Asbjørn Moen

A secondary hybrid zone between diploid Dactylorhiza incarnata ssp. cruenta and allotetraploid D. lapponica (Orchidaceae)

Secondary hybrid zones are not uncommon in Dactylorhiza, but knowledge of ecological and evolutionary consequences of hybridization are scarce. Here, we assess interploidal gene flow and introgression in a hybrid zone between diploid Dactylorhiza incarnata ssp. cruenta (2n=2x=40) and its putative allotetraploid derivative D. lapponica (2n=4x=80). Photometric quantification of DNA content and morphology confirmed that triploids are abundant in sympatric populations in our study area. Allozyme segregation patterns in D. lapponica supported an allopolyploid origin, although unbalanced genotypes suggested rare pairings between homoeologous chromosomes. Photometric data and chromosome counts suggest backcrossing between the triploid hybrid and D. lapponica, and hence some hybrid fertility. Triploids are morphologically more similar to the tetraploids than the diploids, maybe owing to the hybrid origin of both triploids and tetraploids. The diploids and tetraploids were not more similar in the parapatric populations compared to when they occur in allopatry. This indicates that backcrossing rarely leads to introgression, or alternatively that allopatric populations are not isolated enough to prevent influx of pollen from the other species. Despite some evidence of backcrossing, our study gives few indications that widespread hybridization entails local breakdown of species boundaries. Rather, the hybrid zone may be a transient phenomenon due to intensive mowing, resulting in the opening of habitats and hence bringing the parental species into close contact.

Climate warming alters effects of management on population viability of threatened species: results from a 30-year experimental study on a rare orchid

Climate change is expected to influence the viability of populations both directly and indirectly, via species interactions. The effects of large-scale climate change are also likely to interact with local habitat conditions. Management actions designed to preserve threatened species therefore need to adapt both to the prevailing climate and local conditions. Yet, few studies have separated the direct and indirect effects of climatic variables on the viability of local populations and discussed the implications for optimal management. We used 30 years of demographic data to estimate the simultaneous effects of management practice and among-year variation in four climatic variables on individual survival, growth and fecundity in one coastal and one inland population of the perennial orchid Dactylorhiza lapponica in Norway. Current management, mowing, is expected to reduce competitive interactions. Statistical models of how climate and management practice influenced vital rates were incorporated into matrix population models to quantify effects on population growth rate. Effects of climate differed between mown and control plots in both populations. In particular, population growth rate increased more strongly with summer temperature in mown plots than in control plots. Population growth rate declined with spring temperature in the inland population, and with precipitation in the coastal population, and the decline was stronger in control plots in both populations. These results illustrate that both direct and indirect effects of climate change are important for population viability and that net effects depend both on local abiotic conditions and on biotic conditions in terms of management practice and intensity of competition. The results also show that effects of management practices influencing competitive interactions can strongly depend on climatic factors. We conclude that interactions between climate and management should be considered to reliably predict future population viability and optimize conservation actions.

Outlying haymaking lands at S lendet, central Norway: effects of scything and grazing

Solendet Nature Reserve, situated 700-800 m a.s.l., covers 306 ha. Solendet mainly consists of calcareous fens and wooded grasslands that were mown for hay for several centuries; the hay was vital for keeping the livestock through the winter. A vegetational succession commenced as soon as haymaking ceased (c. 1950), the most obvious change being the formation of scrub and a heavy litter layer in the tall fen and swamp communities. Mowing recommenced in the nature reserve in 1974, and the vegetation and landscape is being restored. Permanent plot methods have been applied to follow the effects of scything and cattle grazing on the flora and vegetation, with emphasis on the rich fen vegetation.

Formalized classification of European fen vegetation at the alliance level

Phytosociological classification of fen vegetation (Scheuchzerio palustris-Caricetea fuscae class) differs among European countries. Here we propose a unified vegetation classification of European fens at the alliance level, provide unequivocal assignment rules for individual vegetation plots, identify diagnostic species of fen alliances, and map their distribution. 29 049 vegetation-plot records of fenswere selected fromdatabases using a list of specialist fen species. Formal definitions of alliances were created using the presence, absence and abundance of Cocktail-based species groups and indicator species. DCA visualized the similarities among the alliances in an ordination space. The ISOPAM classification algorithm was applied to regional subsets with homogeneous plot size to check whether the classification based on formal definitions matches the results of unsupervised classifications. The following alliances were defined: Caricion viridulo-trinervis (sub-halophytic Atlantic dune-slack fens), Caricion davallianae (temperate calcareous fens), Caricion atrofusco-saxatilis (arcto-alpine calcareous fens), Stygio-Caricion limosae (boreal topogenic brown-moss fens), Sphagno warnstorfii-Tomentypnion nitentis (Sphagnumbrown-moss rich fens), Saxifrago-Tomentypnion (continental to boreo-continental nitrogen-limited brown-moss rich fens), Narthecion scardici (alpine fens with Balkan endemics), Caricion stantis (arctic brown-moss rich fens), Anagallido tenellae-Juncion bulbosi (Ibero-Atlantic moderately rich fens), Drepanocladion exannulati (arcto-borealalpine non-calcareous fens), Caricion fuscae (temperate moderately rich fens), Sphagno-Caricion canescentis (poor fens) and Scheuchzerion palustris (dystrophic hollows). The main variation in the species composition of European fens reflected site chemistry (pH, mineral richness) and sorted the plots from calcareous and extremely rich fens, through rich andmoderately rich fens, to poor fens and dystrophic hollows.

Landsplan for myrreservater i Norge

An attempt to define the regional characteristics of the hydrotopography and vegetation of mires in Southern Norway is made. The most important criterion for deciding which mires are the most worthy of preservation is that they must be typical for their particular region. In addition, the importance of locating interesting mire ecosystems of more unusual or extreme type is stressed. 10 mires in Southern Norway are proposed for inclusion in the international scheme for mire preservation, one of which is already protected. Another 23 large-scale mire complexes are considered especially worthy of preservation on a national scale. A further 24 mires, more restricted in area, are also considered to be especially worthy on account of their particularly interesting flora, fauna, or hydrotopography. In Northern Norway 3 mires are already protected, and another 36 mires are proposed for preservation.

Hay crop of boreal rich fen communities traditionally used for haymaking

The traditional use of fen areas for hay production had been extensive in boreal Europe, but few studies have investigated the hay crop of different fen plant communities. We studied the hay crop from upper boreal (sub-alpine) rich fens using data from 81 permanent plots over more than 30 years in one coastal (oceanic) area and one inland (continental) area in central Norway. Permanent 12.5 m2 plots were mown with a scythe every year, every 2nd year or every 4th year. A large majority of the plots under study were lawn and open margin communities classified within or related to the phytogeographical order Caricetalia davallianae. There was no difference in the hay crop between the study areas in these communities, indicating that biomass production is about the same in ecologically similar rich fens that share the same dominant species. The first hay crop (including litter) from lawn communities was about 160 g/m2 after 20–30 years of abandonment. Regular mowing every second year reduced the hay crop by more than 30 %, and stabilized it after three mowings. The hay crop decreased with increasing mowing frequency; in lawn and open margin communities, mowing every 4th, every 2nd and every year yielded on average 140, 113 and 65 g/m2, respectively. In earlier times, it used to take farmers about 10 days’ work to harvest one hectare. Thus, the traditional practice of mowing every 2nd year was efficient in terms of the hay crop and labour input, and the quality of the hay was improved due to a lower litter fraction.

Flowering in the Rich Fen Species Eriophorum latifolium Depends on Climate and Reproduction in the Previous Year

In this long-term study, we identify the climate variables most important to flowering density in Eriophorum latifolium in boreal rich fen vegetation, and assess their relative importance. We analysed time-series data (1982–2008) of flowering density in 126 permanent plots in an oceanic and a continental area in Norway, and developed an autoregressive model where the density of flowering plants was determined by the cost of previous flowering, climate during the same year as flowering, and climate during the year prior to flowering. The cost of reproduction was the most influential of the factors affecting flowering. Our results suggest that dry conditions during the previous summer affected flowering negatively in the oceanic population, but had no effect in the continental population. We attribute this to differences in hydrology, with steeply sloping fens in the oceanic area, and gently sloping, spring-fed fens in the continental area. Furthermore, flowering increased with the length of the previous growing season (oceanic population), decreased with the amount of precipitation during the previous spring (continental population), and increased with temperature in spring the same year (both populations). We conclude that climate conditions during the previous year are more important than climate conditions during the year of flowering.

Actuarial senescence in a long-lived orchid challenges our current understanding of ageing

The dominant evolutionary theory of actuarial senescence—an increase in death rate with advancing age—is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain the paucity of evidence for actuarial senescence in plants. We used a 32 year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment, for individuals under two types of land use, in two climatic regions. The mortality trajectory was best approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region. At older ages, senescence was evident only when accounting for a positive effect of reproductive investment on mortality. Our results demonstrate actuarial senescence as well as a survival–reproduction trade-off in plants, and indicate that environmental context may influence senescence rates. This knowledge is crucial for understanding the evolution of demographic senescence and for models of plant population dynamics.

BOOK REVIEWS – LITTERATURANMELDELSER

The study that Tom Kauko has undertaken in Budapest is part of a comparative research project on spatial housing market structures, house prices and locational preferences in European metropolitan areas. It is a follow-up of earlier studies on Helsinki, Amsterdam, Rotterdam, and The Hague, and thus follows the same methodological approach and conceptual framework. The focus is on what creates a competitive real estate or housing strategy. The relative differences between successes and failures are determined along dimensions such as house price levels, the physical features of the urban environment and the people living there. Furthermore, the path dependencies or historic legacies of the urban area studied had to be taken into account, which is important when dealing with a post-socialist city such as Budapest. To be able to undertake a comparative study, Kauko has wisely mainly used a quantitative approach, focusing on a pragmatic classification based on two neural network types: Kohonen’s self-organising map (SOM) (Kohonen 1982) and its extension, the learning vector quantification (LVQ). This follows up Kauko’s studies in Helsinki and the Netherlands, where the same approach was used, both of which create a very interesting basis for comparison. One general conclusion is that the housing market structures in Helsinki and Amsterdam more or less have the same features, whereas the housing market structures in Budapest differ considerably from the two other cities. This, to a large extent, is related to the legacies of the past. First there was in Hungary the state-socialist system until 1990, in which there did not exist a commercial housing market, but allocation of housing of good or bad quality based on a top-down sorting of worthy and not so worthy citizens. Second, there was the ‘give-away-privatisation’ in the 1990s, primarily to sitting tenants which, as pointed out for other past-state socialist countries by Paadam (in press), reproduced the social hierarchies that existed in the previous socialist type of social system: the higher an individuals’ status had been in the previous society the better was the quality of the housing allocated to them and individual actors’ opportunities for purchasing and selling houses in market conditions. One special feature in Budapest, compared to other post-socialist cities, is that the ‘goulash communism’ opened up for some areas of privately built, mostly low quality housing with gardens in parts of the conurbation. Since 1990, these areas have, in addition to pre-World War II villa quarters, become very popular for those who have been able to climb in the real estate market. The result is that there is a very strange mix of new high-class condominiums and villas surrounded by ramshackle self-built houses of the earlier settlers in such neighbourhoods. On the other hand, as pointed out by Kauko, in Budapest there have been higher prices since 1990 and in the 1990s more building output on the Buda side than on the Pest side of the city. A process of social geographical segregation can be noted as the Buda Hills in particular offer more attractive housing areas. However, micro-locational differentiation seems to become increasingly more important than the Buda Pest dichotomy. More finely grained social differences are expected in Budapest, as in West European and American cities. The main part of Kauko’s analyses relates to detailed studies of Districts VIII Józsefváros and IX Ferencváros. This is of special interest as parts of the same districts were also used as case study areas in the NEHOM project (Holt-Jensen et al. 2004). The NEHOM case studies were based on a qualitative approach, with long interviews, and with a common framework for all 29 European cases, involving inhabitants, housing providers and public authorities. Focus was on initiatives to combat social exclusion. Kauko’s approach is primarily quantitative, using the mapping methods mentioned above. Variables in focus were mortgage valuations between May 2001 and January 2002, transactions with dwelling variables and detailed locational identification. Dwelling variables used were market value, collateral value, age of building, dwelling format density and prestige, size, and the effects of inflation. These data were linked with more general district data. Józsefváros and Ferencváros share the same history as inner-city lowerclass neighbourhoods with at least very high densities in the parts closest to the Budapest urban core. Both Kauko’s analysis and the NEHOM project state that the differences between the two districts today are great. In Kauko’s analysis, Ferencváros comes out as a success story while Józsefváros evidently still faces a lot of problems external as well as internal. To this, however, should be added that Józsefváros also in communist times was regarded as the poorest district in Budapest with the largest percentage of Roma population; the initial situation was thus somewhat different between the two. However, the development and housing policies have been different in the two districts since 1990. Ferencváros has attracted private capital, the market value of land has increased fast, and regeneration and new development have taken place expediently. Yet the success has had a social price, which was presented in the NEHOM study: social clients have been moved out of the area. They have been provided with new peripheral housing which easily may develop into new slums. In economic terms, Józsefváros has not experienced the same economic success because a policy was established to integrate social clients and notably Roma in the housing neighbourhoods they always had lived in. This has also meant that the percentage of public housing remains relatively high, and rehabilitation carried out by Rév 8, the local rehabilitation company, is more piecemeal and involves more social considerations than has been the case in Ferencváros. Kauko’s study is important and valuable because it presents a methodological approach that can be used for new comparative studies of urban real estate markets. I cannot provide any criticism of the study and results as such. My concern here is only that there are other approaches that may reveal another side of the coin, and that mainly raise the question of what sustainable urban development really means. The economic dimension (man-made capital) is undoubtedly crucial for the urban future and competitiveness, but also the environmental dimension (natural capital) and social dimension (human capital) as the basis for the institutional dimension (social capital) are crucial for a sustainable future.