Figure 1. Amphibians of the Sonoran Desert span an incredible spectrum of behavioral and life history adaptations to life in an arid environment. Many native anurans (frogs, toads, and spadefoots) are common in the arroyos, cienegas, and canyons of the landscape. Our study occurs primarily during the (A) Monsoon season in the Huachuca Mountains and surrounding ranges, and focuses on (B) Mexican Spadefoot (Spea multiplicata), (C) Red-spotted Toad (Anaxyrus punctatus) and (D) Canyon Treefrog  (Hyla arenicolor). Photo credits: Meryl Mims.

Hydroecology of Intermittent and Ephemeral Streams: Will landscape connectivity sustain aquatic organisms in a changing climate?

Figure 1. Amphibians of the Sonoran Desert span an incredible spectrum of behavioral and life history adaptations to life in an arid environment. Many native anurans (frogs, toads, and spadefoots) are common in the arroyos, cienegas, and canyons of the landscape. Our study occurs primarily during the (A) Monsoon season in the Huachuca Mountains and surrounding ranges, and focuses on (B) Mexican Spadefoot (Spea multiplicata), (C) Red-spotted Toad (Anaxyrus punctatus) and (D) Canyon Treefrog (Hyla arenicolor). Photo credits: Meryl Mims.

OVERVIEW

Dryland streams play a vital role in shaping the hydrological, biogeochemical, and ecological structure and function of arid and semi-arid ecosystems in the American Southwest and elsewhere. Perhaps most importantly, they provide hydrologic connectivity within the landscape during bouts of stream drying and wetting by linking ephemeral, intermittent, and perennial reaches to create a patchwork of habitats at different locations and times during the year. Amphibians face a particularly tenuous existence in desert environments. Suitable habitat patches (i.e. surface water) are often fragmented, ephemeral, and shrink during periods of prolonged droughts (Jaeger and Olden 2012). The opportunity to disperse between habitat patches may occur primarily during rare months with above-average precipitation or during episodic floods. Thus, even small differences in climate and water management are expected to have significant impacts on the disturbance regimes and hydrologic connectivity in dryland streams. This in turn may result in population loss and fragmentation, range shifts, phenological changes and extinctions of species.

A project led by Julian Olden and graduate students in the School of Aquatic and Fishery Sciences uses aquatic invertebrates and amphibians as a model system to ask how flow intermittency and connectivity influences the structure and function of dryland streams in the Madrean Sky Islands of southern Arizona (Figure 1).  Specific objectives include: (1) modeling stream flow to quantify flow permanence and hydrologic connectivity at multiple spatial scales; (2) characterizing the distribution and abundance of obligatory aquatic organisms in relation to hydrology, riparian vegetation, and geomorphology; (3) evaluating population structure (gene flow) of insect and amphibian species with contrasting life-histories along a gradient of flow permanence and hydrologic connectivity; and (4) forecasting the responses of obligatory aquatic species to climate-induced changes in flow permanence and hydrologic connectivity. We are working with the Department of Defense and Fort Huachuca, and our sampling efforts over the past three years have centered on the Huachuca Mountains and surrounding valleys and mountain ranges (including the Santa Ritas, the Whetstones, the Dragoons, and the Mules).

REFERENCES

Jaeger, K, and J.D. Olden. 2012. Electrical resistance sensor arrays as a means to quantify longitudinal connectivity of rivers. River Research and Applications. DOI: 10.1002/rra.1554

CONTACTS

Julian Olden (School of Aquatic and Fishery Sciences, University of Washington) olden@uw.edu