Compositae: Cichorioideae

Systematic Botany (2011), 36(1): pp. 191–208 © Copyright 2011 by the American Society of Plant Taxonomists DOI 10.1600/036364411X553270 A Monograph of the Small Tribe Platycarpheae (Compositae: Cichorioideae) V. A. Funk , 1 , 3 and Marinda Koekemoer 2 1 U.S. National Herbarium, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, U.S.A. 2 South African National Biodiversity Institute, Private Bag X101, Pretoria 0001, South Africa 3 Author for correspondence ( [email protected] ) Communicating Editor: Victoria Sosa Abstract— The tribe Platycarpheae has three species; they are found from South Africa, to Namibia and Botswana. The three species have traditionally been placed in a single genus but were recently divided into two ( Platycarpha and Platycarphella ). All have ‘secondary heads’ formed by tightly clustered heads on the crown of the rhizome. The three species are easily separated from one another based on characters such as leaf type, head size, style and corolla length, and pollen type. Morphological and molecular data support Platycarpheae as a monophyletic group within the subfamily Cichorioideae but no firm sister-group relationship has been determined. The three species form a monophyletic group on a long branch: Platycarphella carlinoides and Platycarphella parvifolia share more characters and are sister-taxa; Platycarpha glomerata has the largest number of unique features and is the sister taxon to the other two species. The distributions and flowering times of the three species are different. Platycarphella carlinoides is the most widespread of the species and grows in northwestern South Africa, the central highlands of Namibia, and southwestern Botswana; its peak flowering time is March-July. Platycarphella parvifolia is found in north central to northeast South Africa and flowers mostly in August to October, and Platycarpha glomerata is from inland eastern South Africa and usually flowers from November to early February. The biogeographic pattern is consistent with one of a widespread ancestral species that became fragmented by the rise of the Great Escarpment and climate change. Keywords— Asteraceae , Arctotideae , biogeography , Botswana , Great Escarpment , Namibia , pollen , South Africa. The genera of the Compositae tribe Platycarpheae ( Platy- (Cardueae), rejected Platycarpha and suggested that it should carpha Less. and Platycarphella V. A. Funk & H. Rob.) fall into be placed back in the Arctotideae, and Norlindh (1977) in his the category of “odd genera that are endemic to southern treatment of the Arctotideae excluded Platycarpha . The most Africa;” the tribe has not previously been monographed. All recent classifications of the family/tribe ( Bremer 1994 ; Karis three species of the Platycarpheae are perennial herbs with- 2007 ) accepted Platycarpha in the Arctotideae but listed it as out aerial stems; the leaves usually lie flat on the ground and ‘unassigned to subtribe.’ spread out around the secondary head like the spokes of a Data from a variety of sources ( Cassini 1816 , 1821 ; Beauverd wagon wheel or are arched. The ‘secondary head’ is formed 1915a , b ; Robinson and Brettell 1973 ; Norlindh 1977 ; Karis et by a tight clustering of heads on the crown of the recepta- al. 1992 ; Robinson 1992 , 1994 ; Bremer 1994 ; Herman et al. cle. The taxa are either acaulescent, without branches, or with 2000 ; Leistner 2000 ; Funk et al. 2004 ) have shown that the tribe subterranean branches. The receptacles have narrow pales, Arctotideae does not have much support for its monophyly. the discoid heads have few-to-many, pink to purple florets, This is true even after several genera, including genera now and the corollas are deeply divided. The anthers have tails (or in the tribe Platycarpheae, have been removed from the anal- are saggitate), and the styles have a small swelling covered ysis ( Funk et al. 2004 ; Funk and Chan 2009 ). Beginning with with small hairs. The achenes are smooth, ribbed or rugose Bentham (1873) the traditional definition of the Arctotideae and the pappus is made up of scales. was based on the presence of a swollen area with a ring of Until recently there was a single genus, Platycarpha, and it hairs located just below the branch point on the style (all Delivered by Ingenta to IP: 192.168.39.151 on: Fri, 01 Oct 2021 11:11:33 Copyright (c) American Society for Plant Taxonomists. All rights reserved. was a member of the tribe Arctotideae, although not with- other characters that have been suggested are either common out dissent ( Norlindh 1977 ; Robinson and Brettell 1973 ), but in other clades in the family or are plesiomorphic) but it is not based on molecular and morphological data it has recently found in the larger of the two subtribes, the Gorteriinae, and been placed in a tribe of its own, Platycarpheae ( Funk and it is found in some thistles (Cardueae). A small swelling with Robinson 2009 ). minute hairs is found in members of the Platycarpheae but its The complex history of the classification of Platycarpha (now appearance is different from those found in the Arctotideae Platycarpha and Platycarphella ) reflects the difficulty of deter- and Cardueae. Platycarpha and Platycarphella also lack the mining the proper assignment for this unique clade. Thunberg characters that would place them in either of the two sub- (1800) described Cynara glomerata thus indicating that it was tribes: they have no latex, the involucral bracts are not fused, part of the thistles, no doubt because of the style morphol- there are no ray florets, their disc florets are pink or purple not ogy and spiny nature of this species. Lessing (1831) described yellow, red or orange, they have slender pales on the recep- Platycarpha based on the Thunberg species. De Candolle (1836) tacle, the achenes are not distinctly ribbed or winged, and placed Platycarpha in the Vernonieae. Bentham and Hooker according to Wortley et al. (2007) the pollen suggests nothing (1873) moved Platycarpha from the Vernonieae into a subtribe that would link this small tribe to any other groups in the sub- of its own in the reestablished Arctotideae; Hoffman agreed family Cichorioideae. (1890). There it remained until Stix (1960) suggested that The analysis of the DNA sequence data showed that the Platycarpha should be in the Mutisieae. Robinson and Brettell three species form a monophyletic group on a long branch (1973) put Platycarpha back in the Cardueae (thistles) based ( Funk et al. 2004 ; Funk and Chan 2009 ; Funk and Chan on the pollens’ “…prominent complex columnar structure unpubl. data) within the subfamily Cichorioideae. The place- in the thickened rather smooth exine” and “the lack of stom- ment of Platycarpheae within the subfamily differed slightly ates on the corolla lobes;” both characters are similar to what in the analyses of the nuclear and cpDNA. The combined and they found in the Cardueae. In the “Biology and Chemistry the ITS analyses produced results that placed Platycarpheae of the Compositae” ( Heywood et al. 1977 ), Platycarpha was as the sister group to the Liabeae-Vernonieae clade. However left out because Dittrich (1977) , in his treatment of the thistles the analysis of the cpDNA data placed it near parts of the 191 192 SYSTEMATIC BOTANY [Volume 36 Arctotideae. Although the individual clades within the The herbaria with the two largest holdings of this genus, PRE and subfamily (Cichorieae, Vernonieae, Liabeae, Arctotideae- WIND, are part of a consortium that has divided southern Africa into quarter degree grid squares ( Edwards and Leistner 1971 ). The distribu- Arctotidinae, Arctotideae-Gorteriinae, Platycarpheae, Ere- tion map ( Fig. 1 ) is divided into grid squares based on one degree, in the mothamneae, Heterolepis ) were present in all parsimony and specimens examined these degrees squares are identified by a number in maximum likelihood trees, there was little resolution among brackets that identifies the NW corner of the longitude (S) latitude (E) of them in the bootstrap analysis. New molecular data and taxa the degree square cell. are being added in an attempt to better resolve the relation- ships among the clades of the subfamily. Discussion Within the tribe Platycarpheae the DNA data show clearly that the two species of Platycarphella, P. carlinoides (Oliv. & Current Distribution and Rainfall Patterns— Platycarphella Hiern) V. A. Funk & H. Rob. and P. parvifolia (S. Moore) V. A. carlinoides is widespread on the high plateau in central Funk & H. Rob., are more closely related to one another than and southern Namibia, the Kalahari Duneveld Bioregion either is to Platycarpha glomerata (Thunb.) Lessing ( Fig. 1 ; Funk ( Rutherford et al. 2006 ; Fig. 1 ) in South Africa, and in nearby and Chan unpubl. data). This matches the morphology in that Botswana. Most of the collections are on the Namibian inland P. glomerata with its spiny leaves, larger heads, long styles, plateau region that is a continuation of the South African style branches and corollas, thick rhizomes, and unique pol- Plateau and comprises mountains and highland areas, all len, is different from the other two species. of which are part of the Great Western Escarpment ( Kundell In this treatment we document the characters that unite the 2007 ). The Plateau has hot, dry conditions with sparse and members and define the genera and species. We also examine erratic rainfall; 92% of the land is hyper-arid or semiarid. the distribution in light of the geologic history and rainfall Within Africa the climate is second in aridity only to the patterns of southern Africa. Sahara Desert. According to Kundell (2007) “Conventional statistical descriptors such as mean and even median are often difficult to use and estimates of rainfall characteris- Materials and Methods tics and patterns based on point measurements are problem- The morphological study was based on new collections for all three spe- atic.” This species has been collected in flower nearly year cies and the extensive collections housed at PRE and WIND, and smaller around, except for November, and December, but 80% of collections at K, M, MO, S, and US.

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