A high degree of morphological variability is expressed between the ornately sculptured siliceous scales formed by species in the chrysophycean genus, Synura. In this study, we aimed to uncover the general principles and trends underlying the evolution of scale morphology in this genus. We assessed the relationships among thirty extant Synura species using a robust molecular analysis that included six genes, coupled with morphological characterization of the species‐specific scales. The analysis was further enriched with addition of morphological information from fossil specimens and by including the unique modern species, Synura punctulosa. We inferred the phylogenetic position of the morphologically unique S. punctulosa, to be an ancient Synura lineage related to S. splendida in the section Curtispinae. Some morphological traits, including development of a keel or a labyrinth ribbing pattern on the scale, appeared once in evolution, whereas other structures, such as a hexagonal meshwork pattern, originated independently several times over geologic time. We further uncovered numerous construction principles governing scale morphology and evolution, as follows: (i) scale roundness and pore diameter decreased during evolution; (ii) elongated scales became strengthened by a higher number of struts or ribs; (iii) as a consequence of scale biogenesis, scales with spines possessed smaller basal holes than scales with a keel and; and (iv) the keel area was proportional to scale area, indicating its potential value in strengthening the scale against breakage.

中文翻译：

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淡水Synura（Stramenopiles）二氧化硅鳞片的形态演变

金绿藻属Synura中的物种所形成的华丽雕刻的硅质鳞片之间表现出高度的形态变异性。在这项研究中，我们旨在揭示该属鳞片形态演变的一般原理和趋势。我们使用包括六个基因在内的稳健的分子分析方法，对三十种现存Synura物种之间的关系进行了评估，并结合了物种特异性尺度的形态特征。通过添加来自化石标本的形态学信息以及包括独特的现代物种Synura punctulosa，进一步丰富了分析工作。我们推断出形态独特的S. punlosa的系统发生位置，是一个古老的Synura血统有关S.蜥在部分Curtispinae。一些形态特征，包括龙骨的发展或规模上的迷宫肋骨图案，在进化中出现过一次，而其他结构（例如六角形网状图案）则在地质时间内独立起源了好几次。我们进一步发现了许多控制结垢形态和演化的构造原理，如下：（i）结垢圆度和孔径在演化过程中减小；（ii）伸缩杆或肋骨数量增加，拉长了鳞片；（iii）由于鳞屑的生物发生，带有刺的鳞片具有比带有龙骨的鳞片更小的基孔；以及 （iv）龙骨面积与水垢面积成正比，表明其在加强水垢抗破损方面的潜在价值。