Allopolyploid speciation inPersicaria(Polygonaceae): Insights from a low-copy nuclear region

Abstract

Using a low-copy nuclear gene region (LEAFY second intron) we show multiple instances of allopolyploid speciation in Persicaria (Polygonaceae), which includes many important weeds. Fifteen species seem to be allopolyploids, which is higher than the number found in previous comparisons of chloroplast DNA and nuclear ribosomal internal transcribed spacer (nrITS) phylogenies. This underestimation of the extent of allopolyploidy is due in at least three cases to homogenization of nrITS toward the maternal lineage. One of the diploid species, P. lapathifolia, has been involved in at least six cases of allopolyploid speciation. Of the diploids, this species is the most widespread geographically and ecologically and also bears more numerous and conspicuous flowers, illustrating ecologic factors that may influence hybridization frequency. With a few exceptions, especially the narrowly endemic hexaploid, P. puritanorum, the allopolyploid species also are widespread, plastic, ecological generalists. Hybridization events fostered by human introductions may be fueling the production of new species that have the potential to become aggressive weeds.hybridization ͉ LEAFY intron ͉ phylogeny ͉ Polygonum ͉ invasive species

Fast Diploidization in Close Mesopolyploid Relatives ofArabidopsis

“…The identification of the ACK as an ancestral karyotype of the closest relatives of the Australian Camelineae species further corroborate our conclusion that these allopolyploids originated from hybridization between taxa with ACK-derived complements. Although a recurrent origin of allopolyploid species was reported for Arabidopsis kamchatica (Shimizu-Inatsugi et al, 2009), Helianthus (Schwarzbach and Rieseberg, 2002), Tragopogon (Lim et al, 2008), Persicaria (Kim et al, 2008), and other genera, we are unable to find clear evidence for recurrent polyploid formation from our data. On the contrary, two paracentric inversions on one of the AK8-like homoeologs shared by five analyzed species (see Supplemental Figure 2 online) as well as the estimated large evolutionary distance between the parental genomes (;4 million years old at the time of the allopolyploidization; see Supplemental Figure 5 online) argue in favor of a single origin.…”

The frequency of polyploid speciation in vascular plants

“…These new estimates may be conservative because: (i) incomplete phylogenetic resolution, common in our phylogeny dataset, will lead, on average, to fewer inferred ploidy shifts than truly occurred, and (ii) multiple polyploid speciation events that share one or both parents may appear to represent a single event in phylogenetic trees (25). Also, our estimates do not include unnamed, intraspecific polyploid cytotypes, which may often represent cryptic biological species (19).…”

DNA methylation mediates genetic variation for adaptive transgenerational plasticity

“…We used zebularine to investigate the functional role of DNA methylation in the adaptive, drought-induced transgenerational plasticity that is differentially expressed by genotypes of the annual plant Polygonum persicaria (¼Persicaria maculosa [8,24,50]). In this common species, seedling offspring of drought-stressed parents or grandparents develop more extensive, deeper root systems, and have enhanced growth and survival, in dry soil [24,51].…”