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ABSTRACT Human activity has reshaped ecological communities for thousands of years. While these activities have typically led to habitat loss, some species have successfully exploited human environments. However, the effects of long‐term human land‐use on the distributions of such species are poorly understood. Here, we investigated how land‐use change over the last 12,000 years has altered habitat distributions for a widespread human‐commensal bird, the Pacific swallow (Hirundo tahitica). LocationSoutheast Asia, Melanesia. MethodsWe assessed habitat availability for Pacific swallows using citizen science‐based occurrence records and species distribution models that included (a) only climate data, (b) only land‐use data and (c) both variable sets combined. We evaluated approaches to address the unique spatial biases that arise in unstructured survey data of human‐associated species and determined which models performed best with present‐day occurrence records. We then hindcasted alternative models at 1000‐year intervals over 12,000 years to evaluate the relative effects of climate and human land‐use on long‐term habitat availability. ResultsModels that included both climate and human land‐use variables were the best fit to occurrence records. Standard methods for controlling for spatial bias performed poorly compared with fully sampling the environmental background, highlighting unique considerations for modelling human‐associated species. Hindcasting showed that while climate‐only models predicted little change in habitat availability over time, combined models showed habitat increases beginning more than 5000 years ago and significant expansions of habitat over the last 2000 years. Main ConclusionsHuman land‐use over the last several thousand years has likely provided Pacific swallows with substantial new habitat, which may have led to population size expansions. Incorporating long‐term human land‐use into species distribution models offers insights into when associations with human environments may have arisen and generates testable predictions for how populations respond and adapt to human land‐use change over millennial timescales. 

Abstract Understanding global patterns of genetic diversity is essential for describing, monitoring, and preserving life on Earth. To date, efforts to map macrogenetic patterns have been restricted to vertebrates, which comprise only a small fraction of Earth’s biodiversity. Here, we construct a global map of predicted insect mitochondrial genetic diversity from cytochrome c oxidase subunit 1 sequences, derived from open data. We calculate the mitochondrial genetic diversity mean and genetic diversity evenness of insect assemblages across the globe, identify their environmental correlates, and make predictions of mitochondrial genetic diversity levels in unsampled areas based on environmental data. Using a large single-locus genetic dataset of over 2 million globally distributed and georeferenced mtDNA sequences, we find that mitochondrial genetic diversity evenness follows a quadratic latitudinal gradient peaking in the subtropics. Both mitochondrial genetic diversity mean and evenness positively correlate with seasonally hot temperatures, as well as climate stability since the last glacial maximum. Our models explain 27.9% and 24.0% of the observed variation in mitochondrial genetic diversity mean and evenness in insects, respectively, making an important step towards understanding global biodiversity patterns in the most diverse animal taxon.