Savanna fires increase rates and distances of seed dispersal by ants |
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Authors: | C L Parr A N Andersen C Chastagnol C Duffaud |
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Institution: | (1) Bushfire Cooperative Research Centre, CSIRO Tropical Ecosystems Research Centre, PMB 44, Winnellie, 0822, NT, Australia;(2) école Nationale Supérieure Agronomique de Montpellier, 2 Place Pierre Viala, Montpellier, 34060, France |
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Abstract: | Myrmecochory (seed dispersal by ants) is a prominent dispersal mechanism in many environments, and can play a key role in
local vegetation dynamics. Here we investigate its interaction with another key process in vegetation dynamics—fire. We examine
ant dispersal of seeds immediately before and after experimental burning in an Australian tropical savanna, one of the world’s
most fire-prone ecosystems. Specifically, our study addressed the effects of burning on: (1) the composition of ants removing
seeds, (2) number of seed removals, and (3) distance of seed dispersal. Fire led to higher rates of seed removal post-fire
when compared with unburnt habitat, and markedly altered dispersal distance, with mean dispersal distance increasing more
than twofold (from 1.6 to 3.8 m), and many distance dispersal events greater than the pre-fire maximum (7.55 m) being recorded.
These changes were due primarily to longer foraging ranges of species of Iridomyrmex, most likely in response to the simplification of their foraging landscape. The significance of enhanced seed-removal rates
and distance dispersal for seedling establishment is unclear because the benefits to plants in having their seeds dispersed
by ants in northern Australia are poorly known. However, an enhanced removal rate would enhance any benefit of reduced predation
by rodents. Similarly, the broader range of dispersal distances would appear to benefit plants in terms of reduced parent–offspring
conflict and sibling competition, and the location of favourable seedling microsites. Given the high frequency of fire in
Australian tropical savannas, enhanced benefits of seed dispersal by ants would apply for much of the year. |
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Keywords: | Ants Burning Seed dispersal Disturbance Dispersal distance |
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