Exploring the genetic consequences of clonality in haplodiplontic taxa

Partially clonality is an incredibly common reproductive mode found across
all the major eukaryotic lineages. Yet, population genetic theory is based
on exclusive sexuality or exclusive asexuality and partial clonality is
often ignored. This is particularly true in haplodiplontic eukaryotes,
including algae, ferns, mosses, and fungi, where somatic development
occurs in both the haploid and diploid stages. Haplodiplontic life cycles
are predicted to be correlated with asexuality, but tests of this
prediction are rare. Moreover, there are unique consequences of having
long-lived haploid and diploid stages in the same life cycle. For example,
clonal processes uncouple the life cycle such that the repetition of the
diploid stage via clonality leads to the loss of the haploid stage. Here,
we surveyed the literature to find studies that had genotyped both haploid
and diploid stages and re-calculated population genetic summary metrics
for seven red algae, one green alga, three brown algae, and three mosses.
We compared these data to recent simulations that explicitly addressed the
population genetic consequences of partial clonality in haplodiplontic
life cycles. Not only was partial clonality found to act as a homogenizing
force, but the combined effects of proportion of haploids, rate of
clonality, and the relative strength of mutation versus genetic drift
impacts the distributions of population genetic indices. We found
remarkably similar patterns across commonly used population genetic
metrics between our empirical and recent theoretical expectations. To
facilitate future studies, we provide some recommendations for sampling
and analyzing population genetic parameters for haplodiplontic taxa.