Viable conservation of pondscapes includes the ecotones with dryland

Abstract

Marshlands are ecotones between standing water and terrestrial environments, where aquatic and terrestrial species overlap. However, little is known about the assembly rules of organisms inhabiting this ecotone, which is inherently dynamic according to the amount of available water. We separated the waterbody/dryland ecotone of 22 standing waterbodies into five zones according to plant composition, structure, and water depth. Here, the waterbodies had limited inflows and outflows, and were highly responsive to seasonal precipitation events. We then determined the extent to which insect species assemblages change across the five zones and identify environmental factors driving these changes. Each zone had a characteristic suite of plant species, which differed greatly among the standing waterbodies. Dragonflies were present across the entire ecotone, although turnover peaked at the ecotone centre, while butterflies peaked in the grassland zone, along with some marsh-associated species. Grasshoppers preferred grassland associated with the smaller waterbodies. Dragonfly, grasshopper, butterfly, and plant species compositions each responded to their own sets of both aquatic and terrestrial variables. Overall, pond ecotones had high species turnover and high conservation value for both aquatic and terrestrial species, indicating that ponds have a much larger footprint than just the extent of wet areas. The terrestrial buffer zones are required for protection of the local biota. In turn, wet areas provide increased opportunities for dryland species. Buffer zones should be determined not so much in linear metres, but rather should also include dryland, which varies among waterbodies according to micro-topography. Pondscape (all the standing waterbodies) conservation must include all the transition zones, so that the full habitat heterogeneity around such waterbodies is built into the set of functionally connected waterbodies.