Nick J. B. Isaac

Defaunation in the Anthropocene

We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this “Anthropocene defaunation”; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet’s sixth mass extinction and also a major driver of global ecological change.

Mammals on the EDGE: Conservation Priorities Based on Threat and Phylogeny

Conservation priority setting based on phylogenetic diversity has frequently been proposed but rarely implemented. Here, we define a simple index that measures the contribution made by different species to phylogenetic diversity and show how the index might contribute towards species-based conservation priorities. We describe procedures to control for missing species, incomplete phylogenetic resolution and uncertainty in node ages that make it possible to apply the method in poorly known clades. We also show that the index is independent of clade size in phylogenies of more than 100 species, indicating that scores from unrelated taxonomic groups are likely to be comparable. Similar scores are returned under two different species concepts, suggesting that the index is robust to taxonomic changes. The approach is applied to a near-complete species-level phylogeny of the Mammalia to generate a global priority list incorporating both phylogenetic diversity and extinction risk. The 100 highest-ranking species represent a high proportion of total mammalian diversity and include many species not usually recognised as conservation priorities. Many species that are both evolutionarily distinct and globally endangered (EDGE species) do not benefit from existing conservation projects or protected areas. The results suggest that global conservation priorities may have to be reassessed in order to prevent a disproportionately large amount of mammalian evolutionary history becoming extinct in the near future.

How Far Do Animals Go? Determinants of Day Range in Mammals

Day range (daily distance traveled) is an important measure for understanding relationships between animal distributions and food resources. However, our understanding of variation in day range across species is limited. Here we present a day range model and compare predictions against a comprehensive analysis of mammalian day range. As found in previous studies, day range scales near the \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Why are metabolic scaling exponents so controversial? Quantifying variance and testing hypotheses

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Radio-tagging technology reveals extreme nest-drifting behavior in a eusocial insect

\end{document} power of body mass. Also, consistent with model predictions, taxonomic groups differ in the way day range scales with mass, associated with the most common diet types and foraging habitats. Faunivores have the longest day ranges and steepest body mass scaling. Frugivores and herbivores show intermediate and low scaling exponents, respectively. Day range in primates did not scale with mass, which may be consistent with the prediction that three‐dimensional foraging habitats lead to lower exponents. Day ranges increase with group size in carnivores but not in other taxonomic groups.

Correlates of Species Richness in Mammals: Body Size, Life History, and Ecology

Summary 1. Policy-makers increasingly demand robust measures of biodiversity change over short time periods. Longterm monitoring schemes provide high-quality data, often on an annual basis, but are taxonomically and geographically restricted. By contrast, opportunistic biological records are relatively unstructured but vast in quantity. Recently, these data have been applied to increasingly elaborate science and policy questions, using a range of methods. At present, we lack a firm understanding of which methods, if any, are capable of delivering unbiased trend estimates on policy-relevant time-scales. 2. We identified a set of candidate methods that employ data filtering criteria and/or correction factors to deal with variation in recorder activity. We designed a computer simulation to compare the statistical properties of these methods under a suite of realistic data collection scenarios. We measured the Type I error rates of each method–scenario combination, as well as the power to detect genuine trends. 3. We found that simple methods produce biased trend estimates, and/or had low power. Most methods are robust to variation in sampling effort, but biases in spatial coverage, sampling effort per visit, and detectability, as well as turnover in community composition, all induced some methods to fail. No method was wholly unaffected by all forms of variation in recorder activity, although some performed well enough to be useful. 4. We warn against the use of simple methods. Sophisticated methods that model the data collection process offer the greatest potential to estimate timely trends, notably Frescalo and occupancy–detection models. 5. The potential of these methods and the value of opportunistic data would be further enhanced by assessing the validity of model assumptions and by capturing small amounts of information about sampling intensity at the point of data collection.

Investing in evolutionary history: implementing a phylogenetic approach for mammal conservation

The metabolic theory of ecology links physiology with ecology, and successfully predicts many allometric scaling relationships. In recent years, proponents and critics of metabolic theory have debated vigorously about the scaling of metabolic rate. We show that the controversy arose, in part, because researchers examined the mean exponent separately from the variance. We estimate both quantities simultaneously using linear mixed-effects models and data from 1242 animal species. Metabolic rate scaling converges on the predicted value of 3/4 but is highly heterogeneous: 50% of orders lie outside the range 0.68-0.82. These findings are robust to several forms of statistical uncertainty. We then test competing hypotheses about the variation. Metabolic theory is currently unable to explain differences in scaling among orders, but the patterns are not consistent with competing explanations either. We conclude that current theories are inadequate to explain the full range of metabolic scaling patterns observed in nature.

Phylogenetically-informed priorities for amphibian conservation.

1. We present a statistical analysis of the scaling of resting (basal) metabolic rate, BMR, with body mass, B(m) and body temperature, T(b), in mammals. 2. Whilst the majority of the variance in ln BMR is explained by ln B(m), the T(b) term is statistically significant. The best fit model was quadratic, indicating that the scaling of ln BMR with ln B(m) varies with body size; the value of any scaling exponent estimated for a sample of mammals will therefore depend on the size distribution of species in the study. This effect can account for much of the variation in scaling exponents reported in the literature for mammals. 3. In all models, inclusion of T(b) reduced the strength of scaling with ln B(m). The model including T(b) suggests that birds and mammals have a similar underlying thermal dependence of BMR, equivalent to a Q(10) of 2.9 across the range of T(b) values 32-42 degrees C. 4. There was significant heterogeneity in both the mass scaling exponent and mean BMR across mammalian orders, with a tendency for orders dominated by larger taxa to have steeper scaling exponents. This heterogeneity was particularly marked across orders with smaller mean B(m) and the taxonomic composition of the sample will thus also affect the observed scaling exponent. After correcting for the effects of ln B(m) and T(b), Soricomorpha, Didelphimorphia and Artiodactyla had the highest BMR of those orders represented by more than 10 species in the data set. 5. Inclusion of T(b) in the model removed the effect of diet category evident from a model in ln B(m) alone and widely reported in the literature; this was caused by a strong interaction between diet category and T(b) in mammals. 6. Inclusion of mean ambient temperature, T(a), in the model indicated a significant inverse relationship between ln BMR and T(a), complicated by an interaction between T(a) and T(b). All other things being equal, a polar mammal living at -10 degrees C has a body temperature approximately 2.7 degrees C warmer and a BMR higher by approximately 40% than a tropical mammal of similar size living at 25 degrees C.