Local adaptation across a fertility gradient is influenced by soil biota in the invasive grass, <Emphasis Type="Italic">Bromus inermis</Emphasis> |
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Authors: | Email author" target="_blank">Mark?E?SherrardEmail author Hafiz?Maherali |
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Institution: | (1) Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada;(2) Present address: Department of Biology, University of Northern Iowa, Cedar Falls, IA 50614, USA |
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Abstract: | Biotic soil factors, such as fungi, bacteria and herbivores affect resource acquisition and fitness in plants, yet little
is known of their role as agents of selection. Evolutionary responses to these selective agents could be an important mechanism
that explains the success of invasive species. In this study, we tested whether populations of the invasive grass Bromus inermis are adapted to their home soil environment, and whether biotic factors influence the magnitude of this adaptation. We selected
three populations growing at sites that differed in soil fertility and grew individuals from each population in each soil.
To assess whether biotic factors influence the magnitude of adaptation, we also grew the same populations in sterilized field
soil. To further examine the role of one element of the soil biota (fungi) in local adaptation, we measured colonization by
arbuscular mycorrhizal (AM) and septate fungi, and tested whether the extent of colonization differed between local and foreign
plants. In non-sterilized (living) soil, there was evidence of a home site advantage because local plants produced significantly
more biomass than at least one of the two populations of foreign plants in all three soil origins. By contrast, there was
no evidence of a home site advantage in sterilized soil because local plants never produced significantly more biomass than
either population of foreign plants. Fungal colonization differed between local and foreign plants in the living soil and
this variation corresponded with biomass differences. When local plants produced more biomass than foreign plants, they were
also less intensively colonized by AM fungi. Colonization by septate fungi did not vary between local and foreign plants.
Our results suggest that biotic soil factors are important causes of plant adaptation, and that selection for reduced interactions
with mycorrhizae could be one mechanism through which adaptation to a novel environment occurs. |
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