Abstract
Ruta, which belongs to tribe Ruteae, is the type genus of the subfamily Rutoideae and the family Rutaceae. Molecular systematic studies have shown that the genera in Ruteae are closer related to Aurantioideae than to most other genera of Rutoideae, some of the genera traditionally placed in Ruteae have been shown to be nested within the Aurantioideae clade, but the diagnostic characters for determining new patterns in the relationship are poor. In this study, we investigated the floral development of Boenninghausenia in Ruteae (sensu stricto), Haplophyllum in the basal position of Aurantioideae and Murraya in traditional Aurantioideae using scanning electron microscopy. The androecium of Boenninghausenia is obdiplostemony. As androecia in other genera within Ruteae (s.s.) are also obdiplostemonous, reconstruction of the ancestral state indicates that obdiplostemony is an ancestral character in this clade. Because the androecia of Haplophyllum and Murraya are also obdiplostemonous, obdiplostemony is also an ancestral character in Aurantioideae clade. The ancestral state reconstruction indicates this character can serve as a synapomorphy of the Ruteae-Aurantioideae clade. The results of our work also shed light on the evolution of the androecium in Rutaceae, as the obdiplostemony of this group is clearly derived from haplostemony in the ancestral genera in Rutaceae and has develop into polyandry by increasing antepetalous stamens.
Highlights
The Rutaceae family, which is well known due to its economic importance (Citrus), is a large family including 154 genera and approximately 2100 species [1]
During the development of the calyx, the floral apex increases in height and flattens, and the five petal primordia appear in the antesepalous position in very close succession (Fig 3D)
Initiation may begin on the abaxial side, as the primordia are slightly larger in the abaxial area
Summary
The Rutaceae family, which is well known due to its economic importance (Citrus), is a large family including 154 genera and approximately 2100 species [1]. The distribution of this family is nearly cosmopolitan, with species in both the Old World and New World, but it is mainly tropical and subtropical [2,3,4,5]. Along with the modern systematics of this family, many of the subfamilies are controversial [8,9]. The consensus consists of traditional subfamilies that are not natural groups, and Rutoideae, Toddalioideae, Flindersioideae and Aurantioideae form a ‘core Rutaceae’ clade [1].
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