Molecular evidence for species separation in the water mite Hygrobates nigromaculatus Lebert, 1879 (Acari, Hydrachnidia): evolutionary consequences of the loss of larval parasitism

Abstract

In the present study, we used mitochondrial cytochrome oxidase subunit I (COI) and nuclear D2 region of 28S rDNA sequence data to examine the taxonomic status of the water mite species Hygrobates nigromaculatus from two types of freshwater habitats: lentic (lakes) and lotic (streams). Previous hypotheses about (sub)species status of populations inhabiting lakes and streams based on differences in morphometric data and life-cycle strategy (parasitic vs. non-parasitic larvae) were strongly supported by molecular data. Levels of COI and D2 28S rDNA differentiation between lake and stream populations were much higher (ca. 18 and 7.5%, respectively) than those typically observed for populations of a single species. Both lake and stream populations showed similar high levels of gene diversity (Hd = 0.894 and 0.836, respectively). However, nucleotide within-population polymorphism was more than twice as high in lake populations as that in stream populations (p = 1.33 and 0.60%, respectively). We hypothesize that the ancestral lake-dwelling population originated from a stream form with parasitic larvae (here: H. setosus nov. stat.). For the observed populations, H. nigromaculatus individuals could be separated from H. setosus by distinct morphometric characters. The loss of phoretic parasitic larvae greatly decreased dispersal ability of lake-dwelling mites and consequently also the gene flow between lake populations. Thus, relatively more differentiated genetic structure in lake populations probably results from a stronger isolation between particular lake habitats, but this hypothesis needs further extensive studies.

DNA-barcoding contradicts morphology in quill mite species Torotrogla merulae and T. rubeculi (Prostigmata: Syringophilidae)

“…ten fold the intraspecific variability and interspecific distance usually equals to or is higher than 3% (D ≥ 0.03 -Sbordoni 2010), making it possible to identify most metazoan species with high confidence. Recently the D1-D2 region of the nuclear 28s rrNA gene has been proposed as a reliable barcode marker complementing analyses based on mitochondrial coi (sonnenberg et al 2007, Martin et al 2010, skoracka and Dabert 2010.it is necessary to mention that the barcoding revolution and concept of DNA taxonomy have been widely debated in the past decade and besides the enthusiastic voices which saw in it a tool of unequivocal judge in taxonomic indecisions, it also provoked voices of opponents, who pointed out some deficiencies and limitations in the methods employed by Hebert et al (2003). they concerned mainly abandoning both morphological data and other crucial species descriptors in favour of a narrow molecular identification system and disregarding the nature of speciation events, different roles of genetic system, natural selection and evolutionary time (sperling 2003(sperling , tautz et al 2003(sperling , Will and rubinoff 2004(sperling , sbordoni 2010.…”

“…ten fold the intraspecific variability and interspecific distance usually equals to or is higher than 3% (D ≥ 0.03 -Sbordoni 2010), making it possible to identify most metazoan species with high confidence. Recently the D1-D2 region of the nuclear 28s rrNA gene has been proposed as a reliable barcode marker complementing analyses based on mitochondrial coi (sonnenberg et al 2007, Martin et al 2010, skoracka and Dabert 2010.…”

Bryobia abyssiniae(Prostigmata: Tetranychidae), a new species from the highlands of Ethiopia

“…Differences of a similar degree were found recently in a species of quill mite, another member of the Prostigmata; despite morphological variation in this species, COI sequences differed by only 1.6-2.4% between variants (Glowska et al 2013). In order to confirm that different forms of water mite are valid species (Acari: Hydrachnidia), a minimum threshold of 17-23% sequence variation has been proposed, which is much higher than the sequence variability observed within populations of a single known species (Martin et al 2010;Stålstedt et al 2013).…”

The Application of Ultraviolet Spectrophotometry (UV) on Some Water Mite Species (Acari, Hydrachnidia)

“…Six different water mite species (Acari, Hydrachnidia) were used in the study. These species are Hydryphantes flexiosus (1), Hydrodroma despiciens (2), Georgella helvatica (3), Eylais infundibulifera (4), Hygrobates nigromacutlatus (5) and Torrenticola brevirostris (6). The UV (ultraviolet spectrophotometer) method used in the study was applied separately to each of the species.…”