Wandering spiders recover more slowly than web-building spiders after fire.

Abstract

Fire is a natural feature of many ecosystems, with some vegetation types highly adapted to fire. However, very little is known about the effect of fire on spiders, especially as fires have become more frequent owing to human activity. We determine whether different spider functional guilds (web builders vs. wanderers) respond differently to fires in the sclerophyllous fynbos. We determine also the effect of rockiness as refuge for these guilds and whether it influences their post-fire recovery. There were three site categories of time-since-last fire: 3 months, 1 year, and 7 years. We found that fire caused a decline in spider richness and abundance, with the 3-month category supporting the lowest. In sites that were burned within 1 year, abundance of wanderers was as high as in sites that had 7 years to recover, whereas species richness and abundance of web builders in sites that were burned 1 year ago were as low as in recently burned sites. However, assemblages of wanderers differed among categories, while no differences were observed for web builders, highlighting that wanderers took longer time to recover than web builders. Species richness and abundance of both guilds were not affected by different levels of rockiness. However, rockiness is important in shaping assemblages of wanderers. The results emphasize that the assemblages of greatest conservation concern with increased fire frequencies are wanderers and are candidate surrogates for monitoring post-fire recovery. These results highlight the need to allow fynbos vegetation to recover fully between fire intervals and draws attention to the dangers of frequent unplanned fires.