Tuatara: Volume 25, Issue 1, July 1981
The Distribution and Abundance of Procordulia Grayi (Selys) (Odonata : Corduliidae) in New Zealand
The Distribution and Abundance of Procordulia Grayi (Selys) (Odonata : Corduliidae) in New Zealand
There are suggestions in the literature that P. grayi is a rare or local species, that it is subalpine in its distribution and that its larvae compete better in colder lakes and streams. However, the combined use of museum material, field observations and literature records shows P. grayi to be a dragonfly which is widespread in its latitudinal and altitudinal distribution and indicates that cold-adaptation in its larvae cannot be substantiated.
New Zealand has an odonate fauna which is sparse in species. Only three zygopteran species were recognised in the fauna by Wise (1973) following the relegation by Tillyard (1913) of two species of Xanthocnemis as synonyms of X. zealandica (McL.). There are rather more Anisoptera: four endemic species- Uropetala carovei (White), Antipodochlora braueri (Selys), Procordulia smithii (White) and Procordulia grayi (Selys) - and four self-introduced species which are known to breed in New Zealand: Hemicordulia australiae (Rambur), Aeshna brevistyla Rambur, Hemianax papuensis (Burmeister) and Diplacodes bipunctata (Brauer). Pantala flavescens (Fabricius) has been recorded as a migrant on the North Island (Lieftinck, 1975) and on the South Island (Corbet, 1979). Another species in the New Zealand list, Tramea transmarina (Brauer) has been identified from the Kermadec Islands (Armstrong, 1973) but not yet from the mainland.
Roughly 250 publications comment in some way on this limited odonate fauna and one might suppose from such a volume of literature that the fauna is well-known. Until recent years, however, there has been no local observer, with the exception of Wolfe (1953) and Armstrong (1958a, 1958b, 1958c, 1975, 1978), who has made original, in-depth investigations into the ecology of the anisopteran fauna. One result has been that much that was anecdotal has become firmly fixed in this mass of literature by repetition and it becomes difficult to separate fact from fancy.
P. grayi is a species about which conflicting generalisations have been made: “it is a very rare dragonfly which has occurred at sub-alpine localities in the South Island” (Hudson, 1950); “it is localised and comparatively rare” (Miller, 1971); “it is a cold lake breeder which is probably the dominant Procorduli in the centre of the North Island and in the South Island lakes" (Armstrong, 1975); “it competes more successfully in colder habitats such as the lakes and mountain streams of Tongariro National Park” (Armstrong, 1978); “it is widely distributed in lakes” (Winterbourn and Lewis, 1975); and “it is restricted to relatively cool lakes and streams primarily in mountain areas” (Deacon, 1979). Is then P. grayi a common, widely-dispersed species or is it a rare, cold-adapted, upland species? My own field observations indicated P. grayi to be a more common and more widely distributed species than many of the foregoing remarks would imply. This paper reports my efforts, by scanning museum specimens and reliable published information, to assess the status of this species.
Distribution Records for P. Grayi
A combination of museum records, published accounts of authors known to be reliable in their identification of P. grayi, and my own field notes have been used to determine the distribution of the species. As is mentioned later, misidentification by some authors has been a problem in evaluating distribution records for P. grayi. Approximate localities from which P. grayi material has been examined are mapped in Figure 1.
All adult P. grayi specimens held in the British Museum (Natural History), London, England (n equals 16), the National Arthropod Collection, Department of Scientific and Industrial Research, Auckland, New Zealand (n equals 47), the National Museum, Wellington, New Zealand (n equals 14), and in the collection of the Ecology Division, Department of Scientific and Industrial Research, Lower Hutt, New Zealand (n equals 3) were examined in this study but for only 73 specimens were there adequate collection records. These localities are contained in the list which follows together with those for larval specimens of P. grayi in the National Museum collection (n equals 7). Following Watt (1979) the abbreviations BMNH, NZAC, NMNZ and EDNZ respectively are used later in this paper to identify the institutions holding specimens. The NZMS 1 map series sheet number, grid reference and altitude for individual collection localities are shown in parenthesis. Map references are necessarily approximate as are the altitudes estimated from the topographical maps. The localities from which P. grayi material has been examined are as follows:
Otatamarae, L. Rotoiti (N76 834190, 275m); Rotorua (N76 710060, 278m — 1 larva ex pond three miles E of Fitzgerald Glade); Matawai, East Cape (N88 946757, 540m—larva ex pond three miles N.E. Matawai); Huka Falls (N94 561422, 345m); Taupo (N94 555375, 357m): Acacia Bay (N94 500357, 357m); Tauhara (N94 631367, 1097m); L. Waikare-iti (N96 582319, 870m); Wanganui Stream, Lake Taupo (N102 219261, 360m); Tokaanu (N102 252040, 360m); Waitahanui Backwater (N103 550254, 360m); Rangitaiki River 60-8 camp (N103 827140, 682m); L. Waikaremoana (N105 577288, 585m); L. Rotoaira (N112 200904, 564m); Mahuia Stream, Tongariro National Park (N112 005820, 840m); Foxton Beach (N148 740220, 3m); Shannon (N152 920117, 30m); Lake Reserve (N161 820368, 15m); Martinborough (N161 963304, 30 m — larvae 10 March, 1975 ex fish pond); Orongorongo Valley (N164 515148, 135m); L. Kohangatera (N164 420120, 9m-larva); Wharariki, Cape Farewell (S1 095238, 3m); Boulder Lake (S8 995765, 960m — adults and numerous exuviae); Muritai (S29 417836, 30m); L. Rotoroa (S33 997669, 444m); Lewis Pass (S46 810963, 914m); Arthurs Pass (S59 056278, 990m); Lake Pearson (S66 253103, 574m-larva); Cass (S66 245158, 579m); L. Paringa (S77 159324, 29m); Hermitage, Mt Cook (S79 761312, 720m); Governors Bush, Mt Cook (S79 763307, 750m); Governors Bay (S84 017445, 60m); Mt Burns (S89 664296, 1050m); Paradise (S122 280064, 345m); Glenorchy (S123, 313913, 327m); Queenstown (S132 552699, 304m); Manapouri (S149 675015, 180m); Oreti Beach (S181 250988, sea level — larva ex gravel pit).
Elsewhere I have recorded P. grayi from Pukepuke near Foxton (N148 780370, 9m) (Winstanley, 1979), Lake Waikaremoana (N105 577288, page 17 585m) and Lake Waikare-iti (N96 582319, 870m (Winstanley, 1980), and from Gollans Valley (N164 448188, 30m) (Winstanley, 1981). I have also recorded final-instar exuviae from three Taranaki lakes: L. Mangamahoe (N109 700840, 142m, 29 Dec. 1978); L. Ratapiko (N109 893742, 195m, 2 Jan. 1979); and L. Rotokare (N119 975440, 179m, 2 Jan 1979). I have found final-instar exuviae at a number of sites further south also: L. Kaikokopu (N148 780327, 9m); L. Koputara (N148 780298, 9m); and L. Kohangapiripiri (N 164 410126, 3m). I have taken P. grayi larvae from Lake Pounui (N165 640152, 30m, August 1978) and adults are common there in summer.
The data presented show that P. grayi is a widespread species south of 38°01′S. Within this study, its use of a lotic situation for larval development has been confirmed at only one site, the Cass Stream (Crumpton, 1977), although Armstrong (1975, 1978) was satisfied that larger pools in rivers and streams provide a tolerable habitat for the species. The preferred larval habitat appears to be in standing waters as others have indicated (Armstrong, 1958, 1975; Penniket, 1966; Winterbourn and Lewis, 1975) and adults appear to be localised to some extent on this account. They may, however, be found over grasslands many kilometres from water (Harrison and White, 1969) and indulge in “hilltopping”, a behaviour I have seen in P. smithii and H. papuensis also. Armstrong (1975) also reported this behaviour in H. papuensis. The dragonflies presumably visit hilltops to exploit the concentrations of other insects which occur there.
Hudson (1950) considered P. grayi to be sub-alpine in its distribution and Armstrong (1975) has observed that it has a tendency to be associated with larger bodies of standing water. Most large lakes in New Zealand lie at a similar and high altitude (Jolly and Irwin, 1975) and this might lead to the impression that an associated dragonfly is influenced in its habitat selection by altitude rather than the lacustrine environment per se. P. grayi larvae have been found in standing waters from close to sea level to 960m and it cannot therefore be considered entirely an upland species.
Adults emerge in large numbers from ponds as small as 0.2ha at Pukepuke; and I have found that both P. grayi and P. smithii emerge in moderate numbers from a much smaller pond, Ngutu Manu, near Waikaremoana (Winstanley, 1980), so that its association with large bodies of water only is unsupported by my observations. Size of the water body does not seem to be an important consideration.
Relative abundance of P. grayi
P. smithii males will attend a small territory in which flight is slow, with frequent hovering, over a regular flight path. P. smithii adults may also form mixed-sex feeding-swarms and I have also seen them in a mixed-species swarm with H. australiae (Winstanley, 1981). They can be taken easily when they swarm. In contrast, P. grayi is a stronger flying, more solitary species and not so easily caught. Armstrong (1975) believed that if P. grayi and P. smithii occurred in equal numbers at a lake, five P. smithii would be taken to each P. grayi. Collections of final-instar exuviae at Lake Waikaremoana in February 1979 showed that P. grayi was page 19 more abundant than P. smithii in the lake (Winstanley, 1980), in the ratio of about 100: 1, yet P. smithii adults in collections made at that time outnumbered P. grayi by 5:1. The collections themselves then are unreliable indicators of relative abundance.
Quantitative studies on the Anisoptera are as yet few in New Zealand. Mylechreest (1978) found P. grayi larvae at winter densities of over 300 per sq.m. in the shallow littoral of Lake Waikaremoana where it was the only anisopteran he recorded. Deacon (1979) found only 30 final-instar exuviae of P. smithii against 145 for P. grayi at Lake Sarah in the two years 1976-77 and 1977-78. In qualitative terms, Armstrong (1958c) implied that at Taupo P. smithii was more widespread but P. grayi more numerous. Later, he stated that P. smithii was never very numerous, and that P. grayi is probably the dominant Procordulia in the centre of the North Island and in the South Island lakes; but he qualified this by saying that practically all of his observations had been made on the Volcanic Plateau (Armstrong, 1975). Martin (1948) evidently considered P. grayi to be common since he applied the title “the common dragonfly” to the male specimen he illustrated. Stout (1969) recorded P. grayi as common in Canterbury. She also listed it as one of the less numerous of the “dominant” organisms of sheltered shores in the lakes of Nelson, Canterbury and Westland (Stout, 1975). In the section on distribution, I listed a number of sites at which I had seen P. grayi: at each body of standing water mentioned I would regard P. grayi as common.
Influence of man on distribution
Deacon (1979) attributes to Armstrong (1958c) the statement that Procordulia species are usually restricted to mountain habitats or lowland areas undisturbed by man. All of the larger lakes in New Zealand are very young, and the smaller lakes and ponds are relatively ephemeral (Watt, 1973, 1975) so that the pastoral practices of man, and impoundments for irrigation, domestic water supplies and hydro-electric developments should have favoured the resident lentic species. P. grayi certainly exploited rapidly the lowland man-made and manipulated ponds with which I am familiar at Pukepuke. Amongst the larval records given earlier are those of a larva taken from a Martinborough fish pond and one from a gravel pit at Oreti Beach, both man-made ponds. Deacon (1979) found final-instar exuviae at Isaacs Pond which is also man-made. It seems likely that the species would readily colonise chemically and physically suitable manmade ponds elsewhere in upland areas or in lowland habitats such as the examples just given.
Cold adaptation in P. grayi
The published data on temperature regimes in New Zealand lakes is limited but from the information summarised by Jolly and Irwin (1975) it appears that temperatures in standing waters are inversely related to altitude. If this is so, the hypothesis that a species with a broad altitudinal tolerance such as P. grayi is exclusively cold-adapted becomes untenable.
Deacon (1979) gave preliminary results which showed that P. grayi eggs did not hatch at temperatures below 9.5°C, and that ova of this species exposed to temperatures of 8.7°C failed to develop. Such a high minimum, survival temperature is not what I would expect in a cold-adapted species and, in contrast, P. smithii has an egg-diapause (Deacon 1978, 1979) which enables it to overwinter successfully in this stage in the cooler page 20 conditions experienced at higher altitude. Deacon (1979) found that P. grayi was attuned to a cool environment by its pattern of emergence earlier in the season than P. smithii which he thought provided a sufficient period of warm conditions for the maturation of adults, reproduction, the completion of egg development and hatching. However, Lake Sarah, one of Deacon's study areas, has a fickle summer climate. Severe temperature falls there after emergence can lead to mass mortality in Uropetala carovei (Wolfe, 1953; Winstanley and Rowe, 1980) and no doubt early-emerging Procordulia specimens would succumb to the same fate. The combination of early emergence and its requirement for high temperatures for egg development must make P. grayi's survival precarious at Lake Sarah in some years.
Misidentification of P. grayi
Each of the corduliid species present in New Zealand can be identified unequivocally by its abdominal colour pattern or wing venation (Armstrong, 1958; Penniket, 1966), or by the morphology of the terminal abdominal appendages (Figure 2). Nevertheless mistaken identity must have played a part in the generalisations made about P. grayi. The confusion seems to stem mainly from the work of Hudson (1892, 1904, 1950) who clearly had difficulty in identifying the Corduliidae. For example, Hudson (1892) illustrated a male P. grayi which he identified as P. smithii stating that it occurs almost everywhere. In his book on the New Zealand Neuroptera (Hudson, 1904), he stated that he was unacquainted with P. grayi and obviously was unaware of his earlier error. In his final publication (Hudson, 1950) he gave diagnoses for the field identification of three corduliids which he regarded as rare or local, and “which might easily be passed over as examples of the common and generally distributed P. smithii” commenting that he had seen only two specimens of P. grayi.
An examination of the sixteen corduliid specimens in the Hudson collection (NMNZ) revealed a male P. grayi (Governor's Bush, Mt Cook 28 January 1945) identified as a male P. smithii, and a male P. smithii (“locality uncertain, probably Wellington”) identified as a female A. braueri. From the foregoing, Hudson's comments on the three endemic corduliids must be treated with reservation. Salmon (1950) attempted to synonymise P. smithii and P. grayi although Armstrong (1958 c) was able to show how the species can even be determined on the wing. Powell (1967) illustrated a male P. grayi, which he identified as P. smithii, calling it “the common dragonfly”, the name which Martin (1948) also applies to P. grayi.
It appears from museum collections, field observations and the reliable literature reports that P. grayi is a common species, widespread in both latitudinal and altitudinal distribution, the larvae of which occur in both lotic and lentic situations, but mainly in lentic waters. Cold adaptation in the species has not been substantiated.
I record my thanks to T. K. Crosby, J. S. Dugdale, R. Kleinpaste and Annette K. Walker (NZAC), R. G. Ordish and R. Palma (NMNZ), M. J. Meads (EDNZ) and S. J. Brooks (BMNH) for their assistance whilst I examined specimens in their institutions. I am most grateful to Mr and Mrs B. Marshall of Auckland, and Mr and Mrs R. Greenslade of London for page 21 their warm hospitality in their respective cities. My thanks go to G. W. Gibbs and J. R. Grehan of Victoria University of Wellington, and to my wife Christine, for commenting on the manuscript and for suggestions which improved it. Nesta Black has cheerfully typed the material through its developmental stages. This research was carried out during the tenure of a Junior Lectureship at Victoria University of Wellington. I am grateful to my family for financing my peregrinations.
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