Contrasting latitudinal clines of nematode diversity in Spartina alterniflora salt marshes between native and introduced ranges

Abstract

AbstractAimIntroduced species may display or foster novel latitudinal clines because they are not well adapted to their new habitats. We tested the hypothesis that the latitudinal cline in nematode diversity in salt marshes would differ between the native (United States) and introduced (China) ranges of Spartina alterniflora.LocationEast Coasts of the United States (30.32–43.33°N) and China (30.36–39.14°N).MethodsWe extracted nematodes from soil samples collected at 32 sites along the United States East Coast and 41 sites along the Chinese coast. We compared latitudinal patterns in nematode diversity and composition between the native and introduced ranges.ResultsIn the native range of S. alterniflora, nematode richness at lower latitudes was almost twice as high as that at higher latitudes. In contrast, we found no latitudinal pattern in nematode richness or diversity in the introduced range of S. alterniflora. Nematode genus richness at all sites in China was about half that at lower latitudes in the United States. Beta diversity of nematodes increased with geographic distance in the United States, but not China.Main conclusionsNematode diversity did not show latitudinal clines in salt marshes dominated by introduced S. alterniflora in China. A likely explanation is that the recently introduced populations are still relatively genetically homogenous, whereas in the native range, genetic variation in plant populations across latitude drives different nematode communities. We suggest that future studies of introduced species will gain additional insights by taking an explicitly geographic perspective.