Data on vascular plants of boreal lakes in Finland were used to compare the e¤ciency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the e¤ciency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally e¤cient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be e¤cient in maintaining di¡erent aspects of biodiversity over time. However, the random selection of lakes seems to be the most ine¤cient option for a reserve network. In general, reserve selection methods seem to favour lakes that maximize one aspect of diversity at the time of selection, but the network may not be the best option for maintaining the maximum diversity over time. The reserve selection methods do a¡ect the long-term outcome but it is impossible to recommend one method over the others unequivocally.

Four major hypotheses have been put forward to explain local species richness of commensal or parasitic species. The resource distribution hypothesis predicts that regionally widespread host species are able to support higher local species richness of commensals or parasites. On the other hand, the resource size hypothesis predicts that larger hosts can support more species than smaller hosts, and comparably, the resource abundance hypothesis predicts that hosts that offer more resources are able to support more species. Finally, the resource concentration hypothesis predicts that hosts that occur in high-density patches support higher species richness. In this study, we tested the first three of the above hypotheses with myrmecophilous beetles and their host ants. In addition to species richness of myrmecophilous beetles, we also applied the above hypotheses to explain the distribution of the beetles. Our data are exclusively based on an extensive literature survey. Myrmecophilous beetles live in naturally fragmented environments composed of host ant colonies and they are exclusively dependent on ants. We found that the distribution of the host ants and the colony size of the host ants had a positive effect on both the species richness and the distribution of myrmecophilous beetles. In the same way, we found that myrmecophilous beetle species that are generalists, i.e. have more than one host ant species, and thus have more abundant resources, were more widely distributed than specialist species. Thus, we found support for the hypothesis that resource distribution, resource size and resource abundance have an effect on species richness and on the distribution of species.

Species inimigriilion, extinction and turnover of vascular plants in boreal hikes. Ecography 22: 240-245.Dierated by limited resource availability for land acquisition, a central question in conservation biology is the ability of areas of different size to maintain species diversity. The selected reserves should not only be species rich ai the moment, but should also maintain speeies diversity in the long run. We used two sets of data on vascular plant species in boreal lakes colleeied in 1933/34 and 1996 to test the relationships between lake area and the extinction, immigration and turnover rates of the species. Moreover, we investigated, whether the number of speeies in 1933/34 or water eoiineclion between lakes was related to extinction, immigratioti and turnover rates of species. We found that lake area or shoreline length was not correlated with immigratioti or turnover rale. But extinction rate was slightly negatively correlated with shoreline length. The original tiumbcr of speeies was positively related to the number of species extinctions and to the absolute turnover rate in the lakes, which indicates that speeies riehness does not create stability in these commutiities. Speeies number was not correlated with immigration rate. Upstream water connections in the lakes did not affect immigration, extinction or turnover rates. We conclude that length of the shoreline is a better measure of suitable area for water plants than the lake area, and that because the correlation between shoreline length and extinction rate was slight, also small lakes can be valuable for conservation. 7". Virola (leiviro@silmu.jyu.fi), V. Kailala. M. Kuilum-n. A.

1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles. 2. We studied latitudinal patterns in long‐term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000‐km range from the northernmost to the southernmost lake. 3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the best predictors of species turnover rate (TR), latitude was the only variable that was highly significantly related to species turnover rate. Area, species number, water transparency, pH and change in transparency did not notably explain the gradient observed. 4. The latitudinal trend was mainly because of lower species immigration rates at higher latitudes, whereas extinction rate did not so strongly decrease with increasing latitude. Immigrations and extinctions in the lakes were not in balance: the species numbers between the 1930s and 1980s increased more strongly in the southern than northern lakes. 5. We suggest that the inverse relationship between latitude and plant species TR in Finland is most probably caused by human influence on lakes, especially eutrophication and immigration of new species in southern latitudes. In addition, although species richness per lake did not decrease towards the north, the total species pool probably does, which means that in the north there are fewer species that can actually immigrate.