Evolutionary History of Poales

Abstract

▪ Abstract The predominantly wind-pollinated order Poales includes about one third of all monocot (Angiosperm) species, with c. 20,000 species dominating modern savanna and steppe vegetation. Recent improvements in understanding relationships within the order allow phylogenetic optimizations of habitat preferences and adaptive character states, enabling exploration of the factors that have influenced evolution in this successful order. Poales probably originated in the late Cretaceous in wet nutrient–poor sunny habitats. By the Paleogene the lineage had diversified into swamps, the forest understory, epiphytic habitats, and nutrient-poor heathlands. The Neogene saw major diversifications of the grasses and possibly the sedges into fire-adapted vegetation in seasonal climates and low atmospheric CO2. Diversification into these habitats was facilitated by morphological features such as the sympodial habit and physiological factors that allowed frequent evolution of CO2-concentrating mechanisms.

Anatomy of the floral scape of Bromeliaceae

“…Harms & Mildbraed that occurs in West Africa (Smith and Till 1998). It is included in the order Poales (APG II 2003), close to the Typhaceae (Typha e Sparganium) and Rapateaceae (Bremer 2002, Davis et al 2004, Linder & Rudall 2005, and has traditionally been divided in to three subfamilies: Pitcairnioideae, Tillandsioideae and Bromelioideae, according to the growth habit, the ovary position and fruit and seed morphology (Smith & Downs 1974, 1977. Recent phylogenetic analyses (Crayn et al 2000, Horres et al 2000, Barfuss et al 2005 confirmed the monophyly of the Bromelioideae and Tillandsioideae, but indicated the Pitcairnioideae as a polyphyletic group (Crayn et al 2000, Horres et al 2000.…”

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

“…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). Our results show that the nectariferous stylar appendages that characterize some Xyridaceae (except Xyris and Achlyphila: Table 3) are vascularized by dorsal carpellary bundles and have a similar early ontogeny.…”

“…Another commelinid family with only three stamens, Mayacaceae (with a single genus, Mayaca), was formerly included among the xyrids (e.g. Linder and Rudall 2005), but a recent molecular analysis (BouchenakKhelladi et al 2014) has tentatively placed Mayacaceae closer to Rapateaceae (Fig. 1).…”

“…Many Poales are characterized by flowers that differ from ''typical'' monocot flowers in several traits that are sometimes associated with wind pollination. 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).…”

“…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). Both Abolbodoideae (Xyridaceae) and Paepalanthoideae (Eriocaulaceae) have flowers with stylar appendages that produce nectar, which is used as a resource by insect pollinators (Rosa and Scatena 2007;Oriani et al 2009;Scatena 2011, 2012).…”