When a plant evolves new traits, it can get a little boost in terms of its ability to spread through a uniform landscape, and a big boost in terms of its ability to spread through a landscape that's "patchy," a new experimental study shows. The results suggest that when predicting how fast certain species -- including invasive species -- will spread, accounting for any evolutionary changes they are undergoing is critical. Among the major threats to natural and managed ecosystems today are range changes of species that result from a warming climate; invasive species - and the way they spread through ecosystems, from warming or otherwise - are another threat. Yet, scientists have only a limited understanding of the ecological and evolutionary dynamics of the spread of species through landscapes. To gain more insights, Jennifer Williams and colleagues set up populations of Arabidopsis thaliana plants in pots in either "continuous landscapes," where the pots were separated by minimal gaps, or in "patchy landscapes," with gaps that were 4, 8, or 12 times the average distance that A. thaliana is able to disperse seeds. After the plants had undergone six generations, the researchers conducted genetic analyses to determine each plant's rate of evolution. They found that, in continuous landscapes, more rapidly evolving plants spread 11% farther than their non-evolving counterparts. In contrast, when the environment was patchy (e.g., the plants were 12 times farther apart), evolving populations spread three times as far as their non-evolving counterparts. Intriguingly, genotype changes did not differ greatly whether the plants were 4-, 8- or 12-times farther apart. But, a patchy environment did correlate with plants evolving greater heights, which allowed them to disperse seeds farther. Thus greater evolution - that favors greater height and seed dispersal, in this case - drives the spread of A. thaliana , these researchers say. Whether landscape patchiness selected directly for better dispersal (or indirectly, via unmeasured traits correlated with dispersal) remains an open question, the authors note.
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Science