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Abstract The size and frequency of resource pulses can affect plant interactions and increase the abundance of invasive species relative to native species. We examined resource pulses generated during the desiccation and rehydration of communities of native biological soil crust (biocrust)‐forming mosses, in the context of positive associations between biocrusts and the invasive forb,Centaurea stoebe.We surveyedCentaureaand biocrust cover and evaluated how interactions amongCentaurea, biocrusts and water pulses influenced plant biomass and soil nitrogen in a field experiment.Centaureaseedling and biocrust interactions were also compared in a greenhouse experiment to evaluate differences related to life stage.In field surveys,Centaureaand biocrusts were positively associated. Across water pulse treatments, biocrust biomass decreased whenCentaureawas removed, indicating thatCentaureafacilitated biocrusts. Biocrusts did not affect adultCentaureain the field, butCentaureaseedling biomass was greater when grown with biocrusts in the greenhouse. Water pulses did not affect plant biomass, but interactions betweenCentaureaand biocrusts corresponded with variation in the effect of water pulses on soil nitrogen which were not evident whenCentaureaor biocrusts were grown alone. Twenty‐four hours after large water pulses were added, soilwas nine times higher in plots where biocrusts andCentaureaco‐occurred compared with small water pulse plots. In these same plots, soiltended to be lower at the end of the experiment.These results highlight positive interactions between an invasive exotic forb and native moss biocrust. Water pulses influenced soil nitrogen availability when both plants co‐occurred, but did not affect plant biomass, suggesting that resource pulses and species interactions can interact to affect ecosystem processes. A freePlain Language Summarycan be found within the Supporting Information of this article.
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Experimental admixture among geographically disjunct populations of an invasive plant yields a global mosaic of reproductive incompatibility and heterosis
Abstract Invasive species have the ability to rapidly adapt in the new regions where they are introduced. Classic evolutionary theory predicts that the accumulation of genetic differences over time in allopatric isolation may lead to reproductive incompatibilities resulting in decreases in reproductive success and, eventually, to speciation. However, experimental evidence for this theoretical prediction in the context of invasive species is lacking. We aimed to test for the potential of allopatry to determine reproductive success of invasive plants, by experimentally admixing genotypes from six different native and non‐native regions ofCentaurea solstitialis, an invasive forb for which preliminary studies have detected some degree of reproductive isolation between one native and non‐native region.We grew plants under common garden conditions and outcrossed individuals originating from different source populations in the native and introduced range to evaluate reproductive success in terms of seed to ovule ratio produced. We also assessed geographical and genetic isolation amongC.solstitialisregions as a potential driving factor of reproductive success.Experimental admixture generated mixed fitness effects, including significant increases, decreases and no differences in reproductive success as compared to crosses within population (control).Centaurea solstitialisinvasive populations in the Americas generated preponderantly negative fitness interactions, regardless of the pollen source, suggesting selection against immigrants and reinforcement. Other non‐native populations (Australia) as well as individuals from the native range of Spain demonstrated an increase in fitness for between‐region crosses, indicating inbreeding. These differences show an asymmetrical response to inter‐regional gene flow, but no evidence of isolation by distance.Synthesis. The speed of adaptation and the accumulation of reproductive incompatibilities among allopatric populations of invasive species might be more rapid than previously assumed. Our data show a global mosaic of reproductive outputs, showcasing an array of evolutionary processes unfolding during colonization at large biogeographical scales.
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- Award ID(s):
- 1757351
- PAR ID:
- 10452553
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 109
- Issue:
- 5
- ISSN:
- 0022-0477
- Page Range / eLocation ID:
- p. 2152-2162
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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