Evolution of floral morphology in Brunsvigia and Crossyne (Amaryllidaceae)

Abstract

Floral morphology and its relationship to pollination syndromes is examined, for the genera Brunsvigia and Crossyne (Amaryllidaceae). These two genera have similar vegetative morphologies and share the same mode of seed dispersal (anemogeochory). They differ in their floral and inflorescence structures. The species Brunsvigia bosmaniae and Crossyne flava are chosen as representative species of the two genera Brunsvigia and Crossyne. Floral morphology is studied in relationship to an outgroup species Nerine humilis. Pollination syndrome, ability to self-pollinate, levels of natural seed set and patterns of seed dispersal are studied so that reproductive strategies pf the two species can be compared. Crossyne flava is pollinated by a suite of small diurnal insects and can be considered to have a generalist pollination syndrome. The first observation of pollination by moths in Brunsvigia bosmaniae is reported. I show that neither species is able to self, hence pollination events are important. Experimental manipulation reveals that Brunsvigia bosmaniae is pollinator limited. Although this experimental manipulation was not possible for Crossyne flava, high seed set levels in Crossyne flava suggests that levels of pollination are high in Crossyne and low for Brunsvigia. The amount of pollination that takes place is shown to be closely related to floral morphology. Floral divergence of the two genera is thus proposed to be the result of adaptation to a pollinator driven selective regime.