Print PageFunctional diversity (FD) is a dimension of biodiversity directly related to the adaptation and function of organisms in their environment, which is well suited to reveal the mechanisms by which communities respond to disturbance. We monitored the response of spider FD to fire in grasslands of South Brazil (Campos). Our goals were to: (1) investigate resilience of spider community at different time intervals after fire (a.f.); and (2) detect relationships between spiders and plant functional traits. Our experiment comprised 14 paired plots (10 m2); one plot per pair was burned in late spring 2009, and the other served as a control. Spiders were sampled with pitfall traps and sweep nets in all plots at one, six and twelve months a.f. A total of 1755 individuals representing 23 families were collected. Four feeding strategy traits were assigned based on family affiliation, representative of guilds, and four morphological traits were measured directly on each individual. Plants were sampled nine months a.f.; three life form and four morphological traits were attributed for each of the 47 plant species. FD and Community Weighted Mean of the trait values were calculated for spiders and for plants.
Results/Conclusions
Spider communities were very resilient to fire disturbance with respect to family diversity, overall abundance, and FD. These diversity measures did not differ between treatments for any time interval since burning. The analysis of spider’s CWM traits revealed positive effects of fire on chelicerae size and vegetation hunters (one month a.f.), and on orb web builders (six months a.f.), and negative effects on irregular web builders (one month a.f.) and ground hunters (six months a.f.). Co-inertia analysis of plant and spider traits (six months a.f.) showed significant relationships between the two trophic levels in terms of post fire dynamics. Taller plants and graminoids were associated with unburned plots, along with ground hunters. In contrast, rosette plants, plants with broader leaves and orb web builders were favored in burned sites. Partial correlations between trait-based spider communities and plant ecological gradients revealed trait-convergence of ground hunters to plant biomass, and of orb web builders, eye and spider chelicerae to plant FD. Trait-divergence was found for spider FD (subset of optimal traits) and plant FD. These results illustrate the direct effects of the habitat structure determined by fire on spider communities and contribute to a better understanding of the ecological effects of disturbance.
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