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Title: Low Frequency of Stabilimenta in Orb Webs of Argiope appensa (Araneae: Araneidae) from Guam: An Indirect Effect of an Introduced Avian Predator
Authors: Kerr, Alexander M.
Issue Date: Oct-1993
Publisher: University of Hawaii Press
Citation: Kerr AM. 1993. Low frequency of stabilimenta in orb webs of Argiope appensa (Araneae: Araneidae) from Guam: an indirect effect of an introduced avian predator. Pac Sci 47(4): 328-337.
Abstract: The occurrence and patterns of stabilimenta in 1195 webs of the
orb weaver Argiope appensa (Walckenaer) from four islands in the Mariana
Archipelago were recorded. Webs on the largest and southernmost island,
Guam, had significantly fewer stabilimenta (16.4%, n = 359) than webs of
conspecifics from the neighboring islands of Rota (56.9%, n = 211), Tinian
(41.9%, n = 315), and Saipan (50.3%, n = 310), as well as from webs of Argiope
spp. worldwide (47.8%, n = 5662). The differences in stabilimentum frequency
in webs between sites in the Marianas were not correlated with vegetation, light
levels, the distribution of individuals within web size classes, or the presence of
certain stabilimentum patterns. Factors operating at scales smaller than the
sample sites may influence stabilimentum frequency, because several locations
showed nonrandom clumping of decorated webs. One theory for the function
of stabilimenta is that they reduce damage to the web by warning flying birds of
the web's location. Because Guam's native birds have been eliminated recently
by the introduction of the brown tree snake, Boiga irregularis (Merrem), the low
frequency of decorated webs of A. appensa on Guam might, therefore, be either
a behavioral response to the avian extinctions or a result of reduced selection
for stabilimenta in the absence of birds.
ISSN: 0030-8870
Appears in Collections:Pacific Science Volume 47, Number 4, 1993

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