Dynamics of within-leaf spatial distribution patterns of greenhouse whiteflies and the biological interpretations.
Abstract
A biological interpretation was made of spatial distributions of the aleyrodid Trialeurodes vaporariorum reared on Phaseolus vulgaris from various aggregation indices. Adults were more aggregated than all the other stages (a′ (log a) and b of L.R. Taylor (1965) were equal to 0.4642 and 1.2617, respectively). This is due to pairing and the tendency of T. vaporariorum to feed near the major veins of the leaves. Grouping of individuals was moderate while the distribution of the groups was most highly aggregated. Eggs were laid in clusters, grouping of individuals was increased and the clusters were relatively sparsely distributed. As a whole, aggregation was decreased (a′=0.3582, b=1.1496), yet higher than all nymphal stages. Due to the relatively high mortality rate (18.6%) in the early nymphal stages and the density dependent dispersal of the 1st-instar nymphs, the 3rd-instar nymphs were much less aggregated (a′=0.1092, b=1.0610). During the later nymphal stages, the nymphs suffered a high mortality rate (22.8%), which was density and crowding dependent. By the method of Taylor, the populations were approaching random but still with some degree of aggregation (a′=0.0880, b=1.0518). In fact, most populations were random, but some were not. However, S. Iwao's (1968) regression appears to be linear only when Taylor's b=1 or 2. In this case, some relationships are apparently not linear, especially with adults and early stages. Thus, interpretation of the parameters α and β is questionable.