might be anticipated. Although subalpine/alpine vegetation types attracting special protection measures under the provisions of the Habitats Directive are recognisable on the sites surveyed, it seems possible that their associated fauna is now to a significant extent lost, both on these sites and elsewhere. That, in turn, points to a need for more comparative studies to establish whether a wider diversity of taxomonic groups is exhibiting the same impoverished condition on these sites and whether other sites with a more intact fauna still exist.

Acknowledgements

The authors thank DIREN Rhône-Alpes, ASTERS (Conservatoire des Espaces Naturels de Haute-Savoie) and in particular Juliette Vodinh, Franck Horon, Bernard Bal and Denis Jordan, the Comité Scientifique des Réserves Naturelles of Haute- Savoie, the Préfecture of Haute-Savoie, Patrick Perret, Jean-José Richard-Pomet, Laurent Delomez, and all the nature reserve wardens who participated in installation and maintenance of the Malaise traps, Jessica Castella-Muller for her help in production of the French version of this report, Christiane Ilg and Amael Paillex for their help in Malaise trap installation and Jean-Marie Gourreau for permission to use some of the photographs of syrphids used in the French version of this report.

References

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Speight, M.C.D., Castella, E. & Obrdlik, P. (2000) Use of the Syrph the Net database 2000. In: Speight, M.C.D., Castella, E., Obrdlik, P. and Ball, S. (eds.) Syrph the Net, the database of European Syrphidae, vol.25, 99 pp., Syrph the Net publications, Dublin. Speight, M., Castella, E., Sarthou, J.-P. & Monteil, C. (eds.) (2004) Syrph the Net on CD, Issue 2. The database of European Syrphidae. ISSN 1649-1917. Syrph the Net Publications, Dublin. Speight, M.C.D. Good, J.A. & Castella, E. (2002) Predicting the changes in farm syrphid faunas that could be caused by changes in farm management regimes (Diptera: Syrphidae). Volucella, 6: 125-137.

Appendix 1: results obtained on the Pormenaz site in 2003

Three Malaise traps were installed on the Pormenaz site, to sample syrphids during the period 15 July - 31 August 2003. The extremely high temperatures reached in the Alps during the summer of 2003, coupled with the brevity of the sampling programme and the lack of sample data from earlier parts of the flight season, make the Pormenaz results difficult to interpret. Indeed, the climatic conditions in 2003 were such that the flight season for syrphids could have been well underway in May, at the altitude (1800m) of the Pormenaz site, long before the traps were operational. Despite these limitations, it is possible to subject the Pormenaz syrphid data to the same forms of scrutiny as the data from the sites surveyed in 2004. This exercise has been carried out here, simply to provide some form of direct comparison between the data sets.

The Pormenaz Malaise traps collected a total of 51 syrphids, belonging to 26 species (Table A1).

The habitats observed at the Pormenaz sites were as follows: PZ1: unimproved, acidophilous, alpine grassland PZ2: montane/subalpine heath with flushes PZ3: alpine scrub thickets of Alnus viridis with flushes and grassy, open areas

Using these habitats to engender a list of the species predicted to occur on the site (as described elsewhere in this report), comparison between predicted and observed species lists produces the result shown in Figure A1. This suggests that the alpine grassland fauna is the least well-represented component of the fauna of the site, and that, even with the restricted data available, the alpine scrub fauna is reasonably represented. At microhabitat level, representation of predicted species is as in Figure A2, taking all the habitats together. One similarity between the Pormenaz results and the results from the sites surveyed in 2004 is the extremely poor representation of species with larvae feeding in the tissues of herb layer plants. These species would also seem to be one of the least well-represented microhabitat faunas on the site. The observed Pormenaz syrphid fauna of 2003 thus shows similarities with the syrphid faunas of the sites surveyed in 2004. But whether these similarities are caused primarily by the extreme summer conditions of 2003, by the incomplete data set or by features intrinsic to the Pormenaz site is not readily - if at all - accessible to investigation. Interestingly, 12 of the 26 species observed at Pormenaz would not be predicted to occur there, on the basis of the habitats present. In this high proportion of unpredicted species the observed Pormenaz fauna also resembles the fauna of the sites surveyed in 2004. Of those 12 species 5 are recognised migrants, but the others would be indicative of a mosaic of montane mixed scrub forest and rather humid, grassy open areas subject to grazing by cows - which could presumably occur down-slope of the Pormenaz site.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 unimproved, montane/subalpine Alnus viridis scrubs acidophilous, alpine heath w ith flushes w ith flushes and grassland grassy open areas

Figure A1: representation of species predicted for each habitat category observed on the Pormenaz site.

migrants included migrants excluded

100 90 80 70 60 50 40 30 20 10 0 shrubs on tall herbs on low herbs in herbs grass root zone

Figure A2: representation of predicted species in the observed fauna of selected microhabitats on the Pormenaz site, all habitats combined.

TRAPS: A B C SPECIES Arctophila bombiforme 1 Cheilosia faucis 1 1 Chrysotoxum bicinctum 1 Chrysotoxum fasciatum 1 Chrysotoxum fasciolatum 1 Episyrphus balteatus 2 1 4 Eristalis tenax 2 Eupeodes luniger 1 Leucozona glaucia 1 Melangyna arctica 2 Melanostoma dubium 1 Melanostoma mellinum 2 Melanostoma scalare 1 1 Meligramma triangulifera 1 Meliscaeva auricollis 2 1 1 Meliscaeva cinctella 2 Paragus punctulatus 1 Platycheirus albimanus 1 Platycheirus angustipes 8 2 Platycheirus aurolateralis 1 Platycheirus nielseni 1 Rhingia campestris 1 Scaeva pyrastri 1 Scaeva selenitica 1 Syrphus ribesii 1 Volucella bombylans 2 Number of specimens 9 22 20 Number of species 7 13 13

Table A1: number of individuals of each species of syrphid collected by the Malaise traps on the Pormenaz site in 2003.

Appendix 2: surveillance of invertebrate biodiversity in subalpine/alpine habitats

There is a potential requirement for establishment of long-term biodiversity surveillance regimes, in areas selected for inclusion in the Natura-2000 network. This suggests it is worthwhile considering what can be learned of the potential suitability of syrphids, and the trapping regime used to survey them on the sites sampled during 2004, for application in a biodiversity surveillance context.

The Malaise traps used in this study proved sufficiently robust to survive the climatic conditions experienced during the sampling programme season, including snow-fall. Malaise traps are now produced commercially to standard specifications and so can be relied upon to perform mechanically in the same way on all sites. As flight interception traps they collect material belonging to a range of taxonomic groups, not just Syrphidae, and this material can be available for future use, given that the MHN in Geneva is prepared to store the bottles of collected samples and that the collected samples are in alcohol, which is an appropriate preservative.

The system of Malaise trap erection and collection by researchers, and trap maintenance and sample collection by Reserve wardens, worked very well, though more attention could usefully be given to maintenance of alcohol levels in sample bottles. The one factor that adversely influenced the sampling programme to a serious extent was livestock damage to traps. The incompatibility of livestock with Malaise- trapping programmes is well known and not confined to alpine grasslands! Essentially, if trapping is to be carried out where livestock are present the need is to install sturdy exclosures that will prevent access to the traps by the livestock. In the context of establishing sampling stations for repeated survey of invertebrate biodiversity the simplest solution is not to use locations where livestock damage to traps might be expected - locations like the Carlaveyron site sampled during the 2004 project would be excluded on this basis.

The logistic considerations that most limited the number of Malaise traps deployed in 2004 was apparently transport of the traps and trap poles to their intended destinations on-site and the process of erection of the traps once they were on-site. Maintenance of the traps and regular collection of samples seems to have been less problematic. If this assessment of the situation is correct it is worthwhile to consider how these logistic problems might be reduced e.g. by involvement of a greater number of individuals in trap transport/installation procedures, because collection of twice as many sample bottles from a site, per visit, could be achieved with almost no extra effort. Certainly, the 2004 survey would have benefited from the availability of twice the amount of sample data! The approach adopted here, basing interpretation upon use of the StN database, has made it possible to extract information from species recorded only as solitary specimens - without the database it is arguable that the data would have been inadequate as a basis for interpretation. Even so, there remains some uncertainty concerning the potential contribution made to the survey results by particular habitats at both Anterne (Seslerion) and Passy (Adenostylion), because no traps were installed in them. Clearly, if a visit to a site has to be made, for purposes of sample collection, it is advisable to maximise the value of that visit by ensuring that the maximum number of samples that can reasonably be transported is available for collection.

There is no "long tradition" of the use of syrphids in environmental interpretation. They have been brought into focus as potential tools for use in issues relating to maintenance of biodiversity largely because of the existence of the "expert system" character of the StN database, which has been available for less than 10 years. As familiarity with use of the database increases so does the number of projects in which syrphids are employed. An overview of these issues is provided by Speight (2005). Syrphids represent only a notional 1% of the invertebrate fauna and it is unreasonable to assume that, used alone, they might provide a comprehensive reflection of the invertebrate biodiversity of a site. This suggests that there is need to develop a strategy to investigation of invertebrate biodiversity that involves a suite of carefully selected taxonomic groups of invertebrates, that complement each other in their interpretive capacity and can provide independent, comparable data sets for use in evaluation of particular problems. For instance, in the case of the syrphid surveys that form the basis for the body of this report, it would have been most useful to have data from other taxonomic groups to challenge or corroborate the findings derived from the Syrphidae.

The question of the number of sites, and the range of types of site, that may require to be examined, if an adequate basis for distinguishing between site-based and regional impacts is to be established, has been touched upon in other sections of this report. Essentially, there is need for some form of "control" sites to be surveyed, along with sites targeted for investigation for particular reasons. As data accumulate from sites supporting different types of habitat it is possible that, progressively, a regional picture will emerge from them, with which to compare the situation of particular sites or habitats. But adoption of such an approach would imply greater standardisation of survey methodology than exists at present and also survey of sites supporting a wider range of habitat types than has been achieved so far.

Reference Speight, M.C.D. (2005) An "expert system" approach to development of decision tools for use in maintenance of invertebrate biodiversity in forests. Pan- European Ecological Network in forests: Conservation of biodiversity and sustainable management. Proc.5th Internat. Symposium, Pan-European Ecological Network. Environmental Encounters No.57, 133-141. Council of Europe, Strasbourg.