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| As post-disturbance community response
depends on the characteristics of the ecosystem and the
species composition, so does the invasion of exotic
species rely on their suitability to the new environment.
Here, we test two hypotheses: exotic spider
species dominate the community after burning; and
two traits are prevalent for their colonisation ability:
ballooning and body size, the latter being correlated
with their dispersal ability. We established spring
burn, summer burn and unburned experimental plots in
a New Zealand tussock grassland area and collected
annual samples 3 and 4 years before and after the
burning, respectively. Exotic spider abundance
increased in the two burn treatments, driven by an
increase in Linyphiidae. Indicator analysis showed
that exotic and native species characterised burned and
unburned plots, respectively. Generalised linear
mixed-effects models indicated that ballooning had a
positive effect on the post-burning establishment
(density) of spiders in summer burn plots but not in
spring plots. Body size had a positive effect on
colonisation and establishment. The ability to balloon
may partly explain the dominance of exotic Linyphiidae
species. Larger spiders are better at moving into
and colonising burned sites probably because of their
ability to travel longer distances over land. Native species showed a low resilience to burning, and
although confirmation requires longer-term data, our
findings suggest that frequent fires could cause long
lasting damage to the native spider fauna of tussock
grasslands, and we propose limiting the use of fire to
essential situations. | |
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