Are any primroses (Primula) primitively monomorphic?

Abstract

Summary• Primula ( c . 430 species) and relatives (Primulaceae) are paradigmatic to our understanding of distyly. However, the common co-occurrence of distyly and monomorphy in closely related groups within the family has made the interpretation of its evolution difficult.• Here, we infer a chloroplast DNA (cpDNA) phylogeny for 207 accessions, including 51% of the species and 95% of the sections of Primula with monomorphic populations, using Bayesian methods. With this tree, we infer the distribution of ancestral states on critical nodes using parsimony and likelihood methods.• The inferred cpDNA phylogeny is consistent with prior estimates. The most recent common ancestor (MRCA) of Primula is resolved as distylous using both methods of inference. However, whether the distyly in Primula , Hottonia , and Vitaliana arose once or three independent times is not clear.• We conclude that monomorphism in descendants of the MRCA of Primula is derived from distyly in all cases. Thus, scenarios for the evolution of distyly that rely on the persistence of primitive monomorphy (such as in Primula section Sphondylia ) require re-evaluation.

Heterostyly accelerates diversification via reduced extinction in primroses

“…with high posterior probabilities for three main clades), consistent with previous results [45][46][47][48][49] (figure 2; electronic supplementary material, figure S1). These three clades differ markedly in species numbers: /Primula (slashes indicate clade names [45]), with 190 species (151 heterostylous); /Soldanella, nine species (one heterostylous) and /Androsace, 66 species (one heterostylous).…”

“…Bayesian and maximum-likelihood character-state estimates indicate that heterostyly arose early in the history of Primulaceae (electronic supplementary material, table S1) and imply that the most recent common ancestor of /Primula was heterostylous [47]. The single origin of heterostyly along the stem lineage of /Primula (figure 2, branch b-c) is inferred to have been followed by several, recent losses within deeply nested lineages.…”

Mixed Mating in Homostylous Species: Genetic and Experimental Evidence from an Alpine Plant with Variable Herkogamy, Primula halleri

“…Its occurrence in self-compatible, monomorphic (i.e., homostylous) primrose species that evolved from obligately outcrossing, heterostylous ancestors (Mast et al 2006;de Vos et al 2014ade Vos et al , 2014b) is therefore enigmatic. The loss of traits that enforce outcrossing is thought to be favored in environmental conditions where outcrossing opportunities are limited due to mate limitation and/or pollinator limitation, so that autonomous selfing may provide reproductive assurance (Eckert et al 2006;Busch and Delph 2012).…”

The stability of Quaternary speciation: a case study in Primula sect. Auricula

“…Apart from the differentiation of flower colour as exemplified by P. lutea and P. hirsuta, flowers of the different species of the section are very similar in morphology and size. Also, all species of the section have heterostylous flowers as found in most species of Primula (Mast et al 2006). As all species thus are likely to be self-incompatible, differences in breeding system are not likely to contribute to reproductive isolation between species.…”