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A little more than 10% of the vascular plant flora native to the European Alps is endemic to this area. It has long been noticed that the distribution of endemics across the Alps is very uneven. While most endemics are found along the southern edge of the Alps, with some also on its western, eastern, and northeastern edges, the northern edge of the Alps more or less between Lake Geneva in the west and Lake Traun in the east harbours almost no endemics. The distribution of endemics in the Alps has often been related to the location of glacial refugia. Accordingly, the virtual absence of endemics from the northern edge of the Alps has been explained with the unsuitability of climatic conditions for glacial survival of alpine plants there. After discussing evidence for the existence of glacial refugia for alpine species along the northern edge of the Alps and north of the Alps, I will examine how these refugia differed from refugia along the southern edge of the Alps. I conclude that the uneven distribution of endemics in the Alps is best explained by the different climate through time north and south of the Alps. These climatic differences affected the spatial structure and extent of refugia, the length of isolation of refugial populations, and selective conditions in refugia. [ABSTRACT FROM AUTHOR]

In contrast to adult plants, little is known about the frost-tolerance of seedlings of alpine species, despite the fact that frost has been considered as one of the main factors limiting plant recruitment in high elevation. Here we report the results of a comparative study on seedling frost-tolerance of nine congeneric species pairs with lowland (0–900 m a.s.l.) and alpine (1800–2700 m a.s.l.) distribution. Similarly to adult alpine plants, we expected seedlings of alpine species to be more frost-tolerant than their lowland counterparts. Frost-tolerance was estimated under laboratory conditions by exposing seedlings to frost events from − 1 to − 9 °C, calculated as the temperature at which 50% of the seedlings were lethally damaged by frost (LT50). The LT50 values varied between − 1.95 and − 6.11 °C suggesting that seedling of all tested species could potentially survive mild and/or short frosts, but might be lethally damaged by severe and/or continuous frost events. The LT50 values for lowland and alpine species did not differ statistically and were on average − 3.96 ± 0.18 °C and − 4.16 ± 0.43 °C, respectively. These findings did not confirm our hypothesis that seedlings of alpine species have higher frost-tolerance than seedlings of lowland species. Four possible reasons could explain this pattern. They include (1) comparable levels of negative-stress in both lowland and alpine habitats, (2) opportunistic seed germination strategy in alpine plants, (3) peculiarities of our experimental set up and (4) potentially stronger effects of drought on alpine seedling survival than frost. [ABSTRACT FROM AUTHOR]

Cherleria sedoides, a plant species widespread in alpine areas of the major European mountain ranges and in Scotland, contains two highly divergent chloroplast haplotype groups, one widespread (WH) and one present only in some populations in the Alps (AH). We investigated whether this haplotype diversity is the result of (1) intraspecific differentiation, (2) retention of an ancestral polymorphism or (3) hybridisation. For this purpose, 106 matK sequences from throughout the Caryophyllaceae and 80 trnQ- rps16 and psbD- trnT sequences of C. sedoides (51) and other species of Cherleria (29) were used for the construction of phylogenies and haplotype networks. As the two haplotype groups were never each other's closest relatives, haplotype diversity as a result of intraspecific differentiation is unlikely. Patterns of genetic differentiation within the WH and AH groups are very different. Whereas WH shows a radial pattern typical of rapid expansion, AH is divided into two divergent subgroups each containing more variation than the WH group. This suggests that the two haplotype groups have dissimilar histories and are therefore unlikely to represent an ancestral polymorphism. Instead, we conclude that the polymorphism is best interpreted as the result of hybridisation. As the WH and AH haplotype groups fall into Cherleria, but do not group with any extant species, we conclude that the rare AH group represents the original C. sedoides, and that the WH group was captured from another, now extinct, species of Cherleria. [ABSTRACT FROM AUTHOR]

The so far coldest location for flowering plant life was found at 4,505 m asl at the Dom summit in Valais (Switzerland). On an ice-free crest, Saxifraga oppositifolia, a typical arctic-alpine arbuscular mycorrhizal (AM) plant forms several cushions. Here, we report on a surprisingly diverse fungal community of mycorrhizal and non-mycorrhizal species at this particular location. A few grams of fine sand and organic material obtained from the rhizospheric lithic 'soil' and fine roots of S. oppositifolia were examined for fungal spores and hyphae. We found five different species of AM fungi (Glomeromycota) that belonged to all three glomeromycotan classes, to four orders and five different families. We also found hyphae of dark-septate endophytes (unidentified on the species and genus level, members of Vibrisseaceae, Helotiales, Ascomycota) and a few cleistothecia of a putative fungal leaf pathogen resembling Podosphaera alpina (Erysiphaceae, Erysiphales, Ascomycota), which is known to cause powdery mildew on S. oppositifolia. Given the size of the cushions and their annual growth, these microcosms of life may not be older than 30 years, obviously sufficient time to establish a rich fungal community despite the extreme cold at this location, which in terms of higher level mycorrhizal fungal taxa is obviously comparable with fungal communities of well-established alpine, mountainous and even temperate lowland grasslands. [ABSTRACT FROM AUTHOR]

In the Western Alps, two subspecies of Saussurea alpina are found in a partly overlapping distribution area; however, they prefer distinct habitats. While Saussurea alpina ssp. alpina is distributed throughout the Alps and beyond, S. alpina ssp. depressa is endemic to the region ranging from the Maritime Alps (France) to the Valais (Switzerland). The sympatric occurrence of closely related taxa raises general questions which factors drive speciation. In order to investigate the genetic and ecological differentiation of the two subspecies, we applied Amplified Fragment Length Polymorphisms and analyzed the habitat preferences via soil pH measurements and vegetation relevés. Overall, we studied 12 populations (five populations of S. alpina ssp. alpina and seven of S. alpina ssp. depressa). The populations were found to be genetically highly differentiated ( F = 0.42). Nevertheless, a weak, but significant genetic differentiation between the subspecies could be detected ( F = 0.04) and the results of the ecological analyses showed a clear differentiation in habitat types. While S. alpina ssp. alpina occurs in alpine grasslands, S. alpina ssp. depressa occurs mainly on calcareous scree with a significantly higher soil pH (median pH = 7 and median of pH = 8.14 for S. alpina ssp. alpina and S. alpina ssp. depressa, respectively) and different surrounding vegetation. We conclude from the clear difference in ecology that ecological plant speciation is a major factor in establishing and maintaining a reproductive barrier. We explain the weak genetic differentiation with a recent separation of the two evolutionary units during the last glaciation cycles or even in postglacial periods. [ABSTRACT FROM AUTHOR]

Based on evidence for herbaceous plants we expected that trees become more efficient in terms of soil exploration by roots and, thus, produce longer and finer roots (higher specific root length, SRL) with increasing elevation. We tested this hypothesis in situ by excavating roots of eight tree taxa, all belonging to genera found frequently in both lowland and high elevation sites. Across three treeline, one montane and four lowland sites from elevations ranging from 320 masl to 2,235 masl, no elevational differences were found in SRL for both broadleaved and conifer tree species. Irrespective of the elevation preference of a species, SRL of evergreen conifers was significantly lower than that of deciduous species. However, there is an increase in total root length for a given 3rd order root diameter with elevation in the broad-leaved taxa. Our findings clearly demonstrate that a high SRL is not an essential attribute of trees growing in a cold high elevation climate in temperate regions, but there is some indication that fine roots get longer as elevation increases. [ABSTRACT FROM AUTHOR]