Genetic variation in lowland and mountain populations of Tofieldia calyculata and their ability to survive within low levels of genetic diversity

Abstract

Loss of genetic diversity is expected to be a common reason for decline of populations of many rare species. To what extent this is true for populations at the range periphery remains to be explored. Alpine species with peripheral lowland populations are ideal but poorly known model system to address this issue. We investigated genetic diversity and structure of populations of Tofieldia calyculata, species common in central European mountains but highly endangered in lowlands using 17 microsatellite loci. We showed that lowland populations have lower genetic diversity than mountain populations and they are not clearly differentiated from mountain populations. Species probably survived the last glaciation in refugia in margins of Alps and western Carpathians. Some lowland populations are probably relict as well and contain unique genetic information. Their low genetic diversity is likely the result the of reduction of population sizes, gene flow during the Holocene and selfing. However postglacial colonization is also a case of some lowland populations. Based on data from herbarium specimens from extinct lowland populations, we demonstrated that lowland populations had low genetic diversity also in the past and main part of the genetic diversity was lost due to extinction of whole populations. Within population genetic diversity has not changed since the last century suggesting that these populations are able to survive with low levels of genetic diversity under suitable habitat conditions. This idea is also supported by finding of large viable recent populations with very low genetic diversity. We conclude that lowland populations are unique and deserve adequate conservation.