Chapter 10 the CYNIPOID FAMILIES Introduction
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Chapter 10 THE CYNIPOID FAMILIES Introduction Authors: Introduction, Ibaliidae and Liopteridae: Fredrik Ronquist Figitidae: Fredrik Ronquist, Paul Hanson, Matt Buffington, Felix Fontal-Cazalla, Palmira Ros-Farré Addresses: Fredrik Ronquist, Dept. Systematic Zoology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden, email [email protected] Paul Hanson Matthew L. Buffington, Dept. Entomology, University of California, Riverside, CA 92521-0314, USA, email: [email protected] Felix Fontal-Cazalla, Dept. Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales, José Gutierrez Abascal 2, ES-28006 Madrid, Spain, email: [email protected] Palmira Ros-Farré, Universitat de Barcelona, Facultat de Biologia, Departament de Biologia Animal, Avda Diagonal 645, ES-08028 Barcelona, Spain, email: [email protected] The vast majority of cynipoids are small wasps, 1.0 to 5.0 mm in length, although a few species (those that parasitise wood-boring insects) can reach 30 mm. Cynipoids are usually brown or black in colour (never metallic). Both sexes are fully winged except in some brachypterous or apterous species of Cynipidae and Figitidae. Unlike most other Hymenoptera, females usually have 13 antennal articles (11 flagellomeres) and males 14 or 15. Males usually have the first flagellomere swollen and excavated laterally (exceptions include Anacharitinae (Figitidae), Liopteridae and Heteribalia (Ibaliidae)). The modified article houses a sex gland and is used to smear pheromones directly onto the female antenna during courtship. Occasionally, the modifications of the male antenna may involve the second and third flagellomeres instead of or in addition to the first (some charipines and eucoilines). The pronotum reaches the tegulae and is frequently equipped with an anterior plate, which may be raised off the surrounding pronotal surface (particularly prominent in many eucoilines). The forewing venation is characteristic (Figs. 10.04-10.07): the costa (C) is lacking, the pterostigma is reduced to a cross-vein- like structure (other parasitic wasps with a reduced pterostigma usually have a linear remnant along the anterior wing margin), the media (M) is displaced anteriorly, and one of the few closed wing cells is the distinctive trapezoid marginal cell, also known as the radial cell, which may be open (Figs. 10.04, 10.07, mc) or closed (Figs. 10.05, 10.06) on the anterior wing margin. The Australian Austrocynipidae are exceptional in having a well-developed pterostigma but the other venational features are typical of cynipoids (Ronquist 1995b). Tarsi have five tarsomeres. Proposed autapomorphies for the superfamily include (Ronquist 1999): 1 • Radicle absent from base of antennal scape (unique in Hymenoptera). • Fore wing with costa (C) absent (absent also in ground plan of Chalcidoidea). • Fore wing with media (M) displaced anteriorly, approaching the posterior end of the marginal cell. • Metasoma distinctly laterally compressed (also in ground plan of Evaniidae, Austroniidae, and possibly Roproniidae) • Metasomal sterna 1 and 2 abutting or fused (most other hymenopterans have in their ground plan the anterior end of the postpetiolar sternum telescoped inside the posterior part of the petiolar sternum, just like the remaining sterna and terga are telescoped into each other). • Venom gland unbranched, although this character has been described for only a few cynipoids (Frühauf 1924; Rizki & Rizki 1990) and has not yet been comprehensively surveyed in other parasitic Hymenoptera. Rasnitsyn (1988) proposed a sister-group relationship between Cynipoidea and Diapriidae based on a number of characters. Although most of these characters are problematic, two deserve further consideration (Ronquist 1999): (1) hind wing vein M (+Cu) is concave above in diapriids and cynipoids but convex in other Hymenoptera; and (2) the basal flagellomere is modified similarly in males of Diapriidae and Cynipoidea. The latter modification consists of a ridge and an excavation, both of which are perforated with pores connected to an internal pheromone gland (Ronquist & Nordlander 1989; Ronquist 1995b; Isidoro et al. 1996; Isidoro et al. 1999). Similar male antennal glands occur in other parasitic Hymenoptera, but the external morphology and position of the gland-bearing article(s) is unique to cynipoids and diapriids. Additional evidence for a link between diapriids and cynipoids can possibly be found in fossils from the early Cretaceous placed in the family Arachaeocynipidae (Rasnitsyn & Kovalev 1988). They have a linear pterostigmal remnant and other venational characters suggesting diapriid affinities but a short and compressed metasoma and other features typical of cynipoids (Ronquist 1999). However, their exact phylogenetic position is still unclear. Molecular analyses of apocritan relationships have thus far failed to resolve the position of cynipoids convincingly. The Cynipoidea consist of nearly 3,000 described species in 223 genera (Ronquist 1999). The phylogeny of the superfamily has been analysed in several recent papers (Ronquist 1994, 1995a, 1995b, 1999; Nordlander et al. 1996; Liljeblad & Ronquist 1998; Ros-Farré et al. 2000; Fontal-Cazalla et al. subm.) and this has resulted in major rearrangements in the higher classification (reviewed by Ronquist 1999; see also Ronquist & Nieves-Aldrey in press). Based on these analyses, the superfamily is now divided into five putatively monophyletic families: the Austrocynipidae, Ibaliidae, Liopteridae, Figitidae and Cynipidae. The Cynipidae comprise the phytophagous gall wasps; most of these are gall inducers but some of them develop as inquilines feeding on the plant tissue inside the galls of other species. The members of the other families are, as far as is currently known, all insect-parasitic. They develop initially as koinobiont endoparasitoids but spend the last one or two instars feeding externally on the host remains. They exclusively attack endopterygote insect larvae, usually as primary parasitoids. 2 In terms of many morphological characters, the cynipoids fall into two groups: the “macrocynipoids” and the “microcynipoids”. The macrocynipoids (Austrocynipidae, Ibaliidae and Liopteridae) (Fig. 10.02) are typically relatively large insects that develop as parasitoids of wood-, twig- or cone-boring insect larvae. The adult pupates inside a hard substrate and the newly emerged adult chews its way out. Therefore, the adults are relatively elongate, fairly strongly sclerotised insects with typical adaptations for boring in wood. These adaptations include strong mandibles and legs as well as structures serving to brace the insect against the tunnel walls, such as transverse ridges and crests on the dorsum of the mesosoma and sometimes conspicuous tarsal processes. The microcynipoids (Figitidae and Cynipidae) are typically smaller insects (Fig. 10.03). The mesosoma is higher and more compact and the metasoma is characteristically short, such that the wings project far beyond the posterior end of the body. This body plan appears to originally have been an adaptation to pupation in spherical chambers inside softer substrates, such as galls. Transverse ridges and crests are typically lacking on the dorsum of the mesosoma and the legs are more slender and weaker than in macrocynipoids. In terms of life histories, the microcynipoids are more diverse than the macrocynipoids. As mentioned above, all cynipids are phytophagous and develop as gall inducers or inquilines. Figitids, on the other hand, are insect-parasitic. Most species attack dipteran larvae, typically those developing inside plants or in rotting or decomposing organic substrates. Several figitid lineages develop on hosts in the aphid or psyllid communities, including aphid-feeding Diptera and Neuroptera larvae and aphid- and psyllid-parasitic Hymenoptera larvae. Some figitids (the so-called “figitoid inquilines”) develop inside galls, probably as parasitoids of gall-inducing Hymenoptera larvae (Ronquist 1994; Ronquist & Nieves-Aldrey in press). Phylogenetic analysis of 55 characters of adult morphology informative about inter-family relationships indicates that the microcynipoids form a monophyletic group whereas the macrocynipoids constitute a paraphyletic assemblage of more basal cynipoid lineages, with the Austrocynipidae being the sister group of all other Cynipoidea (Fig. 10.01; Ronquist 1995b). In the Figitidae, the figitoid inquilines (Parnipinae and Thrasorinae) constitute the most basal lineages, indicating that figitids originally developed inside galls, just like cynipids (Ronquist 1999; see Fig. 10.24). (PRINTER: FIG. 10.01 approximately here) There is some uncertainty concerning the exact position of liopterids: the most likely hypothesis has them as the sister group of microcynipoids (Fig. 10.01) but it cannot be excluded that they instead form a monophyletic group together with the ibaliids, as suggested originally by Rasnitsyn (1980) and later by Fergusson (1988, 1990). Except for this uncertainty, the clades in the higher cynipoid phylogeny indicated in Fig. 10.01 are robust, with bootstrap confidence levels exceeding 95 % in parsimony analyses of the known morphological characters informative about these relationships (Ronquist 1995b, 1999). Alternative views on higher cynipoid relationships exist but are not well supported 3 by data. They are either based on a narrow selection of the available characters or on unpublished analyses (for a detailed review,