Adaptations for insect‐trapping in brood‐site pollinated Colocasia (Araceae)

Abstract

The Araceae include both taxa with rewarding and deceptive trap pollination systems. Here we report on a genus in which rewarding and imprisonment of the pollinators co-occur. We studied the pollination of four species of Colocasia in Southwest China and investigated the morpho-anatomical adaptations of the spathe related to the attraction and capture of pollinators. All four species were pollinated by drosophilid flies of the genus Colocasiomyia. The flies are temporally arrested within the inflorescence and departure is only possible after pollen release. Trapping of the flies is accomplished by the closure of the spathe during anthesis. Moreover, in two species the spathe is covered with papillate epidermal cells known to form slippery surfaces in deceptive traps of Araceae. However, in Colocasia the papillae proved not slippery for the flies. The morpho-anatomical properties of the spathe epidermis indicate that it is an elaborate osmophore and serves for the emission of odours only. Despite its similarity to deceptive traps of other aroids, Colocasia and Colocasiomyia have a close symbiotic relationship, as the attracted flies use the inflorescence as a site for mating and breeding. The trap mechanism has presumably evolved independently in Colocasia and is supposed to facilitate more efficient pollen export.

Floral diversity and pollination strategies of three rheophytic Schismatoglottideae (Araceae)

“…In other Colocasiomyia ‐pollinated Araceae a shift to flowering at dusk has been observed in Colocasia affinis Schott, whereas C. esculenta (L.) Schott, C. fontanesii Schott and C. lihengiae C. L. Long & K. M. Liu flower before dawn (Bröderbauer et al . ). However, C. affinis does not occur in the same clade as the other three Colocasia (Nauheimer et al .…”

“…However, in Colocasia Schott, Colocasiomyia are trapped during the pistillate phase of anthesis by a narrowing of the spathe constriction, which then reopens at the end of the pistillate phase, enabling the trapped flies to access the staminate flowers (Bröderbauer et al . ). In Arisaema Mart.…”

Plant-pollinator interactions in East Asia: a review

“…Non-rewarding specialized pollination systems involving Drosophilidae have been reported among the Orchidaceae (Liu et al 2010;Li et al 2012;Suetsugu 2018). Brood-site pollination by Drosophilidae was reported in Araceae (Miyake & Yafuso 2003;Takenaka et al 2006;Bröderbauer et al 2014). Flowers of a water lily, Nuphar subintegerrima (Nymphaeaceae), are visited by ephydrid flies that mate and oviposit in the flowers (Nagasaki 2007).…”

A review of taxonomy and flower-breeding ecology of the Colocasiomyia toshiokai species group (Diptera: Drosophilidae), with description of a new species from Indonesia

“…The constriction in the spathe between the staminate and pistillate regions of the spadix is seen in many genera of Araceae (Bröderbauer et al, 2012;Wong et al, 2013). Spathe constriction facilitates effective pollination by specifi c insects (e.g., Takenaka, 2006;Bröderbauer et al, 2014) but restricts access by non-pollinators to the pistillate region (e.g., Takano et al, 2012) by functioning as a sieve (Low et al, 2016). The spathe is swollen below the constriction (Figs S5B, S9, S10).…”