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Home , Cymatia, Cymatia bonsdorffii, Dryopidae, Hairy dragonfly, Haliplus ruficollis, Odontomyia ornata

A survey of the aquatic invertebrates of RSPB Otmoor Reserve, Oxfordshire

C. Martin Drake 2009

Dr C. M. Drake Orchid House Burridge Axminster Devon EX13 7DF

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Summary Aquatic invertebrates in all major groups except were sampled at 25 water-bodies at Greenaways field at RSPB’s Otmoor Reserve on 24 – 25 July 2009.

A total of 139 distinct taxa (nearly all species) were identified. These included 61 species of water , 20 bugs and 16 molluscs.

Twenty-one nationally scarce or rare species were found. Three beetles (, Berosus signaticollis and Enochrus nigritus) are not characteristic of grazing marshes and all three had good populations here. The rare soldierfly ornata is an exceptional inland record for a species rarely found away from coastal grazing marshes. The remaining species are often found in ditch systems.

Three distinct assemblages were identified using ordination. These corresponded closely to the three main ditch types: gutters, new shallow ditches, and old or deep ditches. Gutters were characterised by many species and individuals of beetles but a paucity of many other groups, and by high species quality scores and many uncommon species. New shallow ditches had high quality scores and high species richness in many groups and many uncommon species. Old or deep ditches had high species richness in many groups except beetles and markedly lower species quality scores and numbers of uncommon species.

Creating gutters and shallow ditches was highly beneficial to the aquatic invertebrate fauna at Otmoor.

Introduction Otmoor is a large grazing marsh on the floodplain of the River Ray in Oxfordshire. Large parts of it were drained in the 1960s and 1970s for arable farming. In 1997, RSPB started restoration back to pasture and reedbed. A dense network of ditches, gutters and scrapes has been dug over several years primarily to benefit waders.

This survey was commissioned to investigate the aquatic invertebrates of the Greenaways field which is the first area to have the new water-bodies. Many of the ditches here are now between 5 and 8 years old [CHECK AGES] and have well established aquatic and marginal vegetation.

The project brief required samples from 25 water-bodies. After discussion with the reserve staff, it was agreed that all samples should be taken from the Greenaways field rather than include some on other parts of the reserve.

Methods Samples were taken using a pond-net. Three to four net-hauls were taken at each point and the material was inspected on a polythene sheet and in a white tray containing shallow water. A separate procedure was used to find small molluscs that were often difficult to see among the weed on the sheet and tray. After sorting, each batch of weed and debris was put in bucket,

1 dunked about and most weed removed. The remaining material was washed crudely while allowing molluscs to sink to the bottom. Most water was decanted and the residue inspected in the tray. As 12-13 samples had to be collected on each day, 40-45 minutes was allocated to each point.

A few environmental features were noted but these included only a small number of those that the author normally collects at ditches, since filling the forms takes too much time which was better spent in sampling. They are givenin Appendix 2.

Ditches were selected to cover most of the Greenaways field and to include the range of types from old to new, deep to shallow, and gutters. Many gutters and scrapes were dry or nearly dry but samples were obtained from plenty of them by gently stamping the vegetation to create a pool from which were netted. Sampling points are shown in Figure 1.

The site was visited on 24-25 July 2009. The weather was good for most of the visit, with only one very heavy shower.

Rarity statuses were obtained from Recorder 3.3 and checked using the JNCC website (updated in 2008). Some groups have been revised using the more recent IUCN criteria, but one draft review that still awaits publication by JNCC have been used for water beetles (Foster, in prep.). The geographic distribution of most scarce species was obtained using the NBN Gateway. Definitions of the status categories are given in Appendix 4. Species Quality Score was calculated for all aquatic grazing marsh species listed in Palmer et al. (2007); this excludes wetland species such as donacine reed beetles. The values used are given with the raw data in Appendix 1.

Odination used DECORANA on presence/absence data with no downweighting of species that were scarce in the dataset, using the software Community Analysis Package 4 (Pisces 2007). Median values rather than means were calcuated as the samples had not been selected randomly. TWINSPAN was used to classify the samples.

Results

Species richness A total of 139 distinct aquatic taxa were identified, all but five of which were species, and excludes possible duplicates such as larvae that were identified only to . These included 61 species of water beetles, 20 water bugs, 16 molluscs (not including Pisidium pea-mussels which were not identified), nine (larvae), five mayflies (larvae), eight species and three genera of caddisflies, five leeches and the remainder comprising alderfly, two crustaceans and water spider. were excluded in the project specification as there was good information from adults already, but these were noted in any case; this added another six species and one genus. Both common sticklebacks were present. Another 32 species of ‘terrestrial’ beetles, flies and bugs were identified incidentally; some of these are wetland species and a few have aquatic larvae but are not traditionally included in ‘aquatic’ groups. Appendix 1 gives the raw data.

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Rare and scarce species There were 21 species with nationally rare or scarce status using the old JNCC system (Table 1). Four of the water beetles are likely to be down-graded when a long-awaited review using the IUCN criteria is published (Foster, in prep.); these are shown with the IUCN status of ‘Lower Risk, least concern’ (LRlc) in Table 1. Odonata have recently been re-evaluated using the IUCN criteria and Hairy , Brachytron pratense, is now classed as ‘Least Concern’ (LC) (Daguet et al., 2008; Taylor, 2008).

Figure 1. RSPB Otmoor Reserve, Greenaways Field, showing invertebrate sampling points.

Many of these rare and scarce species are frequently found in ditches on grazing marshes and, despite their rarity status, are among the expected fauna. Species that are not part of the usual grazing marsh fauna are the beetles Dryops similaris, Berosus signaticollis and Enochrus nigritus. All three have been recorded previously either on Otmoor SSSI or nearby.

Dryops similaris is found mainly in lowland England and coastal Wales, and is regarded as a ‘moss-edge dweller’ characteristic of temporary fens, although can also be found at mossy edges of man-made pools. Its distribution shows no hint that it occupies the large grazing marsh

3 systems of England and Wales. At Otmoor it was identified at four places in shallow or deep new ditches, although possible females (which cannot be identified) of a large dark Dryops were present at more sites here.

Berosus signaticollis was moderately frequent at Otmoor in gutters and shallow new ditches. It is widespread in lowland England with many records following the distribution of some clay formations and sandy soils. It is normally associated with shallow temporary pools.

Enochrus nigritus was one of the most interesting species found. It is moderately frequent in northern East Anglia where it lives in mesotrophic and base-rich fens and pools. Outside of this area it is scarce and appears to have been lost from some parts of the south-east. It was present at 20 sampling points, was sometimes numerous and showed no preference for any type of ditch. Records on the NBN Gateway indicate that it has been frequently recorded here.

The most unexpected record was for the large aquatic soldierfly Odontomyia ornata. This can be regarded as a flagship species for grazing marsh ditch systems where it can be quite a common , but it is almost confined to them. Its distribution follows almost exactly that of the major marshes of England and Wales. Its discovery so far inland and away from old marsh was completely unexpected. Well grown individuals were found at three new deep or shallow ditches, and this agrees with the species’ known preference for fairly large ditches. Small individuals that may have been this species were at another ten ditches. There is some doubt about their identification as they had characters used for O. ornata in keys but resembled small O. tigrina. Clearly some taxonomic work is needed on small larvae to be sure of their identity. These were found widely at Otmoor and were found in all types of ditch which militates against them being O. ornata.

Several other scarce water beetles have been recorded from the adjacent Otmoor SSSI before: Cercyon tristis, Enochrus melanocephalus and, Limnebius papposus (frequently), and Berosus affinis and Peltodytes caesus have been recorded nearby at the edge of Otmoor. There are no records in the NBN Gateway for the water beetles Cercyon sternalis, Dytiscus circumflexus, Hydaticus seminiger, the reed Donacia thalassina, the tiny but distinctive fornicatus or the soldierflies Odontomyia tigrina and Stratiomys singularior. All these species are within their geographic range with the possible exception of Berosus affinis which may be close to its north-west limit in Oxfordshire.

Some other species deserve special mention, even though they are not especially uncommon nationally. The corixid bug bonsdorffi was frequent at Otmoor and has been recorded on the RSPB reserve before. It is widespread in Britain, but there are relatively few records for the upper Thames catchment. The local but widespread obliquus feeds on Chara so it was expected that they would be frequent at Otmoor. Haliplus confinis also appeared to be present where Chara was more abundant. The cranefly Phalacrocera replicata has a striking aquatic with long almost hair-like gills, giving it the appearance of a bedraggled woolly-bear caterpillar. It was found several times, mostly in the new shallow ditches where the marginal moss provided an abundant food source for this moss-feeder.

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Table 1. Nationally rare and scarce species recorded at Greenaways field.

Order Family Species Status Frequency JNCC IUCN Coleoptera Dryopidae Dryops similaris pRDB3 LRnsA 4 Dytiscidae Dytiscus circumflexus Scarce LRnsB 1 Hydaticus seminiger Scarce LRnsB 2 Hydroglyphus pusillus Scarce LRlc 4 Rhantus suturalis Scarce LRlc 6 Peltodytes caesus Scarce LRnsB 2 Limnebius papposus Scarce LRnsB 6 Hydrophilidae Berosus affinis Scarce LRnsB 7 Berosus signaticollis Scarce LRnsB 9 Cercyon sternalis Scarce LRnsB 1 Cercyon tristis Scarce LRlc 2 Enochrus melanocephalus Scarce LRnsB 1 Enochrus nigritus RDB3 VU 20 Helochares lividus Scarce LRlc 15 Diptera Cylindrotomidae Phalacrocera replicata Scarce 4 Odontomyia ornata RDB2 3 (+10?) Odontomyia tigrina Scarce 6 Stratiomys singularior Scarce 2 Odonata Brachytron pratense Scarce LC 1 Terrestrial Coleoptera Chrysomelidae Donacia thalassina Scarce 2 Staphylinidae Stenus fornicatus Scarce 1

Assemblages An ordination plot of the first two axes for samples showed a clear trend along the first axis, corresponding to the different types of ditch. Gutters (green in Figure 2) formed a discreet group with high scores on axis 1, and old drains and deep new ones were at the left of the figure with low scores on axis 1 (red, purple and dark blue). Shallow new ditches (pale blue) fell between these extremes. Axis 1 therefore appeared to be correlate partly with water depth and partly with the ‘age’ of ditches. The second axis did not appear to show any useful pattern except perhaps separating the water depth in old ditches (red were deep ditches, purple were shallow ones).

The first two TWINSPAN divisions produced three recognisable groups. The first division separated the gutters from the permanent ditches (Figure 3), and the next split most of the deep or old ditches from the new shallow ones. Further division of the deep or old ditches did not separate them by age or depth. The exceptions that did not neatly follow the classification by ditch type can be seen by comparing the grouping by TWINSPAN group with those by ditch type in Figures 2 and 3. The most interesting of the misplaced samples was 16.1 taken in a short (3m) section of gutter that had been deepened to allow the drainpipe to pass under a crossing point just a few meters along from the sample 16, showing that the animals responded even to

5 this apparently minor management. Appendix 3 gives the output direct from the program for these divisions.

The median number of total taxa in the gutters was markedly lower than in the permanent ditches, and this drop in numbers was due to low numbers in several groups, notably bugs, caddis and molluscs (Table 2). Gutters and the mainly shallow permanent ditches were, on average, equally rich in beetles and all rare and scarce species, and richer for these taxa than old or deep ditches, although there was a wide range of values (Table 4). The Species Quality Score for all taxa was highest overall for the mainly new and shallow ditches, closely followed by the gutters, and notably lower in the old or deep group.

Table 2. Median number of species in each major group, with the range for total and uncommon species, and Species Quality Score.

TWINSPAN Group Permanent ditches Gutters P1 P2 G old or deep mainly new and shallow Number of ditches 9 10 7 Coleoptera 14 19 19 Diptera 1 2 1 Ephemeroptera 2 2 1 9 8 1 Neuroptera 1 1 1 Trichoptera 3 1 0 Araneae 1 1 0 Amphipoda 1 1 1 Isopoda 1 1 1 Mollusca 7 5 4 Leeches 2.5 2 1 total (excluding Odonata) 42 (38 – 50) 42 (21 – 51) 28 (23 – 36) all rare and scarce species 3 (0 – 5) 5 (1 – 8) 5 (1 – 8) SQI score for all taxa 1.59 (1.19 - 1.93) 2.13 (1.33 - 2.4) 1.93 (1.46 - 2.39)

Species composition differed markedly between the gutters and permanent ditches, and less clearly but still evidently between the deep ditches and the shallower ones. Gutters (all falling into one TWINSPAN group) were characterised by the dominance of beetles and the scarcity of bugs and snails, with the exception mainly very common species with wide tolerances, such as the water scorpion Nepa cinerea and the snails Planorbis planorbis and Radix balthica. Diving beetles in the genera Agabus, Ilybius and Hydroporus, and predominantly small to tiny crawling water beetles (Anacaena, Cercyon, Ochthebius) were the main taxa in these nearly dry ditches with dense emergent vegetation or moss. Beetle groups that were conspicuous absent were whirligigs (Gyrinus) and Haliplus which prefer more open conditions. Sympetrum (darters) were often quite numerous in these nearly dry ditches, showing that they are not merely of use to beetles. Scarce or uncommon beetles that showed a slight preference for gutters were Hydaticus

6 seminiger, Rhantus suturalis, Berosus signaticollis, Cercyon tristis and Limnebius papposus, although nearly all of these were also found in the dense marginal vegetation of permanent ditches. Other uncommon species also found in the gutters but were equally well represented in permanent ditches were the beetles Enochrus nigrita, E. quadripunctatus, Helochares lividus and the soldierfly Odontomyia tigrina.

The vegetation of the gutters was dominated by emergent plants (rush, spike-rush, sedge), usually with a mossy mat below and with very little or no open water.

Permanent ditches were characterised by supporting a much wider range of main taxa, including those that are conventionally expected in ponds and ditches, such as mayflies, damselflies, bugs, caddis and snails. Some common species among these, such as the bugs, were completely absent from gutters but were ubiquitous elsewhere. The differences between deep and shallow ditches was less clear-cut than between permanent and temporary water, as indicated by slight lack of concordance between the next TWINSPAN division and the types of ditch.

Species showing a slight preference for the deep or old ditches (shown blue in Figure 3) were the beetles Hyphydrus ovatus, Haliplus obliquus (which feeds on Chara so should have been present in shallower ones too), the mayfly Caenis robusta, the water-boatmen and Sigara dorsalis, water spider Argyroneta aquatica and the two Holocentropus caddis that feed like water spiders with a web to catch small animals, the caddis Triaenodes bicolor (which swims about in a long thin case), and the leeches Erpobdella octoculata and Theromyzon tessellatum which feeds on water birds. Some molluscs (Physa fontinalis, Sphaerium corneum) were much more frequent in the deeper ditches and this may reflect age rather than water depth, and slow colonisation of new ditches because of their low mobility.

These structure of these ditches varied depending upon whether their margins had been re- profiled from the original steep-sided edge to a gently sloping one. They usually had plenty of open water, often with frequent floating plants (Potamogeton natans mostly), often but not invariably with abundant submerged vegetation, and usually a good fringe of emergent vegetation but not often with moss at the edges.

The TWINSPAN group shown as red in Figure 3 fell between these two extremes and comprised mainly new shallow ditches. Some of the more numerous species showing a slight preference for this group were diving beetle Hygrotus impressopunctatus, Liopterus haemorrhoidalis which was frequent but almost confined to this group, the declining beetle Porhydrus linearis, the screech beetle hermanni and the water boatman Hesperocorixa moesta. Uncommon species showing a slight preference for this group were beetles Dryops similaris and Berosus signaticollis, and the soldierfly Odontomyia ornata.

These ditches were nearly all new and shallow. Like the old or deep ditch group, they usually had plenty of open water, moderate cover of submerged vegetation, emergents that formed either a good fringe or a continuous sparse cover across the ditch, and variable presence of a mossy margin. The main differences from the old or deep ditches was the scarcity of floating Potamogeton, and frequently partly bare or only sparsely covered bottoms.

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DECORANA Ordination Plot - Otmoor 1 190 180 22 170 160 10 24 150 6 140 19 20 5 130 18 23 17 120 110 100 11 4 8 90 3 2 80

Axis2 16 12 70 60 25 9 14 50 15 40 7 21 30 13 16.1 20 10 1 0 -10 -20

0 50 100 150 200 250 300 Axis 1

Figure 2. Ordination plot of samples showing ditch types. Footdrains - green; deep old – red; shallow old – purple; deep new – dark blue; shallow new – light blue.

DECORANA Ordination Plot - Otmoor 1 190 180 22 170 160 10 24 150 6 140 20 130 23 19 120 5 18 110 17 100 11 4 8 90 3 2 80

Axis2 16 12 70 60 25 9 14 50 15 40 7 30 16.1 20 21 1 10 13 0 -10 -20

0 50 100 150 200 250 300 Axis 1

Figure 3. Ordination plot of samples showing TWINSPAN groups.

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Discussion

The newly created and restored older ditches at Greenaways Field provided an excellent habitat for aquatic invertebrates. The total numbers of species was high, especially for beetles and bugs, and higher than often found in ditch systems for caddisflies. A large number of rare and scarce species were present, and several of these were widespread and among the commoner species here. Three of the rare or scarce species are not characteristic of coastal grazing marshes or of those inland in Somerset. They have been recorded at Otmoor before the RSPB restoration but have small and fairly isolated populations here in the Ray floodplain and nearby. This indicates that Otmoor is an important site for them. The strongly inland population of the rare soldierfly Odontomyia ornata was also noteworthy.

Analysis of the assemblages of invertebrates clearly distinguished between those of the shallow gutters and permanent ditches, and to a lesser extent between new shallow ditches and the group of new deep and old pre-RSPB ditches. Ditch management has therefore directly affected the invertebrates, and in a positive way by adding habitat that is catering for distinctly different assemblages.

The only major group that appeared not to be well represented at Otmoor is molluscs. All those recorded are common species and only a few were widespread or abundant. Usually ditches on grazing marshes support about ten species in most ditches but this was the maximum reached in only old ditches, and the new shallow ones had a median of only five species. Slow colonisation may explain the paucity in all the new ditches but not the clear sparseness in the old ditches. Small species such as Hippeutis and Gyraulus crista were almost absent, and no Valvata were found at all.

Gutters were notably poorer in total species and lacked large elements of the fauna that need permanent or open water, but had large numbers of beetles and species quality scores as high as those in permanent ditches. Later in summer, or in dry years, even the water beetles will abandon completely dry gutters, but while there is still water below the litter layer under emergent vegetation or moss, many will survive and presumably breed in these conditions. As most of the permanent ditches had gently shelving shores, these supported almost all the species found in the gutters since the mossy or emergent-choked margins provide the same type of habitat as found in the gutters. Only one scarce diving beetle (Hydaticus seminiger) was found in the gutters alone, but even this species is likely to be found in permanent ditches if they were searched more thoroughly.

Shallow permanent ditches supported a consistently interesting fauna that was usually more species-rich and included more nationally rare or scarce species than in the old or deep ditches. The features that appeared to be of most value in these ditches were the huge width of shallow water, which is usually always of more value than deep water for ditch faunas, and the very gentle slope to the margins. The ease with which cattle can reach the edges probably helped to reduce excessive trampling on many ditches by spreading the pressure, but grazing and trampling

9 may still have been sufficient to reduce the growth of dense rush. Having less rush is beneficial to the marginal aquatic fauna which does not thrive in the leaf litter of dense rush and sedge. abandoning the drying gutters may well have found refuge in the shallow ditches. Although this survey investigated only aquatic species, it is expected that wetland flies would also benefit from the wide wet shores.

Deep ditches, especially the old original ones, had a moderately distinct assemblage with more snails, leeches and caddisflies but with fewer beetles. They supported fewer rare and scarce species than the other two types of ditch. One of the features thought to be responsible for the different fauna is the steep sides of many of the older ditches, although this alone does not explain the differences because some old deep ditches had re-profiled gently sloping margins, yet the fauna of these ditches still resembled that of other deep ones. Deep water per se is unlikely to be the key driver since many invertebrates characteristic of shallow water can be found in dense marginal vegetation. Whatever the reason for the slightly lower interest in these ditches, they may be improved by re-profiling.

RSPB has undertaken a similar reversion from arable to pasture with numerous new ditches at their Greylake reserve on the Somerset Moors (Drake, 2008). As at Otmoor, shallow ditches and gutters have been dug at a high density, and at about the same time so they are of similar ages. A survey of the aquatic fauna came to similar conclusions as those for Otmoor. Distinctly different assemblages occupied gutters, new permanent ditches and old ditches, and the same trends in the species-richness of major groups and species quality score as described for Otmoor were found there too. Even some of the fine detail of the preferences of individual scarce species was the same, such as the beetles Hydaticus seminiger and Cercyon tristis preferring the gutters.

RSPB’s policy of ditch and gutter creation appears to be having a highly beneficial impact on the aquatic invertebrates of restored pasture. It is difficult to see what further improvement can be made. Two suggestions are made:

 Maintaining marginally greater wetness in gutters throughout the summer would ensure that they were not abandoned and that larvae of libellulid dragonflies reach emergence. There may be a problem with water-supply that may prevent this, and there may be some advantage in allowing gutters to dry out as this will keep rank emergents in check.  Steep-edged ditches could be re-profiled so that the margin below water level was more gently sloping although there is probably no need to have every ditch with a very shallow slope since some invertebrates, notably snails and damselfly larvae, do not have a need for shallow water and flourish in submerged vegetation in deep water.

Acknowledgements Distributions and records of rare species were checked using the NBN Gateway, accessed 13 August 2009.

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References Daguet, C.A., French, G.C. and Taylor, P. (eds). 2008. The Odonata Red List of Great Britain. Species Status no. 11. Joint Nature Conservation Committee, Peterborough.

Drake, C.M. 2008. Aquatic invertebrate survey at Greylake RSPB Reserve, Somerset. Unpublished report to RSPB.

Foster, G. N. (in prep). A review of the scarce and threatened Coleoptera of Great Britain. Part 3. Aquatic Coleoptera. Joint Nature Conservation Committee, Peterborough.

Palmer, M., Drake, M. & Stewart, N. 2007. A manual for the survey and evaluation of the plant and invertebrate assemblages of ditches. Version 1. Buglife, Peterborough.

Pisces Conservation Ltd. 2007. Community Analysis Package v4. www.pisces- conservation.com [Computer software.]

Taylor, P. 2008. Comments on the Odonata Red List for Great Britain. Journal of the British Dragonfly Society 24, 37-44.

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Appendix 1. Raw data Samples are ordered by depth then age, and coloured by TWINSPAN group.

3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 TWINSPAN group P1 P1 P1 P1 P1 P1 P2 P1 P1 P1 P2 P2 P2 P2 P2 P2 P2 P2 G G G G G P2 G G depth (deep, shallow, gutter) d d d d d d d d s s s s s s s s s s g g g g g g g g age (old, new) o o o o n n n n o o o n n n n n n n

Family Species Status SQI COLEOPTERA Dryopidae Dryops luridus Common 1 - - - - - + - - + + - + ------4 Dryops similaris pRDB3 8 - - - - - + - - - - - + - + + ------4 Dytiscidae Acilius sulcatus Common 1 ------+ - - 1 Agabus bipustulatus Common 1 + - - - - + - + + - + + + + + + + - + + + + + + + + 19 Agabus nebulosus Common 1 ------+ - - + + + + - - - - 5 Colymbetes fuscus Common 1 + + - + - + - + ------+ - - - - - + + - 8 Dytiscus circumflexus Scarce 4 - - - - + ------1 Dytiscus marginalis Common 1 ------+ ------+ - - 2 Dytiscus semisulcatus Local 2 ------+ ------+ - - - - 2 Hydaticus seminiger Scarce 4 ------+ + ------2 Hydroglyphus pusillus Scarce 2 + - - - - - + ------+ ------+ - - - - 4 Hydroporus angustatus Common 1 ------+ - + - - - + + - + - + - - + 7 Hydroporus memnonius Common 1 ------+ ------1 Hydroporus palustris Common 1 - + + - - - + - - - - + + - - - - - + + - - - - - + 8 Hydroporus planus Common 1 - - - - + ------+ - + - - - + + + + + - - + 9 Hydroporus pubescens Common 1 - - - - - + ------+ - - - + + + + + - - - 7 Hygrotus impressopunctatus Local 2 - - + ------+ + + - + + - + + + + + + - + + 14 Hygrotus inaequalis Common 1 + + + + + + + + + + + + + + + + - + - - - + - - - + 19 Hyphydrus ovatus Common 1 + + + + + + - + - + + + + + ------12 Ilybius ater Common 1 - - - + + - + - - - + - - - - + - - - - - + - - + + 8 Ilybius fuliginosus Common 1 + ------+ - + ------+ - - - - 4 Ilybius montanus Common 1 ------+ + ------2 Ilybius quadriguttatus Common 1 + - + - - + - - + - + - - + + - - + + + + - + + + + 15 Laccophilus minutus Local 2 + - - - - + - + + - - + - + - + - + - - - - - + - - 9 Liopterus haemorrhoidalis Local 2 ------+ - - - + + + + + + + + + + + - + + - + 15

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3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 Porhydrus lineatus Local 2 - + ------+ - + + + ------5 Rhantus suturalis Scarce 2 ------+ - - - - - + - + - - - + + + - - - - 6 Gyrinidae Gyrinus marinus Common 1 - + + + + + - + + + + + - + - + - + ------13 Gyrinus substriatus Common 1 ------+ ------1 Gyrinus (larva) - - + ------1 Haliplidae Haliplus confinis Common 1 - - - + - - + + + + + - + + + - + + ------11 Haliplus flavicollis Local 2 ------+ ------1 Haliplus immaculatus Local 2 - - - + ------1 Haliplus obliquus Local 2 - - - - - + - + + - - - - + ------4 Haliplus ruficollis Common 1 - + - + + - + + - + - - + + + - - + ------10 Peltodytes caesus Scarce 4 - - - + - - + ------2 Haliplus ruficollis group female - - - + + + + - + + - + - + + + - - - + - - + - - - + - 13 Helophoridae aequalis Common 1 ------+ ------1 Helophorus brevipalpis Common 1 ------+ - - + - - + + - + + - - - 6 Helophorus grandis Common 1 ------+ ------1 Helophorus minutus Common 1 - + + + + + + + + + + + + + + + + + + - + + + + + + 24 Hydraenidae Limnebius papposus Scarce 4 + - + ------+ - - - - - + - - + - - - + 6 Ochthebius dilatatus Local 2 ------+ + + - - - - - 3 Ochthebius minimus Common 1 ------+ - - - - - + - + - - - - 3 Hydrophilidae Anacaena limbata Common 1 ------+ - + - - - - + + - - + - + - 6 Anacaena lutescens Common 1 + + + + + + + + + + + + + + + + + + + + + + + + + + 26 Berosus affinis Scarce 4 + - - - - + - + - - - - - + - - - + - - - + - + - - 7 Berosus signaticollis Scarce 4 ------+ + + + + + + + + - - - 9 Cercyon marinus Local 2 ------+ - 1 Cercyon sternalis Scarce 4 ------+ ------1 Cercyon tristis Scarce 2 ------+ + - - - - - 2 Coelostoma orbiculare Common 2 - - - - - + + - - - + - - - + - + ------+ 6 Cymbiodyta marginellus Local 2 ------+ + ------2 Enochrus coarctatus Local 2 ------+ - 1 Enochrus melanocephalus Scarce 4 ------+ ------1 Enochrus nigritus RDB3 16 - + + + + + + - - - + + + + + + + + - + + + + - + + 20 Enochrus quadripunctatus Common 4 - + ------+ - + ------+ + 5 Helochares lividus Scarce 2 + - + + + + - + - + + + + - + - - + + - + - - - - + 15 Hydrobius fuscipes Common 1 - - - - - + - + - - + + + + + + - + + - + + + - + + 15 Laccobius bipunctatus Common 1 - - - - + + - - - - - + + - + - - - + ------6

13

3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 Laccobius minutus Local 2 + - + + - + - - - - + - + - + - + ------8 Noteridae Noterus clavicornis Local 2 + + + + + + + + + + + + + + + + + + + + + + + + + + 26 Paelobiidae Hygrobia hermanni Local 2 ------+ - - + + + + + - + ------7 DIPTERA Culicidae Anopheles atroparvus Common 1 - - - - + + - + - + + - - - - + + ------7 Anopheles claviger Common 1 ------+ - - - - 1 Cylindrotomidae Phalacrocera replicata Scarce 4 + ------+ + - + ------4 Dixidae Dixella amphibia Common 1 ------+ ------1 Ptychopteridae Ptychoptera minuta Local 2 ------+ ------1 Stratiomyidae Odontomyia ornata RDB2 16 - ? - - ? - + + - - ? ? ? ? + ? - ? - - - ? - - - ? 3 Odontomyia tigrina Scarce 4 ------+ - - - + - + + ------+ + - - - - 6 Oplodontha viridula Local 2 ------+ + ------2 Stratiomys singularior Scarce 4 ------+ + ------2 EPHEMEROPTERA Baetidae Cloeon dipterum Common 1 + + + + + + + + + + + + - + + + + + - - - + - - - - 18 Cloeon simile Local 2 - - - - - + + - + + - - - - + + - + ------7 Caenidae Caenis horaria Common 1 + ------+ + - - - + - + ------5 Caenis luctuosa Local 2 ------+ - - - - + - + ------3 Caenis robusta Nr 2 + + + ------3 HEMIPTERA Callicorixa praeusta Common 1 ------+ ------+ ------2 Corixa panzeri Local 2 ------+ - - - - - + - + ------3 Corixa punctata Common 1 - + + - - - - + - + + - - + - + + - - - - + - + - - 10 Local 2 + - + - + + - + + + - + - + - + - + ------11 Cymatia coleoptrata Local 2 + - - + + + - + + + + + - + ------10 Hesperocorixa linnaei Common 1 + + - - + - - - - + + - + - - - + ------7 Hesperocorixa moesta Local 2 + + - - - - + - - + + + + + + + + + - - - + - + - - 14 Hesperocorixa sahlbergi Common 1 ------+ - - - - + - - 2 Micronecta scholtzi Common 1 ------+ ------+ ------2 Sigara dorsalis Common 1 + ------+ + ------3 Sigara falleni Common 1 ------+ - - - - - + ------2 Sigara fossarum Common 1 + + + - + + - + + + - + - + - + - + - + - - - + - - 14 Gerridae Gerris odontogaster Common 1 ------+ - + - - + ------3 Gerris thoracicus Common 1 ------+ ------1 Gerris (immature) - - + + - + + + - - + - - - - + - - + ------8

14

3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 Naucoridae Ilyocoris cimicoides Common 1 + + + + + + + + + - + + + + + + + + ------+ - 18 Nepidae Nepa cinerea Common 1 ------+ - - + + - + + ------+ + + 8 Ranatra linearis Local 2 + - - - - + - + + - - - - + - + - + ------7 Notonectidae Notonecta glauca Common 1 + + + + + + + + + + + + + + - + + + - - - + - - - - 18 Pleidae Plea minutissima Common 1 + + - + + + + + + + + + + + + - + + ------16 Veliidae Microvelia reticulata Common 1 - + - + + - - - - + - - + ------5 NEUROPTERA Sialidae Sialis lutaria Common 1 + + + + - + - + + + - - - + + + + + + - - + + + - - 17 TRICHOPTERA Leptoceridae Athripsodes ------+ ------1 Mystacides ------+ ------1 Oecetis lacustris Common 1 - - + ------1 Triaenodes bicolor Common 1 + + + + - + - + - - - + + - - - - + ------9 Limnephilidae Limnephilus decipiens Common 1 - - - + ------1 Limnephilus marmoratus Common 1 + ------1 Molannidae Molanna angustata Common 1 ------+ ------1 Phryganeidae Agrypnia pagetana Local 2 + ------1 Phryganea ------+ ------+ ------2 Polycentropodidae Holocentropus dubius Common 1 + ------+ - + ------3 Holocentropus picicornis Common 1 - + + - + - - + - + + ------6 ARANEAE Cybaeidae Argyroneta aquatica Local 2 - + + + + + - + + - + + - - - - + ------10 AMPHIPODA Crangonycitidae Crangonyx pseudogracilis Naturalised -2 + + + + + + - + + + + + + + + + + + + + + + + - + + 24 ISOPODA Asellidae Asellus aquaticus Common 1 + + + + + + - + + + + + + + + + + - + + + + + + + + 24 MOLLUSCA Acroloxidae Acroloxus lacustris Common 1 + - - + ------2 Bithyniidae Bithynia tentaculata Common 1 + + + + + + + - + + - + + + + + - - - - + - - - - - 15 Hydrobiidae Potamopyrgus antipodarum Naturalised 1 ------+ ------1 Lymnaeidae Galba truncatula Common 1 ------+ ------1 Lymnaea palustris Common 2 ------+ ------+ 2 Lymnaea stagnalis Common 1 - + + + + + + + + - + + + + + + + + - - - - + + - - 18 Radix balthica Common 1 + + + - + - + + + - + - + + + + + + - - + + + + + + 20 Physidae Physa fontinalis Common 1 + + + + - - - + - + + ------7

15

3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 Planorbidae Anisus vortex Common 1 + + + + + + + + + + + + + - - + + - + + - - - - + + 19 Gyraulus albus Local 2 ------+ ------1 Gyraulus crista Common 1 ------+ ------+ - - - + 3 Hippeutis complanatus Local 2 + + ------+ ------3 Planorbarius corneus Common 1 - + - - - - + ------2 Planorbis planorbis Common 1 + + + + + + + + + - + + + + + + + + - + + + + + + + 24 Sphaeriidae Musculium lacustre Common 1 + + + - - - + + - + - + + - - - + ------+ + 11 Pisidium - - + + + + - + - - - - + ------+ + + - + + - + + 13 Sphaerium corneum Common 1 + - + + + + - + + + - + - - - - - + ------10 HIRUDINEA Erpobdellidae Erpobdella octoculata Common 1 + + + + + - + + ------+ - + - - - - - 9 Erpobdella testacea Local 2 ------+ ------1 Erpobdella (immature) - - + ------1 Glossiphoniidae Glossiphonia heteroclita Local 2 - - - - + ------+ - - - 2 Hemiclepsis marginata Local 2 - - - - + ------1 Theromyzon tessulatum Common 1 + + + - + - + + + + - - - - - + ------9 total aquatic species 50 43 39 38 40 45 31 50 38 42 43 43 44 51 39 43 30 41 36 28 26 35 23 21 24 29

NON -TARGET GROUPS

ODONATA Aeshnidae Anax imperator Common - - - - + ------1 Brachytron pratense Scarce + ------1 Coenagriidae Ischnura elegans Common ------+ - - - + ------2 Pyrrhosoma nymphula Common - - - - + ------1 Coenagrionidae Coenagrionidae ------+ ------1 Libellulidae Libellula depressa Common ------+ ------1 Libellula quadrimaculata Common ------+ ------1 Sympetrum - + ------+ - - - - - + + - - - + + + + - - + 9

Gasterosteidae Gasterosteus aculeatus Common ------+ - + ------2 Pungitius pungitius Common ------+ ------+ + - - - + - - - - 4 TERRESTRIAL OR WETLAND SPECIES ------COLEOPTERA

16

3 10 19 22 5 15 24 25 1 8 18 2 6 7 11 13 17 21 4 9 12 14 16 16 20 23 Cantharidae Rhagonycha fulva Common ------+ ------1 Carabidae Agonum piceum Local ------+ ------1 Bembidion guttula Common ------+ + - - - - 2 Bembidion lunulatum Common ------+ - + - - - - 2 Stenolophus mixtus Local ------+ + - - - - 2 Chrysomelidae Donacia thalassina Scarce ------+ - - - + ------2 Donacia versicolorea Local ------+ - + - - - - + + ------4 Galerucella nymphaeae Local - + - - + + + + - - + + + - + ------9 Coccinellidae Anisosticta novemdecimpunctata Local + + + + - + + - - + - + + + + + + + + + + + - - + + 20 Coccidula rufa Common + - + - - + ------+ ------+ + + + - - + 9 Propylea quattuordecimpunctata Common ------+ - - - - 1 Staphylinidae Anotylus rugosus Common ------+ - - - - - 1 Stenus bifoveolatus Local ------+ ------1 Stenus boops Common ------+ ------1 Stenus fornicatus Scarce ------+ 1 Stenus latifrons Common ------+ ------1 DIPTERA Dolichopodidae Campsicnemus scambus Common ------+ ------1 Dolichopus latilimbatus Local - - + ------1 Ephydridae Notiphila riparia Common + ------1 Notiphila uliginosa Local ------+ ------1 Parydra pusilla Local ------+ ------1 Ptychopteridae Ptychoptera contaminata Local - - + ------1 Syrphidae Platycheirus clypeatus Common ------+ ------1 Sphaerophoria interrupta Local + ------1 Tabanidae Haematopota pluvialis Common ------+ - - + + 3 HEMIPTERA Berytinidae Cymus glandicolor Common ------+ ------1 Cymus melanocephalus Common ------+ ------1 Cercopidae Neophilaenus lineatus Common ------+ ------1 Cicadellidae Cicadula frontalis Common ------+ ------1 Limotettix striola Local ------+ ------1 Saldidae Chartoscirta cincta Common - + ------+ - - - + + + - - - - - 5 Tingidae Dictyla convergens Local ------+ ------+ + - - + - - - 4

17

Appendix 2. Environmental measurements and TWINSPAN group details.

Sample Date Grid Width Depth Conductivity Profile Vegetation cover Structure TWINSPAN 2009 reference m cm mS/cm under scale 5 – 1 = DAFOR arbitary scale 0-3 water

degrees

(old,

new)

depth

group

age

(shallow, (shallow,

deep, gutter) deep,

open floating algae floating submerged algae sub. substrate emergent matmoss grazing poaching shelf tangled margin grass

1 24 July SP56801306 5 30 0.38 10 5 2 0 4 0 4 2 0 2 2 3 1 1 P1 s o 2 24 July SP56661309 5 25 0.37 10 2 2 2 1 1 P2 s n 3 24 July SP56611298 5 100 0.43 10 3 0 2 5 2 0 4 2 1 1 2 3 1 P1 d o 4 24 July SP56611301 1 10 0.23 10 1 0 0 0 0 0 5 4 1 1 0 2 1 G g 5 24 July SP56481301 80 0.38 90 4 5 1 0 0 0 3 0 1 0 0 1 0 P1 d n 6 24 July SP56401315 4 40 0.28 10 2 3 3 0 0 0 5 4 0 0 3 2 1 P2 s n 7 24 July SP56311320 4 20 0.37 10 5 0 0 4 1 2 4 2 2 2 1 2 1 P2 s n 8 24 July SP56201323 10 30 0.43 30 5 4 2 4 2 2 3 0 2 2 0 1 0 P1 s o 9 24 July SP56311327 1 5 0.49 10 1 0 0 0 0 0 5 4 1 1 0 1 2 G g 10 24 July SP56411339 3 80 0.42 90 4 4 2 0 0 0 4 3 0 0 3 2 1 P1 d o 11 24 July SP56501324 4 25 0.38 10 4 0 0 4 0 3 3 0 1 1 2 2 1 P2 s n 12 24 July SP56491316 5 0.98 10 1 0 0 0 0 0 5 4 1 1 0 2 1 G g 13 25 July SP57051304 10 10 0.35 10 4 0 0 3 0 4 3 0 1 2 0 1 0 P2 s n 14 25 July SP57071313 1 10 0.30 10 1 0 0 0 0 2 5 3 2 3 0 2 3 G g 15 25 July SP57121317 6 80 0.39 10 5 4 1 4 1 2 4 3 2 2 1 2 2 P1 d n 16 25 July SP57111327 1 5 0.53 10 1 0 0 0 0 2 5 3 3 3 0 2 2 G g 17 25 July SP56981325 10 15 0.39 10 4 1 1 3 4 3 5 2 2 3 3 2 2 P2 s n 18 25 July SP56841330 5 25 0.37 10 2 1 1 3 1 0 5 3 0 0 0 2 1 P2 s o 19 25 July SP56871339 5 110 0.41 60 5 3 0 2 0 3 4 0 1 1 0 2 0 P1 d o 20 25 July SP56921350 2 0.33 10 0 0 0 0 0 0 5 3 2 2 0 1 2 G g 21 25 July SP56921358 10 25 0.31 10 5 1 0 4 0 4 4 3 1 1 1 2 1 P2 s n 22 25 July SP56761372 7 100 0.36 30 5 3 0 4 0 0 4 0 1 1 2 2 0 P1 d o 23 25 July SP56691363 1 2 0.89 10 1 0 0 0 0 0 5 3 2 2 0 1 1 G g 24 25 July SP56621365 6 80 0.40 10 5 4 1 3 1 2 4 0 1 2 2 2 1 P2 d n 25 25 July SP56491359 3 90 0.42 60 4 4 0 3 0 0 0 0 1 1 0 1 0 P1 d n

18

Appendix 3. TWINSPAN using presence/absence data for Otmoor samples.

Only the first two divisions are shown. This is the output from the Pisces version in CAPIV. ______QUADRAT DIVISION 1 Number of quadrates in cluster = 26 eigenvalue = 0.305183 number of iterations = 3 Indicators and their sign Plea minutissima [-]; Cloeon dipterum [-]; Ilyocoris cimicoides [-]; The maximum indicator score for the negative group = -2 The minimum indicator score for the positive group = -1 Negative group: 2 Number of objects = 19 comprising: 5, 15, 24, 25, 3, 10, 19, 22, 16.1, 2, 6, 7, 8, 11, 13, 17, 21, 1, 18,

The misclassified negatives: Number of objects = 1 comprising: 16.1,

The positive group: 3 Number of objects = 7 comprising: 4, 9, 12, 14, 16, 20, 23,

Variables preferring the negative group of quadrats

Dryops luridus 1 (4, 0) Dryops similaris 1 (4, 0) Colymbetes fuscus 1 (7, 1) Hygrotus inaequalis 1 (17, 2) Hyphydrus ovatus 1 (12, 0) Laccophilus minutus 1 (9, 0) Porhydrus lineatus 1 (5, 0) Gyrinus marinus 1 (13, 0) Haliplus confinis 1 (11, 0) Haliplus obliquus 1 (4, 0) Haliplus ruficollis 1 (10, 0) Berosus affinis 1 (6, 1) Laccobius minutus 1 (8, 0) Hygrobia hermanni 1 (7, 0) Anopheles atroparvus 1 (7, 0) Phalacrocera replicata 1 (4, 0) Odontomyia ornata 1 (11, 2) Cloeon dipterum 1 (17, 1) Cloeon simile 1 (7, 0) Caenis horaria 1 (5, 0) Corixa punctata 1 (9, 1) Cymatia bonsdorffii 1 (11, 0) Cymatia coleoptrata 1 (10, 0) Hesperocorixa linnaei 1 (7, 0) Hesperocorixa moesta 1 (13, 1) Sigara fossarum 1 (13, 1) Gerris (immature) 1 (8, 0) Ilyocoris cimicoides 1 (17, 1) Ranatra linearis 1 (7, 0) Notonecta glauca 1 (17, 1) Plea minutissima 1 (16, 0) Microvelia reticulata 1 (5, 0) Triaenodes bicolor 1 (9, 0) Holocentropus picicornis 1 (6, 0) Argyroneta aquatica 1 (10, 0) Bithynia tentaculata 1 (14, 1) Lymnaea stagnalis 1 (17, 1) Physa fontinalis 1 (7, 0) Sphaerium corneum 1 (10, 0) Theromyzon tessulatum 1 (9, 0)

Variables biased towards the positive group of quadrats

Agabus nebulosus 1 (1, 4) Hydaticus seminiger 1 (0, 2) Hydroporus angustatus 1 (3, 4) Hydroporus planus 1 (3, 6) Hydroporus pubescens 1 (2, 5) Hygrotus impressopunctatus 1 (7, 7) Ilybius montanus 1 (0, 2) Rhantus suturalis 1 (3, 3) Helophorus brevipalpis 1 (2, 4) Limnebius papposus 1 (3, 3) Ochthebius dilatatus 1 (0, 3) Ochthebius minimus 1 (1, 2) Anacaena limbata 1 (2, 4) Berosus signaticollis 1 (4, 5) Cercyon tristis 1 (0, 2) Cymbiodyta marginellus 1 (0, 2) Lymnaea palustris 1 (0, 2) Gyraulus crista 1 (1, 2) Pisidium 1 (7, 6)

Variables with no quadrat preference

Agabus bipustulatus 1 (12, 7) Hydroporus palustris 1 (5, 3) Ilybius ater 1 (5, 3) Ilybius quadriguttatus 1 (9, 6) Liopterus haemorrhoidalis 1 (10, 5) Helophorus minutus 1 (18, 6) Anacaena lutescens 1 (19, 7) Coelostoma orbiculare 1 (5, 1) Enochrus nigritus 1 (14, 6) Enochrus quadripunctatus 1 (3, 2) Helochares lividus 1 (12, 3) Hydrobius fuscipes 1 (9, 6) Laccobius bipunctatus 1 (5, 1) Noterus clavicornis 1 (19, 7) Odontomyia tigrina 1 (4, 2) Nepa cinerea 1 (6, 2) Sialis lutaria 1 (14, 3) Crangonyx pseudogracilis 1 (17, 7) Asellus aquaticus 1 (17, 7) Radix balthica 1 (15, 5) Anisus vortex 1 (15, 4) Planorbis planorbis 1 (18, 6) Musculium lacustre 1 (9, 2) Erpobdella octoculata 1 (7, 2)

END OF LEVEL 1

TWINSPAN QUADRAT CLASSIFICATION LEVEL 1 ______

19

QUADRAT DIVISION 2 Number of quadrates in cluster = 19 eigenvalue = 0.180127 number of iterations = 5 Indicators and their sign Liopterus haemorrhoidalis [+]; The maximum indicator score for the negative group = 0 The minimum indicator score for the positive group = 1 Negative group: 4 Number of objects = 9 comprising: 5, 15, 25, 3, 10, 19, 22, 8, 1,

The positive group: 5 Number of objects = 10 comprising: 24, 16.1, 2, 6, 7, 11, 13, 17, 21, 18,

The borderline positive group: Number of objects = 1 comprising: 24,

Variables preferring the negative group of quadrats

Dryops luridus 1 (3, 1) Colymbetes fuscus 1 (5, 2) Hyphydrus ovatus 1 (8, 4) Ilybius fuliginosus 1 (3, 0) Haliplus obliquus 1 (3, 1) Limnebius papposus 1 (2, 1) Caenis robusta 1 (3, 0) Cymatia coleoptrata 1 (7, 3) Sigara dorsalis 1 (3, 0) Gerris (immature) 1 (6, 2) Microvelia reticulata 1 (4, 1) Triaenodes bicolor 1 (6, 3) Holocentropus dubius 1 (3, 0) Holocentropus picicornis 1 (5, 1) Argyroneta aquatica 1 (7, 3) Acroloxus lacustris 1 (2, 0) Physa fontinalis 1 (6, 1) Hippeutis complanatus 1 (2, 1) Pisidium 1 (5, 2) Sphaerium corneum 1 (8, 2) Erpobdella octoculata 1 (6, 1) Theromyzon tessulatum 1 (7, 2)

Variables biased towards the positive group of quadrats

Dryops similaris 1 (1, 3) Hydroporus angustatus 1 (0, 3) Hygrotus impressopunctatus 1 (1, 6) Liopterus haemorrhoidalis 1 (0, 10) Porhydrus lineatus 1 (1, 4) Berosus signaticollis 1 (0, 4) Coelostoma orbiculare 1 (1, 4) Hydrobius fuscipes 1 (2, 7) Hygrobia hermanni 1 (1, 6) Phalacrocera replicata 1 (1, 3) Odontomyia ornata 1 (3, 8) Odontomyia tigrina 1 (0, 4) Hesperocorixa moesta 1 (3, 10) Gerris odontogaster 1 (0, 3) Nepa cinerea 1 (1, 5)

Variables with no quadrat preference

Agabus bipustulatus 1 (4, 8) Hydroporus palustris 1 (2, 3) Hygrotus inaequalis 1 (9, 8) Ilybius ater 1 (2, 3) Ilybius quadriguttatus 1 (4, 5) Laccophilus minutus 1 (4, 5) Gyrinus marinus 1 (8, 5) Haliplus confinis 1 (4, 7) Haliplus ruficollis 1 (5, 5) Helophorus minutus 1 (8, 10) Anacaena lutescens 1 (9, 10) Berosus affinis 1 (3, 3) Enochrus nigritus 1 (5, 9) Helochares lividus 1 (7, 5) Laccobius bipunctatus 1 (2, 3) Laccobius minutus 1 (4, 4) Noterus clavicornis 1 (9, 10) Anopheles atroparvus 1 (4, 3) Cloeon dipterum 1 (9, 8) Cloeon simile 1 (3, 4) Caenis horaria 1 (3, 2) Corixa punctata 1 (4, 5) Cymatia bonsdorffii 1 (7, 4) Hesperocorixa linnaei 1 (4, 3) Sigara fossarum 1 (8, 5) Ilyocoris cimicoides 1 (8, 9) Ranatra linearis 1 (4, 3) Notonecta glauca 1 (9, 8) Plea minutissima 1 (8, 8) Sialis lutaria 1 (8, 6) Crangonyx pseudogracilis 1 (9, 8) Asellus aquaticus 1 (9, 8) Bithynia tentaculata 1 (8, 6) Lymnaea stagnalis 1 (7, 10) Radix balthica 1 (6, 9) Anisus vortex 1 (9, 6) Planorbis planorbis 1 (8, 10) Musculium lacustre 1 (5, 4)

20

Appendix 4. Invertebrate Status Categories

Red Data Book Category 1. RDB1 - Endangered Species in danger of extinction and whose survival is unlikely if the causal factors continue operating and whose numbers have been reduced to a critical level or whose habitats have dramatically reduced.

Red Data Book Category 2. RDB2 - Vulnerable Species likely to move into the Endangered category in the near future if the causal factors continue operating. Includes species of which most or all of the populations are declining throughout their range and those in vulnerable habitats.

Red Data Book Category 3. RDB3 - Rare Species with small populations that are not at present Endangered or Vulnerable, but are at risk. They are estimated to exist in only fifteen or fewer 10 km squares, and are usually localised within restricted geographical areas or habitats or are thinly scattered over a more extensive range.

Red Data Book Category I. RDBI - Indeterminate Species considered to be Endangered, Vulnerable or Rare, but where there is not enough information to say which of the three categories (RDB1 to 3) is appropriate.

Red Data Book Category K. RDBK - Insufficiently Known Species that are suspected, but not definitely known, to belong to any of the above categories, because of lack of information. They include species recently discovered or recognised in Britain, in poorly recorded or taxonomically difficult or unstable groups, inhabiting inaccessible or infrequently sampled but widespread habitats or of questionable native status.

Provisional Red Data Book pRDB The prefix "p" before any Red Data Book category indicates a provisional grading.

Nationally Scarce (Notable) Category A - Na Species which do not fall within RDB categories but which are uncommon and thought to occur in 30 or fewer 10 km squares of the National Grid or, for less well recorded groups, within seven or fewer Vice Counties.

Nationally Scarce (Notable) Category B - Nb Species which do not fall within RDB categories but which are uncommon and thought to occur in between 31 and 100 10 km squares of the National Grid or, for less well recorded groups, within between eight and twenty Vice Counties.

Nationally Scarce (Notable) Definition. Species which are estimated to occur in 16 to 100 10km squares in Great Britain. The subdividing of this category into Nationally Scarce A and Nationally Scarce B has not been attempted for some species because of either the degree of recording that has been carried out in the group to which the species belongs, or because there is some other reason why it is not sensible to be so exact.

Definitions of lUCN threat categories (IUCN 1994)

EXTINCT (EX). A taxon is Extinct when there is no reasonable doubt that the last individual has died.

EXTINCT IN THE WILD (EW). A taxon is Extinct in the wild when it is known to survive only in cultivation, in captivity or as a naturalised population (or populations) well outside the past range. A taxon is presumed extinct in the wild when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual) throughout its range have failed to record an individual. Surveys should be over a time frame appropriate to the

21 taxon's life cycle and life form.

CRITICALLY ENDANGERED (CR). A taxon is Critically Endangered when it is facing an extremely high risk of extinction in the wild in the immediate future, as detailed by any of the criteria A to E.

ENDANGERED (EN). A taxon is Endangered when it is not Critically Endangered but is facing a very high risk of extinction in the wild in the near future, as defined by any of the criteria A to E.

VULNERABLE (VU). A taxon is Vulnerable when it is not Critically Endangered or endangered but is facing a high risk of extinction in the wild in the medium term future, as defined by any of the criteria A to D.

LOWER RISK (LR). A taxon is Lower Risk when it has been evaluated but does not satisfy the criteria for any of the categories Critically Endangered, Endangered or Vulnerable. Taxa included in the Lower Risk category can be separated into three sub-categories:

• Conservation Dependent (cd). Taxa which are the focus of a continuing taxon-specific or habitat-specific conservation programme targeted towards the taxon in question, the cessation of which would result in the taxon qualifying for one of the threatened categories above within a period of five years. • Near Threatened (nt). Taxa which do not qualify for Lower Risk (Conservation Dependent), but which are close to qualifying for Vulnerable; occurring in 15 or fewer hectads. • Nationally Scarce (ns). Taxa occurring in 16-100 hectads, but which are not Threatened, Lower Risk (near threatened) or Lower Risk (conservation dependent). • Least Concern (lc). Taxa which do not qualify for Lower Risk (Conservation Dependent) or Lower Risk (Near Threatened).

DATA DEFICIENT (DD). A taxon is Data Deficient when there is inadequate information to make a direct or indirect assessment of its risk of extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. Data Deficient is therefore not a category of threat or Lower Risk. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that a threatened category is appropriate.

NOT EVALUATED (NE). A taxon is Not Evaluated when it has not been assessed against the criteria.

Summary of the thresholds for the IUCN Criteria

Criterion Main thresholds Critically Endangered Endangered Vulnerable A. Rapid decline >80% over 10 years or 3 >50% over 10 years or 3 >20% over 10 years or 3 generations in past or future generations in past or generations in past or future future B. Small range – extent of occurrence extent of occurrence extent of occurrence fragmented, declining or <100km2 or area of <5000km2 or area of <20,000km2 or area of fluctuating occupancy <10km2 (<1 x occupancy <500km2 (<5 x occupancy <2000km2 (<20 x 10km2) 10km2) 10km2) C small population and <250 mature individuals, <2500 mature individuals, <10,000 mature individuals, declining population declining population declining population declining D1 Very small population <50 mature individuals <250 mature individuals <1000 mature individuals D2 Very small range <100km2 or <5 locations E. Probability of >50% within 10 years >20% within 20 years >10% within 100 years extinction

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