Present‐day sympatry belies the evolutionary origin of a high‐order polyploid

Abstract

Summary Disentangling the evolutionary histories of polyploids, especially those with high ploidies, can reveal fundamental processes in speciation. Despite occurring frequently during evolution, the origins of many extant polyploid plant species remain largely unknown.By integrating linkage mapping, polyploid phylogeny and sex‐determining region (SDR) in a unified framework, we statistically evaluated evolutionary hypotheses concerning the origin of a recently recognized decaploid strawberry (Fragaria cascadensis).The maximum‐likelihood phylogenies and topology tests across homeologous groups consistently rejected the seemingly parsimonious hypothesis of ‘contemporary sympatric speciation’ via hybridization between octoploid and diploid congeners. Instead, most chromosomes supported ‘ancient hybrid speciation’ between a maternal octoploid progenitor ancestral to extant octoploid strawberries and a paternal, extinct Fragaria iinumae‐like diploid progenitor, probably in Beringia during the Pleistocene. The absence of a shared SDR between the decaploid and other Fragaria is also consistent with an older origin rather than a recent hybrid origin in situ.Our study reveals a long evolutionary history of the decaploid despite its recent discovery, and highlights the pitfalls of inferring polyploid origins from niche/range alone or combined with morphology. It can serve as an exemplary starting step towards building much‐needed model systems of established polyploids that have been, and remain to be, recognized.

Functional trait divergence and trait plasticity confer polyploid advantage in heterogeneous environments

“…bracteata , F. iinumae and an extinct F. iinumae ‐like 2 x taxon (Fig. ; Tennessen et al ., ; Wei et al ., ,b), and the 6 x is derived from the 2 x F. viridis and F. vesca ssp. vesca as well as the Asian 2 x F. mandshurica (Fig.…”

“…In April 2015, we germinated and grew four genotypes (i.e. each from a single, open-pollinated seed of a distinct wild plant) from each of 72 total populations across the 11 taxa (10 populations of less than four genotypes; Table S1), in a glasshouse at the University of Pittsburgh following standard protocols (Wei et al, 2017b). In September 2015, we harvested 12 plantlets (clones) from stolons of each of the 269 genotypes (24 genotypes of < 12 clones; Table S1).…”

“…The 10x F. cascadensis has two sets of chromosomes from F. vesca ssp. bracteata, two sets from F. iinumae and six sets from the F. iinumaelike diploid (Wei et al, 2017b). The 6x F. moschata is derived from F. vesca ssp.…”

“…), among which repeated and independent events of allopolyploid speciation (Fig. ) have been revealed by polyploid Fragaria genomes (Tennessen et al ., ; Kamneva et al ., ; Wei et al ., ,b; Dillenberger et al ., ).…”

Genome duplication effects on functional traits and fitness are genetic context and species dependent: studies of synthetic polyploid Fragaria

“…), and New Mexico (LNF; 32.9684°N, 105.7458°W, 2664 m a.s.l.). From each population, three to four plants (i.e., each from a single, open‐pollinated seed of a distinct wild plant) were sowed in 2015 and replicated clonally via plantlets, and raised under 24°C day/18°C night temperatures and 12‐h days in a greenhouse at the University of Pittsburgh, following previous protocols (Wei et al., , b). During March–May 2016, we self‐pollinated clones ( N = 15–20) of each genotype by hand three times per week, and harvested these selfed full‐sib seeds (i.e., a selfed “genetic family”; Fig.…”