Multi-axis spatiotemporal niche partitioning between coexisting top predators in ponds

Abstract

O_LIUnderstanding how ecologically similar species coexist remains a central challenge in ecology, particularly in small, spatially constrained systems where opportunities for segregation may be limited. Classical niche theory predicts that coexistence is facilitated when species partition resources across multiple niche axes, yet few empirical studies quantify how spatial, temporal, and environmental dimensions jointly structure realized niches in natural systems. C_LIO_LIWe examined spatiotemporal niche partitioning between two coexisting top predators--the eastern red-spotted newt (Notophthalmus viridescens) and bluegill sunfish (Lepomis macrochirus)--in a pond lacking piscivorous fish. Using year-round trapping data collected across depth strata, diel periods, and seasons, we combined hierarchical count models, temperature-informed partial effect analyses, and null-model tests of niche overlap. C_LIO_LINewts and sunfish exhibited strongly contrasting patterns of habitat use across multiple axes. Newt capture rates were highest during cooler periods, in deeper habitats, and during morning sampling, whereas sunfish capture rates peaked during warmer periods, in shallow habitats, and during afternoon sampling. Model-based analyses revealed opposing responses to temperature, with predicted newt captures declining and sunfish captures increasing as temperature rose, even after accounting for seasonal effects. As a result, niche overlap across combined season-by-depth-by-time states was consistently lower than expected under randomized null models. C_LIO_LIAcross all analyses, newts and sunfish exhibited strong and consistent spatiotemporal niche partitioning, with opposing seasonal trajectories, contrasting depth and diel activity patterns, divergent thermal responses, and niche overlap significantly lower than expected under null models. These results demonstrate that fine-scale spatiotemporal structure across interacting niche axes can generate pronounced segregation among coexisting top predators, even in small and physically constrained ecosystems. Rather than reflecting partitioning along a single dominant axis, niche differentiation in this system appears to emerge from the coordinated interaction of season, habitat, diel activity, and temperature, highlighting how multi-axis dynamics shape realized niches in natural communities. C_LI Significance StatementCoexisting predators often exploit the same prey and habitats, raising the question of how overlap is reduced in spatially constrained ecosystems such as ponds. By integrating seasonal, diel, habitat, and thermal dimensions, this study demonstrates that two ecologically similar top predators--newts and sunfish--exhibit strong spatiotemporal niche partitioning that substantially lowers overlap relative to random expectations. Our results show that fine-scale temporal and habitat structure can play a major role in organizing predator assemblages, even in small freshwater systems, and highlight the importance of multi-axis niche frameworks for understanding species interactions and persistence in natural communities.