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Phylogeny, taxonomy and species delimitation of water mites and velvet mites
Stockholm University, Faculty of Science, Department of Zoology. Enheten för Zoologi, Naturhistoriska riksmuseet.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This study is part of the Swedish Taxonomy Initiative (STI) - one of the most ambitious all taxa biodiversity inventories in the world. One of the pillars in STI is to support taxonomic research on the most neglected taxonomic groups with the aim to lift the level of knowledge of biodiversity in the country. There is still a lot to be discovered, especially in the microscopic world, and this includes mites. Many aspects of mite biology and diversity are poorly known, such as species richness, abundance, distribution, lifestyle and behavior of species. Mites inhabits all sorts of aquatic, terrestrial, arboreal and parasitic habitats, nevertheless even in well-studied systems mites are often overlooked. Despite being among the smallest of arthropods, they are of medical and economical importance and may be very abundant in the ecosystems they inhabit. This thesis focuses on Parasitengona (Acariformes: Prostigmata), one of the most diverse taxa among the arachnids. It includes the aquatic Hydrachnidia (water mites) and the terrestrial Trombidia (e.g. velvet mites, chiggers). A unifying characteristic of Parasitengona is their complex life cycle of active and inactive stages, parasitic larvae and predatory deutonymphs and adults. They typically parasitize and prey on arthropods, except the chiggers which have vertebrates as hosts. The aim of this thesis is to shed light on the phylogeny and taxonomy of Parasitengona with emphasis on the Swedish fauna. To achieve this, mites were collected from different localities throughout the country between the years 2007-2016. Water mites were sampled with a hand net. Larvae of terrestrial Parasitengona were collected with sweeping nets and sorted out from malaise trap samples from the Swedish Malaise Trap Project. To collect the adults Berlese-Tullgren extractor and pitfall traps were used as well as hand collecting and sifting with litter reducer. The material collected abroad was kindly provided through collaboration.  Methods used in the papers included morphometrics, multivariate analyses, experimental rearing, DNA extraction and sequencing, Bayesian phylogenetic analyses and molecular species delimitation. In paper I and II, we combine molecular species delimitation models and morphological data to resolve taxonomical issues. This integrative taxonomic approach of combining data resulted in Piona dispersa Sokolow, 1926 as a valid species and redescriptions, new synonyms and neotypes provided for Erythraeus phalangoides (De Geer, 1778),  E. cinereus (Dugès, 1834) and E. regalis (C.L. Koch, 1837). Based on the new inventories we produce an updated and annotated checklist of 105 terrestrial Parasitengona species for Fennoscandia in paper III, and use metadata to increase the knowledge on distribution, habitat preferences, life stages and abundance. Out of these, 20 species are new findings for the region and five are potential new species for science. In paper IV, we provide a molecular phylogeny of Parasitengona based on the genes 18S, 28S and COI for 80 taxa with a sampling focus on the terrestrial lineages. Based on the results we offer a revised higher-level classification of the group. In particular the analyses supported Tanaupodoidea Thor, 1935 as a separate superfamily, but Trombiculoidea Ewing, 1929 was not monophyletic and was synonymized, along with Chyzerioidea Womersley, 1954, with Trombidioidea Leach, 1815.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University , 2017. , p. 33
Keyword [en]
Acariformes, Parasitengona, Hydrachnidia, Trombidia, water mites, velvet mites, taxonomy, cryptic species, species delimitation, DNA, GMYC, experimental rearing, new synonyms, distribution, phylogeny, revised classification
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
URN: urn:nbn:se:su:diva-139045ISBN: 978-91-7649-688-6 (print)ISBN: 978-91-7649-689-3 (electronic)OAI: oai:DiVA.org:su-139045DiVA, id: diva2:1070675
Public defence
2017-03-17, Lilla hörsalen, Naturhistoriska riksmuseet, Frescativägen 40, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

 

Available from: 2017-02-22 Created: 2017-02-02 Last updated: 2017-02-16Bibliographically approved
List of papers
1. “Forms” of water mites (Acari: Hydrachnidia): intraspecificvariation or valid species?
Open this publication in new window or tab >>“Forms” of water mites (Acari: Hydrachnidia): intraspecificvariation or valid species?
2013 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 3, no 10, p. 3415-3435Article in journal (Refereed) Published
Abstract [en]

In many groups of organisms, especially in the older literature, it has been common practice to recognize sympatrically occurring phenotypic variants of a species as “forms”. However, what these forms really represent often remains unclear, especially in poorly studied groups. With new algorithms for DNA-based species delimitation, the status of forms can be explicitly tested with molecular data. In this study, we test a number of what is now recognized as valid species of water mites (Hydrachnidia), but have in the past been treated as forms sympatrically occurring with their nominate species. We also test a form without prior taxonomical status, using DNA and morphometrics. The barcoding fragment of COI, nuclear 28S and quantitative analyses of morphological data were used to test whether these taxa merit species status, as suggested by several taxonomists. Our results confirm valid species. Genetic distances between the form and nominate species (Piona dispersa and Piona variabilis, COI 11%), as well as likelihood ratio tests under the general mixed-Yule coalescent model, supported that these are separately evolving lineages as defined by the unified species concept. In addition, they can be diagnosed with morphological characters. The study also reveals that some taxa genetically represent more than one species. We propose that P. dispersa are recognized as valid taxa at the species level. Unionicola minor (which may consist of several species), Piona stjordalensis, P. imminuta s. lat., and P. rotundoides are confirmed as species using this model. The results also imply that future studies of other water mite species complexes are likely to reveal many more genetically and morphologically distinct species.

Keyword
Bayesian analysis, cryptic species, DNA barcoding, GMYC model, principal Pcomponent analysis, species delimitation
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-94304 (URN)10.1002/ece3.704 (DOI)
Projects
Doktorandprojekt "Taxonomi och fylogeni hos vattenkvalster och sammetskvalster (Acari)
Available from: 2013-10-02 Created: 2013-10-02 Last updated: 2017-12-06Bibliographically approved
2. Towards resolving the double classification in Erythraeus (Actinotrichida: Erythraeidae): matching larvae with adults using 28S sequence data and experimental rearing
Open this publication in new window or tab >>Towards resolving the double classification in Erythraeus (Actinotrichida: Erythraeidae): matching larvae with adults using 28S sequence data and experimental rearing
2016 (English)In: Organisms Diversity & Evolution, ISSN 1439-6092, E-ISSN 1618-1077, Vol. 16, no 4, p. 761-790Article in journal (Refereed) Published
Abstract [en]

The taxonomy of free-living adults and heteromorphic parasitic larvae of Parasitengona mites has in the past been treated independently resulting in a double classification. Correct linkage of names still remains unknown for many species. A holistic understanding of species is imperative for understanding their role in ecosystems. This is particularly true for groups like parasitengone mites with a radically altered lifestyle during development-parasitic to predatory. Here, we infer linkages of three nominal species of Erythraeus, using matching with 28S DNA sequence data from field-collected specimens and through laboratory rearing. The general mixed Yule coalescent method (GMYC) was used to explicitly test if field-collected specimens representing heteromorphic life instars were conspecific. The field-collected larvae were allocated to adults of Erythraeus cinereus and Erythraeus regalis, respectively. Laboratory rearing of the same two species confirmed the matching done by DNA. Rearing was also successful for Erythraeus phalangoides after eggs were treated to an imitated winter diapause. This integrative taxonomic approach of molecular, morphological, and rearing data resulted in the following synonyms: E. phalangoides (De Geer, 1778) [= Erythraeus adrastus (Southcott, 1961), syn. nov.], E. cinereus (DugSs, 1834) [= Erythraeus jowitae Haitlinger, 1987, syn. nov.], and E. regalis (C.L. Koch, 1837) [= Erythraeus kuyperi (Oudemans, 1910), syn. nov., = Erythraeus gertrudae Haitlinger, 1987, syn. nov.]. The molecular evidence confirmed the separate identity of three further members of the genus. We provide redescriptions of E. phalangoides, E. cinereus, and E. regalis after modern standards, and neotypes are designated.

Keyword
Biology, GMYC, Molecular species delimitation, Morphology, New synonyms, Parasitengona
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-137602 (URN)10.1007/s13127-016-0283-5 (DOI)000387843900009 ()
Available from: 2017-01-16 Created: 2017-01-09 Last updated: 2017-11-29Bibliographically approved
3. Checklist of Terrestrial Parasitengona mites (Acariformes: Prostigmata) in Fennoscandia
Open this publication in new window or tab >>Checklist of Terrestrial Parasitengona mites (Acariformes: Prostigmata) in Fennoscandia
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The knowledge on terrestrial Parasitengona in Fennoscandia lies far behind that of the aquatic counterpart, the water mites (Hydrachnidia). Based on new inventories we provide primary data and an annotated checklist of terrestrial Parasitengona in Fennoscandia including 105 species. Out of these, twenty species are new findings for the region and five are potential new species for science. Eighteen species are new for Norway, fifteen for Finland and eight for Sweden. The known recorded fauna today of terrestrial Parasitengona is 73 species for Norway, 47 for Sweden and 47 for Finland. Primary data include georeferenced locality data as well as collecting techniques and microhabitat to increase the knowledge on species' habitat requirements.

National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-139032 (URN)
Funder
The Swedish Taxonomy Initiative (ArtDatabanken, SLU)
Available from: 2017-02-01 Created: 2017-02-01 Last updated: 2017-02-13Bibliographically approved
4. Phylogeny and revised classification of terrestrial Parasitengona
Open this publication in new window or tab >>Phylogeny and revised classification of terrestrial Parasitengona
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Parasitengona mites include the aquatic water mites (Hydrachnidia) and the terrestrial parasitengones (Trombidia). They are characterised by having a parasitic larval stage and a complex life cycle with alternating active and inactive instars. The phylogenetic relationship between Hydrachnidia and Trombidia has been debated and the molecular phylogeny of Hydrachnidia was recently tested. Here we provide and analyze the most comprehensive molecular dataset of terrestrial Parasitengones to date based on the nuclear ribosomal genes 18S and 28S, and mitochondrial COI for 80 taxa. We find Hydrachnidia nested within Trombidia with Calyptostomatoidea being the sister group to Hydrachnidia. Stygothrombioidea is sister to remaining Parasitengona, Erythraeoidea and Tanaupodoidea are sister taxa and Trombiculoidea is a paraphyletic grade along with Chyzerioidea in relation to Trombidioidea. These results were supported and largely stable across various sensitivity analyses excluding sections of the ribosomal genes that were difficult to align as well as third codon position of COI. The exception was the relationship between the three groups (Calyptostomatoidea+Hydrachnidia), (Erythraeoidea+Tanaupodoidea) and (Trombidioidea+Trombiculoidea+Chyzerioidea) which was not resolved but varied between analyses. An elevated substitution rate was discovered in the taxon Neothrombiidae that created an extremely long branch and problems with long-branch attraction. Based on the result we provide a revised higher-level classification of Parasitengona where we recognize five non-Hydrachnidia superfamilies: Stygothrombioidea Thor, 1935, Tanaupodoidea Thor, 1935, Calyptostomatoidea Oudemans, 1923, Erythraeoidea Robineau-Desvoidy, 1828 and Trombidioidea Leach, 1815 (=Trombiculoidea Ewing, 1929 (n. syn.); =Chyzerioidea Womersley, 1954 (n. syn.); =Yurebilloidea Southcott, 1996) (n. syn.)). We also recognize Podothrombiidae Thor, 1935 at family level (n. stat.).

National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-139042 (URN)
Funder
The Swedish Taxonomy Initiative (ArtDatabanken, SLU)
Available from: 2017-02-01 Created: 2017-02-01 Last updated: 2017-02-23

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