Phylogeny of the Family Sialidae (Insecta: Megaloptera) Inferred from Morphological Data, with Implications for Generic Classification and Historical Biogeography
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Cladistics Cladistics (2014) 1–32 10.1111/cla.12071 Phylogeny of the family Sialidae (Insecta: Megaloptera) inferred from morphological data, with implications for generic classification and historical biogeography Xingyue Liua,*, Fumio Hayashib and Ding Yanga,* aDepartment of Entomology, China Agricultural University, Beijing, 100193, China; bDepartment of Biology, Tokyo Metropolitan University, Minamiosawa 1–1, Hachioji, Tokyo, 192–0397, Japan Accepted 6 January 2014 Abstract Sialidae (alderflies) is a family of the holometabolous insect order Megaloptera, with ca. 75 extant species in eight genera dis- tributed worldwide. Alderflies are a group of “living fossils” with a long evolutionary history. The oldest fossil attributed to Sialidae dates back to the Early Jurassic period. Further, the global distribution of modern-day species shows a remarkably dis- junctive pattern. However, due to the rareness of most species and scarcity of comprehensive taxonomic revisions, the phylogeny of Sialidae remains largely unexplored, and the present classification system is in great need of renewal. Here we reconstruct the first phylogeny for Sialidae worldwide based on the most comprehensive sampling and broadest morphological data ever pre- sented for this group of insects. All Cenozoic alderflies belong to a monophyletic clade, which may also include the Early Juras- sic genus †Dobbertinia, and the Late Jurassic genus †Sharasialis is their putative sister taxon. Two subfamilies of Sialidae are proposed, namely †Sharasialinae subfam. nov. and Sialidinae. Austrosialis is the sister of all other extant genera, an assemblage which comprises three monophyletic lineages: the Stenosialis lineage, the Ilyobius lineage, and the Sialis lineage. The revised clas- sification of Sialidae is composed of 12 valid genera and 87 valid species. Ilyobius and Protosialis are recognized as valid generic names, while Nipponosialis is treated as a synonym of Sialis. Reconstruction of the ancestral area proposes a global distribution of alderflies in Pangaea before their diversification. The generic diversification of alderflies might have occurred before the breakup of Pangaea, but the divergence of some lineages or genera was probably promoted by the splitting of this superconti- nent. © The Willi Hennig Society 2014. Introduction of nygmata on wings, and the loss of callus cerci, while their larvae are distinguished by the presence of The family Sialidae, commonly called alderflies, is a terminal filament on the tenth abdominal segment. group of little-known insects belonging to Megalopter- More obviously, in general appearance, the adult sia- a, which is a holometabolous insect order placed in lids are much smaller than corydalids and have the superorder Neuropterida and contains only two uniformly dark wings (Fig. 1). The alderfly larvae are extant families: Corydalidae and Sialidae. Compared predaceous, exclusively aquatic, and inhabit streams, with Corydalidae, the adults of Sialidae are character- rivers, or lakes where the substrate is soft and detritus ized by the absence of ocelli, the pronotum shorter is abundant (Flint et al., 2008). Adult alderflies gener- than wide, the dilated fourth tarsomeres, the absence ally do not feed, although some species have been observed to visit flowers (Kaiser, 1961; Azam and Anderson, 1969). Further, they are poor fliers, and *Corresponding author: E-mail address: [email protected] and [email protected] remain in the same general area where the larvae © The Willi Hennig Society 2014 2 X. Liu et al. / Cladistics (2014) 1–32 (a) (b) (c) (d) (e) (f) (g) (h) (i) Fig. 1. Habitus of alderfly adults, male: (a) Austrosialis ignicollis; (b) Stenosialis australiensis; (c) Leptosialis africana; (d) Haplosialis afra; (e) Indosialis bannaensis; (f) Ilyobius mexicana; (g) Protosialis americana; (h) Sialis jezoensis; (i) Sialis annae. Scale bar = 5.0 mm. occurred (Flint et al., 2008). In contrast to corydalids, 1920 from the Lower Jurassic of Germany, which was sialid adults are mostly diurnal and seldom captured originally placed in Mecoptera (Handlirsch, 1920) and by light (New and Theischinger, 1993). Although some was transferred to Sialidae by Ansorge (2001). The alderfly species from Palaearctic and Nearctic realms second Mesozoic alderfly †Sharasialis fusiformis are readily found in the field, most species from other Ponomarenko, 2012 was discovered very recently by zoogeographical realms are extremely rare in collec- Ponomarenko (2012); it is a larval fossil from the tions. Upper Jurassic of Mongolia. All other alderfly fossils Some European alderfly species were described very occur from the Cenozoic. They include 10 species early, and aspects of their morphology, physiology, placed in six genera (Lambkin, 1992; Nel et al., 2002; and ecology have been extensively studied. The first Wichard and Engel, 2006; Engel and Grimaldi, 2007). described species, Sialis lutaria (Linnaeus, 1758), was Currently, extant Sialidae contain eight valid genera originally placed in the brown lacewing genus Hemero- and ca. 75 valid species, while fossil Sialidae encom- bius (Geigy and DuBois, 1935; Selman, 1960; Elliott, pass seven valid genera (including five extant genera) 1996). Latreille (1802) erected the genus Sialis, which and a total of 12 valid species (Yang and Liu, 2010; is the first valid generic taxon in Sialidae and included Oswald, 2012). almost all alderfly species described in the 19th cen- The Sialidae occur in all continents of the world tury. Previously, Sialidae was defined in a broader (except Antarctica), and their geographical distribution sense, and included Corydalidae and Sialidae until is interesting in that the modern fauna differs greatly Davis (1903) divided the “Sialididae” into two subfam- at the genus and species level among main zoogeo- ilies: Sialidinae and Corydalinae. Both subfamilies graphical realms. Five extant genera are presently dis- were raised to full familial status by Tillyard (1919). tributed in the Southern Hemisphere, namely Most genera and nearly a half of all extant species of Austrosialis Tillyard, 1919 and Stenosialis Tillyard, Sialidae were described in the first half of the 20th cen- 1919; which are endemic to Australia, Protosialis van tury. Since then, the generic classification system has der Weele, 1909; currently endemic to Neotropics but hardly changed (van der Weele, 1910; Tillyard, 1919; also found in the Eocene Baltic amber, Leptosialis Esben-Petersen, 1920; Lestage, 1927; Barnard, 1931; Esben-Petersen, 1920; endemic to South Africa, and Ross, 1937). Several additional regional revisionary Haplosialis Navas, 1936, endemic to Madagascar. works on Sialidae were published from 1950 to 2010s Altogether they contain 18 species, ca. 20% of the and described ca. 40 new species, e.g. Kuwayama world’s species. The remaining species are distributed (1962), Flint (1964), Aspock€ et al. (1980, 2001a), in the Northern Hemisphere, with ca. 50 species placed Vshivkova (1985), Whiting (1991), Hayashi and Suda in the dominant genus Sialis, which is widespread in (1995), Theischinger (2000), Liu and Yang (2006a,b), Eurasia and North America, and a few species placed Liu et al. (2008), Contreras-Ramos (2008), and Price in Nipponosialis Kuwayama, 1962 (ranging mainly in et al. (2012). Considering the extinct Sialidae, the earli- Taiwan, Ryukyus, and Japan) and Indosialis Lestage, est definite fossil is †Dobbertinia reticulata Handlirsch, 1927 (endemic to Oriental realm). Fossil alderflies were X. Liu et al. / Cladistics (2014) 1–32 3 found mainly in the Northern Hemisphere and most of Sialidae is discussed in light of the proposed of them are restricted to Europe (Engel and Grimaldi, phylogenetic hypothesis and fossil evidence. 2007), while an unnamed species of Austrosialis is recorded from the Palaeocene of Australia (Lambkin, 1992). Materials and methods Interpreting historical biogeography of the group requires appropriate phylogenetic data. The nature of Specimens examined and terminology the sister-group to Sialidae has been debated. The sis- ter relationship between Sialidae and Raphidioptera We aimed to include all valid species of both fossil was supported by the basal fusion of MP and CuA and extant Sialidae as the ingroup taxa in the present veins in the forewing by Hennig (1953), the female phylogenetic analysis. However, a few species subse- telotrophic ovarioles by Stys and Bilinski (1990), and quently were excluded from the primary taxa list. the molecular evidence presented by Winterton et al. First, a fossil species, Sialis strausi Illies, 1967 was (2010), which indicates a paraphyletic Megaloptera. excluded because it is known only based on a poorly Alternatively, Sialidae was considered to be the sister preserved larva, without any informative characters of the corydalid subfamily Chauliodinae within a for the analysis. Second, Protosialis brasiliensis monophyletic Megaloptera based on a greater reduc- Navas, 1936, Sialis vanderweelei Aspock€ & Aspock,€ tion or fusion of genital structures according to Con- 1983, Sialis dorochovae Vshivkova, 1985, and Sialis treras-Ramos (2004). Contrary to this, the sister gonzalezi Vshivkova, 1985 were also excluded because relationship between Sialidae and Corydalidae was they are considered as invalid species in the present recovered in both morphological and molecular data study (see updated world catalog of Sialidae in Table (Aspock€ et al., 2001b; Beutel and Friedrich, 2008). S4). Finally, a total of 86 species of Sialidae were More recently a mitochondrial