Integrative taxonomy: Combining morphological, molecular and chemical data for species delineation in the parthenogenetic Trhypochthonius tectorum complex (Acari, Oribatida, Trhypochthoniidae)

Abstract

BackgroundThere is a long-standing controversial about how parthenogenetic species can be defined in absence of a generally accepted species concept for this reproductive mode. An integrative approach was suggested, combining molecular and morphological data to identify distinct monophyletic entities. Using this approach, speciation of parthenogenetic lineages was recently demonstrated for groups of bdelloid rotifers and oribatid mites. Trhypochthonius tectorum, an oribatid mite from the entirely parthenogenetic desmonomatan family Trhypochthoniidae, is traditionally treated as a single species in Central Europe. However, two new morphological lineages were recently proposed for some Austrian populations of T. tectorum, and were described as novel subspecies (T. silvestris europaeus) or form (T. japonicus forma occidentalis). We used the morphological and morphometrical data which led to this separation, and added mitochondrial and nuclear DNA sequences and the chemical composition of complex exocrine oil gland secretions to test this taxonomical hypothesis. This is the first attempt to combine these three types of data for integrative taxonomical investigations of oribatid mites.ResultsWe show that the previous European species T. tectorum represents a species complex consisting of three distinct lineages in Austria (T.tectorum, T. silvestris europaeus and T. japonicus forma occidentalis), each clearly separated by morphology, oil gland secretion profiles and mitochondrial cox1 sequences. This diversification happened in the last ten million years. In contrast to these results, no variation among the lineages was found in the nuclear 18S rDNA.ConclusionsOur approach combined morphological, molecular and chemical data to investigate diversity and species delineation in a parthenogenetic oribatid mite species complex. To date, hypotheses of a general oribatid mite phylogeny are manifold, and mostly based on single-method approaches. Probably, the integrative approach proposed here can be used to uncover further hidden biodiversity of glandulate Oribatida and help to build up more stable phylogenetic hypotheses in the future.

Cryptic Species in Putative Ancient Asexual Darwinulids (Crustacea, Ostracoda)

“…Such ecological differentiation has been described in bdelloid rotifers [16], [17] and oribatid mites [54], [65], [66]. Within the family Darwinulidae, no clear ecological specialization has so far been found.…”

Morphological, molecular and cross-breeding analysis of geographic populations of coconut-mite associated predatory mites identified as Neoseiulus baraki: evidence for cryptic species?

“…Other cases where an integrative approach was also used to identify cryptic species (or complex of species) have been reported in other mite taxa. For example, Heethoff et al (2011) used integrative taxonomy, combining morphological, molecular and chemical methods to delineate species in the parthenogenetic Trhypochthonius tectorum complex. Klimov et al (2004) employed the same methods, as used in the present study (morphological, crossbreeding and molecular) to identify two cryptic species of Sancassania mites, Sancassania salasi and S. ochoai (Klimov et al 2004).…”

Triggering chemical defense in an oribatid mite using artificial stimuli

“…Thomas 2002;Heethoff et al 2007;Bergmann et al 2008;Laumann et al 2010;Alberti et al 2011). The oil gland secretions of A. longisetosus are already well known and comprise a set of terpenes, aromatics and hydrocarbons, the so-called 'Astigmata-compounds' (sensu Sakata and Norton 2001;Heethoff and Raspotnig 2011;Heethoff et al 2011b), which are considered synapomorphic for the glandulate Oribatida (including the clade known as Astigmata; Sakata and Norton 2001). Adult specimens from the laboratory strain A. longisetosus ran were cultured in constant dark at 28°C and saturated air humidity; the unicellular alga Chlorella (as commercially available powder) was provided as food and applied on filter paper every 3 days.…”