Timo Pajunen

Small-scale heterogeneity in the spatial distribution of carabid beetles in the southern Finnish taiga

Small-scale distribution of ground beetles (Cole- optera, Carabidae) was examined, based on catches among 300 pitfall traps, in a coniferous forest in southern Finland. The sample from the whole snow-free season comprised 2405 individuals of twenty-two species. Each of the most numerous species (Pterostichus oblongopunctatus (F.), Calathus micropterus (Dft.), Leistus terminatus (Hellw. in Pz.), Notiophilus biguttatus (F.) and Cychrus caraboides (L.)) was non-randomly distributed and formed aggrega- tions within the site of c. 1.3 ha in area. Although the five species occurred in every microhabitat defined in the plot, four of them (N. biguttatus was an exception) were more abundantly found in certain microhabitat types than in the others. In addition to vegetation around the traps, the numbers of Formica ants in the traps correlated with the numbers of carabids caught, mostly negatively. The consid- erable variation in catches and species richness among single traps and among blocks of 16 traps tended to even out, when larger subsamples were taken from the total pool (blocks of 48 traps). The distribution patterns observed within the plot were compared to a reference data set from similar habitat in the same region. Species distributions among microhabitats were slightly different in the reference set and the predic- tive success was relatively poor, probably due to different scales of study in the two data sets. Variation in species distribution in the two spatial scales studied (within a habitat patch and among them) is suppos- edly due to different factors. Although no direct evidence is available from our study area, we suggest that active micro- habitat selection explains the small-scale distribution within the study plot, whereas dynamics of local populations, influenced by regional-scale differences in habitat composi- tion, are the most likely explanation for the distribution pat- terns among habitat patches.

Colonisation of clearcut forests by ants in the southern Finnish taiga: a quantitative survey

We assessed the colonisation of clearcut forests by ants by using pitfall-trap data collected from clearcut areas of different age in southern Finland. We compared mature forests (age over 120 yr) with areas cleared 0, 2 and 10 yr before trapping. We concluded that the old-forest wood-ant systems are destroyed by clear-cutting, and that this is probably based on the loss of food resources. In the colonisation stage the role of stochasticity is counter-balanced by a number of deterministic species-specific factors in the succession of ant assemblages

Urban mires as hotspots of epigaeic arthropod diversity

Natural habitats are lost and fragmented by urbanization globally, resulting in isolated urban remnants of low biodiversity, devoid of specialist species. This homogenization of the urban landscape can be redressed if urban biodiversity hotspots are identified and conserved. Mires have the potential of being such refuges, since they host many mire specialist species of, e.g. arthropods. Here we investigated twenty pine mires that differed in urbanization level (low, intermediate and high) in southern Finland by evaluating the responses of carabid beetle and spider species and communities to potential landscape (level of urbanization, total mire area) and local (pH of peat, vegetation cover, wood volume) drivers. Pitfall trapping was used to collect the arthropods. We showed that high levels of urbanization have a negative effect on mire arthropod biodiversity. However, urban mire community structure seems not to be very different from rural communities as urban mires are still inhabited by mire specialists. Furthermore, tree-covered parts of urbanized mires can serve as refuges for rare forest specialist species and Sphagnum mosses play an important role in supporting mire species and communities, thus Sphagnum growth should be promoted. We showed that urban mires can be considered urban biodiversity hotspots and their protection should be secured in urban development.

Standardized spider (Arachnida, Araneae) inventory of Hankoniemi, Finland

Abstract Background During a field course on spider taxonomy and ecology at the University of Helsinki, the authors had the opportunity to sample four plots with a dual objective of both teaching on field methods, spider identification and behaviour and uncovering the spider diversity patterns found in the southern coastal forests of Hankoniemi, Finland. As an ultimate goal, this field course intended to contribute to a global project that intends to uncover spider diversity patterns worldwide. With that purpose, a set of standardised methods and procedures was followed that allow the comparability of obtained data with numerous other projects being conducted across all continents. New information A total of 104 species and 1997 adults was collected. Of these, 41 species (39%) were Linyphiidae and 13 (12%) Theridiidae. All other families had 6 or less species represented. Linyphiidae were also dominant in terms of adult individuals captured, with 1015 (51%), followed by 428 (21%) Lycosidae, 158 (8%) Tetragnathidae and 145 (7%) Theridiidae. All other families had less than 100 individuals. The most abundant species were Neriene peltata, Alopecosa taeniata, Piratula hygrophila and Dismodicus elevatus, all with more than 100 individuals. All sites had between 56 and 62 species and between 445 and 569 individuals.