The Ecology of Saltmarsh Acarina

Abstract

A study was made of the acarine communities of 2 saltmarsh zones at Llanrhidian, South Wales. An analysis of variance on preliminary samples showed both the landward (Plot A) and seaward (Plot B) sampling areas to be basically homogenous with some evidence of a microgradient of density from sea to land in Plot A. Seasonal variations in the densities of the mite populations were plotted for both areas. It was found that mite numbers reached their peak in Aug. and fluctuations are attributed to the effects of soil moisture originating both from precipitation and the tidal effect. Moisture level had a more significant effect in Plot B. There was often a lapse in the attainment of peak populations of the same species in the different plots. The sex ratios of a number of Mesostigmata were plotted throughout the year and seasonal fluctuations in the relative abundances of the sexes were evident. There was a complete absence of any males of any species during the months of Jan. and Feb. in Plot A. Only with Halolaelaps nodosus did the numbers of males exceed the numbers females at any time. A comparison of the 2 plots on the basis of presence or absence, dominance and frequency of the acarine species was made. It was found that Hygroribates schneideri was the most frequently occurring and dominant species of Plot A, whereas Punctoribates quadrivertex was the dominant species of Plot B. Leio seius salinus was the most important acarine predator for both plots. The species associations of each of the plots were calculated. It was concluded that Plot B contains a more closely knit microarthropod community than Plot A.