Human impacts on genetic diversity are poorly understood yet critical to biodiversity conservation. We used 175 247 COI sequences collected between 1980 and 2016 to assess the global effects of land use and human density on the intraspecific genetic diversity of 17 082 species of birds, fishes, insects and mammals. Human impacts on mtDNA diversity were taxon and scale‐dependent, and were generally weak or non‐significant. Spatial analyses identified weak latitudinal diversity gradients as well as negative effects of human density on insect diversity, and negative effects of intensive land use on fish diversity. The observed effects were predominantly associated with species turnover. Time series analyses found nearly an equal number of positive and negative temporal trends in diversity, resulting in no net monotonic trend in diversity over this time period. Our analyses reveal critical data and theory gaps and call for increased efforts to monitor global genetic diversity.

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Visiting multiple locations and returning to the start via the shortest route, referred to as the traveling salesman (or salesperson) problem (TSP), is a valuable skill for both humans and non-humans. In the current study, pigeons were trained with increasing set sizes of up to six goals, with each set size presented in three distinct configurations, until consistency in route selection emerged. After training at each set size, the pigeons were tested with two novel configurations. All pigeons acquired routes that were significantly more efficient (i.e., shorter in length) than expected by chance selection of the goals. On average, the pigeons also selected routes that were more efficient than expected based on a local nearest-neighbor strategy and were as efficient as the average route generated by a crossing-avoidance strategy. Analysis of the routes taken indicated that they conformed to both a nearest-neighbor and a crossing-avoidance strategy significantly more often than expected by chance. Both the time taken to visit all goals and the actual distance traveled decreased from the first to the last trials of training in each set size. On the first trial with novel configurations, average efficiency was higher than chance, but was not higher than expected from a nearest-neighbor or crossing-avoidance strategy. These results indicate that pigeons can learn to select efficient routes on a TSP problem.

For biologists, creating your first publishable mathematical model often occurs in grad school. While many new modellers understand what is the desired end product, a “finished model”, few students may be aware of the challenges that could hinder achieving that goal - at least we were not. Now as graduate students with significantly more experience building models, we decided to write ten simple rules about our process of creating, testing and fitting mathematical models. These are the rules we wish we had internalized when we began our modelling journeys. Our proposed rules cover a range of topics spanning the more technical - study good coding practices and develop key skills required - to more philosophical - give yourself enough time and care about more than the endpoint. Overall, we hope our rules emphasize to readers that model-building is a process where skills are gained, and lessons are learned with every iteration.

SummaryHuman impacts on genetic diversity are poorly understood yet critical to understanding the evolutionary capacity of the world’s biodiversity. We used global maps of land use and human density to assess human impacts on the intraspecific genetic diversity of 15,946 species of birds, fishes, insects, and mammals over time and across four spatial scales worldwide. We analyzed 164,518 mitochondrial cytochrome c oxidase subunit I (COI) sequences to quantify changes in genetic diversity between 1980-2016. We found temporal change in genetic diversity, with both increasing and decreasing trends observed. The magnitude and sign of human impacts on genetic diversity depended on scale and taxon. In contrast, latitude was a strong predictor of diversity in fish, insects, and mammals. Our analyses provide a first worldwide picture of human impacts on animal genetic diversity. A global effort to systematically monitor genetic diversity is needed to fill the gaps in taxonomic and geographic coverage in this dataset.