Atripliceae

Abstract: Pollen morphology of 58 species from 17 putative genera of the tribe Atripliceae (Chenopodiaceae) was investigated using light (LM) and scanning electron microscopy (SEM). Morphological variation was analyzed based on a dense sampling of the subtribes Atriplicinae and Eurotiinae, including many of the species in the two largest genera: Atriplex and Obione. The pantoporate pollen grains of Atripliceae are characterized by their spheroidal or subspheroidal shape, flat or moderately vaulted mesoporia with 21–120 pores, tectum with 1–8 spinules and 5–28(−38) puncta per µm2, and 1–13 ectexinous bodies bearing 1–7 spinules each. Taxonomic relevance of the most important pollen morphological characters is discussed (pollen diameter, pore number, pore diameter, interporal distance, spinule and puncta density and ratio, number of ectexinous bodies, and their spinules). Pollen morphological data support the exclusion of Suckleya from the tribe and the recognition of subtribe Eurotiinae, but suggest that it needs to...

Abstract: A phylogenetic investigation of American members of the tribe Atripliceae (Chenopodiaceae) was conducted to examine evolutionary patterns and ecophysiological change in the North American lineages. Molecular phylogenetic analyses including representatives of all American genera of Atripliceae and data from 18S–26S nuclear ribosomal (ITS, ETS) and cpDNA (3′trnK intron) sequences suggest that neither Atriplex, as traditionally recognized, nor the North American members of Atriplex constitute a monophyletic group. Congruence between well-supported nuclear and cpDNA clades and results of expanded leaf anatomical and isotopic analyses indicate that American taxa belong to two distantly related lineages with different photosynthetic pathways; only one shift from C3 to C4 photosynthesis is required to explain photosynthetic pathway evolution in sampled lineages of Atripliceae. Conservatism in photosynthetic pathway evolution in the tribe is exemplified by the endemic, C3 North American Atriplex taxa, wh...

Abstract: FLORES, H. AND J. I DAVIS. (L. H. Bailey Hortorium, Cornell University, 462 Mann Library, Ithaca, New York 14853-4301). A cladistic analysis of Atripliceae (Chenopodiaceae) based on morphological data. J. Torrey Bot. Soc. 128: 297-319. 2001.-Although there is considerable controversy regarding the phylogenetic structure and infrafamilial classification of Chenopodiaceae, the tribe Atripliceae generally has been recognized as a natural group. Relationships within this tribe remain controversial, especially with regard to the taxonomic delimitation and infrageneric classification of the largest genus, Atriplex. Most of the genera that have been segregated from Atriplex are monotypic or include few species that are variously distributed in Africa, Australia, or North America; however, one of these genera, Obione, includes half of all species of Atriplex sens. lat., and has a worldwide distribution. Seventy terminals were included in a cladistic analysis, based on morphological characters, to test the monophyly of Atripliceae and its subtribes, and of Atriplex, Obione, and several infrageneric groups. The taxonomic sample includes representatives of 22 putative genera of the tribe Atripliceae, and all sections of Atriplex (except Austrobione) and Obione, following Ulbrich's (1934) classification, from throughout the geographic range of the tribe. Primary hypotheses of homology were postulated for 78 characters reflecting variation in gross morphology, leaf anatomy, and chromosome number. Results, as reflected in the strict consensus tree, suggest that both Atripliceae and Atriplex are paraphyletic, with three outgroup genera from tribe Chenopodieae (Chenopodium, Monolepis, and Suckleya) nested among species of Atriplex. Also, monophyly of the subtribes of Atripliceae is not supported. The results suggest that the deepest branch within Atripliceae is between Ceratocarpus and all other members of the tribe. Krascheninnikovia, the next genus to diverge, is the sister of a diverse clade that consists of two subclades. One of these includes Theleophyton plus Endolepis, Zuckia, and Grayia, and the other includes all species of Atriplex in the sample, plus all sampled species of Obione, the remaining genera of Atripliceae, and the three sampled genera of Chenopodieae, with Halimione pedunculata as the sister of all other members of this clade. Resolution generally is poor among species of Atriplex, and neither Obione nor most of the sections of Atriplex is resolved as monophyletic, though there is support for the monophyly of section Spongiocarpus. Also nested among species of Atriplex and Obione is a well resolved clade with four defined subgroups: Suckleya by itself; Atriplex hortensis and Chenopodium; Archiatriplex, Axyris, and Microgynoecium; and Monolepis, Proatriplex, Manochlamys, and Exomis. The results support the recognition of Endolepis, Theleophyton, and Zuckia (sensu Standley 1915) as segregates of Atriplex, but not Blackiella, Halimione, Haloxanthium, Morrisiella, Neopreissia, Obione, Pachypharynx, or Senniella. In addition, the results suggest that the continued recognition of Archiatriplex, Axyris, Exomis, Manochlamys, Microgynoecium, Proatripex, and Spinacia (Atripliceae), as well as Chenopodium, Suckleya, and Monolepis (Chenopodieae) should be reconsidered. If these results are confirmed by further analyses using other character sets and a wider taxonomic sample, it will be necessary either to transfer several genera to Atriplex or to circumscribe Atriplex narrowly, and segregate a number of additional genera from it.