Heterochrony in Tingidae (Insecta: Heteroptera): paedomorphosis and/or peramorphosis? ERIC GUILBERT*, LAURE DESUTTER-GRANDCOLAS and PHILIPPE GRANDCOLAS UMR 5202 CNRS, Muséum National d’Histoire Naturelle, Département Systématique et Evolution, CP50 - 45 rue Buffon, 75005 Paris, France Received 24 November 2006; accepted for publication 19 March 2007 Tingidae (Heteroptera: Insecta) exhibit cephalic tubercles that present a very diverse shape in larvae but that are much simpler in adults. A phylogeny based on adult and last instar characters showed that these tubercles evolved independently from simple to complex states in two clades, and reversed from complex to simple in some taxa. These homoplasies are analysed in the light of ontogenetic sequences and interpreted as heterochronic events. The general trend of evolution of the cephalic tubercles in Tingidae is in mosaic, and could be generally peramorphic, with some isolated cases of paedomorphosis. Journal compilation © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 71–80. No claim to original French government works. ADDITIONAL KEYWORDS: Ontogenetic sequence – ontogenetic stage – ontogeny – phylogeny. INTRODUCTION Heterochrony is defined as a change in rate of development that produces changes in morphology between an immediate ancestor (i.e. an ancestral morphotype in phylogeny) and its descendant(s). ‘It could be a source of evolutionary innovations, includ- ing homoplasy’ (Brooks & McLennan, 2002). Accord- ing to DeBeerian classification (DeBeer, 1958; Raff & Wray, 1989), and restricting heterochrony to what Smith (2002) called ‘growth heterochrony’ (affecting only size and shape) or to what Alberch et al. (1979) called ‘allometric heterochrony’ (in opposition to het- erochrony s.s., affecting age and shape), there are six different cases of heterochronic phenomena leading to two general categories of heterochronic expressions: paedomorphosis and peramorphosis. Paedomorphosis leads to a descendant with ‘underdeveloped’ character states compared to its immediate ancestor; peramor- phosis leads to a descendant with ‘overdeveloped’ character states compared to its immediate ancestor, which implies a recapitulation sensu Agassiz (1833–1843) of the ancestral ontogeny during devel- opment (Futuyma, 1998). Heterochrony has been widely studied in evolution and developmental biology (the so-called ‘evo-devo’), and has recently been a matter of most interest in a phylogenetic frame. In a first approach, Gould (1977) considered the different ways heterochrony has been treated with regard to phylogeny. Alberch et al. (1979) developed a general model describing heterochronic changes of size and shape in the frame of phylogeny. Fink (1982) replaced comparative analyses of ontog- eny in the context of phylogenetic hypotheses to explain homoplastic changes by heterochronic events: paedomorphosis would then be characterized by a reversal to the ancestral state in a phylogenetic context, and recurring peramorphosis would produce homoplasious changes, revealed by a parallelism pattern (for terminology about convergence versus parallelism, see Desutter-Grandcolas et al., 2005). Steyer (2000) proposed a method based on a com- parison between a total evidence approach (involving all the available ontogenetic stages) and a systematic congruence approach (involving a phylogeny for each ontogenetic stage, represented by ‘ontotree’). The ‘event pairing’ or ‘sequence units’ method was pro- posed to analyse sequence heterochrony in the frame *Corresponding author. E-mail: guilbert@mnhn.fr Biological Journal of the Linnean Society, 2008, 93, 71–80. With 4 figures Journal compilation © 2008 The Linnean Society of London No claim to original French government works , Biological Journal of the Linnean Society, 2008, 93, 71–80 71