Silk decorations in Argiope spiders: Consolidation of pattern variation and specific signal function

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The silk decorations in the webs of many orb-weaving spiders are considered visual signals. However, high variation in the arrangement of the extra silk bands reduces the plausibility of a single signal function. The current literature presents a range of functional explanations that are often contradicting. One of the main reasons for the controversy is a confusion about whether a specific web decoration shape may be linked to a specific signal function or how otherwise various silk band arrangements can serve one and the same signal function. I here studied the inherent characteristics of the variation of silk decoration shapes in Argiope bruennichi, in the field and under invariant laboratory conditions. The aim was to detect a potential preference for particular decorations shapes and, accordingly, the predictability of variation to infer conclusions on signal functionality. The results show, that even within a few days and with a small repertoire of options, A. bruennichi frequently varies the decoration shape intra-individually. However, both field and laboratory data reveal that this variation follows a predictable pattern and is significantly differing from random. Spiders show a preference for two-banded decorations and omit decorating altogether rather than building one-banded decorations. Irrespective of the actual signal function of web decorations, my results indicate that the shape of web decorations matters, indirectly also supporting the idea of a single signal function in spite of the presence of pattern variability. Previous studies demonstrated that this variation might be important for the maintenance of the signal effect through an avoidance of receiver learning, and my results support this. Finally, I discuss potential reasons for the proximate emergence of the observed decoration pattern variability.
TidsskriftJournal of Arachnology
Sider (fra-til)271-275
StatusUdgivet - 2019

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