Pollination biology and evolutionary history of angraecoid orchids: from Darwin to the present day

[Extract] Pollination systems provide unique opportunities to establish clear connections between the ecological bases of phenotypic differentiation and the establishment of prezygotic barriers, reproductive isolation, and speciation (e.g. Bradshaw and Schemske 2003, Rundle and Nosil 2005; Rieseberg and Willis 2007; Whittall and Hodges 2007; Hodges and Derieg 2009; Ramírez et al. 2011b). No other plant family shows as wide an assortment of mutualistic interactions with insect pollinators as the Orchidaceae. With the 1862 publication of On the Various Contrivances by which British and Foreign Orchids Are Fertilised by Insects, and on the Good Effects of Intercrossing, Charles Darwin first demonstrated that orchids provide strong evidence for adaptations that promote cross-pollination. It is now acknowledged that within the orchid family, pollinators have probably played a crucial role in the unprecedented diversification of the extant floral forms (e.g. van der Pijl and Dodson 1966; Tremblay 1992; Johnson et al. 2005; Ramírez et al. 2011a,b), resulting in more that 25000 species (Chase et al. 2003; Govaerts et al. 2012)