Evolutionary associations between polyploidy, clonal reproduction, and perenniality in the angiosperms

Abstract

Clonal reproduction is thought to facilitate polyploid establishment in the angiosperms, but the evolutionary relationship between polyploidy and clonality has not been thoroughly tested. A perennial life history may confer many of the same advantages, and the relative importance of clonality versus perenniality is unknown.We used phylogenetic comparative analyses of 1751 species to examine associations between polyploidy, clonality, and life history. We test hypotheses of co-evolution by determining the sequence of trait development.Polyploidy is associated with both clonality and perenniality across species, and analyses show that clonality can be an important predictor of polyploidy beyond perenniality. Tests of directionality on our full dataset suggest that polyploidy is more likely to promote clonality or perenniality than vice versa, although there are significant differences in patterns of co-evolution among major angiosperm groups.Our results suggest that polyploidy and clonal reproduction are evolutionarily associated across the angiosperms, even when perenniality is considered, but we find little evidence at the whole-angiosperm level for the hypothesis that clonality promotes polyploidy. However, variation among different clades indicates that polyploidy and clonality are interacting in diverse ways, likely to be due to the variable roles of clonality in their evolutionary histories.

Habitat Shape Affects Polyploid Establishment in a Spatial, Stochastic Model

“…It also decreases the probability that the offspring of another cytotype will disperse into a "clump" of plants and begin to displace them. Polyploidy and clonality are very strongly associated in angiosperms (Herben et al, 2017;Van Drunen and Husband, 2019). While there is a possibility that WGD may induce or enhance clonality (Van Drunen and Husband, 2019), this study demonstrates that preexisting clonal traits may facilitate polyploid establishment, even when these traits do not differ between diploids and polyploids.…”

“…This makes intuitive sense: annual populations turn over much more quickly, so the minimum time required for either diploids or polyploids to reach fixation is reduced. This distinction may be important in explaining the differential frequency of occurrence of polyploids among annuals and perennials in nature-polyploidy appears to be much more common in herbaceous perennials than in annuals (Stebbins, 1938;Husband et al, 2013;Van Drunen and Husband, 2019). If rapid fixation in annuals reduces the probability of overlapping WGDs and intercytotype gene flow within the population, then annual polyploid populations may be more prone to extinction because of a lack of genetic diversity and eventual deterioration through inbreeding depression or the accumulation of deleterious alleles.…”

“…Polyploidy may also promote the expression of clonality (Van Drunen and Husband, 2018) or serve as a precursor for apomictic reproductive pathways (Hörandl and Hojsgaard, 2012;Hojsgaard et al, 2014;Hojsgaard and Hörandl, 2019). There is a strong association between polyploidy and clonality, yet phylogenetic analyses of evolutionary order (i.e., whether polyploidy precedes clonality or vice versa) have produced inconsistent results, particularly among clades (Herben et al, 2017;Van Drunen and Husband, 2019). Finally, polyploidy may spur the evolution of perenniality, possibly through a decrease in the rate of growth and development (as noted in Te Beest et al, 2012), but this is certainly not the rule.…”

“…Finally, polyploidy may spur the evolution of perenniality, possibly through a decrease in the rate of growth and development (as noted in Te Beest et al, 2012), but this is certainly not the rule. As with clonality, which is highly correlated with perenniality, inferring the order of evolution between these two traits yields inconclusive results (Van Drunen and Husband, 2019).…”

The ecology, evolution, and genetics of plant reproductive systems

“…They find that the influence of ploidy on diversification may be best explained by its correlation with mating system, and possibly by additional unknown factors associated with the mating system. Ploidy is also the focus of the angiosperm‐wide comparative analysis of Van Drunen & Husband (, in this issue pp. 1266–1277), which finds that polyploidy and clonality are correlated, but that there is little evidence for the hypothesis that clonality leads to the evolution of polyploidy.…”