Interpopulation variation in kairomone use by Cyrba algerina, an araneophagic jumping spider from Portugal

Geographic variation in a predator’s reliance on kairomones from prey was investigated. The predator studied, Cyrba algerina, is an araneophagic (spider-eating) jumping spider (Salticidae) and the prey were oecobiid spiders (Oecobiidae). There were two study sites (Sintra and Tavira), both in Portugal. Oecobius machadoi was a common oecobiid in Sintra, but no oecobiids were found in Tavira. Staged encounters showed that oecobiid-specific prey-capture behaviour was adopted by the C. algerina in Sintra but not in Tavira. In experiments using a Y-shaped olfactometer, significantly more Sintra C. algerina individuals chose the side with oecobiid odour instead of the blank side when the odour came from females of a sympatric species (O. machadoi), but not when the odour came from O. machadoi males or from females of an allopatric species (O. amboseli). Regardless of whether the odour came from O. machadoi or O. amboseli, the Tavira C. algerina did not choose the odour side significantly more often than the blank side. These findings suggest that, in Sintra, C. algerina is locally adapted to a locally abundant oecobiid species. Whether this example of geographic variation in kairomone use is a behavioural ecotype or instead an instance of phenotypic plasticity is currently unknown.