Achene Morphology and Anatomy of Clematis L. (Ranunculaceae) in Korea and Its Taxonomic Implications

Abstract

Clematis, a widely distributed genus in Ranunculaceae, is one of the most difficult groups of taxa in the family from a taxonomic point of view. A comprehensive study on achene morphology and the anatomy of 19 taxa of Clematis from Korea was carried out using scanning electron and light microscopy to evaluate the taxonomic significance of achene characters. Clematis achenes are elliptical, obovate or fusiform in shape, light yellow or brown to black in color and completely or sparsely covered with hairs. The permanent style is elongated and plumose in all the studied taxa except C. brachyura. We found that the size, indument, permanent style, surface sculpture, shape in cross-section, and nature and thickness of the exocarp, and endocarp were valuable achene features for species delimitation and may contribute to the unraveling of the taxonomic problems in the genus Clematis. One-way analysis of variance (ANOVA) indicated that the quantitative achene variables among the species were highly significant (p < 0.001). Principal component analyses based on seven quantitative characters and UPGMA (unweighted pair-group method with arithmetic mean) analysis based on seven quantitative and 18 qualitative characters also signify the utility of achene features for taxonomic discriminations of the Clematis taxa within the genus. Similar to other morphological characters in the genus Clematis, achene morphological and anatomical characters with the limited taxonomic value alone cannot be expected to resolve the infrageneric relationships but certain achene features combined with other morphological features could be useful as an alternative means of determining the infrageneric relationships within the genus.

Taxonomic relevance of petiole anatomical and micro-morphological characteristics ofClematisL. (Ranunculaceae) taxa from South Korea

“…Notably,petiole features alone can be more useful for species delimitation than for distinguishing infrageneric relationships and thus are not indicative of infrageneric classifications. Similar explanations were provided by Ghimire et al (2020) and Xie & Li (2012) based on the achene morphology and pollen morphology of Clematis , respectively.…”

“…However, in this study, it remained connected to the Viorna and Atragene sections. In fact, this uncertainty is a common and typical interpretation for this large genus, as previous morphological and molecular studies also found a similar tendency ( Grey-Wilson, 2000 ; Wang & Li, 2005 ; Miikeda et al, 2006 ; Xie, Wen & Li, 2011 ; Xie & Li, 2012 ; Lehtonen, Christenhusz & Falck, 2016 ; Ghimire et al, 2020 ).…”

“…The voucher specimens were deposited in the herbarium of the Korea National Arboretum (KH). Data were collected as previously described in Ghimire et al (2020) …”

“…At least three petioles of each taxon were subjected to microtome sectioning according to the following procedure used in Ghimire et al (2020) . Freshly collected leaf petioles were fixed in formalin, acetic acid, and 50% ethyl alcohol (FAA) at a ratio of 5:5:90 for one week and preserved in 50% ethyl alcohol.…”

“…Due to the vast morphological disparity among its species Clematis has been a subject of investigation since the early 19th century and has been subjected to several infrageneric revisions. Several systematic studies based on the anatomy of different parts, palynology, and cytology of Clematis have been carried out ( Tobe, 1974 ; Tobe, 1980a ; Tobe, 1980b ; Tobe, 1980c ; Tobe, 1980d ; Essig, 1991 ; Zhang & He, 1991 ; Yano, 1993 ; Yang & Moore, 1999 ; Shi & Li, 2003 ; Xie & Li, 2012 ; Ghimire et al, 2020 ). The morphological characters that have been extensively studied and considered in the infrageneric classifications of Clematis include the habit, seed germination, seedling phyllotaxy, leaf structure, inflorescence vertical structure, floral morphology, and pollen and achene morphology (see Wang & Li, 2005 ).…”