Latitudinal gradients of α- and β-diversity of aquatic plant communities across eastern China: Helophytes and hydrophytes show inconsistent patterns

Abstract

The decrease of diversity from the equator to the poles is one of the most well-established patterns in ecology. However, there are exceptions to this general pattern and some groups have not been well studied, especially for the taxonomic and phylogenetic diversity of aquatic plants along latitudinal gradients. Using the field survey data of 152 sampling sites across eastern China, we analyzed the α- and β-diversity-latitude relationships for the total 217 aquatic plant species, as well as for their two main components, 149 helophytes and 68 hydrophytes. We also explored the relationships between diversity measures and two types of climatic variables (energy- and water-related variables). We found that the latitudinal gradient of α-diversity of aquatic plants is a hump-shaped pattern with the highest peak at 45°N. The net relatedness index of hydrophytes is negatively correlated with mean annual temperature and annual precipitation, which is consistent with the prediction of the “tropical niche conservatism” hypothesis. The β-diversity is lowest in the warm temperate zone, which is located in the middle latitudes of our study area. The latitudinal patterns of aquatic plant α- and β-diversity are different between helophytes and hydrophytes. Energy-related climatic variables could more affect the diversity of hydrophytes, while water-related climate variables could more affect the diversity of helophytes. Thus, compared with hydrophytes, helophytes are more similar to terrestrial plants, which are more affected by water-related climatic varibales. This work provided the ideas for further understanding the composition of aquatic plant community and the relationship between its diversity with latitude and climatic variables.

Keywords

• Latitude
• Aquatic
• Taxonomic
• Phylogenetic
• Structure
• TNC hypothesis