Phylogenetic Implications of Pollen Ultrastructure in the Oldfieldioideae (Euphorbiaceae) Author(s):

The pollen structure of members of Euphorbiaceae subfamilies Oldfieldioideae and Phyllanthoideae was studied using scanning and transmission electron microscopy in order to assess taxonomic relationships. We identified 10 palynological characters that appear to have systematic significance. We also identified 37 characters of vegetative morphology and anatomy, mostly based on data obtained by Hayden, and five characters of reproductive morphology, based on data in the literature. Cladistic analysis of the Oldfieldioideae along with selected genera in the Phyllanthoideae, using various putative relatives of the Euphorbiaceae as outgroups, provided great insight into the phylogeny of the Oldfieldioideae. Synapomorphies of this subfamily are all palynological: brevicolporate to pororate or porate apertures, echinate sculpturing, and exine with the interstitium consisting of columellae discontinuous from the foot-layer (where present). With the exception of Croizatia, the basal member of the subfamily, all Oldfieldioideae also share the synapomorphies of four or more pollen apertures and no petals; two homoplastic synapomorphies, an exinous footlayer that is irregular to absent and a caruncle on the seeds, also characterize these genera. A clade consisting of Paradrypetes and Podocalyx is supported by the synapomorphies of an extremely reduced pollen exine interstitium and sclerified crystalliferous axial xylem parenchyma, whereas the remaining Oldfieldioideae share the synapomorphies of a "microperforate/baculate" tectum consisting of numerous closely appressed rod-shaped elements, some of which are continuous with the columellae and/or echinae; uniformly simple perforation plates; and alternate intervascular pitting. These Oldfieldioideae represent two clades, taxonomically recognized as the tribes Picrodendreae and Caletieae. The Picrodendreae are diagnosed by the synapomorphy of alternate, circular vessel-ray pitting, and except for Tetracoccus, the basal member of the clade, also share four additional synapomorphies, all foliar: compound or unifoliolate leaves, well-developed bundle sheath extensions, fimbriate marginal ultimate venation, and well-developed areoles. Within the Picrodendreae, synapomorphies distinguish a South American clade and an African/Madagascan/ Indian clade, but do not resolve the position of Oldfieldia within the Picrodendreae. The Caletieae share the synapomorphy of stomatal subsidiary cells that have a crenulate (rather than straight) wall nearest the stomatal pore. Within the tribe, the African genus Hyaenanche is the basal member, with the remaining genera, all of which are Australasian, being united by the synapomorphy of chambered foliar epidermal cells. The Australasian genera comprise two major clades, but the relationships among these clades and Petalostigma are ambiguous. In addition to clarifying relationships within the Oldfieldioideae, these results (1) support the transfer of Croizatia and Paradrypetes from the Phyllanthoideae to the Oldfieldioideae, (2) support inclusion of Scagea, despite its single ovule/locule, in the Oldfieldioideae, (3) demonstrate that Androstachys and Stachyandra are bona fide members of the Oldfieldioideae rather than belonging in their own family, and (4) indicate that Neoroepera, as currently circumscribed, is diphyletic. We propose a revised classification of the subfamily in which all suprageneric taxa are monophyletic according to this phylogeny. 'We extend our warmest thanks to John Hayden, who generously shared his data and thoughts with us as we pursued our study. Without his generous cooperation, our work would have been far less complete. We accept full responsibility for any interpretations that may differ from his. We thank the curators at DAV, GH, K, MO, P, QRS, RSA/POM, and US for removing or allowing us to remove pollen from collections in their care. Jon Blevitt, Kitty Huntley, and Nicki Watson embedded and sectioned much of the pollen for EM and printed most of the plates. Discussion at the International Conference on the Systematics of the Euphorbiaceae provided valuable insights. We thank Grady Webster and Mike Huft for inviting us to participate. Mike Huft and an anonymous reviewer made valuable comments on an earlier version of this paper. Levin thanks Rick Brusca and Regina Wetzer of Marine Invertebrates Department, San Diego Natural History Museum, for allowing him use of their Apple computers, and Mark Donnelly of the Exhibits Department, San Diego Natural History Department, for help with the cladogram illustrations. He saves his greatest thanks for Mike Simpson, without whose generous sharing of pollen expertise and cladistic insight this research would not have been possible. This research was supported in part by a San Diego State University Foundation Grant-in-aid Award to MGS. 2 Department of Botany, San Diego Natural History Museum, P. O. Box 1390, San Diego, California 921 12, U.S.A. Current address: Center for Biodiversity, Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820, U.S.A. 3Department of Biology, San Diego State University, San Diego, California 92182, U.S.A. ANN. MISSOURI BOT. CARD. 81: 203-238. 1994. This content downloaded from 146.244.235.206 on Mon, 13 Apr 2015 18:50:29 UTC All use subject to JSTOR Terms and Conditions 204 Annals of the Missouri Botanical Garden Light microscopy (LM) of pollen morphology in the Euphorbiaceae (Erdtman, 1952: 165-175; Punt, 1962; Kohler, 1965) has been particularly influential in the development of recent classifications of the family (e.g., Webster, 1975, 1994). More recently, researchers have begun using scanning electron microscopy (SEM) to study pollen of Euphorbiaceae, and though no comprehensive surveys have yet been published, several papers have treated a variety of genera throughout the family, but especially from subfamilies Phyllanthoideae and Oldfieldioideae (Bonnefille & Riollet, 1980; Dechamps et al., 1985; El-Ghazaly & Raj, 1986; Hayden et al., 1984; McPherson & Tirel, 1987; Poole, 1981; Punt, 1980, 1987; Webster, 1984; Webster et al., 1987). However, only two studies of Euphorbiaceae pollen (Hayden et al., 1984; Poole, 1981) have utilized transmission electron microscopy (TEM) to describe the details of exine architecture, and these papers treated only five genera. We initiated a study of pollen ultrastructure in the Phyllanthoideae and Oldfieldioideae to help resolve intergeneric relationships. These two subfamilies have two ovules in each locule, which is generally regarded as the plesiomorphic condition in contrast to the single ovule per locule found in the remaining three subfamilies. Of the two biovulate subfamilies, Phyllanthoideae is by far the larger and presumably is paraphyletic and basal to the Oldfieldioideae and the uniovulate subfamilies (Webster, 1967, 1975, 1994; Webster et al., 1987). Details of our pollen study will be published elsewhere (Simpson & Levin, in press). Here we present an overview and phylogenetic analysis of the results, concentrating on the Oldfieldioideae. To evaluate pollen characters and better understand relationships within the subfamily, we also include a phylogenetic analysis of vegetative morphological and anatomical data compiled by Hayden (1980, 1994, this issue) and of selected reproductive characters. MATERIALS AND METHODS