The temperature response of soil respiration in deserts is not well quantified. We evaluated the response of respiration to temperatures spanning 67°C from seven deserts across North America and Greenland. Deserts have similar respiration rates in dry soil at 20°C, and as expected, respiration rates are greater under wet conditions, rivaling rates observed for more mesic systems. However, deserts differ in their respiration rates under wet soil at 20°C and in the strength of the effect of current and antecedent soil moisture on the sensitivity and magnitude of respiration. Respiration increases with temperature below 30°C but declines for temperatures exceeding 35°C. Hot deserts have lower temperature sensitivity than cold deserts, and insensitive or negative temperature sensitivities were predicted under certain moisture conditions that differed among deserts. These results have implications for large-scale modeling efforts because we highlight the unique behavior of desert soil respiration relative to other systems. These behaviors include variable temperature responses and the importance of antecedent moisture conditions for soil respiration.Electronic supplementary material The online version of this article

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Understanding the natal origins of migratory animals is critical for understanding their population dynamics and conservation. However, quantitative estimates of population recruitment from different natal habitats can be difficult to assess for many species, especially those with large geographic ranges. These limitations hinder the evaluation of alternative hypotheses about the key movements and ecological interactions of migratory species. Here, we quantitatively investigated intra‐population variation in the natal origins of western North American monarch butterflies Danaus plexippus using spatial analyses of stable isotope ratios and correlations with wing morphology. A map of hydrogen isotope values in western monarch butterfly wings (δ2Hm) was estimated using a transfer function that relates the δ2Hm values of monarch butterfly wing keratin to a long‐term dataset of precipitation isotope (δ2Hp) values across the western United States. Isotopic analyses of 114 monarch butterfly wings collected at four California overwintering locations indicated substantial individual variation in natal origins, with most recruitment coming from broad regions along the Pacific coast, the southwestern US and the northern intermountain region. These observed patterns may partially resolve and reconcile several past hypotheses about the natal origins of western monarch butterflies, while also raising new questions. More negative δ2Hm values (associated with longer migratory distance) were significantly correlated with larger forewing sizes, consistent with expectations based on the aerodynamic and energetic costs of long‐distance migration, while analyses of wing shape suggest potential differences in the movement behaviors and constraints observed in the western range, compared with previous observations in eastern North America. Taken together, the results of this study indicate substantial individual variation in the natal origins of overwintering western monarch butterflies, suggesting both local and long‐distance movement to overwintering sites.

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