Styx Mill Conservation Reserve Invertebrate Assessment Styx Mill Conservation Reserve Invertebrate Assessment
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Purakaunui Prepared by R.P Macfarlane Prepared for Christchurch City Council April 2007 Styx Report: 2007/1 Styx Mill Conservation Reserve Invertebrate Assessment Styx Mill Conservation Reserve Invertebrate Assessment Implications for Management April 2007 R.P. Macfarlane 5 McAllister Place, Kaiapoi [email protected] R R Scott Editing support KEY WORDS: biodiversity, invertebrate community, wetland, waterway ecology, willow woodlands, insects, spiders, weka, fernbirds, bitterns, habitat conservation values, habitat management Contents page SUMMARY 6 1. Entomology — insect conservation perspective 6 2. Entomology – undescribed species and guild diversity 6 3. Wetland flies 7 4. Waterway insects including clarification of habitat use for flies 7 5. Insect species habitat use 8 6. Habitat management recommendations 9 7. Wetlands, waterways and integrated management goals 9 8. Native forest and shrubland restoration 10 9. Weed control in wetlands and woodlands 10 10. Insect community survey planning 10 1.0 INTRODUCTION 11 1.1 Botanical significance and history 11 1.2 Christchurch - Banks Peninsula reference invertebrate surveys 12 1.3 Wetland invertebrates 13 1.4 Woodland and shrubland invertebrates 14 1.5 Waterway invertebrates and fish 15 1.6 Threats to the terrestrial invertebrate fauna 16 1.7 Survey objectives 17 12 2.0 METHODS 17 2.1 Site habitats and sampling procedure 17 2.1.1 Yellow pan trapping 19 2.1.2 Sweep netting 19 2.1.3 Malaise trapping 19 2.1.4 Light trapping and seasonal duration of sampling 20 2.2 Representative Habitats 21 2.2.1 Waterways and Riprian margins 21 2.2.2 Woodlands 23 2.2.3 Woodlands 24 2.2.4 Grasslands 25 2.3 Fauna investigated and identification 26 Contents page 3.0 RESULTS AND DISCUSSION 26 3.1 Abundance and Diversity 26 3.2 Unusual herbivores 35 3.3 The Habitats 36 3.3.1 Waterways 36 3.3.2 Wetlands 38 3.3.3 Woodlands 39 3.3.4 Pasture, grassland and grazing 47 3.3.5 Carrion and dung 48 3.4 The Guilds 48 3.4.1 Parasites 48 3.4.2 Spiders and other predators 49 3.4.3 Flower visitors and pollination 50 3.4.4 Ground and litter dwellers 50 3.5 Identification comments and funding of invertebrate surveys 51 4.0 CONCLUSIONS AND RECOMMENDATIONS 52 4.1 Diversity, species rarity and habitat management for rare species 52 4.2 General principles in restoration planting - general animal principles 52 4.3 Native forest regeneration, Redwood Springs flats and some 53 resolution of botany/insect recommendations 4.4 Shrubland restoration and diversification of insect habitat 54 4.5 Wetland bird restoration 55 4.6 Coastal Canterbury insect community studies- status and way forward 55 ACKNOWLEDGEMENTS 57 REFERENCES 58 FIGURES AND TABLES Table 1: Recorded Invertebrate diversity in Christchurch 13 Table 2: Styx Mill Conservation Reserve invertebrate sampling details 18 Table 3: Specimens collected in Styx Mill Conservation Reserve 28 Table 4: Christchurch invertebrates in remnant and planted native bush 41 Figure 1: Styx Mill Conservation Reserve - sample sites 29 -34 Figure 2: North east willow woodland - pond fringe and damming 54 SPECIES DETAILS AND ILLUSTRATIIONS Appendix 1: Invertebrates Recorded from Styx Mill Conservation Reserve 62 Photographs of Styx Mill Conservation Reserve Insects and Spiders 77 1. Spiders - predators 77 2. Hymenoptera parasites 81 3. Wetland and waterway flies 89 4. Grasslands and wetland herbivore flies 94 5. Beetles and bugs 97 Appendix 2 Styx Mill Conservation Reserve 2003/ 2004 insect survey summary 99 Appendix 3 Styx Mill Conservation Reserve 2003/ 2004 insect survey of different habitats 106 SUMMARY 1. Entomology — insect conservation perspective • The survey principally used yellow pan traps (2 sites) supplemented by sweep netting, light traps (8 sites) and malaise traps (two sites). Thus it sampled mainly the aerial component of the insect fauna. • Over 9300 specimens were collected comprising 354-38 insect species (Table 3) and 27 spider species. The total insect biodiversity of the reserve is estimated to be between 800 and 1000 insect species. • The boggy ditches and adjacent vegetation in the eastern part of the Styx Mill Conservation Reserve have exceptional diversity of shore flies (Ephydridae) with 15 species, which is around 20% of all known New Zealand species. The rediscovery of Hydrellia acutipennis (Harrison 1959) from only the second known site proves it is associated with more than salt marshes. This is a significant advance in our knowledge of this rarely collected species. H. acutipennis was described from three specimens taken from Allans Beach, Otago Peninsula, from a salt marsh flat. Mathis (pers. comm.) did not find any specimens from Allans Beach in January 2004. The Styx Mill Conservation Reserve specimens are the first good quality males of the species for description coming from only the second site known for H. acutipennis. Hydrellia species are herbivores, but the host plant for H. acutipennis is unknown. Between 2003-04 and the summer of 2005, flooding of part of the north east willow woodland, evident from the increased flow in the stockyard ditch, seems to have led to the loss of the population of H. acutipennis. I could not recover any H. acutipennis in 2005 from two sites along the ditch. • In Styx Mill Reserve, the relatively large Ephydrella shore flies were chiefly found along the ‘mud flats’ of ditches, which are difficult to sample readily even by experienced sweep netters of shore flies. An Ephydrella species was initially ascribed to E. thermarum, but all previous specimens were associated with hot springs at four sites in the North Island in Bay of Plenty and Taupo. Mathis has yet to fully recheck these specimens, especially the genitalia, to verify this identification. The Reserve also has one or two rather small new species of Hydrellia. • Conservation of the pointed wing H. acutipennis and retention of a spectrum of shore flies Empididae, e.g., Isodrapetes, and Muscidae flies directly conflicts with the proposal based on botanical values to restore forest to the eastern grassland in the Reserve. Waterways are of minimal botanical value for native plant species. The upper Styx River invertebrate fauna has also become much more significant ecologically, on a regional basis, due to the adverse effect of declining flow in lowland waterways in rural Canterbury with heavier irrigation use and cattle pollution of waterways. • The flightless crane fly, Gynoplistia pedestris, may merit ‘vulnerable’ conservation species status. G. pedestris is now known from 1 sites from the Waipara coast to the Halswell River (Macfarlane 2004), but urbanization has almost certainly reduced and altered sites since the initial collections from the 1920s to 1950s. Three insect surveys (Travis Wetland, south west Christchurch waterways and Styx Mill) financed by the Christchurch City Council have provided useful information about the current distribution and status of this distinctive fly. 2. Entomology – undescribed species and guild diversity • At Styx Mill Reserve, the recorded level of endemic species (found only in New Zealand) was about 80%, the same as for Travis Wetland, but the actual level is probably about or somewhat above 90%. An estimated -12 insects (2.2 – 4.2%). the salticid spider and some tetragnathid spider species may well be undescribed. Certainly undescribed insect species include Molophilus (2 species), Hercostomus species, 7 Isodrapetes species and the small Hydrellia species. Several of the Muscidae species (genus Millerina), some of the midge species and perhaps up to three dark metallic species of Dolichopodidae are also likely to be undescribed. Most of these species were not present at Travis Wetland, but some, including the undescribed Hercostomus species, but not Isodrapetes or Ceratomerus crassipennis, were found in the concurrent south west Christchurch waterway survey, which I carried out. • At least four insect species previously known from one to six sites in the South or Stewart Islands, and known from fewer than 10 specimens, have been discovered in the Styx Mill Reserve and in the sand dunes at New Brighton. • Fuller access to specialists for this survey could have revealed further interesting species and habitat distributions. • For the different guilds (e.g., predators, parasites) of invertebrates, the ratios in species diversity seem to be reasonably consistent with other major land habitats within coastal Canterbury. 3. Wetland flies • Characteristic fly species for this wetland are the marsh fly, Dilophus nigrostigma, and two Dolichopodidae species (Tetrachaetus bipunctatus, Sympycnus sp.), which were more abundant away from the freshwater. The flightless crane fly, Gynoplistia pedestris, preferred open swampy areas and apparently favours muddy areas. The crane fly Molophilus quadrifidus preferred either wetland or ephemeral pools. • The apparent localized loss of H. acutipennis, which was found only in open sites, would be adversely affected by shading of the forestation proposal by botanists. • The presence of undescribed Diptera species in the wetlands and along at least only partly shaded waterways, e.g., Hercostomus, is fully to possibly partly incompatible with shading of their wetland or waterways. 4. Waterway insects including clarification of habitat use for flies • The survey identified Scaptia ricardoae (Tabanidae) as a first record for Christchurch waterways and confirmed that Ceratomerus crassinervis (Empididae) still exists in Christchurch and Canterbury. The diversity of species and genera for midges (Chironomidae), dance flies (Empididae) and Muscidae from freshwater streams and ponds was partly clarified compared with previous invertebrate surveys from within the Styx Mill Reserve, but was hampered by inadequate taxonomy of the adults. With perhaps 20 species of midges and Muscidae, it would not be a large task to photograph and provide a working key to distinguish these waterway flies for any further survey of the upper reaches of the Styx River. • The introduced Hydrophorus praecox (Dolichopodidae) and two genera of biting midge (Ceratopogonidae) were also identified from the Styx catchment for the first time.