Colleters in American Spermacoceae Genera (Rubiaceae): Morphoanatomical and Evolutionary Aspects

Abstract

Premise of research. The primary goal of this study is to describe the colleters on vegetative and reproductive organs in the Spermacoceae tribe and to characterize their morphoanatomy, their distribution, and some functional and evolutionary aspects.Methodology. The anatomy, development, and vascularization of colleters from 28 species were studied using standard light and scanning electron microscopy based on fresh and fixed material. Our results are interpreted within the framework of recent molecular phylogenies.Pivotal results. Standard-type colleters were found on stipules, calyx, and bracteoles, and they were also found on underground buds in five species of Galianthe. Six species have green colleters, and two have vascularized colleters. We discuss previously unknown functional aspects based on the Staelia glandulosa colleters and propose a new term: long-lived colleters.Conclusions. This article describes the anatomy of colleters in the Spermacoceae tribe of the family Rubiaceae in detail. The pr...