Clonal and spatial genetic structures of aspen (Populus tremuloides Michx.)

Abstract

To portray aspen clonal and spatial genetic structures, we mapped and genotyped trees in two 1-ha plots, each containing three aspen cohorts originating from fire or subsequent secondary disturbances. We used four microsatellite loci to identify aspen clones and increment core analysis to determine tree age. Clonal dimensions were measured by the maximum distance between two ramets and the number of ramets per genet. Standard normal deviate (SND) was used to assess the spatial distribution of aspen genets and cohorts, and multivariate spatial genetic autocorrelations to assess the spatial distribution of aspen genetic variation. Most aspen genets consisted of only one ramet (> 75%). Median clonal dimensions were 19 and 29 m (maxima: 104 and 72 m in the two plots). No segregation was observed between clones. Aspen cohorts were spatially segregated but trees were spatially aggregated within old and medium-aged cohorts. In contrast, trees were more randomly distributed within the youngest cohorts. This coincided with a spatial genetic autocorrelation at small scales (up to 30 m) in the older cohorts and a more random genetic distribution in the youngest ones. Our results suggest that aspen spatial genetic structuring reflects the spatial patterns produced by the regeneration of discrete cohorts at different stages of succession. Vegetative reproduction leads to aspen genetic spatial structuring at small scales (few metres) until midsuccession. However, as the stand gets older, the spatial distribution of aspen trees and genetic structure evolve from a structured pattern to a more random one under a gap disturbances regime.

Genetic diversity in fragmented populations of Populus talassica inferred from microsatellites: implications for conservation

“…In our study, the mean H O and H E were 0.476 and 0.591, respectively. Similar values were also reported in other related species, such as P. tremuloides (H O = 0.472, H E = 0.67; Namroud et al, 2005) and Populus tremula (H O = 0.474, H E = 0.500; Lexer et al, 2005).…”

Sex-specific pattern of spatial genetic structure in dioecious and clonal tree species, Populus alba L.

“…Based on dominance index, we inferred that the ramets of both sexes presented a rather clumped occurrence within a genet, a pattern defined as the phalanx strategy of growth, commonly found in many woody species (Peterson and Jones 1997) including species from Populus (Namroud et al 2005;Chenault et al 2011;Cristobal et al 2014). Spatial analysis also detected the non-random distribution of individuals (ramets) of both sexes in space (Table 2).…”

Simulations of clonal species genotypic diversity – trembling aspen (Populus tremuloïdes) as a case study

“…DNA amplification was performed using Taq polymerase (Gibco from Invitrogen TM Life Technologies, Burlington, Canada) and four dyelabeled oligonucleotide primers (PTR1, PTR2, PTR3, and PTR4) at microsatellite loci complementary to Simple Sequence Repeat (SSR) flanking regions. The resolving power of these four microsatellites was tested in a previous study (Namroud et al, 2005b) and was found to be sufficiently high to reject the null hypothesis of similar genotypes (P (ID) <0.001).…”