Morphological Evidence for an Extended Tribe ‐ Coccocypseleae (Rubiaceae‐Rubioideae)

Abstract

Coccocypselum is a small neotropical genus of creeping herbs belonging to the Rubiaceae (Rubioideae). A recent macromolecular study suggested a previously unknown relationship between Coccocypselum and two other neotropical genera, Declieuxia and Hindsia, but the morphological evidence for this relationship was obscure. In the present paper, morphological characters supporting the conclusions from macromolecular data are presented. The most important similarities between Coccocypselum, Declieuxia, and Hindsia are found in their pollen and stipule morphology. Pollen of the three genera share a typical exine ornamentation, called a complex reticulum, which consists of a psilate suprareticulum and spinulate infrareticulum. In some specimens of Hindsia longiflora, a transitional stage between a complex reticulum and a simple, spinulate reticulum is encountered. The interpetiolar stipules of Hindsia, Declieuxia and Coccocypselum have an identical basic structure: they bear a central, colleter‐tipped awn that extends downwards to the next node as a distinct stem ridge. Some less conspicuous similarities of habit, calyx, and corolla are also discussed. The morphological data are, in part, confirmed by distributional data, Declieuxia and Hindsia having a remarkably congruent centre of diversity in the southeast of Brazil. It is concluded that the macromolecular data, combined with this new morphological and distributional evidence, justify an extended tribe Coccocypseleae, comprising the genera Coccocypselum, Hindsia, and Declieuxia.

Pollen morphology of Rubiaceae Juss. species occurring in an area of caatinga (dryland) vegetation in Bahia State, Brazil

“…Th e pollen morphology of Declieuxia fruticosa was described by Piesschaert et al (2000) using an SEM, and these authors reported similar results to those of the present study; they also observed a "complex reticulum" in this species. Th is type of ornamentation is very similar to the bireticulate pattern described by Punt et al (2007) as a reticulum composed of two layers (a suprareticulum sustained by a microreticulate tectum).…”

“…Among the heterostylous species studied, Declieuxia fruticosa and Leptoscela ruelioides had pollen grains of the two morpho-fl oral types analyzed, and the data presented here corroborates information in the literature concerning heterostyly in the family; the pollen grains from the brevistylous (thrum) morpho-fl oral type had larger diameters (Ganders 1979;Jung-Mendaçolli & Melhem 1995;Dessein et al 2000;Piesschaert et al 2000;Melhem et al 2003). Th ere were no diff erences between the specimens investigated in terms of aperture types or exine ornamentation.…”

“…Th is type of ornamentation is very similar to the bireticulate pattern described by Punt et al (2007) as a reticulum composed of two layers (a suprareticulum sustained by a microreticulate tectum). As such, the ornamentation types encountered in the specimens in the present study diff ered from the patterns described by Piesschaert et al (2000) in that micro-spines were not observed in the infrareticulum.…”

“…Medium-sized pollen grains have been reported for this species by a number of authors (Colinvaux et al 1999;Jung-Mendaçolli & Melhem 1995;Piesschaert et al 2000;Melhem et al 2003); amb triangular to sub-triangular has also been described (Jung-Mendaçolli & Melhem 1995;Melhem et al 2003). Pollen grains with a diff erent type of aperture, 3-porate, have only been reported by Delprete & Cortés (2006), while Colinvaux et al (1999) noted the occurrence of annuli in the ectoapertures.…”

“…Pollen grains with a diff erent type of aperture, 3-porate, have only been reported by Delprete & Cortés (2006), while Colinvaux et al (1999) noted the occurrence of annuli in the ectoapertures. In terms of the Piesschaert et al (2000), using an SEM, as being a "complex reticulum" formed by a suprareticulum psilate with an echinate infrareticulum, with fusion of the muri of both of the reticula. Delprete & Cortés (2006) reported the occurrence of bireticulate pollen grains for the genus.…”