Importance of using many taxa and having adequate controls for monitoring impacts of fire for arthropod conservation

Abstract

Fire is a key natural and anthropogenic disturbance factor across many ecosystems, and also an important conservation management tool. However, little is known about arthropod responses to fire, particularly in Mediterranean-type ecosystems, including the biodiverse Cape Floristic Region (CFR). We investigate here the relative variety of responses by different arthropod taxa to fire, and ask whether single-taxon or multi-taxa approaches better suit post-fire biomonitoring for conservation management. Sampling involved multiple techniques and was conducted before fire, 1 year after fire, and 3 years after fire, with unburned areas as controls. Before-and-after statistics were used to identify changes in arthropod populations and assemblages as a result of fire, and between treatment and control sites. However, this was against a background of the annual effects having a major influence on the arthropods, irrespective of fire. Abundance was so variable, even in control plots, that we found it an unreliable indicator of the impact of fire. Overall, arthropods were remarkably resilient to fire, with most taxa recovering in species richness and assemblage composition within 3 years of the fire. Although all taxa showed resilience to fire, there was nevertheless little congruence in temporal recovery of the various taxa. Our results highlight the shortcomings of monitoring fire impacts using only a single-taxon without prior testing for complementarity or sensitivity to fire, while emphasizing the importance of sampling a wide range of taxa to represent overall responses of compositional biodiversity. From this, we recommend, at least for the CFR, that a cross-section of taxa, such as butterflies, ants, and scarab beetles, be used for monitoring arthropods in recovery/fire management conservation programmes. We also recommend that such monitoring be considered against the background of large annual variation seen in unburned areas.

Effects of a fast-burning spring fire on the ground-dwelling spider assemblages (Arachnida: Araneae) in a central South African grassland habitat

“…Pryke and Samways (2012) suggested that fires in grasslands require arthropods to recolonise or re-emerge over a much larger spatial scale, as most of the above-ground biomass is removed. We found that, although fire interacts with time to affect spider abundance and richness, there was little evidence to suggest that this fire had a significant large-scale impact on spider diversity.…”

“…are able to exploit microrefugia to escape fires. While insects can escape fires through flight, non-flying arthropods are dependent on other strategies to survive, including exploiting microrefugia such as bush clumps, rocks and marshy areas (Uys et al 2006;Pryke and Samways 2012), burrows (Dippenaar-Schoeman 2002) or moving beneath the soil surface (Villani et al 1999). Temperatures in the soil stay relatively low, even when there is a fire, enabling survival of soil invertebrates (Tainton and Mentis 1984).…”

“…Taking a multiple taxon approach to assess fire effects is critical, as different groups show contrasting responses and a variety of taxa can better indicate overall responses of compositional biodiversity than single taxa (Pryke and Samways 2012). The focus of the current study was to assess the effects on the ground-dwelling spider communities in the reserve; data on mites (Hugo-Coetzee and Avenant 2011) and small mammals (Avenant and Schulze 2012) have been dealt with separately.…”

“…It is therefore critical to consider the effects that different disturbances may have on them (Gerlach et al 2013). Even though some invertebrates have adaptations to fire by, for example, being able to flee or seek refuge (Uys et al 2006;Pryke and Samways 2012), there may be considerable short-term (Hartley et al 2007) and long-term (Nekola 2002;Lubin and Crouch 2003;Elia et al 2012) local declines of invertebrate species. Notably, the season of fires may significantly affect some macroarthropods (Ford 2007;Johnson et al 2008), but has little effect on microarthropods such as mites and springtails (Barratt et al 2006;Hugo-Coetzee and Avenant 2011).…”

Short-term effects of fire on Papilionoidea (Lepidoptera) communities: a pilot study in Mediterranean maquis shrubland

“…Some insects, including ants, are very resilient to fire, and show no change in species richness following fire in tropical savanna, but they often undergo significant increases in abundance (Parr & Andersen 2008;Vasconcelos et al 2009). In contrast, other species of Hymenoptera (wasps and bees) and Orthoptera (crickets), as well as other arthropods, such as chilopods (centipedes) and terrestrial crustaceans, show no changes in richness and abundance after fire in the same environment (Andersen & Müller 2000;Pryke & Samways 2012). However, another study, although in agreement with these results about the surface fire (persistence of tree canopy), showed that centipede communities affected by canopy fire (complete vegetation destruction) were simply structured and poor in both species richness and diversity (Trucchi et al 2009), whereas isopods and springtails take advantage of fire in oak and pine forests, showing higher values of Shannon diversity and evenness than in unburned forests, even if no differences were reported for richness in pine forests (Pitzalis et al 2005).…”