Latitude shapes diel patterns in insect biodiversity

Area of Science:

• Ecology
• Biogeography
• Zoology

Background:

• Historical naturalists noted differences in diurnal and nocturnal species between tropical and temperate zones.
• Ecologists are now systematically exploring global geographic variations in diel (daily) activity patterns.

Purpose of the Study:

• To investigate the geographic variation in diel activity patterns of insect communities globally.
• To determine how the proportion of nocturnal, diurnal, and cathemeral species changes with latitude.

Main Methods:

• Analysis of data from 60 insect communities across global latitudes.
• Quantification of the proportion of species active at different times of day (nocturnal, diurnal, cathemeral).

Main Results:

• The proportion of nocturnal insect species declines from 36% at the equator to 8% at 60° latitude.
• The proportion of diurnal species shows no significant latitudinal trend.
• The proportion of cathemeral species increases from 18% at the equator to 68% at 60° latitude.

Conclusions:

• Latitudinal gradients significantly shape the partitioning of diel activity time in insect communities.
• Observed trends in insect diel activity broadly mirror patterns in vertebrate species occupying different temporal niches.
• Understanding the mechanisms behind these patterns is crucial for addressing insect declines.