Dispersal of the Solitary Coral Balanophyllia Elegans by Demersal Planular Larvae
1981
Gerrodette, Tim
The solitary scleractinian coral Balanophyllia elegans has nonpelagic planulae which remain on the bottom for several days before attaching and undergoing metamorphosis. Laboratory observations and field experiments suggest that the mean larval dispersal distance is <0.5 m from the parent. An isolated, 16—yr—old artificial reef has not been colonized by B. elegans, although a breeding population is present 4 km away and transplant experiments showed that the species can live and reproduce there. The corals tend to be spatially aggregated, which may result from their very limited dispersal. The dispersal of B. elegans planulae from a point source on a large settling plant placed on the sea bottom can be described by a diffusion model assuming random movement and settling behavior of the larvae. The maximum rate at which the species can spread demersally, even assuming exponential population growth is occurring, is calculated to be <0.1 m/yr. Since such a rate would not allow dispersal over the coral's 2000—km range even over evolutionary time, occasional dispersal by other means is considered probable. Previous observations of morphological variation in B. elegans may be related to low rates of gene flow in this species with demersal larvae and sessile adults. Distributions of other Balanophyllia species in the eastern Pacific suggest that limited dispersal ability may have played a role in the evolution of this genus.
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