Rancho Santa Ana Botanic Garden and Claremont Graduate University, 1500 North College Avenue, Claremont, California 91711 USA.
Am J Bot. 2013 Dec;100(12):2388-402. doi: 10.3732/ajb.1300094. Epub 2013 Nov 19.
Portulacaceae is a family with a remarkable diversity in photosynthetic pathways. This lineage not only has species with different C4 biochemistry (NADP-ME and NAD-ME types) and C3-C4 intermediacy, but also displays different leaf anatomical configurations. Here we addressed the evolutionary history of leaf anatomy and photosynthetic pathways in Portulacaceae.
Photosynthetic pathways were assessed based on leaf anatomy and carbon isotope ratios. Information on the NADP-ME and NAD-ME C4 variants was obtained from the literature. The evolutionary relationships and trait evolution were estimated under a Bayesian framework, and divergence times were calibrated using the ages obtained in a previous study.
C4 photosynthesis is the main pathway in Portulacaceae. One clade (Cryptopetala), however, includes species that have non-Kranz anatomy and C3 type isotope values, two of which are C3-C4 intermediates. The ancestral leaf anatomy for the family is uncertain. The analysis showed one origin of the C4 pathway, which was lost in the Cryptopetala clade. Nevertheless, when a second analysis was performed taking into account the limited number of species with NAD-ME and NADP-ME data, a secondary gain of the C4 pathway from a C3-C4 intermediate was inferred.
The C4 pathway evolved ca. 23 Myr in the Portulacaceae. The number of times that the pathway evolved in the family is uncertain. The diversity of leaf anatomical types and C4 biochemical variants suggest multiple independent origins of C4 photosynthesis. Evidence for a switch from C4 to C3-C4 intermediacy supports the hypothesis that intermediates represent a distinct successful strategy.
马齿苋科在光合作用途径方面具有显著的多样性。该谱系不仅具有不同的 C4 生物化学特性（NADP-ME 和 NAD-ME 类型）和 C3-C4 中间型，而且还表现出不同的叶片解剖结构。在这里，我们探讨了马齿苋科叶片解剖结构和光合作用途径的进化历史。
基于叶片解剖结构和碳同位素比值评估光合作用途径。NADP-ME 和 NAD-ME C4 变体的信息来自文献。在贝叶斯框架下估计进化关系和特征进化，并使用先前研究中获得的年龄来校准分歧时间。
C4 光合作用是马齿苋科的主要途径。然而，一个分支（Cryptopetala）包括具有非 Kranz 解剖结构和 C3 型同位素值的物种，其中有两个是 C3-C4 中间型。该科的祖先进化叶片解剖结构不确定。分析表明，C4 途径有一个起源，在 Cryptopetala 分支中丢失了。然而，当考虑到具有 NAD-ME 和 NADP-ME 数据的物种数量有限而进行第二次分析时，推断出 C4 途径从 C3-C4 中间型获得了第二次获得。
C4 途径在马齿苋科中进化了约 2300 万年。该途径在该科中进化的次数不确定。叶片解剖结构类型和 C4 生化变体的多样性表明 C4 光合作用有多个独立起源。从 C4 到 C3-C4 中间型的转变证据支持中间型代表一种独特的成功策略的假说。
