Understanding population history for conservation purposes: population genetics of Saxifraga aizoides (Saxifragaceae) in the lowlands and lower mountains north of the Alps

Abstract

Several alpine species have outlying populations in the lowlands and lower mountains north of the Alps. These small, isolated populations are usually described as either (1) glacial relics, (2) descendants from populations living on forelands and moraines during the ice ages, or (3) populations founded by long-distance dispersal after glaciation. A floristic survey of the historic and present distributions and an allozyme investigation were performed on one of these relic species, Saxifraga aizoides. The species was historically more abundant and had more stations in more regions of northeastern Switzerland. The former population structures within regions, nowadays destroyed, were still reflected in distinct and high regional genetic diversity and variation. There was weak evidence of increased inbreeding in outlying populations, but populations did not deviate from Hardy-Weinberg equilibrium. No geographic pattern of genetic variation above the regional scale (Ͼ10 km) was found. Based on the spatial and genetic structures found, it was not possible to discriminate between the abovementioned hypotheses. Nevertheless, the study shows how a thorough evaluation of distribution and abundance data aids the interpretation of genetic data with respect to population history, biogeography, and conservation biology. Key words:allozymes; Alps; biogeography; conservation biology; floristic survey; glacial relics; long-distance dispersal; Saxifraga aizoides; Saxifragaceae.Past events play an important role in the evolution of species and populations. Plant biogeography and phylogeography are especially informative of how the ice ages have shaped the genetic structure of species (Soltis et al., 1997). Partial extinctions, recurrent (re-)immigration, different migration routes, long-distance dispersal events, bottleneck situations, in situ survival in refugia, or gentic drift are crucial phenomena in this context. In Europe, most molecular studies have so far focused on arcticalpine plants or on tree species (Comes and Kadereit, 1998). Available results on arctic-alpine plants are contradictionary, giving either evidence in favor of glacial refugia or against them (Abbott et al., 1995;Brochmann et al., 1996;Gabrielsen et al., 1997; Bauert et al., 1998). Smouse (1998) stressed that contradictions between different studies even on the same organism may result from inaccurate sampling strategies or inappropriate choice of genetic markers to test particular biogeographic hypotheses.In the mountainous Prealps and the hilly adjacent lowlands north of the Alps, several subalpine or alpine plant 1 Manuscript received 19 January 1999; revision accepted 23 July 1999.The authors thank Andreas Keel, Elias Landolt, and Hansruedi Wildermuth for providing present stations of Saxifraga aizoides, and Richard J. Abbott, Alex Bernhard, Robert M. M. Crawford, and two anonymous reviewers for critical comments on the manuscript. A grant for laboratory consumables by the Ü etliberg-Verein to JJS and RH and financial support by the Swiss National Sci...

Genetic structure of Saxifraga rosacea subsp. sponhemica, a rare endemic rock plant of Central Europe

“…In contrast, despite their long isolation, the overall genetic diversity of populations of S. sponhemica was similar to that found in other species with a mixed mating system (Nybom 2004). Similarly, other central European ice age relicts, such as S. paniculata (Reisch et al 2003), and S. aizoides (Lutz et al 2000), that occur on rocks have also maintained high genetic diversity despite a fragmented distribution. The maintenance of genetic diversity of these plants is probably due to their longevity and the long-term stability of their habitats (Young et al 1996;Tang et al 2010).…”

“…Strong genetic differentiation has been reported for isolated alpine relict populations, such as Saxifraga cernua (Bauert et al 1998), Erinus alpinus (Stehlik et al 2002) and for the lowland remnant populations of Saxifraga paniculata (Reisch et al 2003). However, not all studies have found low genetic diversity in ice age relicts (Lutz et al 2000;Reisch et al 2003), presumably due to the longevity of the species buffering random genetic drift. Genetic variation has profound implications for species conservation (Schaal et al 1991;Ellstrand and Elam 1993;Ouborg et al 2006) and assessing genetic variation within and between populations is essential for efficient conservation measures for rare species.…”

Marie Brockmann-Jerosch and her influence on Alpine phylogeography

“…This scenario has been recently confirmed by phylogeographic work (Tremetsberger et al 2002;Parisod and Besnard 2007). In accordance, Reisch et al (2003) found some evidence in favour of the glacial relict hypothesis for lowland stations of Saxifraga paniculata in Germany, but no corresponding evidence was detected for Sesleria albicans in Germany (Reisch et al 2002) or Saxifraga aizoides in the Swiss Canton of Zürich (Lutz et al 2000). For the especially scattered and small populations of Asplenium septentrionale mainly occurring on erratic rocks in the Swiss lowlands and being one of the historically most prominent examples of a glacial relict species (p. 1165), Holderegger and Schneller (1994) showed that the present lowland stations are rather the result of long-distance dispersal of spores than being glacial remnants.…”

Untitled

“…Combinada esta circunstancia con la estructura insular de cumbres y valles, semejantes a archipiélagos entre cuyos elementos es difícíl un intercambio que suavice los vaivenes genéticos, ello resulta en una rápida multiplicación de los endemismos. En efecto, las montañas en general, y los niveles subalpino, alpino y sus homólogos en particular, son especialmente ricos en especies endémicas (LUTZ et al, 2000).…”