Homoplasy and morphological stasis revealed through multilocus phylogeny of new myrmecophilous species in Armadillidiidae (Isopoda: Oniscidea)

Abstract

Abstract The terrestrial isopod family Armadillidiidae presents higher diversity in karstic areas, with fewer species present in areas with reduced suitable subterranean habitats, such as siliceous sandy soils. Myrmecophily, although not widespread in the family Armadillidiidae, can help these animals to colonize sandy substrates, as is observed in several populations of myrmecophilous Armadillidiidae species in central and southern Spain. Morphological examination and multilocus phylogenetic analyses, including mitochondrial DNA (Cox1) and nuclear DNA (18S, 28S and H3) markers, indicate that these myrmecophilous populations represent four new taxa: Iberiarmadillidium pinicola gen. & sp. nov., Iberiarmadillidium psammophilum sp. nov., Iberiarmadillidium sakura sp. nov. and Cristarmadillidium myrmecophilum sp. nov. Some of the main diagnostic characters used in the taxonomy of Armadillidiidae are not clearly apomorphic. Among head morphologies, Eluma type seems to be the ancestral state, being typical of several unrelated lineages; duplocarinate and Armadillidium types are derived states observed in unrelated lineages. The presence of a schisma is a convergent character state, because it has been identified in several taxa nested in unrelated clades. The newly described taxa present patterns of morphological stasis and homoplasy, likely to be associated with their shared myrmecophilous habits. The generic taxonomy of the family needs a deep revision including phylogenetic approaches and thorough taxon sampling.