Phylogeny of the family Sialidae (Insecta: Megaloptera) inferred from morphological data, with implications for generic classification and historical biogeography

Abstract

Sialidae (alderflies) is a family of the holometabolous insect order Megaloptera, with ca. 75 extant species in eight genera distributed 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 disjunctive 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 presented for this group of insects. All Cenozoic alderflies belong to a monophyletic clade, which may also include the Early Jurassic 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 classification 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 supercontinent.

Taxonomic notes of the Neotropical alderfly genus Ilyobius Enderlein, 1910 (Megaloptera, Sialidae), with description of a new species

“…In addition, an undetermined species was recorded in Ecuador (Contreras-Ramos 2008). Considering fossils, Ilyobius might have been distributed in Eurasia based on the two species described from the Eocene Baltic ambers (Wichard 1997(Wichard , 2002 although their generic placements need further clarification (Liu et al 2015). Another species from the Miocene Dominican amber (Engel and Grimaldi 2007) indicates the past occurrence of Ilyobius in Dominica.…”

“…Ectoprocts (Fig. 13 Liu et al (2015), but a re-description and a detailed comparison of these two species was not provided in that paper. The evidence for synonymizing these two species is: 1) the same cephalic color patterns with broad black area approaching the compound eyes, 2) the same black pronotum, 3) the same wing shape, which is narrowed with distinctly dilated costal area; 4) the same distribution area.…”

“…This genus was previously treated to be a junior synonym of Protosialis van der Weele, 1909(Penny 1981, but was recently recovered to be valid based on a comprehensive phylogenetic study on the world Sialidae (Liu et al 2015). The adults of Ilyobius are characterized by the distinct coloration (generally orange, sometimes with dark markings) of head and pronotum, the wing venation (Rs with two simple branches, MP with one simple anterior and one bifurcate posterior branch), the presence of male endophallus with blackish thorny setae, the female sternite 7 being distinctly prominent at the posterior middle, and the female gonocoxites plus gonapophyses 8 together presenting as a sclerotized complex.…”

“…12); female gonapophysis 8 posteriorly broadly concaved (Fig. 14) Discussion Liu et al (2015) separated Ilyobius into two species-groups, i.e., the I. chilensis group and the I. mexicana group, according to a morphology-based phylogenetic analysis of the world's alderfly species. The I. chilensis group is composed of I. chilensis, I. hauseri, and I. nubila, and its monophyly is supported by the male sternite 9 with an elongate median projection, the hook-like male ectoprocts, the transversely band-like male gonocoxite 11 with short median processes, and the female fused gonocoxites 8 reduced and fused with gonapophyses 8 (Liu et al 2015).…”

First record of the family Sialidae (Megaloptera) from Thailand and description of the female and putative larva of Indosialis bannaensis

“…In their phylogenetic analysis of the family Sialidae, Liu et al (2015a) showed that Indosialis is sister to Haplosialis Navás of Madagascar. An additional fossil species, Indosialis beskonakensis Nel is known from the Oligo-Miocene of modern day Turkey (Nel 1988).…”