Research Article |
Corresponding author: Igor M. Sokolov ( igbembi@yahoo.com ) Academic editor: Borislav Guéorguiev
© 2019 Igor M. Sokolov.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Sokolov IM (2019) A review of the genus Pelodiaetus Jeannel (Coleoptera: Carabidae: Anillini) of New Zealand, with re-description of the genus, description of a new species and notes on the evolutionary history. ZooKeys 879: 33-56. https://doi.org/10.3897/zookeys.879.37684
|
On the basis of new morphological data a re-description of the genus Pelodiaetus is provided, a new species of the genus P. nunni sp. nov. (Christchurch, Canterbury, South Island) is described, and P. lewisi Jeannel is proposed as a synonym of P. sulcatipennis Jeannel, syn. nov. A taxonomic key as well as distribution maps for species of Pelodiaetus are provided. Data on comparative morphology and biogeographical aspects of speciation in the genus Pelodiaetus and its morphological relatives from Australia and New Zealand are discussed.
Adephaga, biogeography, East Gondwana, identification key, new synonym, Pelodiaetus, syntopic co-occurrence
The genus Pelodiaetus was erected by
The author had the opportunity to investigate the material on Anillini from the New Zealand Arthropod Collection and the private collection of JT Nunn, whose numerous collecting methods included a soil-washing technique that greatly enriched the number of subterranean species available for study. Preliminary sorting of the material of Pelodiaetus showed that this genus includes one undescribed species and one species that needs to be synonymized. In addition, thorough examination of elytral chaetotaxy revealed the discrepancy between the state of this character in the works of previous authors and its actual configuration. Altogether, the description of a new species and corrected re-description of the genus, along with comments on the status of described forms, serves as a basis for this paper.
This study is based on the examination of 83 specimens of Pelodiaetus from the New Zealand Arthropod Collection (NZAC), Auckland, New Zealand, and from the personal collection of John T Nunn (JTN), Dunedin, New Zealand. Verbatim label data are given for type specimens of all newly described taxa, with label breaks indicated by a slash (“/”).
All specimens were measured electronically using a Leica M420 microscope equipped with a Syncroscopy AutoMontage Photomicroscopy system (SYNCROSCOPY, Synoptics Ltd.). Measurements for various body parts, given in mm, are encoded as follows:
LH length of head, measured along midline from anterior margin of labrum to the virtual line connecting posterior supraorbital setae;
WH width of head, at level of anterior supraorbital setae;
WPm maximal width across pronotum;
WPa width across anterior angles of pronotum;
WPp width across posterior angles of pronotum;
LP length of pronotum from base to apex along midline;
WE width of elytra, at level of 4th umbilicate setae;
LE length of the elytra, from apex of scutellum to apex of left elytron;
SBL standardized body length, a sum of LH, LP, and LE.
In addition, nine ratios between these measurements were calculated: WH/WPm, WPm/WE, WPa/WPp, WPm/WPp, WPm/LP, WE/SBL, WE/LE, LE/SBL, and LP/LE. All values are given as mean ± standard deviation.
Digital photographs of the dorsal habitus of new species were taken with the AutoMontage system using a Leica M420 microscope. Line drawings of selected body parts were made using a camera lucida on an Olympus BX 50 microscope. Scanning electron micrographs were made with coating on an ESEM FEI Quanta 200.
Dissections were made using standard techniques. Genitalia were dissected from the abdomens of specimens previously softened in boiling water for 20–30 minutes. Contents of the abdomen were cleared using boiling 10% KOH for 2–3 minutes to remove internal tissues, and then washed in hot water before examination. After examination, genitalia were mounted on plastic transparent boards in dimethylhydantoin formaldehyde resin (DMHF,
The author had no opportunity to investigate the type material of the New Zealand anillines. The concept of Pelodiaetus used in the paper is based on the material identified by Moore during his work on New Zealand fauna of Anillina (
Criteria for recognizing new species were the following (
The terms used in the paper and the scheme of descriptions follow that of the author’s previous publications on New Zealand Anillini (
Subfamily Trechinae Bonelli, 1810
Tribe Anillini Jeannel, 1937
Pelodiaetus Jeannel, 1937: 275 (type species Pelodiaetus sulcatipennis Jeannel, 1937, by original designation).
The members of this genus are distinguished from the other New Zealand representatives of Anillina by the following combination of characters: eyes absent; head with long fronto-lateral carinae; antennae submoniliform, of moderate length; prosternal process slightly dilating to the blunt apex; pronotum cordiform, with prominent anterior angles and with short basal constriction anterior to the projected posterior angles; elytra with oblique longitudinal grooves; elytral apices slightly dehiscent with narrowly rounded sutural angles; pygidium exposed in apical half; 1st elytral discal seta indistinct, only slightly longer then surrounding vestiture, while 2nd and 3d discal setae always clearly visible; elytral margin with umbilicate series of 9 pores: the longest setae in the 2nd, 6th, and 9th pore positions, 7th, 8th, and 9th pores equidistant, not aligned, virtually forming obtuse isosceles triangle with 8th pore shifted towards disc. The developed fronto-lateral carinae, antennae of moderate length, projected pronotal anterior angles, grooved elytra, exposed pygidium and small size separate Pelodiaetus from endogean Hygranillus Moore. Distinct posterior angles of pronotum, dilated prosternal process and grooved elytra distinguish the representatives of Pelodiaetus from the species of Zeanillus Jeannel. Umbilicate series of nine pores, slightly dehiscent apices of grooved elytra and exposed pygidium separate the members of Pelodiaetus from the species of Nesamblyops Jeannel. An absence of the distinct tubercle anterior to the posterior angles of the pronotum and the small size separate the species of Pelodiaetus from the species of Pelodiaetodes Moore.
Size. SBL range 1.19–1.45 mm.
Habitus.
Body form slightly convex, almost subparallel (Fig.
Color. Body rufo-testaceous or testaceous, appendages testaceous.
Microsculpture. Dorsal microsculpture of polygonal sculpticells with isodiametric mesh pattern throughout the dorsal surface. Development of microsculpture varies on different body parts. Head and disc of pronotum with shallow microlines, sometimes partially obliterated, while on elytra microlines are very distinct, forming well-pronounced sculpticells.
Luster. Body surface shiny.
Macrosculpture. Body surface sparsely and finely punctate.
Vestiture. Body surface covered with sparse yellowish short setae. Vestiture of elytra moderately long (around one-half length of discal setae).
Fixed setae.
Primary head setae include a pair of clypeal (cs), a pair of frontal (fs), two pairs of supraorbital (ssa and ssp) and one pair of postorbital (pos) setae (Fig.
SEM illustrations of head, dorsal aspect, and labial complex, ventral aspect, of Pelodiaetus species. A, C P. sulcatipennis B, D P. nunni. Abbreviations: cl – clypeus; cs – clypeal seta; fcc – fronto-clypeal carina; fs – frontal seta; gsc – glossal sclerite; lb – labrum; lms – lateral mental seta; lss – lateral submental setae; m – mentum; mp3 – maxillary palpomere 3; mp4 – maxillary palpomere 4; mt – mental tooth; mss – mental-submental suture; pms – paramedial mental seta; pos – postorbital seta; prss – primary basal submental seta; sm – submentum; ssa – anterior supraorbital seta; ssp – posterior supraorbital seta. Scale bars: 0.1 mm (A, B); 0.05 mm (C, D).
SEM illustrations of pronotum, dorsal aspect, and prothorax, ventral aspect, of Pelodiaetus species. A, C P. sulcatipennis B, D P. nunni. Abbreviations: bs – basilateral pronotal seta; ed2 – scutellar seta; ls – midlateral pronotal seta; mg – marginal pronotal gutter; pep – proepipleuron; pes – proepisternum; prcx – procoxa; ps – prosternum; psp – prosternal intercoxal process; sct – scutellum. Scale bars 0.1 mm.
Head
(Fig.
Eyes. Eyes absent.
Antennae. Submoniliform, 11-segmented, extended to about posterior margin of pronotum. Antennomeres 1 and 2 elongate, of equal length and 1.3–1.4 times longer than antennomere 3, which is slightly elongate and 1.1 times longer than antennomere 4. Antennomeres 4-10 globose, last antennomere conical and 1.7–1.8 times longer than penultimate antennomere.
Labrum
(Fig.
Labium
(Fig.
Prothorax.
Pronotum (Fig.
Scutellum
(Fig.
Elytra
(Fig.
Hind wings. Absent.
Pterothorax
(Fig.
Digital images of pterothorax of Pelodiaetus sulcatipennis (A) and last abdominal ventrites with female genitalia (B), ventral aspect. Abbreviations: ipa – intercoxal process of abdominal ventrite 2; mes – metendosternite; mte – metanepisternum; mtv – metaventrite; v1-v2 – abdominal ventrites 1-2; es – ensiform seta; gc1 – gonocoxite 1; gc2 – gonocoxite 2; lt – laterotergite; ns – nematiform seta; sd – spermathecal duct; sg – spermathecal gland; sp – spermatheca. Scale bars: 200 µm (A); 100 µm (B).
SEM illustrations of chaetotaxy of elytra, dorso-lateral aspect, of Pelodiaetus species. A P. sulcatipennis B P. nunni. Abbreviations: ed2 – scutellar seta; ed3 – 1st discal seta; ed5 – 2nd discal seta; ed6 – 3d discal seta; ed8 – apical seta; eo1–9 – setae 1–9 from the umbilical series. Scale bars 0.2 mm.
Legs
(Fig.
SEM illustrations of structural features of legs of Pelodiaetus sulcatipennis, ventral aspects. A left protarsus and protibia B right mesotibia C left metatibia. Abbreviations: ac – antenna cleaner; as – adhesive setae; asp – anterior spur; asr – anterior setal row; cls – clip seta; msb – mesotibial brush; msms – mesotibial modified seta; mtb – metatibial brush; mtms – metatibial modified seta; mts – metatibial spur; psp – posterior spur; psr – posterior setal row; sb – setal band; ta1–ta2 – tarsomeres 1–2. Scale bars: 0.05 mm.
Abdominal ventrites.
Five visible abdominal ventrites: 2nd ventrite longest, 1.7–2.0 times longer than 3rd or 4th, 3rd and 4th equal in length; the last, 5th, 1.6–1.8 times longer than 4th. Intercoxal process of 2nd ventrite of moderate width, constricted anteriorly, subparallel before blunt apex (Fig.
Male genitalia
(Fig.
Female internal genitalia.
Gonocoxite 1 asetose (Fig.
Included taxa. The genus comprises two species: P. sulcatipennis Jeannel, and P. nunni sp. nov.
Geographic distribution. The species of Pelodiaetus are known from the lowlands of three regions of the South Island of New Zealand (Fig.
Habitat. According to the label information, all specimens of Pelodiaetus were collected from washed soil samples, except one specimen, which was collected under a stone after rain. Collections were made in a vast spectrum of habitats: from improved pasture and tussocks to conifer (kahikatea and podocarp) and broadleaf (Neopanax and beech) forests. Beetles were collected during most months of the year, except February, July, and August.
Relationships. Morphologically, the closest relative of Pelodiaetus among the New Zealand anillines is Pelodiaetodes, the two genera together forming a distinct New Zealand lineage of Anillini. Both genera share developed fronto-lateral carinae, distinct pronotal posterior angles, a dilated prosternal process, nine setae in the elytral umbilical series of pores, longitudinal elytral grooves, and are distinguished by the combination of these characters from any other New Zealand Anillina. Compared with overseas Anillini it seems reasonable to group the members of Pelodiaetus with other anillines having grooved elytra, including the Australian Illaphanus Macleay and the Madagascan Bulirschia Giachino, Malagasytyphlus Giachino, and Malagasydipnus Giachino (
1 | Eyes lacking (Fig. |
2 |
– | Other combination of characters | other genera of New Zealand Anillini |
2 | Male with distal sclerites (ds) of internal sac long (Fig. |
P. nunni sp. nov. |
– | Males with distal sclerites (ds) of internal sac short (Fig. |
P. sulcatipennis Jeannel |
HOLOTYPE, male, in NZAC, labeled: / New Zealand MC Ahuriri SR Port Hills 31 May 08 / Washed soil sample, broad-leaf forest / NZMS 260 M36: 797303 455m /.
PARATYPES (7 specimens, in NZAC, JTN), 4 males and 2 females labeled same as holotype; 1 female labeled: / New Zealand MC Ahuriri SR Port Hills 7 Apr 07 / Washed soil sample, broad-leaf forest /.
The specific epithet is a Latinized eponym in the genitive case, and is based on the surname of John T. Nunn, the collector of this species.
New Zealand, South Island, Canterbury, Port Hills Range.
Adults of this species (Fig.
With character states of the genus as summarized above.
Size. Small to medium for genus (SBL range 1.25–1.32 mm, mean 1.30 ± 0.028 mm, n = 6).
Habitus. Body form subdepressed, subparallel, moderately elongate (WE/SBL 0.33 ± 0.012), head comparatively wide for genus (WH/WPm 0.84 ± 0.011), pronotum of moderate width in comparison to elytra (WPm/WE 0.83 ± 0.045).
Color. Body color rufo-testaceous, appendages testaceous.
Prothorax. Pronotum moderately long (LP/LE 0.41 ± 0.011) and comparatively elongate (WPm/LP 1.19 ± 0.049), with lateral margins arcuately constricted posteriorly (WPm/WPp 1.48 ± 0.059). Width between anterior angles slightly greater than between posterior angles (WPa/WPp 1.21 ± 0.080).
Elytra. Slightly depressed along suture, comparatively long (LE/SBL 0.57 ± 0.004) and moderately narrow (WE/LE 0.58 ± 0.019). Lateral margins slightly divergent at basal third, subparallel at middle and evenly rounded to apex in apical third.
Male genitalia.
Median lobe (Fig.
Line drawings of male genitalia and female spermathecae of Pelodiaetus species. P. nunni (NZ, Canterbury, Ahuriri Scenic Preserve): A median lobe, right lateral aspect B left paramere, left lateral aspect C right paramere, right lateral aspect D spermatheca. P. sulcatipennis (NZ, Otago, Outram): E median lobe, right lateral aspect F left paramere, left lateral aspect G right paramere, right lateral aspect H spermatheca. Abbreviations: ds – dorsal sclerites; sd – spermathecal duct; sg – spermathecal gland; sp – spermatheca. Scale bars: 0.1 mm (A, B, C, E, F, G); 0.05 mm (D, H).
Female internal genitalia.
Spermatheca weakly sclerotized, moderately elongate (Fig.
This species is known from the coastal Mid Canterbury area of
Specimens were collected from soil in a broadleaf forest.
Based on the structure of male genitalia and spermatheca P. nunni is postulated to be the sister, more derived taxon of P. sulcatipennis.
Pelodiaetus sulcatipennis
Jeannel, 1937: 277 (original description);
Pelodiaetus lewisi
Jeannel, 1937: 277 (original description), syn. nov.;
Stewart Island: Ulva Island Nov-Dec 2003 /coastal forest litter (5 specimens).
Southland: Tussock Creek Forest Hill Res 1 Sep 07 / Washed soil sample. Wet Podocarp/broadleaf forest (4 specimens); New Zealand SL Forest Hill Res nr Edendale 1 Sep 07 / Washed soil sample. Kahikitea forest (3 specimens) ; New Zealand SL Alton Burn Tuatapere SR 16 Nov 08 / Washed soil sample, totara/beech forest / NZMS 260 D45: 992419 38m (4 specimens) ; New Zealand SL Tuatapere Domain Tuatapere SR 16 Nov 08 / Washed soil sample, beech forest / NZMS 260 D45: 993403 30m (1 specimen) ; New Zealand SL Tuatapere Scenic Reserve at Tuatapere Domain, 30m J.Nunn 16 Nov 08 / Molecular voucher # 104 Sokolov I.M 2009 (1 specimen); New Zealand SL Tuatapere Scenic Reserve at Tuatapere Domain, 30m J.Nunn 16 Nov 08 / Molecular voucher # 107 Sokolov I.M 2009 (1 specimen); New Zealand SL Bog Burn Taringatura Forest 2 Jan 09 / Washed soil sample, beech forest / NZMS 260 E45: 397596 250m (1 specimen); New Zealand SL Dunsdale Stream, Hokonui Hills, 110m, washed soil sample J.Nunn 26 April 08 / Molecular voucher # 100 Sokolov I.M 2009 (1 specimen); New Zealand MC Pudding Hill Reserve Mt. Hutt 700m J.Nunn 25 Oct 08 / Molecular voucher # 105 Sokolov I.M 2009 (1 specimen); SL Chloris Pass, Catlins 17 Jun 06 (7 specimens); Rakahouka 2 Sep 07 /Neaopanax forest (2 specimens).
Dunedin: Woodside Glen, Outram 18 Nov 06 (3 specimens); Sutton, Salt Lake 21 Jun 09 / tussock and improved pasture (2 specimens); Picnic Gulley, Taieri Mouth 18 May 06 / under stone after rain (29 specimens); New Zealand DN Start of Government Tck Waipori Valley / Washed soil sample 17 Dec 06 (1 specimen).
Central Otago: Logan Burn 900m 13 Dec 1982 / ex. Oreobolus pectinatus (3 specimens); Cromwell, Kawarau Gorge, Roaring Meg 500m 12 Mar 1959 (2 specimens); Garden V., Raggedy Range 10 Sept 68 / Raoulia (1 specimen); Alexandra Hills, the Knobbies 10 Sept 68 / Raoulia (1 specimen).
South Canterbury: Guns Bush Waimate 23 Dec 06 / Washed soil sample, broadleaf forest (1 female).
As mentioned above, the genus Pelodiaetus was established by
Preparing this taxonomic review, I had an opportunity to investigate many more representatives of the genus. For analysis of the variation in body part proportions, measurements of 57 members of the genus were completed, including seven specimens of P. nunni and 50 specimens of P. sulcatipennis. Because of the wide range of P. sulcatipennis, the aim of this investigation was to compare main body ratios between the northeastern and southwestern parts of its range. All investigated ratios showed no difference between the two populations of P. sulcatipennis, as well as between the latter’s populations and the representatives of P. nunni. At the same time, many ratios showed rather high interspecies variability; this was especially true for W/L – ratio of maximal width to length along the midline of the pronotum, one of the characters used by Jeannel for distinguishing his species. According to the obtained data, the variation in the proportions of the pronotum (Fig.
Variation in proportions of pronotum among different taxa and populations of Pelodiaetus. A – P. nunni; B – P. sulcatipennis, mid-eastern populations; C – P. sulcatipennis, south-western populations. Map of southern half of South Island, New Zealand, shows localities from where specimens were measured. Each species location dot (yellow or white) is identical to Fig.
New Zealand: South Island, Nelson, Brightwater, Torpedo Pipe, May 1974 (1 female).
This locality lies far outside the range of Pelodiaetus. To confirm the locality and to clarify the taxonomic status of a local population more material including males is needed. At present the status of this specimen is uncertain and it is not considered in the following discussion.
The range of Pelodiaetus species stretches across three regions of the South Island of New Zealand (Fig.
Geologically, the range of the genus is associated with old terranes composed of Paleozoic to Early Cretaceous volcanics or sediments (
Search of concordant taxon-area relationships reveals that non-montane representatives of another anilline endogean taxon, the genus Zeanillus, demonstrate almost identical distribution to the members of the genus Pelodiaetus (Fig.
Map of southern half of South Island, New Zealand, showing ranges of subterranean non-montane Anillina. A – Zeanillus (combined ranges of subgenera Zeanillus s. str. (heart) and Brounanillus (star), white dots represent approximate boundary between taxon ranges); B – Pelodiaetus. Elevation scale bars are given in meters.
In the history of Zealandia (
Contemporary distribution of the members of the genus Pelodiaetus and its relatives seems to fit better the vicariance model, because it is likely that their ancestors persisted on Zealandia after it’s rifting off and drifting away from Australia. The distribution of putative overseas relatives of Pelodiaetus serves as an indirect support for this assumption. As mentioned under the genus description, the members of Pelodiaetus are very similar to the members of the primarily Australian genus Illaphanus that comprises 29 species of small to medium-large (0.86–1.74 mm) beetles. Besides the Australian mainland, representatives of this genus are known from Tasmania and from the Lord Howe and Norfolk Islands (
One more piece of evidence of the persistence of the representatives of the Pelodiaetus lineage in Zealandia is the geographical distribution of the members of Pelodiaetodes, presumably the sister-taxon to Pelodiaetus (
Additionally, it is worth mentioning a strange ecological pattern of co-occurrences of the members of Pelodiaetus with other anillines. In the examined material, I came across four cases of syntopic co-occurrences of New Zealand anillines. Three of these cases were related to Pelodiaetus species: namely, Pelodiaetus nunni co-occurred with Z. (Zeanillus) phyllobius (Broun) at Ahuriri (Christchurch area, Canterbury), P. sulcatipennis with Z. (Zeanillus) nunni Sokolov at Woodside Glen (Dunedin area, Central Otago), P. sulcatipennis with Z. (Brounanillus) pallidus (Broun) at Picnic Gully (Taieri Mouth, South Otago), and one case related to its sister-taxon, where Z. (Nunnanillus) pellucidus Sokolov co-occurred with Pelodiaetodes (Monosetodes) nunni Sokolov at Glen Warren Reserve (Oamaru, North Otago). In these examples, the co-occurring species were represented by two contrasting morphotypes, a small (first place in the listing above) and a large one. In all cases but one, a small species of the Pelodiaetus lineage co-occurs with a large one from the unrelated clade, i.e., a small Pelodiaetus lives together with a large Zeanillus. However, in the fourth case, on the contrary, a small Zeanillus lives with a large Pelodiaetodes. Generally, miniaturization is one of the ways of speciation in the Anillini allowing species to occur syntopically and to exploit resources more effectively (
Comparison of species composition in Australia and New Zealand helps to explain the origin of the South Island anilline faunas. In Australia, as many as 29 (85.3%) of 34 known species of Anillini belong to the genus Illaphanus, the sister-taxon to the Pelodiaetus lineage. The same dominance of representatives of the Pelodiaetus lineage can be seen on the North Island, where four species (80.0%) of five recorded for the island belong to Pelodiaetodes. At the same time, on the South Island, only three species (20.0%) of 15 anillines belong to the Pelodiaetus lineage. The significant decline in the number of species of the Pelodiaetus lineage on the South Island suggests that the Anillini faunas of the two islands may have different origins. The presence of species with Australian roots on the North Island is in concord with well-documented southeastern Australia-New Zealand connections (
I am grateful to the staff of Louisiana State Arthropod Museum, LSU, Baton Rouge, and the former director, Christopher E. Carlton, and the curator, Victoria M. Bayless, for their diversified assistance and patience that made this paper possible, and, especially, for permission to use the Museum’s equipment. I appreciate help with SEM imaging provided by the staff of the former Microscopy Center at Louisiana State University School of Veterinary Medicine (Baton Rouge, LA). I also would like to thank Richard A.B. Leschen (Landcare Research, Auckland, New Zealand) and John T. Nunn (Dunedin, New Zealand) for the loan of specimens in their care. Additionally, I am particularly thankful to Elisabeth Roberts (Museum Specialist, Systematic Entomology Laboratory, USDA, National Museum of Natural History, Washington, DC, USA), who checked the final version of manuscript for stylistic errors.
The mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA; the USDA is an equal opportunity provider and employer.