An Experimental Study of the Effect of Lizards on Web‐Spider Communities
1988
Spiller, David A. | Schoener, Thomas W.
To determine the effect of lizards on web—spider populations, we conducted an 18—mo field experiment in the Bahamas. Densities of individuals of each common spider species were about three times as high in lizard—removal enclosures as in control enclosures with lizards or in unenclosed plots with lizards; spider densities in control enclosures and unenclosed plots were nearly identical. In the most common spider species, Metepeira datona, lizards reduced juvenile and adult abundance, as well as adult female survivorship and prey consumption. Numbers of spider species were higher where lizards were removed than where they were present; hence, lizards did not promote spider species coexistence in this system. Numbers and biomasses of aerial insects caught in sticky traps were higher in lizard—removal enclosures than in controls; hence, higher spider predation on insects where lizards had been removed did not completely compensate for the lack of lizards. Comparisons between control enclosures and unenclosed plots revealed that the enclosures reduced insect numbers and biomasses. This study and others have demonstrated that lizards play a major role in structuring web—spider communities in the West Indies. Several lines of evidence indicate that predation is the major interaction between lizards and spiders, although some evidence for competition also exists.
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