Testing the assumptions of the pyrodiversity begets biodiversity hypothesis for termites in semi-arid Australia

Abstract

Fire shapes the composition and functioning of ecosystems globally. In many regions, fire is actively managed to create diverse patch mosaics of fire-ages under the assumption that a diversity of post-fire-age classes will provide a greater variety of habitats, thereby enabling species with differing habitat requirements to coexist, and enhancing species diversity (the pyrodiversity begets biodiversity hypothesis). However, studies provide mixed support for this hypothesis. Here, using termite communities in a semi-arid region of southeast Australia, we test four key assumptions of the pyrodiversity begets biodiversity hypothesis (i) that fire shapes vegetation structure over sufficient time frames to influence species' occurrence, (ii) that animal species are linked to resources that are themselves shaped by fire and that peak at different times since fire, (iii) that species’ probability of occurrence or abundance peaks at varying times since fire and (iv) that providing a diversity of fire-ages increases species diversity at the landscape scale. Termite species and habitat elements were sampled in 100 sites across a range of fire-ages, nested within 20 landscapes chosen to represent a gradient of low to high pyrodiversity. We used regression modelling to explore relationships between termites, habitat and fire. Fire affected two habitat elements (coarse woody debris and the cover of woody vegetation) that were associated with the probability of occurrence of three termite species and overall species richness, thus supporting the first two assumptions of the pyrodiversity hypothesis. However, this did not result in those species or species richness being affected by fire history per se. Consequently, landscapes with a low diversity of fire histories had similar numbers of termite species as landscapes with high pyrodiversity. Our work suggests that encouraging a diversity of fire-ages for enhancing termite species richness in this study region is not necessary.

Fire as a key driver of Earth's biodiversity

“…() also noted that species diversity should be greatest with a mixture of patches at different fire frequencies as the extremes were quite different in species composition (although any effect of patch size on S was not considered). Others have observed no effect (Davis et al, ) or a negative effect (Bassett et al, ; Foster et al, ). The extent to which this fails to support intermediate P as maximizing biodiversity due to ( i ) testing an inadequate range of P , thus observing only part of the ‘hump’, ( ii ) not using a fixed reference area, thus not appreciating that increasing patch type is at the expense of patch area and thus species—area limitations come into play, or ( iii ) using different indices of P and diversity, requires further investigation.…”

Fire and Its Interactions With Other Drivers Shape a Distinctive, Semi-Arid ‘Mallee’ Ecosystem

“…In the Murray Mallee, an examination of 21 species of invertebrates from key groups (psyllids, termites, scorpions, centipedes) in Triodia and Chenopod Mallee did not detect any species exhibiting a significant response across a 100year chronosequence (Avitabile, 2010). Many termite species nest in subterranean burrows and appear resilient to fire (Avitabile et al, 2015;Davis et al, 2018). In mallee vegetation of the Eyre Peninsula, South Australia, Teasedale et al (2013) found no difference in abundance between post-fire age classes for 15 orders of invertebrates; but, at a finer resolution, 17 morphospecies did show such variation.…”

Animal movements in fire‐prone landscapes

“…We consider movements in relation to two broad classes of fire‐induced change: ( i ) abrupt changes that occur during and immediately following a fire, in which large amounts of biomass are incinerated, often resulting in radical changes in vegetation structure (Section II), and ( ii ) the longer‐term successional changes that occur in the period following fire (Sections III and IV), in which vegetation gradually returns in a process that can continue for decades or even centuries (Haslem et al ., ; Davis et al ., ). We consider how fire affects movement among habitat patches of differing fire histories that occur across a range of spatial and temporal scales (Fig.…”