Tony Robillard

New Caledonia: a very old Darwinian island?

New Caledonia has generally been considered a continental island, the biota of which largely dates back to Gondwanan times owing to its geological origin and the presence of phylogenetic relicts. This view is contradicted by geological evidence indicating long Palaeocene and Eocene submersions and by recent biogeographic and phylogenetic studies, with molecular or geophysical dating placing the biota no older than the Oligocene. Phylogenetic relicts do not provide conclusive information in this respect, as their presence cannot be explained by simple hypotheses but requires assumption of many ad hoc extinction events. The implication of this new scenario is that all the New Caledonian biota colonized the island since 37 Ma Local richness can be explained by local radiation and adaptation after colonization but also by many dispersal events, often repeated within the same groups of organisms. Local microendemism is another remarkable feature of the biota. It seems to be related to recent speciation mediated by climate, orography, soil type and perhaps unbalanced biotic interactions created by colonization disharmonies. New Caledonia must be considered as a very old Darwinian island, a concept that offers many more fascinating opportunities of study.

Phylogeny and the modalities of acoustic diversification in extant Eneopterinae (Insecta, Orthoptera, Grylloidea, Eneopteridae)

Calling with a tegminal stridulatory apparatus is widespread in crickets. However, the evolution of cricket stridulums has been poorly studied and then only on the basis of prephylogenetic models, which are unable to account for the huge diversity recently documented for acoustic features in crickets. The present paper focuses on the evolution of acoustic devices in the subfamily Eneopterinae. This is the first attempt to reconstruct the phylogeny of a large and diverse cricket clade in order to analyze the evolution of emitting structures using precise homology statements. In the first step, we reconstruct the phylogeny of this clade using a morphological data set of 193 characters and 45 taxa. The resultant phylogeny supports the monophyly of the subfamily and that of the 13 genera represented by at least two species in our taxonomic sample. Phylogenetic relationships within the subfamily also support the definition of five tribes: Eurepini, Eneopterini, Nisitrini, Xenogryllini and Lebinthini. In the second step, the evolution of acoustic devices is studied by optimization of venation characters defined on precise homology statements. As hypothesized by previous authors, losses of acoustic communication occur independently in the course of eneopterine evolution; however, they happen abruptly with no intermediate state. Our results also document for the first time the modalities of forewing evolution: the diversification of male forewing venation originates from two processes, a continuous and regular modification process, responsible for slight venation change; and an irregular, more intense punctuated process, allowing the emergence of different venations. This diversification process with sudden changes could be related to the occurrence of acoustic novelties in advertisement calls.

Phylogeny of Dictyoptera: Dating the Origin of Cockroaches, Praying Mantises and Termites with Molecular Data and Controlled Fossil Evidence

Understanding the origin and diversification of organisms requires a good phylogenetic estimate of their age and diversification rates. This estimate can be difficult to obtain when samples are limited and fossil records are disputed, as in Dictyoptera. To choose among competing hypotheses of origin for dictyopteran suborders, we root a phylogenetic analysis (~800 taxa, 10 kbp) within a large selection of outgroups and calibrate datings with fossils attributed to lineages with clear synapomorphies. We find the following topology: (mantises, (other cockroaches, (Cryptocercidae, termites)). Our datings suggest that crown-Dictyoptera—and stem-mantises—would date back to the Late Carboniferous (~ 300 Mya), a result compatible with the oldest putative fossil of stem-dictyoptera. Crown-mantises, however, would be much more recent (~ 200 Mya; Triassic/Jurassic boundary). This pattern (i.e., old origin and more recent diversification) suggests a scenario of replacement in carnivory among polyneopterous insects. The most recent common ancestor of (cockroaches + termites) would date back to the Permian (~275 Mya), which contradicts the hypothesis of a Devonian origin of cockroaches. Stem-termites would date back to the Triassic/Jurassic boundary, which refutes a Triassic origin. We suggest directions in extant and extinct species sampling to sharpen this chronological framework and dictyopteran evolutionary studies.

Phylogeny and the evolution of calling songs in Gryllus (Insecta, Orthoptera, Gryllidae)

Acoustic signalling is the most important communication modality for crickets. While it has been studied intensively, few authors have analysed the evolution of cricket acoustic signals within a macroevolutionary perspective, still fewer with respect to its phylogenetic aspects. This may be due in part to the lack of acoustic and phylogenetic data; there are also difficulties involved in applying phylogenetic methods to acoustic data. The most critical aspect may be describing calls using characteristics consistent with current criteria for homology. In this paper we discuss, in relation to the evolution of the North American species of Gryllus, the reliability of these criteria and describe songs using two complementary sets of characters: (i) general structure (carrier frequencies and main temporal features), and (ii) ‘special quality’ (particular features at a lower structural level).

Evolution of advertisement signals in North American hylid frogs: vocalizations as end-products of calling behavior

We studied the advertisement signals in two clades of North American hylid frogs in order to characterize the relationships between signal acoustic structure and underlying behavior. A mismatch was found between the acoustic structure and the mechanism of sound production. Two separate sets of phylogenetic characters were coded following acoustic versus mechanistic criteria, and exploratory treatments were made to compare their respective phylogenetic content in comparison with the molecular phylogeny ( Faivovich et al., 2005 ). We discuss the consequences of the acoustic/mechanistic mismatch in terms of significance of acoustic characters for phylogenetic and comparative studies; and the evolution of vocalizations in North American treefrogs. Considering only the acoustic structure of frog vocalizations can lead to misleading results in terms of both phylogenetic signal and evolution of vocalizations. In contrast, interpreting the acoustic signals with regard to the mechanism of sound production results in consistent phylogenetic information. The mechanistic coding also provides strong homologies for use in comparative studies of frog vocalizations, and to derive and test evolutionary hypotheses.

One hundred years of instability in ensiferan relationships

Although Ensifera is a major insect model group, its phylogenetic relationships have been understudied so far. Few phylogenetic hypotheses have been proposed, either with morphological or molecular data. The largest dataset ever used for phylogeny reconstruction on this group is molecular (16S rRNA, 18S rRNA and 28S rRNA sequences for 51 ensiferan species), which has been used twice with different resultant topologies. However, only one of these hypotheses has been adopted commonly as a reference classification. Here we re‐analyse this molecular dataset with different methods and parameters to test the robustness and the stability of the adopted phylogeny. Our study reveals the instability of phylogenetic relationships derived from this dataset, especially for the deepest nodes of the group, and suggests some guidelines for future studies. The comparison between the different classifications proposed in the past 70 years for Ensifera and our results allows the identification of potential monophyletic clades (katydids, mole crickets, scaly crickets + Malgasia, true crickets, leaf roller crickets, cave crickets) and the remaining unresolved clades (wetas, Jerusalem crickets and most of the highest rank clades) in Ensifera phylogeny.

Phylogenetic analysis and alignment of behavioral sequences by direct optimization

We propose a new approach to consider behavioral data in phylogenetic analyses. We show that behavior can be described as sequences of repeated units, and that these behavioral sequences can be analyzed under direct optimization in a way similar to molecular data. This approach provides repeatable hypotheses of homology for behavior when traditional criteria result in multiple alternatives or do not allow to propose any. We exemplify this approach by analyzing the calling songs of the North American Gryllus species under direct optimization. We first use two alternative coding schemes to describe the temporal patterns of the songs as sequences of repeated simple behaviors. We submit these behavioral data to phylogenetic analysis under direct optimization, first as separate analyses, and second in combination with molecular data and additional acoustic characters. The results show that the coding option that consists of discretizing the silent parts of the songs: (1) allows description of the songs in a more precise way; (2) discriminates further the songs between species; and (3) enhances the phylogenetic content of the behavioral sequences. Our study demonstrates that behavioral sequences can be transformed so that they can be used in genuine phylogenetic analysis, in isolation or combined with other data sets. We discuss how this approach may provide phylogenetic signal where none or little is usually available, and the applications to the study of the evolution of behavioral evolution.

Phylogenetic systematics and evolution of Agnotecous in New Caledonia (Orthoptera: Grylloidea, Eneopteridae)

Abstract.  Within a framework for historical analysis of Eneopterinae biogeography the New Caledonian endemic cricket genus Agnotecous Saussure, 1878 is revised: the eight already known species are diagnosed and six new species described, A. azurensis Desutter‐Grandcolas sp.n., A. chopardi Desutter‐Grandcolas sp.n., A. clarus Desutter‐Grandcolas sp.n., A. doensis Desutter‐Grandcolas sp.n., A. meridionalis Desutter‐Grandcolas sp.n. and A. occidentalis Desutter‐Grandcolas sp.n. Four species groups are characterized by male genitalic structures. Identification keys are provided for both males and females. A cladistic analysis was performed using fifty‐eight morphological characters. The two resultant topologies, which differ only in topology of three apical species, support the monophyly of Agnotecous and that of the four species groups. Preliminary hypotheses of Eneopterinae historical biogeography are derived from phylogenetic and distributional data.

Evolution of calling songs as multicomponent signals in crickets (Orthoptera: Grylloidea: Eneopterinae)

Calling songs of crickets are multi-component signals that serve several purposes in the species biology. The multiple functions of calling songs reflect the multiple selective forces shaping signal parameters. We test several predictions about signal evolution at a phylogenetic scale, taking into account the way signals are produced and used. We addressed these predictions in a diverse cricket clade, the Eneopterinae subfamily, using an independently derived phylogeny. Acoustic analyses of the calling songs of 24 eneopterine species permitted the definition of 35 acoustic characters describing the spectral and temporal properties of the songs. These characters proved informative for their phylogenetic content. Our main conclusions were that eneopterine calling songs have evolved as multiple independent characters (atomised evolution hypothesis), although they partly depended on the influence of emitting structures. They experienced a general tendency toward more information delivered per unit time and were driven toward equivalent temporal patterns through the combined action of inheritance from ancestors, parallelism and character convergence.

Laying the foundations of evolutionary and systematic studies in crickets (Insecta, Orthoptera): a multilocus phylogenetic analysis

Orthoptera have been used for decades for numerous evolutionary questions but several of its constituent groups, notably crickets, still suffer from a lack of a robust phylogenetic hypothesis. We propose the first phylogenetic hypothesis for the evolution of crickets sensu lato, based on analysis of 205 species, representing 88% of the subfamilies and 71% tribes currently listed in the database Orthoptera Species File (OSF). We reconstructed parsimony, maximum likelihood and Bayesian phylogenies using fragments of 18S, 28SA, 28SD, H3, 12S, 16S, and cytb (~3600 bp). Our results support the monophyly of the cricket clade, and its subdivision into two clades: mole crickets and ant‐loving crickets on the one hand, and all the other crickets on the other (i.e. crickets sensu stricto). Crickets sensu stricto form seven monophyletic clades, which support part of the OSF families, “subfamily groups”, or subfamilies: the mole crickets (OSF Gryllotalpidae), the scaly crickets (OSF Mogoplistidae), and the true crickets (OSF Gryllidae) are recovered as monophyletic. Among the 22 sampled subfamilies, only six are monophyletic: Gryllotalpinae, Trigonidiinae, Pteroplistinae, Euscyrtinae, Oecanthinae, and Phaloriinae. Most of the 37 tribes sampled are para‐ or polyphyletic. We propose the best‐supported clades as backbones for future definitions of familial groups, validating some taxonomic hypotheses proposed in the past. These clades fit variously with the morphological characters used today to identify crickets. Our study emphasizes the utility of a classificatory system that accommodates diagnostic characters and monophyletic units of evolution. Moreover, the phylogenetic hypotheses proposed by the present study open new perspectives for further evolutionary research, especially on acoustic communication and biogeography.