Floral Anatomy of Xyrids (Poales): Contributions to Their Reproductive Biology, Taxonomy, and Phylogeny

Abstract

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Floral ontogeny and vasculature in Xyridaceae, with particular reference to staminodes and stylar appendages

“…This result makes sense in terms of morphological trait evolution because in Mayaca the three stamens are located opposite the outer tepals and hence represent the outer androecial whorl (e.g. Carvalho et al 2009;Oriani and Scatena 2012), in contrast with Xyridaceae and most Eriocaulaceae, in which only the inner androecial whorl is fertile, thus representing an entirely independent morphological transition in Mayacaceae. On the other hand, it remains equivocal whether the loss of a fertile outer androecial whorl occurred more than once during the evolutionary history of the xyrid clade (Fig.…”

“…Thus, the alternative hypothesis, that the stylar appendages are homologous between the two families, appears unlikely based on our data, but cannot be entirely discounted pending further comparative data on Eriocaulaceae. Because the stylar appendages produce nectar in both families (Rosa and Scatena 2007;Oriani and Scatena 2012), it is plausible to interpret them as a convergent character.…”

“…antesepalous (e.g. Carvalho et al 2009;Ronse de Craene 2010;Oriani and Scatena 2012). Xyridaceae are currently circumscribed into two subfamilies: Xyridoideae, with a single widespread genus Xyris L. (ca 360 species), and Abolbodoideae, with four genera endemic to South America (Table 1).…”

“…These features include petals that are nonshowy and often reduced in size and/or number, absence of nectaries and a reduced number of stamens (Linder and Rudall 2005). Species of Xyridaceae are biotically pollinated but lack septal nectaries; their flowers are relatively showy, possessing a double (heterochlamydeous) perianth of green sepals and colourful petals (Rudall and Sajo 1999;Oriani and Scatena 2012). The absence of septal nectaries in both Xyridaceae and Eriocaulaceae has prompted some authors to speculate that nectaries have evolved de novo in xyrids from ancestors that lacked septal nectaries (Linder and Rudall 2005).…”

“…Floral vasculature of Abolboda, Achlyphila and Orectanthe was described by Carlquist (1960), and flowers of Aratitiyopea were described by Campbell and Stevenson (2007). Oriani and Scatena (2012) also provided information on floral anatomy of Abolboda and Orectanthe. Our primary goals are to elucidate familial systematics and the possible origin of the staminodial whorl that is present in Xyris and some species of Abolboda (Table 2).…”