University of Arkansas, 1 University of Arkansas, SCEN 601, Fayetteville, AR, 72701-1201, USA.
New Phytol. 2018 Jul;219(1):462-473. doi: 10.1111/nph.15137. Epub 2018 Apr 6.
Patterns of species richness are commonly linked to life history strategies. In diatoms, an exceptionally diverse lineage of photosynthetic heterokonts important for global photosynthesis and burial of atmospheric carbon, lineages with different locomotory and reproductive traits differ dramatically in species richness, but any potential association between life history strategy and diversification has not been tested in a phylogenetic framework. We constructed a time-calibrated, 11-gene, 1151-taxon phylogeny of diatoms - the most inclusive diatom species tree to date. We used this phylogeny, together with a comprehensive inventory of first-last occurrences of Cenozoic fossil diatoms, to estimate ranges of expected species richness, diversification and its variation through time and across lineages. Diversification rates varied with life history traits. Although anisogamous lineages diversified faster than oogamous ones, this increase was restricted to a nested clade with active motility in the vegetative cells. We propose that the evolution of motility in vegetative cells, following an earlier transition from oogamy to anisogamy, facilitated outcrossing and improved utilization of habitat complexity, ultimately leading to enhanced opportunity for adaptive divergence across a variety of novel habitats. Together, these contributed to a species radiation that gave rise to the majority of present-day diatom diversity.
生物多样性模式通常与生活史策略有关。在硅藻中，光合异养生物的一个极其多样化的谱系，对全球光合作用和大气碳埋藏至关重要，具有不同运动和繁殖特征的谱系在物种丰富度上有很大差异，但生活史策略和多样化之间的任何潜在关联在系统发育框架中尚未得到检验。我们构建了一个时间校准的、11 个基因、1151 个分类群的硅藻系统发育树——这是迄今为止最全面的硅藻物种树。我们利用这个系统发育树，以及一个关于新生代化石硅藻首次和末次出现的综合目录，来估计预期的物种丰富度、多样化及其随时间和谱系的变化范围。多样化速率随生活史特征而变化。虽然具有不均等分裂的谱系比卵配的谱系多样化得更快，但这种增加仅限于一个具有活跃运动能力的营养细胞的嵌套类群。我们提出，在从卵配性向不均等分裂的早期转变之后，营养细胞运动的进化促进了异交，改善了对栖息地复杂性的利用，最终为各种新栖息地的适应性进化提供了更多的机会。这些因素共同促成了一个物种辐射，产生了现今大多数硅藻的多样性。
