Floral Anatomy of Xyrids (Poales): Contributions to Their Reproductive Biology, Taxonomy, and Phylogeny Author(s): Aline Oriani and Vera L. Scatena Source: International Journal of Plant Sciences, Vol. 173, No. 7 (September 2012), pp. 767-779 Published by: The University of Chicago Press Stable URL: http://www.jstor.org/stable/10.1086/666664 . Accessed: 17/09/2013 10:39 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences. http://www.jstor.org This content downloaded from 200.145.3.55 on Tue, 17 Sep 2013 10:39:12 AM All use subject to JSTOR Terms and Conditions Int. J. Plant Sci. 173(7):767–779. 2012. Ó 2012 by The University of Chicago. All rights reserved. 1058-5893/2012/17307-0003$15.00 DOI: 10.1086/666664 FLORAL ANATOMY OF XYRIDS (POALES): CONTRIBUTIONS TO THEIR REPRODUCTIVE BIOLOGY, TAXONOMY, AND PHYLOGENY Aline Oriani1,* and Vera L. Scatena* *Departamento de Botaˆnica, Instituto de Biocieˆncias, Universidade Estadual Paulista, C. Postal 199, 13506900 Rio Claro, Sa˜o Paulo, Brazil Xyridaceae, Eriocaulaceae, and Mayacaceae form the xyrid clade, which is weakly supported in Poales. The floral anatomy of xyrid species was studied, to contribute to the understanding of the relationships within the group. Both Eriocaulaceae and Xyridaceae have petals with elongated epidermal cells with straight walls, epipetalous stamens, staminodes, anthers with longitudinal dehiscence, an endothecium with band-like thickenings, and a style vascularized by the dorsal carpellary bundles; these characteristics thus corroborate the close relationship of these groups indicated by phylogenetic analyses. Mayacaceae is distinguished by the presence of papillose epidermal cells in the petals, a reduced inner whorl of stamens, poricidal anthers, an endothecium lacking thickenings, a style and stigma vascularized by the dorsal and ventral carpellary bundles, and the presence of an obturator in the ovary wall. A reduction in the inner whorl of fertile stamens also occurs in Juncaceae and Cyperaceae, linking Mayacaceae to the cyperids. The stylar appendages of Orectanthe (Xyridaceae) have been shown to be nectariferous and anatomically similar to those of Abolboda, dif- ferentiating these two genera from Xyris (Xyridoideae) and confirming their placement in Abolbodoideae. Stylar appendages also occur in Eriocaulaceae, with the same function, position, and vascularization, and are therefore homologous structures, reinforcing the phylogenetic proximity between Eriocaulaceae and Xyridaceae. Keywords: Eriocaulaceae, flower, Mayacaceae, Poales, Xyridaceae, xyrids. Introduction Mayacaceae to Eriocaulaceae and Xyridaceae, and there is relatively little evidence that these three families will continue The xyrids are a clade of Poales that comprises Xyridaceae, to form a clade when new data are added to future phyloge- Eriocaulaceae, and Mayacaceae (Linder and Rudall 2005; netic analyses. Givnish et al. 2010). However, the most recent phylogenetic Xyridaceae includes five genera and ;300 herbaceous spe- analysis of the Poales (Givnish et al. 2010), which was per- cies (Kral 1998). Xyris is the largest genus of this family formed on the basis of both morphological and molecular and comprises ;270 species found across a pantropical dis- data, has demonstrated that this is the most weakly supported tribution, mainly in Central and South America (Kral 1998). clade within the order. These three families, together with Abolboda includes ;20 species, whereas Aratitiyopea, Achly- Rapateaceae and Commelinaceae, had been grouped into the phila, and Orectanthe are represented by only one or two Commelinales (Dahlgren and Clifford 1982; Dahlgren et al. species, with distribution restricted to the tropical regions of 1985) because of shared features such as a nuclear endosperm South America (Kral 1998). Studies on the floral anatomy of and showy flowers with a differentiated perianth, which are Xyridaceae have been performed with a taxonomic focus characteristics that are considered plesiomorphic for the com- only for Xyris (Sajo et al. 1997; Rudall and Sajo 1999). The melinids. reproductive biology of Abolboda species has been studied Xyridaceae and Eriocaulaceae are identified as sister groups by Oriani and Scatena (2011), who first demonstrated the in most of the phylogenetic analyses of Poales (Givnish et al. production of nectar by stylar appendages in Xyridaceae and 1999, 2005, 2006; Chase et al. 2000, 2006; Bremer 2002; anatomically characterized these nectariferous structures. Christin et al. 2008). Mayacaceae is clustered as a sister Within the Xyridaceae, stylar appendages also occur in Arati- group to Eriocaulaceae (Givnish et al. 2010); the cyperid tiyopea and Orectanthe (Kral 1992, 1998) and constitute clade, which includes Cyperaceae, Juncaceae, and Thurniaceae one of the characteristics that support the circumscription of (Chase et al. 2000; Christin et al. 2008); or the clade formed the subfamily Abolbodoideae (Stevens 2011). by the cyperids plus Eriocaulaceae-Xyridaceae (Givnish et al. Eriocaulaceae comprises 10 genera and ;1400 herbaceous 2005, 2006; Chase et al. 2006). According to Givnish et al. species with a pantropical distribution (Stu¨tzel 1998; Giulietti (2010), there are a few morphological characteristics that link et al. 2012). Species of this family are found in the tropical and subtropical regions around the world, with diversity con- centrated in South America, especially Brazil (Giulietti and Hensold 1990; Stu¨tzel 1998). Floral anatomy studies with a tax- 1 Author for correspondence; e-mail: [email protected]. onomic and evolutionary focus have been conducted on differ- Manuscript received December 2011; revised manuscript received April 2012. ent species of Eriocaulaceae (Rosa and Scatena 2003, 2007). 767 This content downloaded from 200.145.3.55 on Tue, 17 Sep 2013 10:39:12 AM All use subject to JSTOR Terms and Conditions 768 INTERNATIONAL JOURNAL OF PLANT SCIENCES According to Rosa and Scatena (2007), most representatives A minimum of three individuals of each species was of the family have diclinous and isostemonous flowers that are examined. Isolated flowers were subjected to the n-butyl al- probably derived from a hermaphroditic ancestor with diplo- cohol dehydration series, infiltration, and inclusion in (2- stemonous flowers. Rosa and Scatena (2003, 2007) also hydroxyethyl)-methacrylate (Leica Historesin embedding reported the occurrence of nectariferous structures in the kit; Feder and O’Brien 1968). The embedded material was gynoecium of species of Eriocaulaceae, an important fea- sectioned using a Leica Reichert-Jung 2040 rotatory micro- ture for the phylogeny of Poales, since it may reinforce the tome (6–8-mm thick sections), stained with periodic acid– phylogenetic proximity between this family and Xyridaceae. Schiff’s reagent (PAS) and toluidine blue (Feder and O’Brien Mayacaceae comprises only four to 10 species in the sin- 1968), and mounted on permanent slides with Entellan gle genus Mayaca, and all are herbaceous, aquatic, or am- (Merck). Photomicrographs were obtained with an IM50 phibious plants (Stevenson 1998). With the exception of the (Leica Image Manager V.5.0) digital imaging system, using African species Mayaca baumii, Mayaca is limited to Neo- an image-capturing device (Leica, DFC 290) coupled to a mi- tropical regions, with a higher concentration of species found croscope (Leica, DM LB). Isolated flowers were also immersed in South America (Stevenson 1998). A study conducted on the in a 1 : 10,000 solution of neutral red (Kearns and Inouye floral anatomy of Neotropical species of Mayacaceae identi- 1993), to stain secretory structures. fied characteristics that distinguish the species as well as char- For analysis using SEM (Zeiss, DSM 950), flowers fixed in acteristics that support the positioning of this family within FAA 50 and dehydrated in 70% ethanol were immersed in Poales (Carvalho et al. 2009). According to Carvalho et al. FDA (formaldehyde-dimethylacetate; Gerstberger and Leins (2009), the number of stamens and microsporangia and the 1978), subjected to critical-point drying (Balzers, CPD 030), type of ovule and placentation link Mayacaceae to other and metallized with gold (Bal-Tec, SCD 050). The results families of the order. were recorded using a DIPS (Digital Image Processing Soft- Given the numerous uncertainties regarding the interfamily ware 2.2; Leipzig) digital imaging system. relationships within the Poales—particularly the relationships among the Xyridaceae, Eriocaulaceae, and Mayacaceae—this study aims to investigate the floral anatomy of xyrid species Results in order to identify characteristics on which to base the rela- tive positioning of these three families within the order. For Mayaca this purpose, we used data already published about represen- Mayaca fluviatilis and Mayaca sellowiana have monoclinous, tatives of Xyridaceae, Eriocaulaceae, and Mayacaceae (Sajo dichlamydeous, heterochlamydeous, and actinomorphic