The evolution of social behaviour in Blaberid cockroaches with diverse habitats and social systems: phylogenetic analysis of behavioural sequences

Abstract

International audienceThe adequacy and utility of behavioural characters in phylogenetics is widely acknowledged, especially for stereotyped behaviours. However, the most common behaviours are not stereotyped, and these are usually seen as inappropriate or more difficult to analyze in a phylogenetic context. A few methods have been proposed to deal with such data, although they have never been tested on samples larger than six species, which limits their evolutionary interest. In the present study, we perform behavioural observations on 13 cockroach species and derive behavioural phylogenetic characters with the successive event-pairing method. We combine these characters with morphological and molecular data (approximately 6800 bp) in a phylogenetic study of 41 species. We then reconstruct ancestral states of the behavioural data to study evolution of social behaviour in these insects with regard to their social systems (i.e. solitary, gregarious, and subsocial) and diversity of habitat choice. We report for the first time that nonstereotyped behavioural data are adequate for phylogenetic analyses: they are no more homoplastic than traditional data, and support several phylogenetic relationships that we discuss. From an evolutionary perspective, we show that the solitary species Thanatophyllum akinetum does not display original behavioural interactions, suggesting phylogenetic inertia of interactive behaviours despite a radical change in social structure. Conversely, the subsocial species Parasphaeria boleiriana shows original behavioural interactions, which could result from its peculiar social system or habitat. We conclude that phylogenetic approaches in studies of behaviour are useful for deciphering evolution of behaviour and discriminating between its different modalities, even for nonstereotyped characters.(c) 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 58-77

Molecular phylogeny of Blaberidae (Dictyoptera, Blattodea) with implications for taxonomy and evolutionary studies

“…These unsurprising results have been suggested several times and concern the monophyly of Blaberidae, (Geoscapheinae + Panesthiinae) and Oxyhaloinae (Maekawa et al 2003;Inward 2007;Pellens et al 2007;Djernaes et al 2012;Legendre et al 2014Legendre et al , 2015. Likewise, a strong support was found, here and in previous studies, for Gyninae, Panchlorinae and Pycnoscelinae.…”

“…Later, cockroach systematists identified several morphological synapomorphies supporting the monophyly of Blaberidae (Grandcolas 1996;Klass & Meier 2006; brood sac underneath the female genitalia, sclerite R3v small, first vein of vannus with many basal rami, tracheation very dense and tracheae vesicle-shaped, presence of a muscle connecting sclerite L2 and pouch lve). Monophyly has also repeatedly been found with molecular data as well (Maekawa et al 2003;Inward 2007;Pellens et al 2007;Djernaes et al 2012;Legendre et al 2014Legendre et al , 2015.…”

“…With their pantropical distribution and their ancestry tracking back to the Mesozoic, Blaberidae can be a relevant model to investigate complex biogeographic scenarios. Nevertheless, the present analysis shows that, before elaborating on them, more robust knowledge of relationships of subfamilies is needed, an issue already raised before (Legendre et al 2014).…”

“…The only largely supported results are the close relationships between Zetoborinae and Blaberinae on the one hand, and Panesthiinae and Geoscapheinae on the other. The position of Panchlorinae as the first diverging lineage within the family also seems to be consistently found lately even though often based on a limited taxon sample (Legendre et al 2014(Legendre et al , 2015. The phylogenetic positions of the seven remaining subfamilies still need to be investigated further, as do the phylogenetic positions of 24 incertae sedis genera (according to the Blattodea Species File, BSF; Beccaloni 2014).…”

“…The current classification systems of cockroaches are thus based mainly on morphological characters (Roth 2003). However, like any set of characters, morphological characters benefit from completion with other kinds of data, as already shown when combining molecular and behavioral characters for instance (Legendre et al 2014).…”