Beyond Generalist Tolerance: Age‐Dependent Impacts of Habitat Fragmentation and Climate on a Widespread Lizard

Abstract

Understanding age-specific selective pressures is fundamental to species persistence. We investigated the spatiotemporal abundance patterns of adult and juvenile Liolaemus wiegmannii in fragmented and non-fragmented coastal dunes over four seasons. Our study revealed that adult abundance decreased significantly at fragmented sites during only one season, suggesting susceptibility to environmental stressors exacerbated by a regional drought. In contrast, juvenile abundance showed no significant spatiotemporal differences. An ontogenetic divergence was evident in the findings. Adult abundance was largely unaffected by landscape metrics, whereas juvenile abundance was positively associated with fine-scale (100 m radius) semi-fixed dune patch number, aggregation and shape complexity. Furthermore, adults showed a negative association with mean daily air temperature, likely reflecting behavioural thermoregulation or post-reproductive mortality. Conversely, juvenile abundance was positively associated with net primary productivity. The ecological flexibility of this generalist lizard is not uniform across all life stages. Juveniles are particularly sensitive to fine-scale habitat structure and resource availability, revealing hidden vulnerabilities in a species often assumed to be tolerant. This ontogenetic divergence suggests that an apparent lack of population-level fragmentation effects can mask critical age-specific vulnerabilities, which is a crucial consideration for conservation.