Whole genome duplication does not promote common modes of reproductive isolation in Trifolium pratense

Abstract

PREMISE:Although polyploidy has been studied since the early 1900s, fundamental aspects of polyploid ecology and evolution remain unexplored. In particular, surprisingly little is known about how newly formed polyploids (neopolyploids) become demographically established. Models predict that most polyploids should go extinct within the first few generations as a result of reproductive disadvantages associated with being the minority in a primarily diploid population (i.e., the minority cytotype principle), yet polyploidy is extremely common. Therefore, a key goal in the study of polyploidy is to determine the mechanisms that promote polyploid establishment in nature. Because premating isolation is critical in order for neopolylpoids to avoid minority cytotype exclusion and thus facilitate establishment, we examined floral morphology and three common premating barriers to determine their importance in generating reproductive isolation of neopolyploids from diploids. METHODS:We induced neopolyploidy in Trifolium pratense and compared their floral traits to the diploid progenitors. In addition to shifts in floral morphology, we examined three premating barriers: isolation by self-fertilization, flowering-time asynchrony, and pollinator-mediated isolation. RESULTS:We found significant differences in the morphology of diploid and neopolyploid flowers, but these changes did not facilitate premating barriers that would generate reproductive isolation of neopolyploids from diploids. There was no difference in flowering phenology, pollinator visitation, or selfing between the cytotypes. CONCLUSIONS:Our results indicate that barriers other than the ones tested in this study-such as geographic isolation, vegetative reproduction, and pistil-stigma incompatibilities-may be more important in facilitating isolation and establishment of neopolyploid T. pratense.

Short‐ and long‐term consequences of genome doubling: a meta‐analysis

“…Although floral traits are on average larger in neotetraploid individuals, they are not significantly different from diploid values. This fits with paucity of confirmed interploidy differences in floral morphology and absent or very subtle assortative mating among cytotypes (Jersáková et al, 2010;Segraves, 2017;Castro et al, 2020;Porturas and Segraves, 2020). We nevertheless found significantly larger floral organs in established tetraploids compared to their diploid progenitors.…”

Polyploidy‐induced floral changes lead to unexpected pollinator behavior in Arabidopsis arenosa

“…However, this did not translate into preferential visitation of tetraploids by insects in our study. This finding is consistent with the few available studies on this topic, yet in different plant families, in the species A. mangium, C. angustifolium and T. pratense (Nghiem et al 2011, Husband et al 2016, Porturas and Segraves 2020, which also did not find any impact of induced polyploidy on insect visitation. However, these studies did not test the quantitative preference of visitors (visit duration) between cytotypes but instead tested if assortative mating occurred, acting as an interploidy reproductive barrier.…”

Host expansion in a specialist herbivore is facilitated by whole‐genome duplication in the host plant

“…The neotetraploids used in this experiment were created using two different methods. The red clover neotetraploids were generated by Porturas and Segraves (2020) using a method modified from Taylor et al (1976) that uses nitrous oxide gas to disrupt the first cell division (Data S1). The neotetraploid red clover in our study was two generations removed from WGD induction.…”