Development of microsatellite markers for partially and putative fully mycoheterotrophic varieties of Pyrola japonica sensu lato (Ericaceae)

We developed microsatellite markers to compare the genetic variation and reproductive biology between the partially mycoheterotrophic Pyrola japonica var. japonica and the putative fully mycoheterotrophic P. japonica var. subaphylla. Fifteen primer pairs were developed for P. japonica sensu lato and they were tested on 77 ramets from three populations of the two varieties. Thirteen loci were polymorphic in at least one of the two var. japonica populations, whereas only four loci were polymorphic in the var. subaphylla population. The considerably lower genetic variation of the var. subaphylla population may be attributed to frequent selfing and/or inbreeding. The markers developed in this study will be useful for comparing the genetic diversity of P. japonica s. l. populations and measuring gene flow within and between populations and varieties.

Variation in vegetative morphology tracks the complex genetic diversification of the mycoheterotrophic species Pyrola japonica sensu lato

PREMISE OF THE STUDY

Although the evolution of full mycoheterotrophy has attracted many plant researchers, molecular phylogenetic studies that focus on the transition from partial to full mycoheterotrophy are limited to a few taxa. Pyrola japonica sensu lato is an ideal model for examining the evolution of mycoheterotrophy, owing to its variable leaf size, which suggests that the species comprises several transitional stages.

METHODS

To elucidate the molecular and morphological changes that occur during the evolutionary transition between partial and full mycoheterotrophy in P. japonica s.l. from 18 populations in Japan, we estimated a parsimony network of plastid haplotypes based on three noncoding regions, measured the leaf size and scape color of the shoots, and compared morphology among haplotypes.

KEY RESULTS

The seven haplotypes exhibited star-like relationships, and at least three divergent haplotypes were associated with differences in morphology. The first was mainly observed in large-leaved and green-scaped populations, whereas the second was observed in extremely small-leaved and reddish-scaped populations, which indicated a high degree of mycoheterotrophy, and the last was detected among mixed populations with both green- and reddish-scaped shoots with intermediate leaf sizes. In addition, the inconsistent association between the haplotypes and morphology suggests a complex relationship.

CONCLUSIONS

Pyrola japonica s.l. has at least three separate genetic lineages that have different leaf morphologies. The genetic lineages and their coexistence could have led to the variable leaf size and suggest the possibility that gene flow from partial to full mycoheterotrophs could reverse the evolutionary transition to full mycoheterotrophy.