Clonality as a driver of spatial genetic structure in populations of clonal tree species

Abstract

Random genetic drift, natural selection and restricted gene dispersal are basic factors of the spatial genetic structure (SGS) in plant populations. Clonal reproduction has a profound effect on population dynamics and genetic structure and thus emerges as a potential factor in contributing to and modelling SGS. In order to assess the impact of clonality on SGS we studied clonal structure and SGS in the population of Populus alba. Six hundred and seventy-two individuals were mapped and genotyped with 16 nuclear microsatellite markers. To answer the more general question regarding the relationship between SGS and clonality we used Sp statistics, which allows for comparisons of the extent of SGS among different studies, and the comparison of published data on SGS in clonal and non-clonal tree species. Sp statistic was extracted for 14 clonal and 27 non-clonal species belonging to 7 and 18 botanical families, respectively. Results of genetic investigations conducted in the population of P. alba showed over-domination of clonal reproduction, which resulted in very low clonal diversity (R = 0.12). Significant SGS was found at both ramet (Sp = 0.095) and genet level (Sp = 0.05) and clonal reproduction was indicated as an important but not sole driving factor of SGS. Within-population structure, probably due to family structure also contributed to high SGS. High mean dominance index (D = 0.82) indicated low intermingling among genets. Literature survey revealed that clonal tree species significantly differ from non-clonal species with respect to SGS, having 2.8-fold higher SGS. This led us to conclude that clonality is a life-history trait that can have deep impact on processes acting in populations of clonal tree species leading to significant SGS.

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

“…Some empirical studies suggest that clonality may indeed strengthen SGS (Reusch et al 1999;Setsuko et al 2004;Chenault et al 2011;Peng et al 2015). Recent meta-analysis on SGS pattern in clonal and non-clonal tree species suggested also that clonal species may display significantly higher SGS in their populations (Dering et al 2015).…”

“…A set of 16 nuclear microsatellite markers (nSSRs) developed by van der Schoot et al (2000) and Tuskan et al (2004) and available at http://web.ornl.gov/sci/ipgc/ssr_resource.htm was used in the genotyping procedure as described in Dering et al (2015) ( Table 2). INEst 1.0 (Chybicki and Burczyk 2009) was used to estimate genetic diversity parameters at the genet level in both sexes: expected (H e ) and observed heterozygosity (H o ), number of alleles per locus (A), inbreeding coefficient of Weir and Cockerham (1984) (F IS ), and frequency of null alleles.…”

“…The lower value of Dc, the looser clonal architecture and higher intermingling of clones is observed which we referred here as phalanx-like type of clonal architecture. The area of the female and male genets, G A (m 2 ), was defined as the sum of the areas taken by all ramets belonging to that genet and was obtained from our previous investigations conducted in this population (Dering et al 2015). Using ESRI® ArcGIS 9.3, we computed the intra-clonal nearest neighbor distance, d near , which is the distance to the nearest ramet of the same clone for each sex independently.…”

Comparison of fine-scale spatial genetic structure of two sympatricRhododendronshrub species in forest habitat having different seed weights: A case study

“…In addition, intrinsic biological traits (e.g., clonality, breeding systems, life form, and regeneration strategy) as well as extrinsic biological traits (e.g., disturbance and behavior of seed dispersers) are important factors that affect SGS (Chung et al, 2004;Vekemans and Hardy, 2004;Dering et al, 2015). These processes determine in combination, interactively, or solely the intensity and dynamics of SGS.…”

“…Previous studies have shown that clonality affects the SGS of tree species (Suvanto and Latva-Karjanmaa, 2005;Dering et al, 2015). Rhododendron species are reported to commonly exhibit clonal structure through layering (Escaravage et al, 1998;Naito et al, 1999;Mejías et al, 2002;Elliott and Vose, 2012).…”