Type of broadleaf forest matters most for ptyctimous mite communities (Acari, Oribatida) in Norway

Abstract

We studied ptyctimous moss mites, which are characteristic of forest habitats, in Norwegian broadleaf forests considered as biodiversity hotspot areas in Fennoscandia. The study aimed to evaluate the effect of different factors (regional locality, annual precipitation, mean annual temperature, forest type, forest wetness and microhabitat) on the ptyctimous mites and on discovering their richness in broadleaf forests. Samples were collected from nine broadleaf forests in Western, Southern and Eastern Norway, in different climatic conditions, six forest types, three forest wetness states and eight microhabitats. Overall, 3341 ptyctimous mites were collected and their abundance differed significantly among the regions, forest types and microhabitats. Forest type turned out to be the most important factor, responsible for 24.5% of the total variation in the abundance of the ptyctimous mites. Other important factors were forest wetness and microhabitat. In total, 27 species, i.e., 87% of all ptyctimous mites known from before in Norway were found and the species richness was highest in the east and lowest in the west of the country. Atropacarus (Atropacarus) striculus was most common and most abundant; it made nearly 30% of all ptyctimous mites collected. On the other hand, a quarter of the species were represented by less than 10 specimens; most of these were new records for Norway. Among ten species discovered as new to Norway, four were also new to Fennoscandia. These findings confirm the unique character and high biological diversity of Norwegian broadleaf forests.

High Diversity of Mites (Acari: Oribatida, Mesostigmata) Supports the High Conservation Value of a Broadleaf Forest in Eastern Norway

“…Both the density and diversity of mites were higher here than in a broadleaf forest studied in Western Norway [15] (see Table 3 for comparison). This observation is in accordance with a well-known pattern that species richness is higher in Eastern Norway than in Western Norway, which was also seen in other groups of arthropods [118][119][120], including some Oribatida (ptyctimous mites) [37], and in plants [121]. This pattern is likely to be related to either the delayed post-glacial migration from east to west due to the geographical barrier of the Scandes Mountains [122] or to climate, since the lower summer temperature and higher precipitation in Western Norway are critical to some taxa.…”

“…A good example is the European spruce bark beetle (Ips typographus L.) which requires dry and warm summers and does not occur in Western Norway [118]. In case of mites, a forest type might be the most important factor if only sites with milder climate are compared [37,123], but when climatic differences are large, then regional differences become more significant [27,124].…”

“…The new records of Oribatida for Norway are based on the checklist [93] and later publications [15,37,94] (and references contained in those papers). Those new to Fennoscandia are based on [95,96] and later publications [31,[97][98][99][100][101][102][103][104][105][106][107][108].…”

“…Studies on the invertebrate fauna in old broadleaf forests in Norway are rare [32] and have mainly focused on a specific insect fauna [33][34][35]. Very few studies on mites from broadleaf forests have been carried out in Norway and they were located mainly in the western part of the country [15,36,37]. Nevertheless, 85 species of Oribatida and 22 of Mesostigmata have been found in those broadleaf forests, and these included 35 new records for Norway and 10 new for Fennoscandia.…”

“…This study is a continuation of a species inventory project of rare and rich forest habitats in Norway. So far, only a small group of oribatid mites (ptyctimous mites) have been studied in this part of the country [37]. The aim of this paper is to evaluate the diversity of two large and important mite groups, Oribatida and Mesostigmata, in a diversity of microhabitats in a broadleaf forest in Eastern Norway, considered to be HCVF.…”