Population-dispersion inTellina Tenuisda Costa

Abstract

A population of the lamellibranchTellina tenuisin the Exe estuary is shown to be uniformly distributed, indicating a significant degree of ‘over-dispersion’.By plotting the position of each shell in squares ofm.2area it is shown that fewer individuals than would be expected occur less than 1 in. from their nearest neighbour, and none occurs closer than 0·6 in.When the population density was artificially increased on the shore the same characteristic spacing was found at a moderate density, but not at a rather higher density.It is suggested that spacing is correlated with the foraging activities of the inhalent siphon on the soil surface.Very dense populations have been found by Stephen in other areas, indicating that the size of the ‘territory’ does not limit density. His results show no evidence of the same phenomena as observed in the Exe.