Contrasting floral biology of Artabotrys species (Annonaceae): Implications for the evolution of pollinator trapping

Abstract

Artabotrys comprises a species-poor early divergent grade (EDG) and a main species-rich clade ("main Artabotrys clade," MAC). All members of the MAC exhibit a remarkably well-conserved floral Bauplan characterized by a tightly enclosed floral chamber with an elaborate rim between the inner petal blade and claw. Conversely, EDG resembles the sister genus Xylopia in lacking the inner petal rim, with one species (Artabotrys brachypetalus) bearing petals that lack the distinction between blade and claw altogether. The floral phenology and pollination ecology of two exemplar species-Artabotrys brachypetalus from the EDG and Artabotrys blumei from the MAC-are compared, including assessment of effective pollinators and their activity patterns, scent chemistry and thermogenesis. Our study revealed that Artabotrys blumei exhibits abbreviated anthesis (c. 27 hr), with a floral phenology and morphology that are clearly consistent with pollinator trapping, and may be pollinated by small beetles. Artabotrys brachypetalus has a typical anthetic duration (c. 45 hr), lacks a pollinator trapping mechanism, and is pollinated by honey bees and curculionid beetles. The "xylopioid" traits of the EDG are likely to be plesiomorphic, whereas the tightly enclosed floral chamber is likely to be apomorphic for the MAC and functionally significant in trapping pollinators.

Reproductive biology of the South American cycad Zamia boliviana, involving brood‐site pollination

“…A number of pollination mechanisms in cycads and palms have provided direct or indirect evidence for a framework of interactions, which combines morphology attributes involving beetle‐pollinated species (Barfod et al, 2011). The most common beetle visitors of cycads strobilis, palm flowers and Annonaceae species are the weevils from the Curculionidae family (Barfod et al, 2011; Chen, Liu, & Saunders, 2020). Exclusive pollination by beetles (or more rarely thrips) that breed on plant tissues is a common condition in palms (De Medeiros et al, 2019), as in Zamiaceae species (Segalla et al, 2019).…”

“…Studies on the ecology and evolution of brood‐site pollination mutualisms and associations may provide new insights into the evolutionary history (e.g., conditions in which these interactions are favored, according to De Medeiros et al, 2019; Chen et al, 2020). In the current global scenario of species loss, vulnerability and their intricate pollination systems, such as New World cycads, such studies are fundamental to direct applicability of conservation (de Medeiros et al, 2019; Nunes, Maruyama, Azevedo‐Silva, & Sazima, 2018; Roemer et al, 2008; Tang, Xu, et al, 2018).…”

Artabotrys chitkokoi (Annonaceae), a new species discovered in Sagaing Region, Myanmar

“…Apart from the distinctive inflorescence hooks, the genus often possesses a raised midrib on the leaves (Turner and Utteridge 2015). The petals of Artabotrys can be divided into two parts: an upper, generally laminar (or terete) region known as the blade, and a basal, concave region known as the claw (Chen et al 2020). In Myanmar, the genus is represented by seven species (viz.…”

New species and new records of Artabotrys (Annonaceae) from peninsular Thailand

“…The outer and inner petals are generally similar in size whereas the sepals are much smaller than the petals. MAC species are characterised by petals with a distinct upper blade and a basal concave claw, and an elaborate rim between the inner petal blade and claw which enables the inner petals to cohere tightly over the reproductive organs (Chen et al 2020). Conversely, EDG species lack a projecting rim on the inner petals, with one species (A. brachypetalus Benth.)…”

“…Conversely, EDG species lack a projecting rim on the inner petals, with one species (A. brachypetalus Benth.) entirely lacking the distinction between petal blade and claw (Chen et al 2020). The flowers of Artabotrys are hermaphroditic, with many stamens and few to many unfused carpels.…”