[Effects of heterogeneous habitats on the coexistence of aquatic ecotype and ].

Species coexistence depends on the comprehensive effects of biological properties and habitat heterogeneity. Based on a large-scale field survey (21°-35° N), we compared the differences on morphological and stoichiometric characteristics between the invasive aquatic species and the native co-occurring species , and examined the effects of environmental factors on such differences. The results showed that the coverage and importance value (IV) of . were all significantly greater than . (34.3% and 104.0%, respectively), whereas the height of . was significantly greater than . (13.8%). Moreover, the total nitrogen concentration (TN) and N:P of . were significantly greater than those of . (55.1% and 55.8%, respectively), whereas the total carbon concentration (TC) and C:N of . were significantly greater than those of . (4.1% and 83.8%, respectively). . coverage increased with the increases of longitude, and its abundance increased with the increases of water nitrate concentration and longitude, while its IV increased with the increases of water ammonium concentration. However, the coverage, abundance, and IV of . decreased with the increases of ammonium concentration. C:N of . decreased with the increase of ammonium concentration. Increased mean annual temperature and mean annual precipitation increased C:N but decreased N:P of . The C:P of both species decreased with the increases of ammonium concentration and electrical conductivity. N:P of . was little affected by environment. These results indicated that . had greater coverage and N absorption capacity than . , and that enriched water nitrogen would aggravate the invasion of . Meanwhile, . improved its C-assimilate reserves and chose the growth competition strategy for resisting . invasion under the superior hydrothermal conditions. Different responses to environmental changes contributed to their coexistence in aquatic ecosystem.