Can the invasive European rabbit (Oryctolagus cuniculus) assume the soil engineering role of locally-extinct natives?

Abstract

Habitat modifying species can play crucial roles in ecosystem function. Invasive engineers may assume these roles where native engineers have been lost from the system. We compared the dynamics of the foraging pits of an invasive engineer, the European rabbit (Oryctolagus cuniculus) with two native mammals, the greater bilby (Macrotis lagotis) and the burrowing bettong (Bettongia lesueur). Foraging pits are small surface depressions created by animals when they forage for seeds, bulbs, roots, invertebrates and fungi. We measured foraging pit density and turnover, and density and richness of plant seedlings in pits and adjacent surfaces across three landforms representing a gradient in resource availability inside (bilbies and bettongs), and outside (rabbits only) a reserve in an arid Australian shrubland over 2 years. Pits of the native engineers contained 80% more seedlings (11.2 plants m -2 ) than rabbit pits (6.22 plants m -2 ). Further, rabbit pits supported 3.6-times fewer seedlings than equivalent non-pit surfaces outside the exclosure. Only one plant species was restricted entirely to pits. The reserve had more foraging pits and greater turnover than outside, but contrary to prediction, pit effects on seedling density were no greater in the more resource-limited dunes. There were some strong temporal and landscape effects on pit density and species composition, but generally trends were similar inside and outside the reserve. Overall, despite their functional similarities, invasive rabbits created fewer pits that were less favourable patches for seedlings than those of native engineers. Our work suggests that a suite of ecosystem processes associated with fertile patch creation has potentially been lost with the extirpation of bilbies and bettongs.

Mammalian engineers drive soil microbial communities and ecosystem functions across a disturbance gradient

“…native vs. exotic engineers, though see James et al . ) and thus whether a change from echidnas to rabbits might alter soil microbial communities and soil biochemical function.…”

“…Although soil disturbance by ecosystem engineers in drylands has been shown to have relatively large effects on plant community structure (Whitford & Kay ; Eldridge & James ; James et al . ), its effects on soil microbial communities and therefore function are poorly known (though see Eldridge et al . ).…”

Does litter decomposition vary between the foraging pits of two soil‐disturbing mammal species?

“…The loss of soil‐foraging mammals from large parts of arid and semi‐arid Australia could potentially alter carbon and nutrient dynamics in these systems. Arid and semi‐arid Australia still supports some soil‐foraging animals such as goannas ( Varanus sp., Whitford, ), echidnas (Eldridge and Mensinga, ) and European rabbits ( Oryctolagus cuniculus , James et al , ), their foraging pits are morphologically distinct, and are constructed at different locations and frequencies to those constructed by locally extinct bilbies and bettongs (James et al , ; Eldridge et al , ). Although echidnas, bilbies and bettongs all produce similar size excavations, they differ in shape and the depth to which they dig (James and Eldridge, ).…”

“…Although the initial burial and rates of organic mass loss may vary between these two uniquely different morphologies, the differences were short‐lived, lasting for only a few months. This suggests that, unlike rabbits (James et al , ), the foraging pits of short‐beaked echidnas have similar functional roles to the foraging pits from the locally extinct bilbies and burrowing bettongs.…”

Soil-foraging animals alter the composition and co-occurrence of microbial communities in a desert shrubland

“…Many of Australia's locally extinct animals forage extensively in the soil for seeds, bulbs, invertebrates and fungi (Robley et al, 2001;James et al, 2011;Eldridge et al, 2012). Foraging disturbs the soil surface and breaks up the surface crust (biocrust), altering rates of water infiltration, and creating small pits and depressions that trap water, soil, organic matter and seed (James et al, 2009).…”