Linking Perennial Surface Water and Aquatic Food Subsidies to Lizards in Arid Environments

Authors: Earyn Mcgee, Noel Hamideh, Rezwana Islam, Michael Bogan

Year: 2017 (xlix)

Abstract

Severe drought driven by climate change and water use by humans is causing formerly perennial streams to flow intermittently, presenting a level of disturbance not documented historically The loss of aquatic prey during drought could negatively impact riparian and terrestrial species, including lizards Because lizards play important roles in riparian food webs (eg predators, nutrient cycling), it is crucial to understand the cascading effects of stream drying on lizard communities We hypothesized that perennial streams provide aquatic subsidies to terrestrial species, which reduces competition and opens niches for riparian lizards We predicted that lizard communities near perennial water are more diverse than communities that do not have access to water and that individuals within a species will grow larger and faster with access to perennial water than those without We surveyed three streams, each of which had paired 100-meter long perennial and ephemeral reaches that were similar in microhabitats but differed in water availability At each of the six reaches, we carried out a 2-month mark-recapture study of three lizard species (Sceloporus jarrovii, Sceloporus virgatus, and Urosaurus ornatus) and measured the snout-vent length, tail length, and mass of each lizard we captured We used emergence traps to quantify the availability of aquatic prey We are still in the process of identifying these insect samples Preliminary analysis suggests that lizards were scarce across ephemeral sites, but common at perennial sites Analyses of mark-recapture data are ongoing, but I expect that the data will reflect my predictions of faster lizard growth along perennial streams This study provides insights into food webs in riparian ecosystems and a greater understanding of how terrestrial and aquatic systems are linked via cross-system subsidies