Niche divergence is a phenomenon associated with reduced interspecific competition, increased community stability, and productivity. While a considerable amount of evidence has been presented that show reductions in competitive effects due to niche separation between neighboring plants, a true evaluation of the scale on which such niche divergence occurs is still missing. We conducted field and greenhouse experiments that tested for the spatial aspect of neighborhood effects in plant communities. In the spring of 2007 genets of two species pairs were collected from two different non-woody plant communities within Northern New Jersey. The two species pairs were of two different classes: native/native from a community with low levels of non-native plant invasion and native/non-native from a highly invaded plant community. One species, Solidago canadensis, was present in both communities and was collected from the immediate border of the species-pair populations while genets of the other test species were collected from three locations that increased in distance from the border (100m, and 1km away from the populations border). The ramets of the target species (Solidago) were planted pair wise with ramets of the two test species (Monarda fistulosa - native and Artemisia vulgaris - non-native) from the 3 distances. The individuals were grown in the greenhouse for three months; directional root data were collected from soil cores following the growing period (total root mass, root length between ramets, root length away from ramets). MANOVA was used for hypothesis testing and the results were interpreted using Wilk’s Lambda. ANOVA was used for descriptive purposes.
Results/Conclusions
The results suggest that native/native species pairs minimize their root level competition within the local community up to the distance of 100 m but not beyond (Wilk’s=0.016). However, within the native/non-native pair this same pattern was not found. The results suggest that native plants could potentially have a sufficiently long evolutionary history together where community building has became a selective trait within individuals and that the relative scale of this phenomenon appears to breakdown at the 1km scale when plants from different communities were paired. However, non-native species did not exhibit any such patterns. This suggests that non-native species may either have undergone a selective process thorough the invasion process that has left them incapable of producing communities in their new range or that the time spent in their new range is not sufficient enough to produce the community building characteristics.
