Ant-mediated seed dispersal contributes to the local spatial pattern and genetic structure of Globba lancangensis...

Globba lancangensis is a typical myrmecochorous perennial herb found in southwest China. In 2002 and 2003, seed dispersal by ants was examined. Twelve ant species were recorded and found to move seeds 0.01-3.35 m. This removal promoted seed dispersal. In 2003, ant exclusion was made in 4 of 8 study plots for 1 year to practically detect the effects of ant dispersal. As a result, nearest neighbor analyses indicated that although ant dispersal could not significantly change the mean nearest neighbor distance, it obviously reduced the clustering degree of seedlings. Spatial genetic structure (SGS) of mature plants in 2003 and sequent seedlings in 2004 were investigated with intersimple sequence repeats. The whole correlagram of all individuals from 2003 showed significant positive autocorrelations between genetic and geographical distances within 4 m, suggesting a patchy structure at such short distances in the studied population. This pattern is likely associated with limited seed dispersal. The comparative analysis of fine-scale correlograms (<4 m) for ant-excluded treatment indicated lacking ants as the primary dispersers could have a similar pattern to ant dispersal presence, which is likely due to the restriction of ant dispersal distance. In conclusion, ant-mediated dispersal contributes to reduce seedling clustering degree and plays a minor role in developing and maintaining the local SGS in G. lancangensis.