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Specialization and Rarity Predict Nonrandom Loss of Interactions from Mutualist Networks Marcelo A. Aizen et al. Science 335, 1486 (2012); DOI: 10.1126/science.1215320

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REPORTS
increase of charcoal lagged Sporormiella declineby ~100 years, grass followed Sporormiella decline by ~300 years, the rise in sclerophyll vegetation lagged Sporormiella decline by ~400 years, and total pollen influx from forest trees increased after 1600 years. The fire increase that followed megafaunal decline could have been anthropogenic, but the extended trajectory of the rise in charcoal and its close matching with falling Sporormiellasuggest instead that relaxation of herbivory directly caused increased fire, presumably by allowing the accumulation of fine fuel. The subsequent vegetation transformation could be explained in two ways: (i) by direct effects of relaxed herbivore pressure on vegetation density and composition or (ii) by release of fire as an ecological force, causing destruction of fire-sensitive rainforestvegetation with replacement by fire-tolerant sclerophyll taxa and grasses. We compared the importance of these two mechanisms by measuring the effects of Sporormiella and charcoal in linear models predicting changes in percent sclerophyll (lagged by four depth intervals, or ~400 years) over the interval shown in Fig. 2. We controlled temporal autocorrelation by fitting generalized least-squares modelswith an exponential correlation structure (26). The standardized regression coefficients (SRCs = coeffcients/SE) were –2.81 for Sporormiella and 2.53 for charcoal when fitted as single-term models; in a two-term model, the respective SRCs were –1.42 and 1.95. The changes in SRC values suggest that (i) there were independent contributions of both falling Sporormiella and rising charcoal to thesubsequent rise in sclerophyll vegetation and (ii) the effect of charcoal was ~35% stronger. After its initial rise charcoal remained high, and around 29 to 31 ka there was a large increase in macrocharcoal indicating that, for the first time in its history, the swamp itself was extensively burnt (20); short-lived spikes in Sporormiella associated with this burning probably represent grazing over the...