A Stephanid Wasp in Mid-Cretaceous Burmese Amber (Hymenoptera: Stephanidae), with Comments on the Antiquity of the Hymenopteran Radiation

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1 A Stephanid Wasp in Mid-Cretaceous Burmese Amber (Hymenoptera: Stephanidae), with Comments on the Antiquity of the Hymenopteran Radiation Author(s): Michael S. Engel, David A. Grimaldi, and Jaime Ortega-Blanco Source: Journal of the Kansas Entomological Society, 86(3): Published By: Kansas Entomological Society DOI: URL: BioOne ( is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne s Terms of Use, available at terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.

2 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY 86(3), 2013, pp A Stephanid Wasp in Mid-Cretaceous Burmese Amber (Hymenoptera: Stephanidae), with Comments on the Antiquity of the Hymenopteran Radiation MICHAEL S. ENGEL, 1,4 DAVID A. GRIMALDI, 2 AND JAIME ORTEGA-BLANCO 3 ABSTRACT: A new fossil stephanid wasp (Stephanidae, or so called crown wasps ) is described and figured from mid-cretaceous Burmese amber. Kronostephanus zigrasi Engel and Grimaldi, new genus and species, is the oldest stephanid currently known in amber, and only the second amber specimen documented from the Mesozoic. Like Archaeostephanus corae Engel and Grimaldi (Turonian, New Jersey), the Burmese species belongs to the basal subfamily Schlettereriinae. The implications of this new taxon are elaborated and comments are provided regarding the age of the clade as well as the Hymenoptera as a whole. KEY WORDS: Apocrita, Euhymenoptera, Mesozoic, paleontology, Stephanoidea, taxonomy The crown wasps, family Stephanidae (Euhymenoptera: Apocrita: Stephanoidea), make up one of the most spectacular lineages of primitive parasitoid wasps. These elongate and often large wasps are parasitoids of wood-boring beetles and siricid wood wasps. Females scour the surface of dead and rotting wood to detect the movements of their host s subcortical larvae. Once located, they characteristically maneuver and insert the elongate ovipositor through the wood and oviposit onto the host. The stephanid larva feeds on the host, ultimately consuming the entire individual during the wasp s last instar, and then pupates. It is interesting to note that the basal genus Schlettererius Ashmead victimizes horntail wood wasps (Siricidae), as do some Orussidae (the basal-most family of Euhymenoptera). This offers the tantalizing suggestion that the earliest phase of parasitoid evolution was parasitoidism on close relatives, with a subsequent shift to and diversification on other wood-boring holometabolans. With about 350 described species worldwide, the family Stephanidae is by no means diverse, particularly when compared with the 43,250 species presently recognized in the Ichneumonoidea, a lineage within which stephanids were included when first discovered (owing to their superficial similarity as relatively large wasps with elongate ovipositors, long legs and bodies, and numerous antennomeres). Nonetheless, modern work on the family continues to reveal new species (e.g., Aguiar et al., 2010; Hong et al., 2011) of this otherwise relic lineage from the great initial radiation of the Apocrita. Stephanids occupy a critical position in the phylogeny of Hymenoptera. Most analyses support Stephanidae as basal within Apocrita (e.g., Grimaldi and Engel, 2005; Sharkey, 1 Division of Entomology, Natural History Museum, and Department of Ecology & Evolutionary Biology, 1501 Crestline Drive Suite 140, University of Kansas, Lawrence, Kansas msengel@ku.edu 2 Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, New York grimaldi@amnh.org 3 Division of Entomology, Natural History Museum, 1501 Crestline Drive Suite 140, University of Kansas, Lawrence, Kansas geoortega@yahoo.es 4 Corresponding author. Accepted 5 May 2013; Revised 16 May 2013 E 2013 Kansas Entomological Society

3 VOLUME 86, ISSUE ; Peters et al., 2011; Sharkey et al., 2012). It is therefore among the ancestors of the Stephanidae that we find the first wave of apocritan diversification. The first fossil stephanid discovered was a compression from the Eocene- Oligocene boundary of Florissant, Colorado. Protostephanus ashmeadi Cockerell is moderately-well preserved with little relief, but which can be placed easily within the Stephanidae (Cockerell, 1906), and even to the subfamily Stephaninae, though clarity on its phylogenetic relationships remain unresolved. Subsequently, Brues (1933) documented three species in mid-eocene Baltic amber which he classified in the extinct genus Electrostephanus Brues. Aguiar and Janzen (1999) provided an elegant review of the fossil stephanids and expanded Brues genus to include a further two species. Engel (2005) provided the first detailed description for a female of Electrostephanus, added yet another species to the group, and considered the species of the genus to occupy a phylogenetic position intermediate between the Schlettereriinae and Stephanine, establishing the subfamily Electrostephaninae. Engel and Grimaldi (2004) extended the fossil record of stephanids significantly with the discovery of the first definitive Cretaceous species, Archaeostephanus corae, and noted that Electrostephanus as defined by Brues (1933) and Aguiar and Janzen (1999) was likely not monophyletic, segregating off a subset of those species into the genus Denaeostephanus. Engel and Ortega-Blanco (2008) further clarified the characters of the Baltic amber species, and proposed Electrostephanodes for Electrostephanus petiolatus Brues. Thus, when all was said and done, A. corae from the Turonian of New Jersey represented the sole fossil of the Schlettereriinae (as well as the only Mesozoic stephanid), Electrostephanus was removed to a distinct subfamily with only four species, and Denaeostephanus (with two species) and the monotypic Protostephanus were considered as incertae sedis within Stephaninae (Engel, 2005; Engel and Ortega-Blanco, 2008). Together these taxa represent an interesting phylogenetic spread across the basal branches of the family. It is interesting that no definitive Stephanidae have yet been reported as compressions from the numerous Mesozoic localities, particularly those of eastern Russia, Mongolia, and northern China. Herein we report the discovery of an interesting new genus and species preserved in mid-cretaceous amber from Myanmar (Fig. 1A). The new taxon significantly extends the known record of crown wasps deeper into the Cretaceous and expands the number and distribution (geographically and temporally) of schlettereriines. Additionally, comments on the origin and antiquity of Hymenoptera are provided. Material and Methods The age, origin, and paleobiota of Burmese amber have been recently reviewed by Grimaldi et al. (2002), Ross et al. (2010), and Shi et al. (2012). Based on radiometric dating, this amber was formed very close to the Aptian Cenomanian boundary, ca. 99 mya. The amber piece containing the wasp was ground and polished on a waterfed lapidary wheel with a graded series of abrasive disks, and then examined using reflected and transmitted light under both stereo and compound microscopes. Photomicrography and measurements were done with Nikon SMZ1500 stereomicroscope and NIS-Elements software. Format and terminology for the descriptions follows that used by Engel and Grimaldi (2004).

4 246 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Fig. 1. Photomicrographs of holotype female of Kronostephanus zigrasi Engel and Grimaldi, new genus and species (JZC-Bu230). A. Right lateral view of holotype. B. Detail of head. C. Detail of mesosoma. D. Detail of metasomal apex. E. Metafemur.

5 VOLUME 86, ISSUE Systematic Paleontology Subfamily Schlettereriinae Orfila Kronostephanus Engel and Grimaldi, new genus TYPE SPECIES: Kronostephanus zigrasi Engel and Grimaldi, new species. DIAGNOSIS: Head globose (Fig. 1B), with distinct tubercles on upper frons and vertex near ocelli; three sets of paired tubercles (tbb B9, tbc C9, and tbd D9) and a single, unpaired anteriormost tubercle (tba) (Fig. 2A), in addition a posteriormost row of three short tubercles (row of tbe); vertex and occiput posterior to tubercles strongly delineated and with fine, transverse striae (Fig. 2B); face transversely rugose; labrum short, projecting and densely setose (Fig. 2A); mandibles short and blunt, with some ventral setae. Posterior part of pronotum with shallow elevation to anterior part (Fig. 1C). Forewing with basal vein short, faintly arched, less oblique than in more derived stephanids; r-rs relatively short, at most one-quarter length of distalmost abscissa of Rs (Fig. 2E); submarginal cell not extending beyond pterostigmal apex; membrane hyaline and apparently without any areas of infuscation; hind wing apparently with cu-a present (very difficult to discern). Legs long and slender; metacoxa with small, dorsal tubercle ( dorsal tooth ) (Fig. 2C); metatibia not strongly petiolate, slender, tapering gently throughout length from apex to base (Fig. 2C); metafemur greatly swollen, ventrally with two large teeth each followed by three smaller, slender teeth, first tooth particularly massive (resembling a tooth of Carcharodon megalodon Agassiz [Lamniformes]) and positioned just prior to metafemoral midlength (Figs. 1E, 2C); tarsi pentamerous; metatarsomere IV prolonged beneath metatarsomere V (Fig. 2C); pretarsal claws simple, small arolium present. Metasomal petiole short, length about 2.25 times height, tergum and sternum not fused, length of tergum I subequal to that of tergum II; apicalmost tergum with short apicolateral spines (Figs. 1D, 2D); ovipositor greatly elongate, longer than remainder of body (Fig. 1A). ETYMOLOGY: The new genus-group name is a combination of the Kronos (youngest of the Greek Titans and father of the Olympian gods) and stephanos (meaning, crown ). The name is masculine. Kronostephanus zigrasi Engel and Grimaldi, new species (Figs. 1, 2) DIAGNOSIS: As for the genus (vide supra). DESCRIPTION: R: As described for the genus, with the following minor additions: Total body length (excluding ovipositor and antennae) as preserved 5.54 mm; forewing length (estimated) 3.78 mm; petiole length mm, height mm. Integument dark reddish brown, nearly black in some places (e.g., apical spines on metasomal apex) as preserved; wing membranes hyaline, veins black. Face with median-anterior tubercle (tba) high, at about upper third or upper quarter of compound eye length; three pairs of tubercles posterior to tba and forming crown, with pair tbc C9 apparently most widest set; pair tbd-d9 with posterior bordering row of shorter tubercles (Fig. 2B); ocelli present, median ocellus not evident but perhaps set between pair tbc C9, lateral ocelli positioned just behind and alongside tbe; coronal area of vertex with strongly demarcated area with fine transverse striae (Fig. 2B); antenna elongate, filiform, with at least 14 flagellomeres (apex not visible);

6 248 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Fig. 2. Details of Kronostephanus zigrasi Engel and Grimaldi, new genus and species (JZC-Bu230). A. Detail of head in frontal-oblique view. B. Vertex of head. C. Hind leg. D. Abdominal apex as preserved. E. Forewing. individual flagellomeres longer than wide; gena rounded, narrower than compound eye, without pronounced sculpturing; preoccipital area carinate. Mesosoma coarsely sculptured; pleura coarsely punctured, basically foveolate, foveae with narrow separations between them, integument between (where evident) glabrous, with mesal

7 VOLUME 86, ISSUE depression for reception of leg. Forewing venation as depicted in figure 2E. Legs with scattered, fine, minute setae; metacoxa large, foveolate, with pronounced dorsal ridge leading to dorsal median tubercle; metatrochanter and metatrochantellus subequal in size; individual femur-trochantellus lengths 0.84 mm (pro), 0.68 mm (meso), 0.93 mm (meta); metafemur greatly crassate, with pronounced ventral dentition, larges tooth just prior to midlength, broad and massive in comparison to following denticles, next largest tooth at apical quarter, slender and elongate, almost as long as basalmost tooth, also followed by shorter denticles (Figs. 1E, 2C); metatibia not strongly petiolate, slightly longer than combined lengths of metafemur, metatrochantellus, and metatrochanter, with two short metatibial spurs at apex; metabasitarsus nearly as long as combined lengths of remaining tarsomeres; entire tarsus about three-quarters length of metatibia. Metasoma largely cleared and hollowed as preserved (thus few details can be ascertained); apicalmost segments appear finely sculptured (perhaps imbricate); paired apical spines blunt at apices; ovipositor elongate, preserved portion 7.8 mm (apex missing), much longer than wasp itself (preserved portion longer than wasp and eventually cutoff at amber surface, thus it was even longer in life but perhaps not too much more so). : Unknown. HOLOTYPE: R, Myanmar, JZC-Bu230; in the private collection of Mr. James Zigras, available for study through the Division of Invertebrate Zoology, American Museum of Natural History, New York. ETYMOLOGY: The specific epithet is a patronym honoring James S. Zigras who brought this amazing specimen to our attention and permitted its study. Discussion The new species can be readily placed within the Schlettereriinae owing to the presence of the dorsal metacoxal tubercle, a putative apomorphy for this clade. Additional features consistent with schlettereriines, albeit plesiomorphic, include the pentamerous tarsi and unfused first and second metasomal tergum and sternum (present also in Electrostephaninae), and the lack of a strongly petiolate metatibia. Similar to Schlettererius, Kronostephanus possesses an apical protuberance on the metasoma. However, in Schlettererius this is merely a single, medioapical spine, while in Kronostephanus there are paired spines just on either side of the midline (Figs. 1D, 2D), and representing a notable apomorphic trait for the fossil genus. Kronostephanus differs from Archaeostephanus in the form and dentition of the metafemur, particularly the massive shark-tooth-like medial blade (Figs. 1E, 2C), another putative apomorphy for the Burmese species; the absent or spectral 2Cu b (distinctly tubular and pigmented in A. corae); the presence of tubercle pair tbd D9 (Fig. 2A) (absent in A. corae); and various details of surface sculpturing (cf. Engel and Grimaldi, 2004). The form of the labrum, mandibles, and post-ocellar vertex are also unique to K. zigrasi (Figs. 2A, B). Unfortunately, the sole specimen of A. corae is not as well preserved as the holotype of K. zigrasi and so much remains to be discovered of the Turonian species. Together, all of the schlettereriines (as well as the electrostephanines), living and fossil, have a primitive wing venation relative to that of other Stephanidae, although the form of the basal vein is certainly more pronounced in Schlettererius, emphasizing that the modern species are monophyletic relative to the aforementioned fossils. Today, Schlettereriinae are represented by two

8 250 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY species, one in principally western North America (Townes, 1949; Smith, 1997; Aguiar and Johnson, 2003) and the other in Palearctic China and North and South Korea (Madl, 1991; Hong et al., 2011; Kim and Lee, 2012), although the genus has been artificially introduced into Tasmania and Victoria, Australia for the control of non-native horntails (Taylor, 1967; Aguiar, 2001; Collett and Elms, 2009). It is interesting that the two fossils of this group are found roughly in the same pattern, namely North America and Asia, albeit southern Asia in the case of K. zigrasi. It is admittedly too early to come to definitive conclusions regarding stephanid diversification, but the limited data does permit some gross speculations. Most notably, the only Cretaceous records are of the Schlettereriinae and those of the Eocene Baltic amber are of the more derived Electrostephaninae and putatively primitive members of Stephaninae. It is possible that the Electrostephaninae + Stephaninae are younger than previously hypothesized (e.g., Engel, 2005), and instead diverged from one another during the Early Tertiary. In this scenario, together they would extend back into the Cretaceous on the basis of stem groups that shared a common ancestor with the Schlettereriinae in the earliest Cretaceous or Jurassic. Certainly the recovery of further fossils is needed before any robust reconstruction of the family s evolutionary history is established. Given the important phylogenetic position held by the Stephanoidea (vide Introduction, supra), it is disappointing that the clade has such a meager fossil record. Although the known fossils occupy a spread across the three principle branches of the family, they are few in number and relatively modern (even the mid- Cretaceous species described herein!) for a lineage which very likely has its roots in the Early Jurassic. Admittedly, one cannot confuse crown-group stephanids such as the known fossils with earlier fossil stem lineages that may not have apomorphic features which we today consider as defining a stephanid. Instead, what we recognize as stephanids may only date to the Early Cretaceous or latest Jurassic, and that stemgroup fossils (e.g., a grade of extinct, related families) may carry the stephanoid line back to their earliest common ancestor with the remainder of Apocrita. Such taxa may be found among the Ephialtitidae and Karatavitidae (Early-Late Jurassic, and earliest Cretaceous), although critical cladistic tests of this hypothesis are lacking. If this were the case, then we would not expect a Liassic stephanid, despite an otherwise ancient age for the line. It is oversight of the reality of stem-groups that has perhaps led some to consider the order Hymenoptera as originating in the Carboniferous (e.g., Ronquist et al., 2012), a time prior to any presently definitive evidence for Holometabola. Hymenoptera have a robust fossil record which reveals xyelids (the most basal family of Hymenoptera) in the latest Triassic, the parasitoid diversification in the Jurassic, an initial aculeate origin around the Jurassic Cretaceous boundary, and subsequent Cretaceous radiations of various families (Grimaldi and Engel, 2005; Rasnitsyn and Quicke, 2002). Crown-group Hymenoptera appears to have originated in the Middle to Early Triassic (certainly no earlier than the latest Permian), diverging then from an even more ancient grade of Paleozoic Triassic mecopteroid-like fossils from which other ordinal clades also diverged at differing times (some older and younger than the Hymenoptera itself; e.g., Willmann, 1989). In essence, dating the divergence of Hymenoptera and extant holometabolous orders would yield an estimate far older than the most basal living node for Hymenoptera. This is because hymenopteran ancestors were likely among the paraphyletic cloud of

9 VOLUME 86, ISSUE panorpoids known from the Triassic and Permian (certainly extending into the latest Carboniferous) (e.g., Willmann, 1989). In fact, one such Permian group that has been suggested as a stem-group to the Hymenoptera is Palaeomanteidae (order Miomoptera of Martynov, Palaeomanteida of Handlirsch) (Rasnistyn and Quicke, 2002). Even though none of these ancient stem groups could hardly be defined as true Hymenoptera they do form a ghost lineage to the larger hymenopteran line (stem Hymenopterida), and this is precisely what molecular studies are recovering in their divergence estimates (e.g., Ronquist et al., 2012), rather than the purported common ancestor between the Xyelidae and Neohymenoptera. Unfortunately, rarely do proponents of molecular estimates of divergence consider alternative explanations which explain better or equally well the results of their models (e.g., Ronquist et al., 2012). In this case, even a cursory consideration of the paraphyletic Paleozoic mecopteroids (here and elsewhere denoting a heterogenous mix of families which are not placed in any living order and yet subsets of which comprise the stemsgroups of several ordinal or even supraordinal clades), might have led to radically different interpretations and conclusions from prior studies. Inclusion of the Paleozoic mecopteroids in serious cladistic inquiries of holometabolan phylogeny will have profound implications toward understanding this hyperdiverse radiation and give us robust estimates for origins of the orders as we understand them. Acknowledgements We are deeply grateful to James S. Zigras for his generosity in permitting us to study the material in his extensive holdings of Burmese amber and for supporting the work of M.S.E. at the AMNH. J.O.-B. was supported by the Ministerio de Economía y Competitividad, Fulbright España and FECYT (Fundación Española para la Ciencia y la Tecnología). The manuscript benefited from the reviews of two anonymous referees to whom we are very grateful. This is a contribution of the Division of Entomology, University of Kansas Natural History Museum. Literature Cited Aguiar, A. P Revision of the Australian Stephanidae (Hymenoptera). Invertebrate Taxonomy 15(6): Aguiar, A. P., and J.-W. Janzen [2000]. An overview of fossil Stephanidae (Hymenoptera), with description of two new taxa from Baltic amber, and key to species of Electrostephanus Brues. Entomologica Scandinavica 30(4): Aguiar, A. P., J. T. Jennings, and G. F. Turrisi Three new Middle-Eastern species of Foenatopus Smith (Hymenoptera: Stephanidae) with a new host record and key to species with two spots on the metasoma. Zootaxa 2714: Aguiar, A. P., and N. F. Johnson Stephanidae (Hymenoptera) of America north of Mexico. Proceedings of the Entomological Society of Washington 105(2): Brues, C. T The parasitic Hymenoptera of the Baltic amber. Part 1. Bernstein Forschungen 3: Cockerell, T. D. A Fossil Hymenoptera from Florissant, Colorado. Bulletin of the Museum of Comparative Zoology 50(2): Collett, N. G., and S. Elms The control of sirex wood wasp using biological control agents in Victoria, Australia. Agricultural and Forest Entomology 11(3): Engel, M. S The crown wasp genus Electrostephanus (Hymenoptera: Stephanidae): Discovery of the female and a new species. Polskie Pismo Entomologiczne 74(3): Engel, M. S., and D. A. Grimaldi The first Mesozoic stephanid wasp (Hymenoptera: Stephanidae). Journal of Paleontology 78(6):

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