Zhao et al. BMC Evolutionary Biology 2010, 10:344 http://www.biomedcentral.com/1471-2148/10/344 RESEARCH ARTICLE Open Access Transitional fossil earwigs - a missing link in Dermaptera evolution Jingxia Zhao, Yunyun Zhao, Chungkun Shih, Dong Ren*, Yongjie Wang Abstract Background: The Dermaptera belongs to a group of winged insects of uncertain relationship within Polyneoptera, which has expanded anal region and adds numerous anal veins in the hind wing. Evolutional history and origin of Dermaptera have been in contention. Results: In this paper, we report two new fossil earwigs in a new family of Bellodermatidae fam. nov. The fossils were collected from the Jiulongshan Formation (Middle Jurassic) in Inner Mongolia, northeast China. This new family, characterized by an unexpected combination of primitive and derived characters, is bridging the missing link between suborders of Archidermaptera and Eodermaptera. Phylogenetic analyses support the new family to be a new clade at the base of previously defined Eodermaptera and to be a stem group of (Eodermaptera +Neodermaptera). Conclusion: Evolutional history and origin of Dermaptera have been in contention, with dramatically different viewpoints by contemporary authors. It is suggested that the oldest Dermaptera might possibly be traced back to the Late Triassic-Early Jurassic and they had divided into Archidermaptera and (Eodermaptera+Neodermaptera) in the Middle Jurassic. Background Bellodermatidae fam. nov., from the Middle Jurassic The earwigs (Dermaptera) are familiar insects, often (Bathonian-Callovian) of the Jiulongshan Formation [5-7] unwelcomed, mainly due to their nocturnal habit, some in Daohugou (N41°18’30”, E119°13’00”)ofNingcheng feeding on decaying matters, emitting foul smell, and an County, Inner Mongolia, China. Our study of these two unfounded myth that earwigs would crawl into peoples’ earwigs and phylogenetic results provide new under- ears and penetrate into their brains during sleep. The standing of earwigs’ origin and evolutional process and Dermaptera belongs to a group of winged insects of enable us to update the phylogenetic and evolutional uncertain relationship within Polyneoptera, which has relationships among major lineages of earwigs. expanded anal region and adds numerous anal veins in the hind wing [1]. Earwigs are very scarce in the insect Methods fossil record. Nel et al. in 1994 listed only 73 taxa of The specimens were examined with a Leica MZ12.5 dis- Dermaptera described, figured or simply mentioned in secting microscope and illustrated with the aid of a literature [2]. Even with subsequent addition of 10 spe- drawing tube attached to the microscope. Line drawings cies, the fossil record of the Dermaptera stands at 83 were made with photoshop9.0 graphics software. Mor- species [3,4]. Evolutional history and origin of Dermap- phological terms used here follow those by Michael S. tera have been in contention, especially for the fossil Engel and Fabian Haas [8]. earwigs. Here we report a new genus with two new species (Bel- Phylogenetic Analysis loderma arcuata gen. et sp. nov. (Figure 1) and Bello- The relationships of fossil Dermaptera is re-assessed, the derma ovata sp. nov. (Figure 2)) in a new family of fossil taxa used in the phylogenetic analyses of fossil Dermaptera are listed in Table 1. This study predomi- * Correspondence: [email protected] nantly used body characters, because wing characters Key Laboratory of Insect Evolution and Environmental changes, College of and male genitalia characters are almost always poorly Life Sciences, Capital Normal University, Beijing 100048, China © 2010 Zhao et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Zhao et al. BMC Evolutionary Biology 2010, 10:344 Page 2 of 10 http://www.biomedcentral.com/1471-2148/10/344 Figure 1 Belloderma arcuata gen. et sp. nov., holotype, No. CNU-Der-NN2008002.a,photo.b,Dorsalview.c,Ventralview.d,Enlarged drawing of foreleg tarsi. e, Enlarged drawing of mid-leg tarsi. Scale bar, 2 mm. scl, scutellum; p, pygidium; o, ovipositor; gl, glossae; mp, maxillary palpus; p, palpifer; mt, mentum; gu, gula; lp, labial palpus; dc and bc, disticardo and basicardo; po, postocciput; c, cercus; acs, anterior cervical sclerites; pcs, posterior cervical sclerites; pro-s, pro-sternum; meso-s, meso-sternum; meta-s, meta-sternum. preserved in fossils. We followed the original descrip- All characters were treated as unordered and tions because these fossils were not available to us. Our weighted equally. The data matrices were subjected to phylogenetic analyses of Dermaptera used limited char- the parsimony analyses in NONA and PAUP* (version acters to study the reliability and position of the new 4.0b10) [12]. The two programs implement heuristic family Bellodermatidae fam. nov. rather than the inter- searches somewhat differently, and so both were relationships of Dermaptera. Thus, if a fossil earwig employed. Because program NONA can be only genus contains several species, only one representative defined one outgroup, so weconductedthecladistic species was chosen to keep the number of taxa low for analyses by each outgroups respectively. Heuristic computational reasons. The character matrix for this search in WinClada/NONA used multiple random dataset is shown in Table 2 and Table 3. We con- additions of taxa and tree-bisection resection branch structed matrices with 17 taxa, 20 characters and 20 swapping (options set to hold 10000 trees, perform taxa, 20 characters separately. The two matrices are the 1000 replications with one starting tree replication, same for the fossil species, but they are different in and the multiple TBR+TBR search strategy). Heuristic three additional extant taxa in Table 3. Three species of search in PAUP* (version 4.0b10) employed a heuristic Blattodea (Leucophaea maderae, Polyphaga aegyptiaca, parsimony analyses, with 1000 random stepwise addi- Periplaneta americana) and a species of Plecoptera (Iso- tions of taxa (TBR branch swapping) under ACCTRAN perla obscura) [9-11] are used as outgroup. optimization. Zhao et al. BMC Evolutionary Biology 2010, 10:344 Page 3 of 10 http://www.biomedcentral.com/1471-2148/10/344 Figure 2 Belloderma ovata sp. nov., holotype, No. CNU-Der-NN2008003. a, photo. b, Dorsal view. c, Ventral view. d, Enlarged drawing of foreleg tarsi. e, Enlarged drawing of mid-leg tarsi. Scale bar, 2 mm. gl, glossa; ap, apical papilla. To comply with regulations of the International Code margin of head is strongly notched in Isoperla, Archider- of Zoological Nomenclature (ICZN), we have deposited mapteron, Belloderma gen. nov, Semenoviola, Semeno- paper copies of the above article at the Natural History violoides,*Forficula and *Anechura; the hind margin of Museum, London; the American Museum of Natural head in all other taxa is relatively straight. This charac- History, New York; the Muséum National d’Histoire ter state is uncertain in blattodean species. Naturelle, Paris; the Russian Academy of Sciences, 4. Neck. Blattoid-type (0) or forficuloid-type (1) Moscow; and the Academia Sinica, Taipei. [13,14]. The three blattodean species possess a blattoid- type neck; all other examined dermapterans possess a List of characters and character states for phylogenetic forficuloid-type neck. analysis (*: only present in matrix of Table 3) 5. Shape of pronotum. Disc-like, large, Blattodea-type 1. Head. Opisthognathous (0) or prognathous (1) [13]. (0) or disc-like, small, Dermaptera-type (1) [13]. All der- The three blattodean species have opisthognathous mapteran species have disc-like, small, Dermaptera-type head, while all other taxa possess a prognathous head. pronotum, while being large in three blattodean species. 2. Antennomere. 1st longer than 2nd (0) or 1st shorter 6. Venation of tegmina. Present (0) or absent (1) (Own than or equal to 2nd (1) (Own observation). Character observation). Veins are absent in *Archaeosoma, *Forfi- state 1 is present in Archidermapteron, Asiodiplatys, cula and *Anechura; while all other species have veins Protodiplatys, Microdiplatys, Longicerciata; all other spe- in their tegmina. cies have character state 0. 7. Shape of tegmina. Long, outer margin produced 3. Hind margin of head. Relatively straight (0) or into a point (0) or short, apically blunt (1) (Own obser- strongly notched (1) (Own observation). The hind vation). The tegmina are long and outer margin Zhao et al. BMC Evolutionary Biology 2010, 10:344 Page 4 of 10 http://www.biomedcentral.com/1471-2148/10/344 Table 1 Extant and fossil taxa used in this study Table 2 Character matrix for fossil Dermaptera Taxon Taxon/character 0 1 2 Blattodea Brunner, 1882 123456789 0123456789 0 Leucophaea maderae (Fabricius, 1775) Leucophaea 00?000000 0000000000 1 Periplaneta americana (Linnaeus, 1758) Periplaneta 00?000000 0000000000 1 Polyphaga aegyptiaca (Linnaeus, 1758) Polyphaga 00?000000 0000000000 1 Perlodidae Isoperla 101110000 0010000000 1 Isoperla obscura (Zetterstedt, 1840) Archidermapteron 111110111 1100101000 0 Dermaptera Kirby, 1815 Belloderma gen. nov 10111001? 1011010001 0 Bellodermatidae fam. nov Asiodiplatys 110110111 1100101000 0 Belloderma arcuata gen. et sp. nov Dermapteron 100110011 1000100000 ? Dermapteridae Vishniakova, 1980 Jurassimedeola 100110011 1000100000 0 Dermapteron incertaes (Martynov,