Niche Differences in Coexisting Species: Ecological Insights Into the Role of Activity Patterns, Space Use, and Environmental Preferences

The differences in niche structure enable the coexistence of ecologically similar species by reducing direct competition, combining spatial and temporal segregation with phenotypic variation that influences the differential use of resources and habitats. In this study, we examined niche differences in two coexisting green lizard species, Timon lepidus and Lacerta schreiberi, in northern Portugal. Both species differ in body size and habitat preferences, providing an excellent model to investigate mechanisms of niche differentiation. We integrated field observations on environmental variables (temperature, humidity, and illumination), body temperatures, microhabitat use, and activity patterns to complement previously published experimental results on mechanisms of species coexistence. Our observations revealed that T. lepidus prefers drier, rocky, and open areas and human-built structures, while L. schreiberi was predominantly found in moist microhabitats with dense vegetation. Additionally, we detected differences in activity patterns, where T. lepidus displayed unimodal activity peaks around midday, while L. schreiberi exhibited bimodal patterns with activity peaks in the afternoon. These field-derived patterns of microhabitat use and activity patterns were congruent with the thermal and water balance preferences of the two species quantified through previously published experimental trials. Spatial and temporal variations—particularly microhabitat relative humidity and time of activity—were found to be key factors in niche differences.