Glick Lior, Sabath Niv, Ashman Tia-Lynn, Goldberg Emma, Mayrose Itay
Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel.
Department of Biological Sciences University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
Am J Bot. 2016 Jul;103(7):1223-35. doi: 10.3732/ajb.1500424. Epub 2016 Jun 27.
Flowering plants display a variety of sexual systems, ranging from complete cosexuality (hermaphroditism) to separate-sexed individuals (dioecy). While dioecy is relatively rare, it has evolved many times and is present in many plant families. Transitions in sexual systems are hypothesized to be affected by large genomic events such as whole-genome duplication, or polyploidy, and several models have been proposed to explain the observed patterns of association.
In this study, we assessed the association between ploidy and sexual system (separate or combined sexes). To this end, we assembled a database of ploidy levels and sexual systems for ∼1000 species, spanning 18 genera and 15 families. We applied several phylogenetic comparative approaches, including Pagel's coevolutionary framework and sister clade analyses, for detecting correlations between ploidy level and sexual system.
Our results indicate a broad association between polyploidy and sexual system dimorphism, with low evolutionary stability of the diploid-dioecious condition observed in several clades. A detailed examination of the clades exhibiting this correlation reveals that it is underlain by various patterns of transition rate asymmetry.
We conclude that the long-hypothesized connection between ploidy and sexual system holds in some clades, although it may well be affected by factors that differ from clade to clade. Our results further demonstrate that to better understand the evolutionary processes involved, more sophisticated methods and extensive and detailed data sets are required for both broad and focused inquiry.
开花植物表现出多种性系统，从完全两性同体（雌雄同体）到雌雄异株个体（雌雄异株）。虽然雌雄异株相对罕见，但它已经多次进化，并且存在于许多植物科中。性系统的转变被假设受到诸如全基因组加倍或多倍体等大型基因组事件的影响，并且已经提出了几种模型来解释观察到的关联模式。
在本研究中，我们评估了倍性与性系统（雌雄异株或两性同体）之间的关联。为此，我们组装了一个包含约1000个物种的倍性水平和性系统的数据库，涵盖18个属和15个科。我们应用了几种系统发育比较方法，包括佩格尔的协同进化框架和姐妹分支分析，以检测倍性水平与性系统之间的相关性。
我们的结果表明多倍体与性系统二态性之间存在广泛关联，在几个分支中观察到二倍体 - 雌雄异株状态的进化稳定性较低。对表现出这种相关性的分支进行详细检查发现，它是由各种转变速率不对称模式所支撑的。
我们得出结论，倍性与性系统之间长期假设的联系在某些分支中成立，尽管它很可能受到因分支而异的因素影响。我们的结果进一步表明，为了更好地理解所涉及的进化过程，需要更复杂的方法以及广泛而详细的数据集来进行广泛和重点的探究。
