Pollen morphology supports the reinstatement of Bergera (Rutaceae)

Abstract

Pollen morphology of 11 species of Murraya and Micromelum (Clauseneae: Rutaceae) was investigated using scanning electron microscopy (SEM) and palynological characters including pollen size, aperture number and exine ornamentation were evaluated. The results indicate that species in M. sect. Bergera and sect. Murraya have very distinct pollen morphology. Species in section Bergera have rugulate to foveolate exine, whereas the tectum in section Murraya is crossstriate. This supports the redefinition of the genus Murraya, retaining only the species of section Murraya, while M. sect. Bergera is better treated as a separate genus. From the palynological point of view, it is suggested that Bergera and Murraya s.s. are not closely related, with the latter being more close to Micromelum and Merrillia, a result in accordance with phytochemical, chromosomal and molecular evidence, thus supporting the reinstatement of the generic name Bergera L.

Phylogenetic relationship of Clauseneae (Rutaceae) inferred from plastid and nuclear DNA data and taxonomic implication for some major taxa

“…The genus Bergera (formerly Murraya sect. Bergera) formed a monophyletic clade sister to Clausena This result is congruent with previous studies based on morphology (Swingle and Reece 1967), chemical features , Samuel et al 2001, heterochromatin banding patterns (Guerra et al 2000), and pollen morphology (Mou and Zhang 2009b). Species of Bergera have brown to dark stem bark, undeveloped cork, corymbs with many small flowers, dilated filaments, globular stigmas, glabrous testa and heterogeneous rays which are two cells wide.…”

“…Murraya is the sister of Merrillia and has a more close relationship with the tribe Citreae. The same pattern may also be seen in morphological (Tanaka 1929, Swingle and Reece 1967), palynological (Grant et al 2000, Mou andZhang 2009b) and phytochemical differences , Kong et al 1988, Samuel et al 2001, as well as cytology (Guerra et al 2000) and DNA data (Samuel et al 2001, Groppo et al 2008, Bayer et al 2009). Based on studies of heterochromatin banding patterns in the subfamily Aurantioideae, Guerra et al (2000) proposed to divide Murraya s.l.…”

“…Bergera with rugulate to foveolate exine ornamentation and sect. Murraya with cross-striate exine (Mou and Zhang 2009b).…”

“…Based on all these studies, the genera Murraya and Bergera have previously been treated separately (Kubitzki et al 2011). Therefore, it is proposed to restore the genus Bergera Koenig ex L. (Mou and Zhang 2009b) to accommodate members of Murraya sect. Bergera.…”

Chromosome studies in the tribe Clauseneae and the cytological homogeneity in the orange subfamily (Aurantioideae, Rutaceae)

“…Recent palynological studies suggested that the genus Murraya s.l. should be divided into two genera, Murraya and Bergera (Mou & Zhang, 2009b), in accordance with earlier phytotaxonomical and phylogenetic studies on the group (Guerra et al, 2000;Samuel et al, 2001;Bayer et al, 2009).…”