Begonia involucrata Leibm. is a neotropical herbaceous understory plant in the family Begoniaceae.The genus Begonia is one of the largest genera of angiosperms, with over 1500 species (Twyford 2012).In the neotropics, Begonia is represented by 600+ species and found from northern Mexico to southern South America (Burt-Utley and Utley 2011).Begonia involucrata is endemic to Costa Rica and theChiriquiregion of Panama in mid-elevation moist and wet forests (Burt-Utley 1985).B. involucrata is monoecious (bearing separate male and female flowers on the same plant) and protandrous (producing male flowers first), with male and then female flowers appearing on several inflorescences which project above the level of the leaves between December and April (Argen and Schemske 1991).The flower is composed of two white to rose colored petaloid sepals and the yellow male or female reproductive parts.Under ultraviolet light, the flower appears as a target, improving pollinator attraction (Schemske and Argen 1995).B. involucrata is pollinated by several species of moderate sized bees.The flower only offers pollen as a reward to pollinators.As a result, female B. involucrata flowers rely on intra-species floral mimicry in order to achieve reproductive success (Argen and Schemske 1991).B. involucrata leaves exhibit palmate venation and have an unusual and variable pattern of drip-tips, with different derived from different primary veins (Zuchowski 2007, Jensen pers. obs.).B. involucrata has winged fruits which are wind dispersed (Burt-Utley 1985), an unusual dispersal mechanism for understory plants, owing to the lack of wind in tropical forest understory.
Begonia involucrata is endemic to mid-elevation forests in Costa Rica and the Chiriqui region of western Panama (Burt-Utley 1985).It is generally found between 1400 and 2000m, but can be found above and below that elevation in areas with favorable microclimate (Burt-Utley 1985).On the Atlantic slope of the Tilaran Mountains of Costa Rica, B. involucrata is found as low as 700m near the Pocosol Field Station in Bosque Eterno de los Ninos (pers. obs.)
Begonia involucrata is found in wet montane forests along the mountainous crest of Costa Rica and Panama, but is rarely found in cloud forest, where other Begonia species are dominant (Burt-Utley 1985).B. involucrata is found in the understory of closed primary forests, as well as on the edges of clearings and in regenerating secondary forest (Argen and Schemske 1991, Zuchowski 2007).
Begonia involucrata is a suffrutescent (having a woody, perennial section at its base) herb, usually less than 1 m tall (Burt-Utley 1985).Leaves are dark green above, with a lighter shade of shiny green on the underside, and up to 20cm long (Zuchowski 2007).Leaves heart shaped, with palmate venation.Variable drip tips, 2-5 per leaf, occurring on different primary veins (Jensen pers. obs., Zuchowski 2007).Stems and petioles are pubescent (finely, but densely hairy) and rust-pink, with triangular stipules clasping the stem (Zuchowski 2007)
Begonia involucrata is dispersed by wind.The fruit is a 3-winged capsul which may contain hundreds of seeds (Burt-Utley 1985, Argen and Schemske 1991).Wind dispersal is an unusual adaptation in the understory of tropical forest, as the air is usually still (Keay 1957). While B. involucrata seeds may be utilized for provisioning by seed predators, this has not been observed.
Begonia involucrata is monoecious and protrandrous, producing one to several cymose inflorescences during the dry season from December through April (Argen and Schemske 1991).Male flowers appear first, and are subsequently replaced by female flowers.There is limited temporal overlap between male and female flowers, helping to insure outcross (Schemske and Argen 1995).Flowers consist of two petaloid sepals about 1-3 cm long ranging from creamy white to rose in color (Burt-Utley 1985). Male sepals are larger than females by about 20% (Argen and Schemske 1991). Both anthers and style are yellow and appear as dark target against the light colored sepals under ultraviolet light (Schemske and Argen 1995). Both male and female flowers also produce pheromones which are attractive to pollinators (Schemske and Argen 1995).
Begonia involucrata is largely bee pollinated.In Monteverde, Costa Rica, pollinators include Trigona grandipennis Schwarz, Melipona fasciata Cockerell, and Bombus ephippiatus Say (Schemske and Argen 1995).B. involucrata does not provide nectar, instead it provisions pollinators with pollen.As female flowers do not provide any resources to pollinators, they act as intraspecies floral mimics (Argen and Schemske 1991).Pollinators seem to be able to distinguish between pollen bearing males and female mimics, visiting male flowers 3 to 9 times more often than female flowers, and staying 10 times longer per visit (Argen and Schemske 1991).However, the rate of fruit set in bee pollinated plants is similar to those pollinated by hand, suggesting that limited visits to female flowers is not a barrier to successful reproduction (Argen and Schemske 1991, Schemske and Argen 1995)
