Obtaining molecular data for all life stages of Typhlodromus (Typhlodromus) exhilaratus (Mesostigmata: Phytoseiidae): consequences for species identification

DNA Barcoding and Phylogeny of Acari Species Based on ITS and COI Markers

Acari harbor numerous minute species of agricultural economic importance, mainly Tetranychidae and Phytoseiidae. Great efforts have been established by means of recovering morphological, molecular, and phylogenetic traits for species identification. Traditional identification still relies on external diagnostic characters, which are limited and usually exhibit large phenotypic plasticity within the species, rendering them useless for species delimitation and identification. We decided to increase the number of sequences of the Acari mitochondrial COI (Cytochrome C oxidase I) marker and ITS nuclear ribosomal DNA region for species identification in Tetranychidae and Phytoseiidae. The molecular data allow us to establish species boundaries and phylogenetic relationships among several clades of Acari, mainly Tetranychidae and Phytoseiidae. Sequence comparisons between complete COI and the Acari mitochondrial COI, ITS1-5,8S-ITS2, and ITS2 among all Acari sequences have demonstrated that the selected regions, even small, gave enough informative positions for both species’ identification and phylogenetic studies. Analyses of both DNA regions have unveiled their use as species identification characters, with special emphasis on Acari mitochondrial COI for Tetranychidae and Phytoseiidae species in comparison with the Folmer fragment, which has been universally used as a barcode marker. We demonstrated that the Acari mitochondrial COI region is also a suitable marker to establish a barcode dataset for Acari identification. Our phylogenetic analyses are congruent with other recent works, showing that Acari is a monophyletic group, of which Astigmata, Ixodida, Mesostigmata, Oribatida, and Prostigmata are also monophyletic.

Feeding design in free-living mesostigmatid chelicerae (Acari: Anactinotrichida)

A model based upon mechanics is used in a re-analysis of historical acarine morphological work augmented by an extra seven zoophagous mesostigmatid species. This review shows that predatory mesostigmatids do have cheliceral designs with clear rational purposes. Almost invariably within an overall body size class, the switch in predatory style from a worm-like prey feeding ('crushing/mashing' kill) functional group to a micro-arthropod feeding ('active prey cutting/slicing/slashing' kill) functional group is matched by: an increased cheliceral reach, a bigger chelal gape, a larger morphologically estimated chelal crunch force, and a drop in the adductive lever arm velocity ratio of the chela. Small size matters. Several uropodines (Eviphis ostrinus, the omnivore Trachytes aegrota, Urodiaspis tecta and, Uropoda orbicularis) have more elongate chelicerae (greater reach) than their chelal gape would suggest, even allowing for allometry across mesostigmatids. They may be: plesiosaur-like high-speed strikers of prey, scavenging carrion feeders (like long-necked vultures), probing/burrowing crevice feeders of cryptic nematodes, or small morsel/fragmentary food feeders. Some uropodoids have chelicerae and chelae which probably work like a construction-site mechanical excavator-digger with its small bucket. Possible hoeing/bulldozing, spore-cracking and tiny sabre-tooth cat-like striking actions are discussed for others. Subtle changes lead small mesostigmatids to be predator-scavengers (mesocarnivores) or to be predator-fungivores (hypocarnivores). Some uropodines (e.g., the worm-like prey feeder Alliphis siculus and, Uropoda orbicularis) show chelae similar in design to astigmatids and cryptostigmatids indicating possible facultative saprophagy. Scale matters-obligate predatory designs (hypercarnivory) start for mesostigmatids with chelal gape > 150 μm and cheliceral reach > 350 μm (i.e., about 500-650 μm in body size). Commonality of trophic design in these larger species with solifugids is indicated. Veigaia species with low chelal velocity ratio and other morphological strengthening specialisms, appear specially adapted in a concerted way for predating active soft and fast moving springtails (Collembola). Veigaia cerva shows a markedly bigger chelal gape than its cheliceral reach would proportionately infer suggesting it is a crocodile-like sit-and-wait or ambush predator par excellence. A small chelal gape, low cheliceral reach, moderate velocity ratio variant of the worm-like feeding habit design is supported for phytoseiid pollenophagy. Evidence for a resource partitioning model in the evolution of gnathosomal development is found. A comparison to crustacean claws and vertebrate mandibles is made. Alliphis siculus and Rhodacarus strenzkei are surprisingly powerful mega-cephalics for their small size. Parasitids show a canid-like trophic design. The chelicera of the nematophagous Alliphis halleri shows felid-like features. Glyphtholaspis confusa has hyaena-like cheliceral dentition. The latter species has a markedly smaller chelal gape than its cheliceral reach would suggest proportionately, which together with a high chelal velocity ratio and a high estimated chelal crunch force matches a power specialism of feeding on immobile tough fly eggs/pupae by crushing (durophagy). A consideration of gnathosomal orientation is made. Predatory specialisms appear to often match genera especially in larger mesostigmatids, which may scale quite differently. Comparison to holothyrids and opilioacarids indicates that the cheliceral chelae of the former are cutting-style and those of the latter are crushing-style. A simple validated easy-to-use '2:1 on' predictive algorithm of feeding habit type is included based on a strength-speed tradeoff in chelal velocity ratio for ecologists to test in the field.

Molecular characterization of phytoseiid mites in Turkey based on the internal transcribed spacer (ITS) region, with a new record for the country

The family Phytoseiidae contains many predatory mite species and some are used in biological control programs worldwide. The identification of phytoseiid mites is based on tiny morphological structures and sometimes species diagnosis is not easy especially for non-taxonomists. DNA-based approaches may offer a fast and accurate diagnosis to overcome these difficulties, nevertheless more DNA sequences are needed to determine intra- and inter-specific variations and to provide accurate decision rules based on genetic distances between the taxa considered. In this study, we provide the molecular characterization of seven phytoseiid species based on the internal transcribed spacer (ITS) region. Several populations of these species collected in Turkey were considered. A phylogenetic tree was also constructed. Finally, we record the presence of Neoseiulus reductus (Wainstein) in Turkey.

Which molecular markers for assessing which taxonomic level? The case study of the mite family Phytoseiidae (Acari: Mesostigmata)

The use of molecular markers for resolving systematics issues has improved our knowledge of life history. However, for the taxa studied herein-the predatory mite family Phytoseiidae-molecular phylogeny is impeded by a lack of suitable markers for deeper taxonomic levels. This study aims (i) to establish DNA amplification protocols for molecular markers known to resolve supraspecific nodes in other taxa, (ii) to determine their individual performance in assessing the clustering of species, genera, tribes and subfamilies, and (iii) to characterize the additional information provided when markers are concatenated. A new phylogenetic index is proposed based on ecological concepts, considering trees as a community of nodes. New and efficient protocols for DNA amplification of six molecular markers are provided. The concatenated tree globally provides more robust and reliable information, especially for deeper nodes. However, for assessing species identification and within-genera phylogenies, the combined use of six markers does not seem necessary, underlining the need to resize experiments depending on their taxonomic objectives. Finally, this study lays the methodological foundations with which to test the present Phytoseiidae classification as the first phylogeny obtained shows incongruence with the present morphological classification.

Revealing the hyperdiverse mite fauna of subarctic Canada through DNA barcoding

Although mites are one of the most abundant and diverse groups of arthropods, they are rarely targeted for detailed biodiversity surveys due to taxonomic constraints. We address this gap through DNA barcoding, evaluating acarine diversity at Churchill, Manitoba, a site on the tundra-taiga transition. Barcode analysis of 6279 specimens revealed nearly 900 presumptive species of mites with high species turnover between substrates and between forested and non-forested sites. Accumulation curves have not reached an asymptote for any of the three mite orders investigated, and estimates suggest that more than 1200 species of Acari occur at this locality. The coupling of DNA barcode results with taxonomic assignments revealed that Trombidiformes compose 49% of the fauna, a larger fraction than expected based on prior studies. This investigation demonstrates the efficacy of DNA barcoding in facilitating biodiversity assessments of hyperdiverse taxa.