Abstract
Simple SummaryGaining information about the habitat environment and biological interactions is important for conserving gold-spotted pond frogs, which are faced with a threat of local population extinction in Korea due to artificial habitat changes. Based on stable isotope ratios, we estimated the ecological niche space (ENS) of gold-spotted pond frogs in an ecological wetland park and a rice paddy differing in habitat patch connectivity and analyzed the possibility of their ENS overlapping that of competitive and predatory frogs. Gold-spotted pond frogs showed a broader ENS in the ecological wetland park, wherein predation was relatively easy, than in the rice paddy. However, the ENS of the gold-spotted pond frogs was highly probably overlapped with that of other competing frog species that shared some of the food sources. Nevertheless, since the stable isotope analysis showed that gold-spotted pond frogs fed on more diverse prey than their competitors, it would remain relatively easy to procure alternative food sources, which are less affected by the competition in an environment with abundant food. Therefore, for stable settling of gold-spotted pond frogs into habitats and preserving their population, establishing habitat environments with highly diverse food sources is crucial, following consideration of their feeding behavior.The gold-spotted pond frog (Pelophylax chosenicus) is an endangered amphibian species in South Korea. In order to obtain ecological information regarding the gold-spotted pond frog’s habitat environment and biological interactions, we applied stable isotope analysis to quantify the ecological niche space (ENS) of frogs including black-spotted pond frogs (P. nigromaculatus) and bullfrogs (Lithobates catesbeianus) within the food web of two different habitats—an ecological wetland park and a rice paddy. The gold-spotted pond frog population exhibited a broader ENS in the ecological wetland park than in the rice paddy. According to the carbon stable isotope ratios, gold-spotted pond frogs mainly fed on insects, regardless of habitat type. However, the results comparing the range of both carbon and nitrogen stable isotopes showed that gold-spotted pond frogs living in the rice paddy showed limited feeding behavior, while those living in the ecological wetland park fed on various food sources located in more varied trophic positions. Although the ENS of the gold-spotted pond frog was generally less likely to be overlapped by that of other frog species, it was predicted to overlap with a high probability of 87.3% in the ecological wetland park. Nevertheless, gold-spotted pond frogs in the ecological wetland park were not significantly affected by the prey competition with competitive species by feeding on other prey for which other species’ preference was low. Since these results show that a habitats’ food diversity has an effect on securing the ENS of gold-spotted pond frogs and prey competition, we recommend that the establishment of a food environment that considers the feeding behavior of gold-spotted pond frogs is important for the sustainable preservation of gold-spotted pond frogs and their settlement in alternative habitats.
Highlights
The niche width of a species in an ecosystem represents species-specific characteristics, such as feeding habits, ecological characteristics, food preference and habitat selection; understanding the niche width from a population or community perspective can facilitate assessments of food web structure and function [1]
Measured C stable isotope ratios indicated that the sampled gold-spotted pond frog individuals fed on insects as their primary food source, regardless of the habitat, whereas N stable isotope ratios revealed slightly different distributions regarding trophic diversity depending on the habitat
Black-spotted pond frogs were sharing the ecological niche space (ENS) of gold-spotted pond frogs, and the degree of overlap with competitive species may have increased with the increasing diversity of food sources available to gold-spotted pond frogs within the ecological park habitat
Summary
The niche width of a species in an ecosystem represents species-specific characteristics, such as feeding habits, ecological characteristics, food preference and habitat selection; understanding the niche width from a population or community perspective can facilitate assessments of food web structure and function [1]. The niche concept was defined by Hutchinson [2] as an n-dimensional hypervolume has facilitated numerous community structure studies within ecosystems, in addition to the development of mathematical techniques for quantifying niche dimensionality, spatiotemporal change, trophic contribution, and inter- and intra-specific trophic diversity [1,3,4,5] Such studies have enabled quantitative assessments of changes in community characteristics (e.g., species abundance, richness and evenness) that depend on the presence or absence of competitors and predators, and of biological interactions based on positions within food webs, enhancing our understanding of organisms’ functions within ecosystem food webs [6,7].
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