Genetic structure of dioecious and trioecious Salix myrsinifolia populations at the border of geographic range

Abstract

Gene flow in plant populations is heavily affected by species sexual systems. In order to study the effect of sexual systems on genetic structure, we examined plastid and nuclear DNA of 12 dioecious (males and females) and 18 trioecious (males, females and hermaphrodites) populations of Salix myrsinifolia-a boreal shrub with slow range expansion. Populations were located along latitudinal gradients across submarginal and marginal parts of the range. Individuals of each sex morph were all hexaploid. We identified 10 chloroplast DNA haplotypes and scored 205 polymorphic bands with amplified fragment length polymorphism. We found dioecious populations that differed from trioecious populations via the presence of four unique haplotypes and significant difference in Nei's gene diversity index (0.119 vs. 0.116) and down-weighed marker value (1.17 vs. 1.02). The latter parameter, together with haplotype and nucleotide diversity, significantly decreased with latitude similar to the expansion front. Also, we found that 89% of hermaphrodite individuals belong to one distinct in tree parsimony network haplotype. This frequency significantly decreased with latitude towards the expansion front. We suspect that the presence of hermaphrodites in trioecious populations may represent a trade-off between the possibility of producing progeny by single hermaphrodites and genetic variability loss through autogamy. S. myrsinifolia benefits from trioecious sexual systems under colonization events. This phenomenon is no longer a gain closer to the core of the species range.

Genetic diversity and stand structure of neighboring white willow (Salix alba L.) populations along fragmented riparian corridors: a case study

“…Within the genus Salix, genetic diversity, divergence and gene flow among populations, as well as linkage disequilibrium were also investigated in several species, including S. viminalis L., S. schwerinii E. Wolf, S. herbacea L. and S. myrsinifolia Salisb. (Alsos, et al 2009, Berlin, et al 2011, Mirski, et al 2017. However, owing to the different environments and willow species, within-stand features and between-stand distances, and willow species, this information is not comparable with that emerging from our case study.…”

Environmental stress maintains trioecy in nematode worms

“…These theoretical predictions are now at odds with accumulating empirical evidence for trioecy in crustaceans (Sassaman and Weeks 1993), plants (Mirski et al. 2017), and nematodes (Chaudhuri et al. 2015; Kanzaki et al.…”

“…1A). These theoretical predictions are now at odds with accumulating empirical evi- dence for trioecy in crustaceans (Sassaman and Weeks 1993), plants (Mirski et al 2017), and nematodes (Chaudhuri et al 2015;Kanzaki et al 2017). Auanema is a recently described nematode genus with two trioecious species, A. rhodensis and A. freiburgensis (Kanzaki et al 2017) and is distantly related to the trioecious Heterorhabditis sp.…”

Environmental stress maintains trioecy in nematode worms

“…1a). These theoretical 40 predictions are now at odds with accumulating empirical evidence for trioecy in crustaceans 41 (Sassaman and Weeks, 1993), plants (Mirski et al, 2017), and nematodes (Chaudhuri et al, 2015; three sexes. While there is a body of work studying the molecular underpinnings of reproductive 48 systems in nematodes (Berenson and Baird, 2018;Guo et al, 2009;Hill et al, 2006;Yin and 49 Haag, 2019), there is little understanding of the ecological factors that push some species towards 50 androdioecy while others maintain dioecy or trioecy ( Fig.…”