The Evolution of Tarsal Adhesive Microstructures in Stick and Leaf Insects (Phasmatodea)

Abstract

Insects have developed specialized structures on their feet for adhering to surfaces, with stick and leaf insects or Phasmatodea exhibiting an unexpectedly high diversity of these structures. In Phasmatodea, attachment on different substrates is achieved by two types of pads on the legs: the euplantulae on the tarsomeres and the arolium on the pretarsus. The euplantulae are adhesive structures capable of adaptability to the substrate profile and generation of the required attachment strength. The diversity of euplantular microstructures of 56 species that represent all major lineages recognized within Phasmatodea and the whole biogeographical distribution of the group are examined using scanning electron microscopy (SEM). Nine different types of attachment structures can be distinguished whereby one, the nubby type, can be further divided into three different distinct types based on the specific ratio of each conical outgrowth. We mapped the morphological data from the SEM onto a phylogenetic tree we reconstructed based on molecular data. Previously, the evolution of different adhesive microstructures (AMs) on these pads has been suggested to reflect phylogenetic groups. However, different types of AMs are found within monophyletic groups, and our ancestral character state reconstruction suggests smooth euplantulae in the ground pattern of Euphasmatodea and multiple independent origins of other forms. The type of AM appears to be strongly associated with ecomorphs, e.g., smooth euplantular surfaces are more frequently found in tree-dwellers than in ground-dwellers, whilst the attachment pads of ground-dwelling species primarily bear conical cuticular outgrowths (nubby euplantulae).

Old World and New World Phasmatodea: Phylogenomics Resolve the Evolutionary History of Stick and Leaf Insects

“…A monophyletic Malagasy clade comprises Anisacanthidae (Paranisacantha), Achriopterini (Achrioptera), Antongiliinae (Antongilia), and Phasmatidae taxa incertae sedis (Spathomorpha), with the former two and the latter two forming sister taxa in accordance with previous results (Bradler et al, 2015;Goldberg et al, 2015;Büscher et al, 2018;Robertson et al, 2018;Glaw et al, 2019). Closely related Malagasy stick insects were only recently suggested but not recovered as monophyletic when certain African taxa were included that are lacking in the present analysis (Bradler et al, 2015;Robertson et al, 2018).…”

“…Within Heteropterygidae, the Obriminae (Aretaon, Trachyaretaon) and Dataminae (Epidares, Orestes) (traditionally referred to as Obrimini and Datamini, see Bradler and Buckley, 2018) were recovered, and Heteropteryx (representing the third subgroup Heteropteryginae or, traditionally, Heteropterygini) as sister to Dataminae in the trees inferred from the dataset AA decisive (Figure 2). The latter clade, Dataminae + Heteropteryginae, gained extremely low support (BS = 49), but was repeatedly recovered before (Büscher et al, 2018;Robertson et al, 2018). In contrast, Bradler et al (2015) obtained a topology Dataminae + (Heteropteryginae + Obriminae), which was also favored based on phylogenetic analysis of morphological characters by Bradler (2009) and also in our study supported by the trees inferred from the datasets NT decisive and AA SOS (Supplementary Figures S4, S5).…”

“…Based on morphological evidence, Agathemera was repeatedly placed as sister group to all remaining Euphasmatodea (Bradler, 2000(Bradler, , 2009 = Neophasmatidae sensu Bradler, 2003; = Verophasmatodea sensu Zompro, 2004;Klug and Bradler, 2006;Klug, 2008;Friedemann et al, 2012). However, this assumption and consequently the monophyly of Verophasmatodea have never been supported by molecular studies, which place Agathemera as a subordinate taxon, albeit with unstable position among stick insects (Whiting et al, 2003;Buckley et al, 2009;Bradler et al, 2014Bradler et al, , 2015Goldberg et al, 2015;Büscher et al, 2018). Most recently, Agathemera has been found to be the sister group to Pseudophasmatinae including Heteronemiini and Prisopidini (Robertson et al, 2018), thus basically re-erecting the Pseudophasmatinae that included all these taxa as originally proposed by Günther (1953).…”

Revisão taxonômica e análise filogenética de Paraphasma Redtenbacher, 1906 (Phasmatodea: Pseudophasmatidae: Stratocleinae)

“…Além dos aspectos citados acima, que justificaram e favoreceram a realização da revisão taxonômica aqui apresentada, a execução de uma análise filogenética de Paraphasma com base em dados morfológicos também foi motivada pelos fatos de que: (1) a grande maioria das análises cladísticas realizadas até hoje em Phasmatodea basearam-se somente em dados moleculares (ver Whiting et al 2003;Buckley et al 2009;Kômoto et al 2011;Bradler et al 2014Bradler et al , 2015Goldberg et al 2015;Büscher et al 2018;Robertson et al 2018;Glaw et al 2019); e (2) os estudos filogenéticos na ordem quase sempre focaram nas relações entre táxons de categorias supragenéricas (com exceção de apenas dois trabalhos sobre o gênero Agathemera - Dominguez et al 2009e Vera et al 2012. Assim, este é um dos primeiros estudos a investigar as relações filogenéticas em um gênero de bichos-paus, e o primeiro em um gênero de Pseudophasmatidae, buscando para isso explorar o potencial taxonômico da ainda pouco conhecida genitália masculina de Phasmatodea.…”

“…Autores como Whiting et al (2003), Buckley et al (2009), Kômoto et al (2011) Buckley et al 2009;Bradler et al 2015;Goldberg et al 2015;Büscher et al 2018;Robertson et al 2018). Com exceção de Büscher et al (op.…”