Adaptation, population viability and colonization-extinction dynamics of <em>Silene tatarica</em> in riparian habitats

Abstract Plants in riparian environments have to tolerate disturbances like floods and erosion. In the absence of disturbances, habitats will gradually become unfavorable for early-successional species. This can have fundamental consequences not only for adaptation at the individual level, but also for the viability of local populations as well as for the persistence of the species on a regional scale. Silene tatarica is a rare perennial plant exposed to annual floods of the Oulanka River. After sand burial most plants formed vertical rhizomes and new meristems by bud ramification. The special anatomical features of these fleshy underground structures seemed to allow the plants to be very resilient against fast-flowing water. Seed structure may enhance long-distance dispersal by water. Selection gradients for plant height were positive at the individual and group levels, but for the number of stems they were in opposition, as selection at the group level favored a smaller number of stems. This can be associated with pollination and herbivory, since taller and larger plants often attract more pollinators and mammalian herbivores. At the local level, population growth was most sensitive to the survival and growth of juvenile individuals. The populations showed different fates, and according to stochastic simulations some of them will disappear in the near future. Their colonization and extinction rates varied between the years, but their balance over the study period was positive. Small patches had the highest risk of extinction and recolonization of extinct patches was very rare. Elasticity analysis indicated that the survival of patches made a much greater contribution to patch dynamics than did the production of new patches. The short-term dynamics of S. tatarica depend primarily on local dynamics but, in the long run, the species will track the availability of habitat, and its persistence will depend on successful colonizations. The amount of suitable habitat depends on river disturbance. Conservation of this species requires the creation of new suitable open sites for colonization, a dispersal process leading to successful colonizations, and favorable habitats for survival. These conditions can be maintained either by natural processes of river disturbance or by active conservation management

Tree removal as a management strategy for the lady’s slipper orchid, a flagship species for herb-rich forest conservation

Abstract In boreal herb-rich forests, the dominance of Norway spruce (Picea abies) decreases light availability for understory species, many of which depend on canopy gaps for reproduction. Here, we explored the response of a rare clonal understory herb, the lady’s slipper orchid (Cypripedium calceolus), to tree removal. We used demographic data spanning 16 years from ten unharvested control sites and ten harvest sites which were divided into three treatments with differing harvest intensity: (1) dense spruce forests, where half of the total tree basal area (TBA) was cut, (2) sparse spruce forests, where one-fourth of the spruce TBA was cut and (3) sparse broadleaf forests, where one-fourth of the total TBA was cut. The effects of harvesting on different demographic rates (ramet density, reproduction, survival, and dormancy) were studied with generalized linear mixed models with harvest intensity, time since harvest and the starting level of the response variable as explanatory variables. Tree removal sites had 2.2 times higher orchid ramet density, 2.4 times higher odds of survival, and 2.1–3.1 times higher odds of flowering and fruiting than the control sites, but these effects were not seen at all treatment levels at all times. Tree removal had no effect on dormancy or seedling or flower density. Orchid flowering and fruiting probabilities increased only at the most intensively harvested sites (both spruce forest sites, and dense spruce forest with 50% TBA removal, respectively), while survival and ramet density increased at the moderately harvested broadleaf forest sites. The effects on flowering and fruiting probabilities and survival disappeared quickly (after three years) when the canopy gaps closed, whereas ramet density responded only with a lag of over three years and was maintained to the end of the study. Our results thus demonstrate that for the lady’s slipper orchid, selective tree harvest might be a suitable management method that increases population size at the ramet level

Genetic structure of a regionally endangered orchid, the dark red helleborine (Epipactis atrorubens) at the edge of its distribution

Abstract The genetic structure and diversity of species is determined by both current population dynamics and historical processes. Population genetic structure at the edge of the distribution is often expected to differ substantially from populations at the centre, as these edge populations are often small and fragmented. In addition, populations located in regions that have experienced repeated glaciations throughout the Pleistocene, may still carry imprints from the genetic consequences of frequent distribution shifts. Using chloroplast DNA sequences and nuclear microsatellite markers we studied the genetic structure of Epipactis atrorubens at the northern edge of its distribution. Contrary to populations in the centre of the distribution, populations at the northern range are regionally endangered as they are small and disjunct. Sequence data of 2 chloroplast loci and allelic data from 6 nuclear microsatellite markers were obtained from 297 samples from Finland, Estonia and Russia. We sought for genetic indicators of past population processes, such as post-glacial colonisation history of E. atrorubens. As expected, we observed low genetic variation, in terms of numbers of substitutions, haplotypes and alleles, and significant levels of differentiation, especially pronounced in the chloroplast DNA. These features suggest that the edge populations could be prone to extinction

Low population viability in small endangered orchid populations:genetic variation, seedling recruitment and stochasticity

Abstract There are only few studies that use both demographic and genetic data to assess population viability of plant species. We combined genetic and demographic data from 11 endangered perennial orchid populations of varying size in order to reveal determinants of viability. Small populations had substantially lower viability compared to large populations. Seedling recruitment rates were remarkably lower in small populations; this was not due to pollination limitation or inbreeding depression because the fruit set and heterozygosity were not correlated with population size, suggesting that there may be differences in successful germination. Low recruitment resulted in significantly lower predicted population growth rates in small populations. The impact of stochasticity on viability varied among populations and stochastic simulations indicated that only one large population was viable, whereas all the other large populations were predicted to go extinct within decades. While there was a positive correlation between the deterministic population growth rate and allelic richness, we did not find any other correlations between genetic variation and fitness or population size. The study populations are likely remnant populations of a once large meta-population that decreased in size due to unfavourable environmental conditions. Management should focus on the maintenance of large population size, which is needed to avoid negative consequences of stochasticity and to enhance seedling recruitment rates

Temporal cycles and spatial asynchrony in the reproduction and growth of a rare nectarless orchid, Cypripedium calceolus

Abstract The timing and intensity of plant reproduction vary due to internal and external factors. Although this variation has been widely studied in species exhibiting masting (intermittent synchronous reproduction), it has attracted less attention in nonmasting species. Here, we studied intra-individual variation in the flowering intensity and plant size of a nonmasting, rare terrestrial orchid, Cypripedium calceolus, using long-term monitoring data from three populations in Finland and two populations in Estonia. Flowering intensity and plant size showed 2-year cycles, indicating that reproduction and growth were regulated by past costs of reproduction and extensive clonal growth. In addition, flowering intensity and plant size were positively correlated with size from the previous year and were also affected by the weather conditions of spring and of the previous growing season. However, there was little synchrony among plants, suggesting that the climatic control of reproduction and growth is sufficiently low as to be masked by high annual variation in these two vital rates. Together, these results indicate that the reproduction and growth of C. calceolus depend on individual demographic history and past weather conditions and that intrinsic factors can also lead to cyclic fluctuation in reproduction in nonmasting species

Phylogeography and post-glacial dynamics in the clonal-sexual orchid Cypripedium calceolus L.

Aim: We investigated the phylogeographical history of a clonal-sexual orchid, to test the hypothesis that current patterns of genetic diversity and differentiation retain the traces of climatic fluctuations and of the species reproductive system. Location: Europe, Siberia and Russian Far East. Taxon: Cypripedium calceolus L. (Orchidaceae). Methods: Samples (>900, from 56 locations) were genotyped at 11 nuclear microsatellite loci and plastid sequences were obtained for a subset of them. Analysis of genetic structure and approximate Bayesian computations were performed. Species distribution modelling was used to explore the effects of past climatic fluctuations on the species range. Results: Analysis of genetic diversity reveals high heterozygosity and allele diversity, with no geographical trend. Three genetic clusters are identified with extant gene pools derived from ancestral demes in glacial refugia. Siberian populations exhibit different plastid haplotypes, supporting an early divergence for the Asian gene pool. Demographic results based on genetic data are compatible with an admixture event explaining differentiation in Estonia and Romania and they are consistent with past climatic dynamics inferred through species distribution modelling. Current population differentiation does not follow isolation by distance model and is compatible with a model of isolation by colonization. Main conclusions: The genetic differentiation observed today in C. calceolus preserves the signature of climatic fluctuations in the historical distribution range of the species. Our findings support the central role of clonal reproduction in the reducing loss of diversity through genetic drift. The dynamics of the clonal-sexual reproduction are responsible for the persistence of ancestral variation and stability during glacial periods and post-glacial expansion. © 2019 John Wiley & Sons Lt

The relationship between people’s activities and values with the protection level and biodiversity

Abstract We investigated how people’s recreational activities, values, and land use preferences are related to the protection level, biodiversity and cultural heritage values of nature-based tourism areas in northern Finland. We assessed peoples’ opinions using a public participation geographic information system (PPGIS) and analyzed the data together with spatial biodiversity and cultural heritage data from the same area. Associations between the PPGIS place markings with the protection level and biodiversity values were quite low, and for the cultural heritage sites they were altogether missing. Negative preferences were often marked in areas with high numbers of sites rated as pleasant and they overlapped with each other, indicating conflicting preferences. Since most activities are not noticeably related to the protection level or biodiversity values of a site they can be planned so as to protect the biodiversity of the area