Undervalued Ecosystems: Ponds Boost Regional Macrophyte Diversity

Ponds—depressional wetlands with ≤ 2 ha—are largely undervalued worldwide, despite serving as crucial diversity reservoirs. However, the extent to which ponds support diversity at the landscape scale is still underappreciated. Here, we investigate the contributions of ponds to macrophyte beta and gamma diversity in a subtropical wetland network where streambanks, riverbanks and ponds are the predominant wetland types. To this end, the diversity of riparian areas (streambanks and riverbanks [SR]) was compared to that of the global wetland set (streambanks, riverbanks and ponds [SRP]) so that only ponds could account for increases in diversity from SR to SRP. Three species groups were considered in the analyses: herbaceous, woody and the global pool. Total beta diversity increased significantly from SR to SRP for all plant groups, a pattern driven by the turnover component, not by the nestedness-resultant component. Gamma diversity also increased for all plant groups as a result of increased species turnover, except for the woody component when indices that assign successively greater weights to frequent species were used. Our results demonstrate that ponds make pivotal contributions to macrophyte conservation at the regional level, which is why their inclusion in policy frameworks and legislation that ensure their safeguarding is essential.