Only multi-taxon studies show the full range of arthropod responses to fire

Abstract

Fire is a major driver in many ecosystems. Yet, little is known about how different ground-living arthropods survive fire. Using three sampling methods, and time-since-fire (last fire event: 3 months, 1 year, and 7 years), we investigate how ground-living arthropod diversity responds to fire, and how species richness, diversity, abundance, and composition of the four dominant taxa: ants, beetles, cockroaches and mites, respond. We did this in the naturally fire-prone Mediterranean-type scrubland vegetation (fynbos) of the Cape Floristic Region. Surprisingly, overall species richness and diversity was the same for all time-since-fire categories. However, when each dominant taxon was analysed separately, effect of fire on species richness and abundance varied among taxa. This emphasizes that many taxa must be investigated to really understand fire-driven events. We also highlight the importance of using different diversity measures, as fire did not influence species richness and abundance of particular taxa, while it affected others, overall greatly affecting assemblages of all taxa. Rockiness affected species richness, abundance and composition of a few taxa. We found that all time-since-fire categories supported distinctive assemblages. Some indicator species occurred across all time-since-fire categories, while others were restricted to a single time-since-fire category, showing that there is a wide range of responses to fire between taxa. Details of local landscape structure, abiotic and biotic, and frequency and intensity of fire add complexity to the fire-arthropod interaction. Overall, we show that the relationship between fire and arthropods is phylogenetically constrained, having been honed by many millennia of fire events, and highly complex. Present-day species manifest a variety of adaptations for surviving the great natural selective force of fire.

Congruence between arthropod and plant diversity in a biodiversity hotspot largely driven by underlying abiotic factors

“…If reseeding species do not have enough time between fires to mature and set seed again, repeated short-term fires can have a negative impact on these species (van Wilgen and Forsyth 1992). For arthropods, these results should be interpreted with caution, as there is still a great lack in research on proper implementation of the fire regime (frequency, intensity, season, and size) on fauna (particularly arthropods) in South Africa (Parr and Chown 2003, but see Pryke and Samways 2012, Yekwayo et al 2018.…”

Refuges from fire maintain pollinator–plant interaction networks

“…Conservation of flower-visiting insects, along with much other biodiversity (Pryke & Samways, 2012a,2012bYekwayo et al, 2018), appears to be naturally adapted to these retreats from fire, enabling populations to survive in patches even when much of the area burns. Refuges can be part of this loss reduction, with our fire refuges being, in effect, temporary holding areas into which the flower-visiting insects can retreat while the burned matrix goes through regrowth and succession as part of natural ecosystem recovery.…”

“…It is also promoted by the cragginess of the topography in this system, which provides natural fire refuge areas. Conservation of flower-visiting insects, along with much other biodiversity (Pryke & Samways, 2012a,2012bYekwayo et al, 2018), appears to be naturally adapted to these retreats from fire, enabling populations to survive in patches even when much of the area burns. In turn, it is conceivable in evolutionary terms that this has not only contributed to the generation of high flower diversity in the area, but also that of their insect mutualists.…”

“…Also, specialist bee species decline more than generalists in freshly burned habitat (Peralta, Stevani, Chacoff, Dorado, & Vázquez, 2017). This is seen in South Africa, where the composition of the butterfly assemblage changed over the period of recovery following a major fire event (Pryke & Samways, 2009;Yekwayo, Pryke, Gaigher, & Samways, 2018). Over the postfire period, fire usually transforms landscapes into more open habitat, which may change species composition over time (Case & Staver, 2017).…”

“…Over the postfire period, fire usually transforms landscapes into more open habitat, which may change species composition over time (Case & Staver, 2017). This is seen in South Africa, where the composition of the butterfly assemblage changed over the period of recovery following a major fire event (Pryke & Samways, 2009;Yekwayo, Pryke, Gaigher, & Samways, 2018).…”