Minimal barcode distance between two water mite species from Madeira Island: a cautionary tale

Abstract

In this work, we compare morphological and molecular data in their ability to distinguish between species of water mites (Acari, Prostigmata, Hydrachnidia). We have focused on the two species of the genus Lebertia inhabiting the island of Madeira. While traditional morphological traits were initially sufficient to distinguish between these two species, the molecular data were more dependable on the kind of analysis carried out. Single arbitrary genetic distance (e.g. a K2P distance below 2%) may lead to the conclusion that the specimens under study belong to the same species. Analysing the same specimens with the coalescent model has proved the evolutionary independence of both Lebertia clades in Madeira. Furthermore, multi-rate Poisson Tree Process analysis confirmed both lineages as independent species. Our results agree with previous studies warning of the dangers of rigid species delimitation based on arbitrary molecular distances. In addition, the importance of different molecular data approaches for correct species delimitation in water mites is highlighted.

Cryptic diversity within grass-associated Abacarus species complex (Acariformes: Eriophyidae), with the description of a new species, Abacarus plumiger n. sp.

“…Cryptic speciation is a common phenomenon in all mite taxa (Skoracka et al 2015;Coimbra-Dores et al 2016;García-Jiménez et al 2017;de Rojas et al 2018;Stork 2018), including obligatory phytophagous eriophyoid mites (Lewandowski et al 2014;Cvrković et al 2016). Our study also contributed to disclosing mites' cryptic diversity by demonstrating the existence of highly diverse lineages within the formerly described eriophyoid A. hystrix complex, that exhibit genetic variation along with variation in host use.…”

Hidden biodiversity revealed by integrated morphology and genetic species delimitation of spring dwelling water mite species (Acari, Parasitengona: Hydrachnidia)

“…However, species delimitation solely based on fixed genetic distance thresholds can be misleading and thresholds should be estimated individually for each dataset [38, 95, 96], especially in taxa with clade-specific intraspecific cox 1 distances as demonstrated for water mites in this and previous studies (e.g. [94, 97]). As the 28S marker region did not show a distinct barcoding gap and a clear species identification threshold was not evident, we do not recommend using it as single marker for threshold-based species identification of water mites.…”

A note on centrifugation for improving freshwater invertebrate sample conservation

“…The samples can then be refilled as soon as reaching lab. We have not observed detectable differences in the extractability of genetic material (DNA) using this method (García-Jiménez et al, 2017).…”