Alpine Arthropod Diversity Spatial and Environmental Variation
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Alpine Arthropod Diversity Spatial and Environmental Variation Björn Larsson Degree project for Master of Science in Biology Ecological zoology 45 hec Department of Biological and Environmental Sciences University of Gothenburg April 2014 Abstract Alpine and arctic environments are heavily affected by climate change caused by an ever increasing emission of greenhouse gasses. Temperatures are estimated to have risen by as much as 3 oC since preindustrial times. This development threatens this type of habitats as well as all organisms that inhabit these environments. Knowledge about alpine arthropods is lacking in some areas. Some groups are better known such as Lepidoptera, Coleoptera and Aranea but even among these there are clear gaps. This study took place at Latnjajaure field station, located 16 km west of Abisko in northern Sweden, and looked at the diversity of beetle species as well as the abundance of beetles, spiders and harvestmen at different altitudes and between two different environments. Samples were collected using pitfall traps placed every 50 heightmeter at seven altitudes ranging from 1000 to 1300. Eight traps were placed at each altitude, four in open environment and four at or in proximity to cliffs. An exception was at the 1300 m altitude where only four traps were placed because no suitable cliff environment was found. The study period was colder than average and had periods of heavy rainfall which probably had an impact on the results since both temperature and precipitation seems to have an effect on the activity of the arthropods leading to less individuals and less species caught. The results of the statistical tests showed that there was no significant difference found in the diversity of the beetles between either height or environment. There was a significant difference found between the various altitudes with regards to the number of individuals caught and between the environments for the spiders and beetles. An interesting find was that there were surprisingly high numbers of harvestmen found at higher altitudes. They were by far the most numerous of the studied arthropods. Another interesting find was that there were significantly higher numbers of arthropods caught at the 1150 m altitude as well as higher numbers of species of beetles found there compared to the other measured altitudes. These results seem to indicate that there is a shift in environmental conditions somewhere between the 1150 m altitude and the 1300 m altitude as both low-alpine and mid-alpine are found there. Among the beetles the most abundant species was Amara alpina. Most other species were found with only a few individuals. The overall number and species found were also quite low compared to more southern areas. The results highlights the importance of further studying alpine environments and the organisms that dwell there in order to be able to protect them. 1 Table of contents Introduction..........................................................................................................................................3 Background................................................................................................................................3 Aim.............................................................................................................................................5 Materials and methods.........................................................................................................................5 Study site....................................................................................................................................5 Sampling....................................................................................................................................5 Species identification.................................................................................................................7 Analysis......................................................................................................................................7 Results..................................................................................................................................................8 The insect community................................................................................................................8 Statistics...................................................................................................................................13 Discussion..........................................................................................................................................15 Pitfall traps...............................................................................................................................15 Diversity indexes......................................................................................................................15 Weather.....................................................................................................................................15 Evaluation of results.................................................................................................................16 Interesting finds........................................................................................................................18 Conclusions..............................................................................................................................18 Acknowledgements............................................................................................................................19 References..........................................................................................................................................19 Appendix I..........................................................................................................................................23 Appendix II........................................................................................................................................24 Appendix III.......................................................................................................................................25 Appendix IV.......................................................................................................................................29 2 Introduction Background Alpine and arctic environments are rapidly changing. The main reason for this is anthropogenic causes due to increased emissions of greenhouse gasses such as carbon dioxide. It is estimated that the overall global temperature on the planet have risen with about 1 oC since preindustrial times. In alpine regions however the increase is much greater. Here temperatures might have risen with as much as 3 oC overall and up to 4 oC during the winter (ACIA, 2005). Effects of this increase is already visible. Species that previously were only seen occasionally above the treeline are becoming more common and snowlays are melting out earlier during the summer. This, of course, affects the species that are adapted to this extreme environment, mainly in the sense that their habitat is dwindling and that they are being outcompeted by lowland species. Thus, it is important to study these environments and its inhabitants in order to better understand them and to be able to better protect them. There are clear gaps in the knowledge about the diversity of invertebrates in alpine and arctic environments. Some of the better known groups include Lepidoptera, Coleoptera and Aranaea but even these groups are not well documented (Nagy et al., 2003). A few previous studies have looked at arthropods in the study area. For example Brundin (1934) studied the beetle community in the area surrounding Torne träsk in northern Sweden, where this study took place. Another study looked at the changes in the insect population between 1998 and 2008 in Padjelanta, also in northern Sweden (Franzén & Molander, 2011). Invertebrates have long been used as biological indicators in aquatic ecosystems. A biological indicator is an organism or a group of organisms that can be used to measure the biotic or abiotic state of an area due to their reaction to specific changes in the environment (Hodkinson & Jackson, 2005). It has been recognized that different invertebrates have varying degrees of tolerance towards organic pollution in aquatic ecosystems and that this could be utilized to create effective monitoring systems. Suggestions have been made that insects might also be useful in assessing changes in climate in terrestrial ecosystems, particularly mountain ecosystems (Hodkinson & Jackson, 2005). It has been shown that some insects, for example Neophilaenus lineatus, can vary greatly in their upper altitudinal limit from one year to the next following the annual mean temperatures (Whittaker & Tribe, 1996). Carabid beetles have been mentioned as an especially interesting insect group (Hodkinson & Jackson, 2005). Despite this potential there is no established system for biomonitoring using invertebrates in alpine and arctic habitats. Therefore it is important to gain further knowledge about the arthropod community in these ecosystems. Arthropods in alpine habitats have to be able to endure more extreme environmental conditions than most arthropods in lower regions (Sømme, 1989). Some factors include high fluctuations in temperature both during the year and on a daily basis with a possibility of temperatures dropping below zero during any part of the year. Temperatures