Clonal structure and genetic diversity of three desert phreatophytes

Abstract

The objective of this paper was to assess clone sizes of three perennial desert plant species with AFLP markers and to relate them to clonal and genetic diversity and to hydroecology. The study was carried out at the southern rim of the Taklamakan Desert, where sexual regeneration is only possible shortly after rare flooding events, resulting in rarely established cohorts with subsequent extensive vertical growth and horizontal clonal spread. In this environment, repeated seedling establishment is excluded. We expected decreasing clonal and genetic diversity with increasing clone size and increasing distance to the groundwater table and a common response pattern among all study species. Maximum sizes of Populus euphratica and Alhagi sparsifolia clones were 121 ha and 6.1 ha, respectively, while Tamarix ramosissima clones reached a maximum size of only 38 m(2). In P. euphratica and A. sparsifolia, clonal diversity declined with increasing clone size and increasing distance to the groundwater table, while genetic diversity remained unaffected. Tamarix ramosissima differed from the other species because of a much smaller clonality. Clone size and clonal diversity were found to be good proxy variables for clone age. Despite the considerable age of the clones, genetic diversity is maintained in the populations.

Genetic variation within and between populations of a desert poplar (Populus euphratica) revealed by SSR markers

“…Secondly, the majority of individuals of this species are long-lived (a life span of >200 years has been estimated) and have extensive clonal growth (Wiehle et al 2009). The current stands in most populations are, therefore, likely to be well established for a long time through cloning reproductions while these daughter ramets maintained the same genetic diversity as their parents (Vonlanthen et al 2010). Thirdly, the long isolation between the sampled populations may have occurred recently because of human disturbance and (Chen et al 2006).…”

On the run for water – Root growth of two phreatophytes in the Taklamakan Desert

“…Using the mean RGR of the rooting depth of each species in the field experiment, we extrapolated the number of days needed to grow to 6.5 m, which is the depth to the groundwater in the river valley outside the flooding season (based on drilling groundwater holes, see Vonlanthen et al, 2010). We also extrapolated the number of days needed to grow to the mean depth of the groundwater table in stands of A. sparsifolia (14.62 m) and of K. caspia (10.07 m).…”

Trees in the desert: Reproduction and genetic structure of fragmented Ulmus pumila forests in Mongolian drylands

“…Stands apparently survived the last centuries exclusively by clonal growth (Wesche et al, 2005b). Populus euphratica in river oases of the Taklamakan provides an even more extreme example of clonal persistence over hundreds or even thousands of years (Vonlanthen et al, 2010). Ulmus pumila instead shows only limited evidence of clonal spread as most fingerprinted samples represented different RAPD phenotypes and thus genets.…”

“…Clonal growth may last for centuries or even millennia, allowing plants to survive unfavourable climatic periods. In Central Asia, the most prominent examples are stands of Populus euphratica, which form clonal structures covering more than 120 ha in the Taklamakan (Vonlanthen et al, 2010). The Siberian elm and the related U. minor are known to form root suckers and thus at least also have the potential for clonal growth (Meusel et al, 1965).…”