Data from: Heterochronic developmental shifts underlie floral diversity within Jaltomata (Solanaceae)

Background: Heterochronic shifts during mid- to late stages of organismal development have been proposed as key mechanisms generating phenotypic diversity. To determine whether late heterochronic shifts underlie derived floral morphologies within Jaltomata (Solanaceae)—a genus whose species have extensive and recently evolved floral diversity—we compared floral development of four diverse species (including an ambiguously ancestral or secondarily derived rotate, two putatively independently evolved campanulate, and a tubular morph) to the ancestral rotate floral form, as well as to an outgroup that shares this ancestral floral morphology.

Results: We determined that early floral development (< 1 mm bud diameter, corresponding to completion of organ whorl initiation) is very similar among all species, but that different mature floral forms are distinguishable by mid-development (> 1 mm diameter) due to differential growth acceleration of corolla traits. Floral ontogeny among similar mature rotate forms remains comparable until late stages, while somewhat different patterns of organ growth are found between species with similar campanulate forms.

Conclusions: Our data suggest shared floral patterning during early-stage development, but that different heterochronic shifts during mid- and late-stage development contribute to divergent floral traits. Heterochrony thus appears to have been important in the rapid and repeated diversification of Jaltomata flowers.

背景：生物体发育中晚期的异时性转变（heterochronic shift）被认为是产生表型多样性的关键机制。为探明晚发性异时性转变是否为贾尔托马塔属（Jaltomata，茄科Solanaceae）内衍生花形态的形成基础——该属物种拥有广泛且近期演化形成的花多样性——我们将4个具有多样花型的物种（包括1个形态上不确定为祖先型或次生性衍生的辐状花冠物种、2个推测独立演化出钟状花冠的物种，以及1个管状花型物种）的花发育过程，与该属的祖先辐状花冠花型，以及具有该祖先花型的外类群进行了比较。
结果：我们发现，所有物种的早期花发育阶段（芽直径<1mm，对应器官轮状原基发生完成）均极为相似；但不同成熟花型可在发育中期（芽直径>1mm）通过花冠性状的差异化生长加速加以区分。具有相似成熟辐状花冠的物种，其花个体发育（floral ontogeny）在晚期前仍保持一致；而具有相似钟状花冠的物种间，则存在一定程度的器官生长模式差异。
结论：我们的数据表明，早期发育阶段的花模式建成（floral patterning）具有保守性，但中晚期发育阶段的不同异时性转变推动了花性状的趋异演化。由此可见，异时性（heterochrony）在贾尔托马塔属花卉的快速且重复的多样化演化中发挥了重要作用。