Data from: Inter- and intrapopulation resource use variation of marine subsidized western fence lizards

Marine resource subsidies can alter consumer dynamics of recipient populations in coastal systems. The response to these subsidies by generalist consumers is often not uniform, resulting in inter- and intrapopulation diet variation and niche diversification that may be intensified across heterogeneous landscapes.

We sampled western fence lizards, Sceloporus occidentalis, from Puget Sound beaches and from coastal and inland forest habitats, as well as the lizards' marine and terrestrial prey items to quantify marine and terrestrial resource use with stable isotope analysis (SIA) and mixing models.

Isotopic results reveal beach lizards had higher average δ¹³C and δ¹⁵N values compared to coastal and inland forest lizards, exhibiting a strong mixing line between marine and terrestrial prey items. Across five beach sites, lizard populations received 20 to 51% of their diet from marine resources, on average, with individual lizards ranging between 7% and 86% marine diet.

The hillslope of the transition zone between marine and terrestrial environments at beach sites was positively associated with marine-based diets, as beach sites with the steepest slopes had the highest percent marine diets. Additionally, within-beach variation in transition zone slope was positively correlated with the isotopic niche space of beach lizard populations. Together, these results demonstrate that the physiography of transitional landscapes can mediate resource flow between environments, and variable habitat topography promotes niche diversification within a lizard population.

Marine resource subsidization of Puget Sound beach S. occidentalis populations may facilitate occupation of the northwesternmost edge of the species range.  

Human impacts to the physiography of Puget Sound beaches, such as shoreline armoring, may influence the quantity of driftwood habitat available to support the unique ecology of beach-dwelling S. occidentalis. This highlights the importance of shoreline restoration, and conservation of intact beach habitat.