Systematic significance of cypsela morphology in Lessingianthus (Vernonieae, Asteraceae)

Abstract

The taxonomic significance of cypsela features of South American species of Lessingianthus (Vernonieae, Asteraceae) is analysed for the first time and discussed in relation to other genera of the tribe Vernonieae. The morphology of the cypselae of 112 species of the genus were analysed using stereo-, light and scanning electron microscopy (SEM) to evaluate the infrageneric relationships and their reliability as taxonomic markers at a generic level. Characters such as cypsela pubescence, carpopodium structure, crystals and idioblasts on the fruit wall were examined. We established three types of cypsela on the basis of the presence or absence, and type of trichomes. Carpopodium is present in all species of the genus. Crystals are very variable in shape and size, with prismatic (rectangular and hexagonal) and styloid shapes. Idioblasts are present in all of the species, except for two. Cypsela features of Lessingianthus are often widespread in other related genera of Vernonieae. Therefore, these characters are not good taxonomic markers at the genus level, but they are valuable within genera to differentiate related species from one another.

The taxonomic utility of micromorphology in Lepidaploa (Vernonieae: Asteraceae)

“…However, regarding the corolla of Lepidaploa, the apex of type VII trichome is usually variable, with some trichomes having an acute apex (biseriate filiform trichome) and others an obtuse apex (biseriate digitiform trichome). Type VII trichomes with an obtuse apex is morphologically similar to the trichomes found by Narayana (1979) on the cypsela wall of Vernonia monosis, and type VII trichome with acute apex is similar to the twin hairs on the cypsela of Chrysolaena (Via do Pico et al 2016) and Lessingianthus (Angulo et al 2015). According to Sancho and Katinas (2002), twin hairs on the corolla may be produced as a response to environmental characteristics.…”

“…It was described by Robinson (1988aRobinson ( , b, 1990 as glands and can be found on the anther apex, corolla lobes and cypselae of Lepidaploa, as well as in Chrysolaena and Lessingianthus. However, our morphological study indicates that they are in fact trichomes and should not be considered glands because glandular trichomes are epidermal appendices formed by a few cells, while glands are complex structures consisting of many cells (Evert 2006, Angulo et al 2015, Via do Pico et al 2016. These trichomes were also found on the vegetative parts of some species of…”

“…The terminology of trichome morphology follows Metcalfe and Chalk (1950), Ramayya (1962), Payne (1978), Narayana (1979), Luque et al (1999) and Werker (2000), and that of the other microcharacters follows Robinson (1988aRobinson ( , b, 1990Robinson ( , 1999, Roque et al (2009) and Angulo et al (2015).…”

“…(Keeley et al 2007, Keeley and Robinson 2009, Loeuille et al 2015. However, the characters cited by Robinson (1990Robinson ( , 1999 as characteristic of the genus Lepidaploa are shared with Chrysolaena and Lessingianthus (Angulo and Dematteis 2010a, Via do Pico and Dematteis 2013, Marques and Dematteis 2014, Angulo et al 2015, Via do Pico et al 2016. For example, some species of Lepidaploa have floral microcharacters that also occur in Chrysolaena or Lessingianthus, such as the presence of glands on anthers and cypselae, elongated crystals in cypsela walls, and a basal stylar node Dematteis 2014, Via do Pico et al 2016).…”

“…Cassini (1813aCassini ( , b, c, 1814Cassini ( , 1816aCassini ( , b, 1817Cassini ( , 1818aCassini ( , b, 1819a was a pioneer in studies of floral microcharacters in Asteraceae and he used them to circumscribe several tribes. These kinds of characters have since been repeatedly used as a taxonomic tool in Asteraceae (Robinson 1988a, b, 1990, Isawumi 1999, Meric 2009, Redonda-Martínez et al 2012, Wagner et al 2013, Angulo and Dematteis 2014, Angulo et al 2015, Via do Pico et al 2016, Redonda-Martínez 2017.…”