Thermally moderated firefly activity is delayed by precipitation extremes

Area of Science:

• Ecology
• Entomology
• Climate Change Biology

Background:

• Insect phenology, crucial for life history events like mating, is typically regulated by photoperiod or temperature accumulation.
• Other factors such as rainfall and host plant phenology can also influence insect timing, leading to complex interactions.
• Phenological asynchronies can arise when multiple environmental drivers interact, impacting species interactions.

Purpose of the Study:

• To investigate the phenological patterns of fireflies (Photinus spp.) over a 12-year period.
• To determine if interacting environmental drivers explain variability in adult firefly flight activity density.
• To assess the influence of plant communities on firefly phenology.

Main Methods:

• Long-term monitoring of firefly (Photinus spp.) adult flight activity density from 2004 to 2015.
• Analysis of phenological data across 10 distinct plant communities.
• Statistical modeling to identify key drivers (temperature, precipitation, plant community) and their interactions influencing firefly flight timing.

Main Results:

• Temperature accumulation (base 10°C) was the primary driver, with peak flight activity around 800 degree-day units.
• Significant variation in peak activity timing (±180 degree-day units) was observed annually.
• Precipitation accumulation showed a quadratic relationship with flight timing; extreme wet or dry years delayed activity.
• Herbaceous plant communities with minimal soil disturbance supported higher firefly captures.
• Weak interactions were found between climatic variables and plant community type.

Conclusions:

• While temperature is the main cue for firefly phenology, precipitation extremes significantly modulate this relationship.
• The interaction between temperature and precipitation suggests that altered rainfall patterns can exacerbate climate warming's effects on insect phenology.
• Understanding these complex interactions is vital for predicting the impact of climate change on insect populations and ecological communities.