Chromosome Numbers for North American Euphorbiaceae

Urbatsch, Lowell E.; Bacon, John D.; Hartman, Ronald L.; Johnston, Marshall C.; Watson, Thomas J.; Webster, Grady L.

doi:10.1002/j.1537-2197.1975.tb14075.x

Cited by 16 publications

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“…Agaloma (Perry, 1943;Hans, 1973;Urbatsch et al, 1975;Keil, 1976). Agaloma (Perry, 1943;Hans, 1973;Urbatsch et al, 1975;Keil, 1976).…”

Section: Chromosome Studiesunclassified

Monograph of Euphorbia sect. Tithymalopsis(Euphorbiaceae)

Park

2010

Edinburgh J. Bot.

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Euphorbia sect. Tithymalopsis {Euphorbiaceae) comprises seven species of herbaceous perennials restricted to the south-eastern USA. The species of sect. Tithymalopsis are united and distinguished from other sections in Euphorbia by having a thick and cylindrical root system, a glabrous cyathium, five glands with petaloid appendages, one to three stems arising from the root, absence of vestigial sepals in pistillate flowers, rounded leaf apices, and pitted or smooth seeds without a caruncle. Cladistic analyses indicate that sect. Tithymalopsis consists of two subgroups: (1) E. corollata, E. discoidalis, E. pubentissima and E. polyphylla; and (2) E. curtisii, E. gracilior and E. mercurialina. Comparative data from vegetative morphology, pollen morphology, seed morphology, cytology, crossability, reproductive biology, habitat and distribution are presented. Keys and descriptions to the species are provided. ). Unfortunately, the majority of Boissier's sections appear to be paraphyletic or polyphyletic groups in the cladistic analyses (Park, 1995).Euphorbia subgen. Agaloma sect. Tithymalopsis Boiss. comprises seven species of herbaceous perennials, and is endemic to the south-eastern states of the USA. The centre of diversity is in Georgia, where five of the seven species occur. The species of sect. Tithymalopsis are placed as the sister to a clade consisting of E. strictior and E. wrightii (Park, 1995), and are distinguished from them by having a thick and cylindrical root system, a glabrous cyathium, absence of vestigial sepals in pistillate flowers, and rounded leaf apices. Isozyme-based trees suggest that sect. Tithymalopsis is a group genetically distinct from E. strictior and E. wrightii (Park, 1995). The presence of a fixed unique allele in sect. Tithymalopsis supported hypotheses of monophyly for the section based on morphological data.Circumscription of sect. Tithymalopsis and its relationship to other sections within subg. Agaloma have presented major problems. Several species of subg. Agaloma sect. Alectoroctonum (Schltdl.) Baill., sect. Cyttarospermum Boiss. and sect. Zygophyllidium Boiss. from Mexico and the south-western USA have been placed in the section because of the uncertain limits of Boisser's (1862) sect. Tithymalopsis. Although early workers, such as Rafinesque (1836) and Small (1913), defined the group as containing only species distributed in the south-eastern states of the USA, the sectional concept of Tithymalopsis has been expanded by recent workers to include species in the south-western USA and Mexico (Wheeler, 1939;McVaugh, 1961;Webster, 1967;Huft, 1979). However, cladistic analyses of the New World subtribe Euphorbiinae (Park, 1995) did not support the monophyly of Huft's (1979) sect. Tithymalopsis. Within sect. Tithymalopsis sensu Huft, a group of E. macropus, E. macropodoides + E. ixtlana was closely related with the group possessing tuberculate seeds such as Poinsettia and major sections of herbaceous Agaloma (Park, 1995). Euphorbia innocua and E. ipecacuanhae formed sister groups o...

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“…Agaloma (Perry, 1943;Hans, 1973;Urbatsch et al, 1975;Keil, 1976). Agaloma (Perry, 1943;Hans, 1973;Urbatsch et al, 1975;Keil, 1976).…”

Section: Chromosome Studiesunclassified