Review of competing hypotheses of phylogenetic relationships of Paussinae (Coleoptera: Carabidae) based on larval characters

Abstract

Abstract. Larval structural characters are an important component in phylogenetic reconstruction of the subfamily Paussinae. Based on larval characters, two main cladistic hypotheses have been proposed concerning basal relationships within Paussinae: (1) Metriini as sister-group of Ozaenini þ Paussini, with Ozaenini as a paraphyletic group and the genus Physea as sister-group of Paussini; and (2) Metriini as sister-group only of the monophyletic Ozaenini, with the Paussini as sister-group of Metriini þ Ozaenini. We present here a review of these hypotheses and a new cladistic analysis based on larvae, emphasizing the phylogeny of Ozaenini. The analysis includes the following taxa: Metrius (Metriini), Itamus, Pachyteles, Sphaerostylus, Physea (Ozaenini), Platyrhopalopsis and Paussus (Paussini). For both Physea and Platyropalopsis larvae we provide new detailed descriptions, because previous descriptions are inadequate to allow an advanced phylogenetic discussion. A total of fifty-six characters are analysed. Most characters show alternative states organized into sequences of character states, each of which is logically derivable from its neighbour in the sequence, resulting in an almost completely pectinate cladogram. Metrius is the sister-group of all other Paussinae, and Paussini are a highly derived offshoot within the ozaenine grade. According to the present analysis, Physea, regarded traditionally as a typical ozaenine, represents the ozeanine sister to Paussini, showing that Ozaenini are paraphyletic. As our analysis is based on the few paussine genera sufficiently known at the larval stage, which represent a low number of the extant paussine genera, the results are merely illustrative of the evolution of the major clades within the subfamily. More detailed information about the phylogeny of ozaenines could arise from a more comprehensive analysis, mainly including adult morphological characters.

The long-awaited first instar larva of Paussus favieri (Coleoptera: Carabidae: Paussini)

“…This reduction from the ancestral state found in other Paussinae tribes (e.g., Metriini, Ozaenini) may be related to the secondary acquisition of a prognathous position of mouthparts and head derived from a hyperprognathous ancestral state (Di Giulio et al, 2003). Such a basal degeneration of the head (including the widening of the occipital foramen and a disappearance of the neck) could be an adaptation for living with ants.…”

“…Though our knowledge of Paussinae larvae is very limited, the taxon sampling is broad enough to provide information about relationships among major clades. However since larvae are rarely collected in the field and difficult to rear in the laboratory, phylogenetic analyses based on larval morphology compared different instars of the taxa included in the analyses (Bousquet, 1986;Beutel, 1992;Vigna Taglianti et al, 1998;Di Giulio et al, 2003;Di Giulio & Moore, 2004). For this reason, only morphological characters related to shape of the head capsule, head appendages, legs and terminal disk have been used.…”

“…MacLeay, 1838, Platyrhopalopsis Desneux, 1905, Paussus Linnaeus, 1775, Granulopaussus Kolbe, 1938. Two other larval descriptions (Wasmann, 1918;Brauns, 1914;van Emden, 1922) are too vague and superficial to be useful, the identifications having been based solely upon speculations, and the deposition of material is unknown (Di Giulio et al, 2003;Di Giulio & Moore, 2004;Di Giulio, 2008). While first instar larvae are widely acknowledged to be an important source of diagnostic characters (i.e., primary chaetotaxy and egg burster shape) (Bousquet & Goulet, 1984), most of the described Paussini larvae are second or third instars.…”

Evaluating Alpha and Beta Taxonomy in Ant-Nest Beetles (Coleoptera, Carabidae, Paussini)

“…All Paussini are highly specialized social parasites, depending on ants (mainly associated with Myrmicinae and Formicinae) during any stage of their development [6][7][8][9]. Adults prey on ants and their broods without any obvious benefit for the ant colonies [10][11][12][13][14][15].…”

“…Adults prey on ants and their broods without any obvious benefit for the ant colonies [10][11][12][13][14][15]. Because of their specialised behavioural and morphological adaptations, Paussini have long attracted the interest of entomologists working on myrmecophilous insects [13], and they have been recently into focus because of strong incertitude about their relationships with other Paussinae lineages [6,7]. These studies have prompted our knowledge of Paussini biology, with emphasis on their immature stages and microscopic morphology, but taxonomical work seems to receive little attention.…”