Leaf-cutting ants facilitation to non-native plants is passed from one generation to the next

Abstract

In arid environments where soil resources are limiting factors, the presence of soil ecosystem engineers that create new enriched soil habitats can improve the performance of non-native plants growing there. Moreover, these enriched areas may be considered key sources of high-quality seeds, which would favor the spread and invasion success of non native plant. In Northwestern Patagonian steppe, the non-native grass Bromus tectorum is one of the most frequent species that takes advantage of the soil engineering effect of the leaf-cutting ant Acromyrmex lobicornis. Here, we evaluated if the facilitative effect of the enriched nest sites of A. lobicornis on B. tectorum individuals is also transferred to their offspring. We compared the influence of B. tectorum’s seed source (i.e., from plants growing on nest sites vs steppe soil) on seed mass, seed germination, and performance of new individuals growing under the same conditions (i.e., growing in steppe soil, under the same water and temperature conditions). We showed that individuals of B. tectorum growing on nest sites produced bigger seeds, with germination rate and germination percentage similar to those of individuals from soil seeds; however, they produced 53% larger seedlings, with 30% less root:shoot ratio and higher probability of having shoots with spikelets. This evi- dences that the benefits of growing on nest sites pass on to the offspring of B. tectorum. Moreover, our results highlight the importance of environmental maternal effects on plant growth and development even after germination and show that soil ecosystem engineers can represent a crucial contribution to the invasion of non-native plants.