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2 Polish Journal of Ecology

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Genetic diversity of populations of Brachypodium pinnatum (L.) P. Beauv. : expansive grass in a fragmented landscape

Bąba W., Kurowska M., Kompała-Bąba A., Wilczek A., Długosz J., Szarejko I.

Polish Journal of Ecology

2012

Vol. 60, nr 1

31-40

Brachypodium pinnatum belongs to native grasses which could dramatically decrease the biodiversity of calcareous grasslands, therefore, an examination of the mechanisms of its expansion is of prime importance for their conservation. We studied the genetic structure of 12 subpopulations of the expansive grass B. pinnatum in a heterogeneous landscape with AFLP markers, aiming at determination whether spatial isolation influences the genetic diversity and the population genetic structure of this species. A high level of overall (79%) and within population polymorphic loci (38.44%) were found and 220 different genotypes were distinguished among the 252 samples analysed. No significant population structure nor isolation-bydistance were found, despite their long-time fragmentation history. This confirms that isolation of calcareous grasslands in a landscape cannot prevent the expansion of B. pinnatum grasses because of the high generative dispersal ability. Subsequent quick and extensive clonal growth of this species enables the successful establishment. In most cases mowing or grazing is sufficient to keep this species at a low density within ancient grasslands and to prevent seed and pollen dispersal, but not for restoration of species-rich calcareous grasslands.

Benefits of low-intensive grazing : co-occurrence of umbelliferous plant (Hladnikia pastinacifolia Rchb.) and opilionid species (Phalangium opilio. L) in dry, calcareous grassland

Sajna N., Kusar P., Slana Novak L. L., Novak T.

Polish Journal of Ecology

2011

Vol. 59, nr 4

777-786

The impact of grazing has been discussed in many organisms, and it has been shown that it has considerable influence on the structural variation of vegetation, resulting in its tussocky appearance. Such spatial heterogeneity results in plants formations that facilitate other species by providing safe sites against predation and physical stress. On the Trnovski gozd plateau in western Slovenia, a secondary habitat of the rare, monotypic endemic umbelliferous species, Hladnikia pastinacifolia, was colonized by a relatively isolated population of the wide spread opilionid species, Phalangium opilio. We hypothesized that in this stony pasture, the impact of the structurally heterogenous vegetation that results from low-intensity grazing benefits both species on hot summer days. For this purpose, we classified vegetation formation types (VFT) and measured temperature and relative humidity in places settled by Ph. opilio individuals during their daily rest. According to the predominant species, we recognized six VFTs: Carlina acaulis, Ruta divaricata, Koeleria pyramidata, Juniperus communis, understory vegetation and grazed turf. Only the spiny C. acaulis and unpalatable R. divaricata facilitated H. pastinacifolia, while also acting as nurse plants. On the other hand, Ph. opilio preferred the understory, but also settled on the other VFts, except Ruta. During the highest daily temperature of about 38[degrees]C, Ph. opilio avoided the grazed turf. Temperature preferences refer to frequencies of individuals rather than to absolute temperature values. The frequencies were independent of sex and the VFTs. Females were more frequently found in tussocks showing higher temperature profiles (Juniperus, Koeleria). During the hot daytime, Ph. opilio was most sensitive to relative humidity, and less so to temperature, whilst the height of settlement varied in adjusting these two environmental factors. The distribution of males significantly differed between the subsequent morning, midday and evening series, but not between the morning and evening ones, while in females it differed between all the three time series. In habitats, such as stony dry pastures, low grazing intensity can maintain persistent populations of H. pastinacifolia and Ph. opilio even in extremely hot weather. Such grazing is the most convenient measure for protecting both species, especially the highly endangered Hladnikia. The major threat to such habitats is afforestation by Pinus nigra, which deserves additional management. We found that in stony pastures, low grazing intensity assures the structural heterogeneity of vegetation required to maintain persistent populations, of both H. pastinacifolia and Ph. opilio.