Historically, the speciation rate of marine crustaceans in the Anomura group (including hermit crabs, king crabs, and squat lobsters) has increased when global temperatures have decreased, finds a study published in Nature Communications this week. Global cooling may have altered the habitats occupied by marine crustaceans through changes in tectonic activity and ocean currents, lowered sea level, and increased oxygen availability.

Changes in climate can increase extinction rates by making habitats unsuitable for the species previously living in them. Yet, studies have also found a relationship between climate and speciation rates, with higher speciation rates in groups of terrestrial and marine vertebrates associated with warmer global temperatures.

Katie Davis and colleagues investigated the relationships between speciation rate and climate in the Anomura over the last 200 million years. They found that significant shifts in the rates of speciation have only occurred in the last 100 million years. For marine clades, speciation rate was negatively correlated with temperature. However, for the one freshwater clade in the Anomura, speciation rate increased with increasing temperature.

These findings suggest that future global warming will increase speciation rates in some habitats, but decrease speciation rates in other habitats.