Diel niche variation in mammals associated with expanded trait space

Area of Science:

• Ecology
• Evolutionary Biology
• Mammalogy

Background:

• Most mammal species exhibit nocturnal activity patterns.
• The diversification of mammals into different diel (daily activity) niches raises questions about their functional trait space occupation.

Purpose of the Study:

• To investigate whether mammal species occupying distinct diel niches possess unique functional trait combinations.
• To analyze the functional trait space occupied by nocturnal, cathemeral, and diurnal mammal species.

Main Methods:

• Analysis of five major functional traits: body mass, litter size, diet, foraging strata, and habitat breadth.
• Utilized hypervolumes to assess trait space occupation for 5,104 extant mammal species.
• Compared trait space occupied by species with different diel activity patterns.

Main Results:

• Daytime-active (cathemeral or diurnal) mammal species evolved trait combinations distinct from nocturnal and crepuscular species.
• Nocturnal species occupy 55% unique trait space, while diurnal species occupy 30% unique trait space.
• 44% of trait space for species with obligate diel niches is shared, suggesting potential flexibility in activity patterns for many species.

Conclusions:

• Mammalian functional trait space is structured by diel activity patterns.
• Conservation strategies must consider functional distinctiveness across all diel niches, not just nocturnal ones.
• A significant proportion of mammal species may exhibit greater flexibility in their activity patterns than currently recognized.