Oribatid mites (Acari: Oribatida) in the glacier foreland at Hardangerjøkulen (Norway)

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1 231 BIOLOGICAL LETT. 2006, 43(2): Available online at Oribatid mites (Acari: Oribatida) in the glacier foreland at Hardangerjøkulen (Norway) ANNA SENICZAK 1, TORSTEIN SOLHØY 2 and STANIS AW SENICZAK 1 1 Department of Ecology, University of Technology and Life Sciences, Kordeckiego 20, Bydgoszcz, Poland; aseniczak@utp.edu.pl; 2 Department of Biology, University of Bergen, Allègt. 41, 5007 Bergen, Norway (Received on 2 January 2006, Accepted on 16 November 2006) Abstract: The Oribatida on 3 moraines (from 1955, 1934 and 1750) near the outlet Midtdalsbreen of Hardangerjøkulen glacier (Norway) were investigated. The highest density of mites was observed on the moraine exposed in 1934 (67 years after the glacier s retreat), while the highest number of species (14) was noted on the oldest moraine (206 years after the glacier s retreat). Two species, Tectocepheus velatus and Liochthonius lapponicus, were present in all sites. Tectocepheus velatus was relatively abundant on all moraines, while the density of L. lapponicus decreased with moraine age. The population of Camisia horrida (Hermann, 1804), exhibited variability in the occurrence of notogastral setae f 1. This confirmed that C. borealis Thorell, 1871, with setae f 1 in the adult, is a junior synonym of C. horrida. Key words: primary succession, Camisia horrida, notogastral seta, variability INTRODUCTION Glacier forelands have been studied extensively with regard to plant succession (reviewed by MATTHEWS 1992), while the structure of heterotrophic communities during the colonization of deglaciated areas were not recognized until recently (KAUFMANN 2001, HODKINSON et al. 2002). The succession of mites on glacier forelands is also poorly known, as only a few studies have been done (KAUFMANN et al. 2002, HODKINSON et al. 2004, SKUBA A & GULVIK 2005). Our study aimed to contribute to the knowledge of oribatid mite communities in postglacial succession. STUDY AREA AND METHODS The study sites were 3 moraines (from 1955, 1934 and 1750) at the outlet Midtdalsbreen of the Hardangerjøkulen glacier. This glacier is located in Finse (60 36 N, 7 30 E), southwestern Norway, at altitudes of m. By the late 1980 s the glacier had been retreating, but in recent years its mass has been growing.

2 232 Anna Seniczak, Torstein Solhøy and Stanis³aw Seniczak During our study, the plant community on the youngest moraine consisted of 9 species, including 2 lichens: Cladonia sp., Stereocaulon sp., 2 mosses: Polytrichum cf. piliferum Hedw., Racomitrium sp., and 5 vascular plants: Deschampsia sp., Juncus trifidus L., Salix herbacea L., S. lanata L., Silene acaulis (L.) Jacq. On the moraine from 1934, there were 14 plant species consisting of 5 lichens: Cladina sp., 3 Cladonia spp. and Stereocaulon sp., 2 mosses: Drepanocladus revolvens (Sw.) Warnst., Racomitrium sp. and 7 vascular plants: Bistorta vivipara (L.) S. F. Gray, Deschampsia sp., Empetrum nigrum (L.) ssp. hermaphroditum (Lange) Bocher, Eriophorum scheuchzeri Hoppe, Poa cf. alpina L., Salix herbacea L., Trisetum spicatum (L.) Richter. The oldest moraine was colonized by 16 species, including 5 lichens: Cetraria cf. islandica (L.) Ach., C. nivalis (L.) Ach., Cladina sp., Cladonia sp., Stereocaulon sp., 6 mosses: Dicranum sp., Kiaeria sp., Ptilidium sp., Sanionia sp., Pohlia sp., Polytrichum cf. piliferum Hedw., and 5 vascular plants: Bistorta vivipara (L.) S. F. Gray, Empetrum nigrum (L.) ssp. hermaphroditum (Lange) Bocher, Omalotheca supine, Poa cf. alpina L., Salix herbacea L. From each moraine, 5 samples of soil with plants (area 400 cm 2, depth 5 cm) were taken in July of Oribatid mites were extracted in Berlese funnels, and both adults and juveniles were determined to species or genus. In total, 9137 mites were investigated. The nomenclature follows SUBÍAS (2004). RESULTS The density of oribatids was the lowest on the youngest moraine and the highest on the moraine from 1934 (Table 1). The number of mite species was lower on 2 younger moraines (5 6 species) than on the oldest moraine (14 species). Usually the most abundant was Tectocepheus velatus (Michael, 1880). On the moraines situated closer to the glacier the juveniles dominated, while on the most distant one, adults were more abundant (see Table 1). Less abundant was Liochthonius lapponicus (Trägårdh, 1910), but its abundance decreased with moraine age. In the population of Camisia horrida (Hermann, 1804), the variability of notogastral setae f 1 in the nymphal stages and adults was studied (Fig. 1). Among the nymphs, 33 specimens (43%) had a pair of setae f 1, 33 (43%) had a single seta f 1 on the right or left side, and 11 (14%) had no seta f 1. The numbers of adults with 2, 1 and no seta f 1 were 8 (27%), 14 (46%) and 8 (27%), respectively. DISCUSSION In the investigated moraines the number of plant species increased with moraine age, from 9 to 16 species, which is consistent with KAUFMANN (2001). That author also observed that the invertebrate communities developed rapidly over 50 years and then did not show any big changes, while the vegetation continued to develop. This may indicate that the soil fauna played an important role in improving the growing conditions for plants (KAUFMANN et al. 2002). In our study the oribatid mites showed a peak density about 70 years after the glacier retreat, but species diversity was the highest on the oldest moraine, similar as the number of plant species.

3 233 Table 1. Density (individuals/m 2 ) and number of oribatid mite species near Hardangerjøkulen: ad adults; juv juveniles Mite species Moraine 1955 Moraine 1934 Moraine 1750 ad juv ad juv ad juv Belba verrucosa Bulanova-Zachvatkina, Chamobates sp Camisia horrida (Hermann, 1804) Edwardzetes edwardsi Berlese, Fuscozetes sp Heminothrus punctatus (C. L. Koch, 1879) Liochthonius lapponicus (Trägårdh, 1910) Mycobates sarekensis (Trägårdh, 1910) Nothrus borussicus Sellnick, Oppiella splendens (C. L. Koch, 1841) Oribatella sp Oromurcia bicuspidata Thor, Quadroppia quadricarinata (Michael, 1885) Suctobelbella sp Tectocepheus velatus (Michael, 1880) Total density Proportion of ad or juv (%) Total density: ad + juv No. of species On all moraines Tectocepheus velatus was relatively abundant, which is consistent with the results of HODKINSON et al. (2004) and SKUBA A & GULVIK (2005). In contrast, the abundance of Liochthonius lapponicus depended on successional stage. This species represents successful newcomers in the colonized habitats, but it also is a precise indicator of ecological succession (NIEDBA A 1974). The population of Camisia horrida seemed to be interesting and unique in the genus Camisia, as it showed variability of the notogastral seta f 1 in the nymphal stages and adult. In this genus, seta f 1 is present in the larva, but in many species (C. biurus (Koch, 1839), C. foveolata Hammer, 1955, C. lapponica (Trägårdh, 1910), C. segnis (Hermann, 1804), C. spinifer (Koch, 1835) it is lost in the protonymph and absent in the other developmental stages (SENICZAK 1991a, b, c). In the Polish population of C. horrida this seta was also lost (SENICZAK 1991a). Presence of the seta f 1 was a very important systematic feature, which separated C. horrida from C. borealis Thorell, According to SELLNICK & FORSSLUND (1955) and GILYAROV & KRIVOLUTSKIJ (1975), in the former species this seta was absent while in the later it

4 234 Anna Seniczak, Torstein Solhøy and Stanis³aw Seniczak Fig. 1. Variability of occurrence of setae f 1 in adult Camisia horrida. A no seta f 1 present, B 2 or one setae f 1 present was present. The morphology of adults of C. horrida and C. borealis sensu SELL- NICK & FORSSLUND (1955) was studied in detail by OLSZANOWSKI (1996), who found in the Polish population of C. horrida a few specimens with seta f 1 and rightly suggested that C. borealis was a synonym of C. horrida. This suggestion is fully supported by our observation near Hardangerjøkulen glacier, and is consistent with SUBÍAS (2004). Similar variability of seta f 1 was observed in Heminothrus capillatus (Berlese, 1914) from the Tatra Mts. (SENICZAK et al. 1990), which may suggest that the genera Camisia and Heminothrus, members of the family Camisiidae, are closely related. Acknowledgements: We are grateful to Dr. WENCHE EIDE (University of Bergen) for plant identification, and to the Norwegian Research Council for the grant that enabled A.S. to visit that University. REFERENCES GILYAROV M. A., KRIVOLUTSKIJ D. A A key to the soil-inhabiting mites. Sarcoptiformes. 491 pp., Nauka, Moscow (in Russian). HODKINSON I. D., COULSON S. J., WEBB N. R Invertebrate community assembly along proglacial chronosequences in the high Arctic. J. Anim. Ecol. 73: HODKINSON I. D., WEBB N. R., COULSON S. J Primary community assembly on land- the missing stages: why are the heterotrophic organisms always there first? J. Ecol. 90:

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