Chinese scallops (Chlamys farreri) with an ancient ZZ/ZW sex-determination system. The finding of 350 million years of sex chromosome homomorphy in scallops, sustained by reversible sex-biased genes and sex-determiner translocation, argues against classical theory, which suggests that heteromorphy is the ultimate evolutionary fate of sex chromosomes.

See Han et al.

A mule deer bounds away after being captured, measured and released near Superior, USA. The expansion of natural-gas energy infrastructure over 14 years along a migratory corridor has changed deer behaviour, and has reduced by more than 38% their ability to keep pace with spring vegetation green-up.

See Aikens et al.

A head-to-head interaction between two QR code-marked honeybees. Bees without gut microbiota engage in fewer such interactions and are less selective over their social partners than bees with gut microbiota. This microbial influence over host behaviour seems to be mediated by amino acid metabolism in the brain.

See Liberti et al.

The Carassius polyploid complex contains sexual C. auratus and unisexual C. gibelio. Comparative genome anatomy reveals that C. auratus is amphidiploid and C. gibelio is amphitriploid, providing novel evolutionary insights into the maintenance mechanism of unisexual polyploids in vertebrates.

See Wang et al.

The molecular basis of the division of labour is explored using transcriptomic analysis of the brains of different castes of pharaoh ant (Monomorium pharaonis). In this image, brain structures from 3D brain reconstructions were overlaid on macrophotos of the ant heads.

See See Li et al.

Polar bears diverged from brown bears roughly 500,000 years ago. However, analyses of a >100,000-year-old polar bear palaeogenome reveal that, as habitats shifted during the ice ages, the two species interbred. Today, although all brown bears exhibit ancestry from admixture with polar bears during the last interglacial period, polar bears do not retain brown bear ancestry.

See Wang, M.-S. et al

Hummingbird–plant mutualism is an ideal system to study climate-change pressures on ecological communities, given the availability of interaction and occurrence data. Even though species in Andean communities, such as this spangled coquette (Lophornis stictolophus), tend to have small geographic distributions, the communities appear resilient to future climate changes, unlike communities in lowland South America and in North America.

See Sonne et al.

An adult male gelada in the Simien Mountains National Park, Ethiopia. Geladas are adept rock climbers and descend down steep cliffs at night, where they are safe from predators. In the morning, they rise and ascend to forage for grasses.

See Chiou et al.

Hibernators have longer lifespans than would be expected based on their body weight. Use of epigenetic markers to estimate ageing supports the hypothesis that biological ageing is stalled during hibernation in yellow-bellied marmots, which hibernate for 7–8 months per year.

See Pinho et al.

The aftermath of a wildfire in the conifer forests of the Sierra Nevada in California, USA, shows the differential survival of trees, potentially due to variation in sensitivity to water limitation.

See Rao et al.

A male puma (individual M87) up a tree, immediately prior to sampling. Fountain-Jones et al. provide evidence that male pumas were dominant in feline immunodeficiency virus (FIV) transmission chains when hunting was excluded from the landscape. M87 was at the end of one FIV chain, and probably contracted the virus as a juvenile.

See Fountain-Jones et al.

Stone tools from Denisova Cave linked to new Denisovan fossils. At 200,000 years old, the new fossils are the oldest Denisovans discovered so far, and were found in well-dated archaeological layers that are rich in lithics and animal remains.

See Brown et al.