Seed Production, Pollinator Attractants and Breeding System in Relation to Fire Response — Are There Reproductive Syndromes among Co-occurring Proteaceous Shrubs?

Abstract

The reproductive biology of two species pairs was compared, one member of which (Dryandra sessilis (Knight) Domin, Hakea erinacea Meissner) is susceptible to severe stress and disturbance by fire (nonsprouter) and stores few seeds in its crown, while the other (D. lindleyana Meissner, H. cristata R.Br.) is resilient (resprouter) and also stores most of its seeds for some years. It was hypothesised that the nonsprouter would have a high annual seed production associated with a suite of attributes directed towards that end (forming a reproductive syndrome), and that the resprouter would have the reverse properties. Over 30 attributes were assessed, covering putative pollinators, pollinator attractants and rewards, flower phenology, breeding system, and flower, fruit and seed production. Dryandra sessilis produced far more seeds than D. lindleyana, due to prolific flower production and a high fruit : flower ratio (associated with an effective outcrossing breeding system). Hakea erinacea produced significantly more seeds than H. cristata, which was attributable to its smaller fruits and exceptionally high fruit : flower ratio (associated with highly effective selfing). The correlation of seed production and fruit : flower ratio with susceptibility to fire was not supported by any consistent pattern among the other reproductive attributes.