DOI: 10.5061/dryad.80gb5mkrd
title: High diversity of mites (Acari: Oribatida, Mesostig-mata) supports the high conservation value of a broadleaf forest in Eastern Norway

description: Broadleaf forests are critical habitats for biodiversity and this
 biodiversity is in turn essential for their proper functioning. Mites
 (Acari) are a numerous and functionally essential component of these
 forests. We report the diversity of two important groups, Oribatida and
 Mesostigmata, in a broadleaf forest in Eastern Norway which is considered
 to be a biodiversity hotspot. Eighteen samples, each 500 cm3, were
 collected from diverse microhabitats (moss on ground, lichens on tree
 twigs lying on ground, moss on tree trunk at ground level and 1.5 m above
 ground, moss on decaying wood, log and stump, and decaying wood) from
 which 10,843 specimens and 95 species from 32 families of Oribatida, and
 655 specimens of 34 species from 14 families of Mesostigmata were found.
 Only 30% of the species were previously recorded in broadleaf forests in
 Western Norway. Oribatid communities on tree stumps and in lichens were
 distinct from the other communities, while mesostigmatid communities on
 tree trunks (both at ground level and above ground) and in lichens
 differed most from other communities. Over 30% of the species were found
 in only a single microhabitat. Twenty-three species and the genus
 Zerconopsis are reported from Norway for the first time. Six records are
 also new to Fennoscandia, including (Oribatida) Quadroppia monstruosa,
 Eueremaeus valkanovi, Ramusella furcata, and (Mesostigmata) Dendrolaelaps
 rectus, D. multidentatus, and D. tenuipilus. In addition, several rare
 species were detected, e.g., Achipteria magna, Oribotritia berlesei, and
 Subiasella quadrimaculata, and two were found in their northernmost
 locality (O. berlesei, E. valkanovi). These results confirm the unique
 character and high conservation value of the studied forest in Norway,
 Fennoscandia and at a European scale.
description: 2.1. Study
 Site Samples were collected in a
 plant-rich broadleaf forest located in Kjeøya (59.093° N 11.222° E, 120 m
 a.s.l.), a peninsula in Viken province, Halden municipality, in Eastern
 Norway (Figure 1). The study site was characterized by an oceanic climate,
 with mean annual temperature 6.4 °C and annual precipitation 820 mm [38].
 Summer is relatively mild with average temperatures between 16.0–16.7 °C
 in July and August. In the coldest months (January and February) the
 average temperatures are between −2.9 °C and −3.8 °C. The vegetation zone
 is Boreonemoral and slightly oceanic <i>sensu</i> [39]. The
 bedrock is composed mainly of different gneiss and granite
 rocks.  The forest (Figure 2) has an area of 2.32 ha
 and is considered an important habitat, since many rare species, mainly
 fungi, have been detected there [40]. Forest was characterized by old and
 large oak (mostly common oak, <i>Quercus robur
 </i>L<i>.</i>), hollow oaks of 100 years and older
 (&gt;50 cm dbh) [41], and small-leaved<b> </b>lime
 (<i>Tilia cordata </i>Mill.) trees. Other tree species were
 hazel (<i>Corylus avellana </i>L.), common ash
 (<i>Fraxinus excelsior </i>L.), Norway maple (<i>Acer
 platanoides </i>L.), and some additional Norway spruce
 [<i>Picea abies</i> (L.) H.Karst] and Scots pine
 (<i>Pinus sylvestris</i> L.). The herb vegetation was partly
 sparse. 2.2. Sampling and
 Identification In total, 18 samples, each
 of a volume of 500 cm<sup>3</sup>, were collected on 12 June
 2017 from several microhabitats: (1) mosses on ground (four samples), (2)
 lichens on tree twigs lying on ground (three samples), (3) mosses on tree
 trunks on ground level (three samples), (4) mosses on tree trunks 1.5 m
 above ground (two samples), (5) mosses on stump (one sample), (6) mosses
 on decaying wood (three samples), and (7) decaying wood (two
 samples). Arthropods were extracted using modified
 Tullgren funnels for 14 days into 90% ethanol and sorted out from the
 samples under stereomicroscope. Oribatida were mounted on temporary slides
 with cavity in lactic acid and adult specimens were identified using the
 keys of [42–45], while juveniles were identified based on [46–61]. The
 nomenclature of oribatid species follows [62, 63] and partly [45,57,58].
 Mesostigmata were mounted on permanent slides in PVA mounting medium
 (Lactic Acid, Poly Vinyl Acetate and Phenol Solution, BioQuip Products,
 Inc., Compton, CA, USA) and identified following [64–84]. Full names of
 species are given in Table 1 while in other tables and figures
 abbreviations are used.  Specimens representing all species are deposited
 at the University Museum of Bergen, Norway. Information on other mite
 groups that were sorted out from the samples will be published
 later. Habitat preferences (Table 1) of oribatid mites
 are based on [45,85–87], and those of Mesostigmata on
 [67,69,70,72,73,75–78,80–82,88–91]. These habitats include the following
 types: aquatic (reproduction and all stages of life cycle in water or at
 its margins), hygrophilous (living in wet places), mesohygrophilous
 (preferring high moisture but not wet places), xerophilous (living in dry
 places), arboricolous (living on trees), lichenicolous (living on
 lichens), merocenophilous (living in bark beetle galleries and anthills),
 muscicolous (living in mosses), praticolous (meadow species), silvicolous
 (forest species), tyrphophilous (bog species) and eurytopic (occurring in
 more than three habitat types). The new records of
 Oribatida for Norway are based on the checklist [92] and later
 publications [15,37,93]. Those new to Fennoscandia are based on [94,95]
 and later publications [31,96–107]. The new records of Mesostigmata for
 Norway are based on [91,108–110] and those new to Fennoscandia are based
 on [90,111]. 2.3. Statistical
 Analyses Oribatid and mesostigmatid mite
 populations were quantified as abundance (individuals in 500
 cm<sup>3</sup>), dominance (<i>D</i>, percentage
 of specimens of a particular species in the average abundance of Oribatida
 or Mesostigmata), and frequency (<i>F</i>, percentage of the
 samples where the species was present), and by the number of species (mean
 per sample in habitat and total species richness per habitat), and the
 Shannon (<i>H</i>') diversity index [112]. Categories
 summarizing the status of occurrence of species (Table 2) follow
 [113]. The basic statistical descriptors included the
 mean values and standard deviation and were calculated in MS Excel. The
 species similarities of the Oribatida and Mesostigmata between
 microhabitats were analyzed using an unweighted pair group method with
 arithmetic mean (UPGMA) with Bray-Curtis coefficient [114] using MVSP 3.2
 [115]. Chao −1 indices and individual-based rarefaction curves were
 computed using 100 randomizations in EstimateS for Windows (version 9)
 [116].