Intraspecific Variation in and Environment-Dependent Resource Allocation to Embryonic Development Time in Common...

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Ecology

Background:

• Embryonic development time is hypothesized to influence life histories via trade-offs, but this is mainly inferred from interspecific comparisons.
• Intraspecific variation in embryonic development time, independent of environmental factors, is crucial for detecting life-history trade-offs but remains poorly understood.

Purpose of the Study:

• To investigate intraspecific variation in embryonic development time in common terns (Sterna hirundo).
• To determine if intrinsic factors influence embryonic development rate and resource allocation.
• To explore the potential for detecting life-history trade-offs related to embryonic development.

Main Methods:

• A common-garden experiment was conducted using free-living common tern eggs incubated at two different temperatures.
• Hatching success, incubation time, and embryonic heart rate were measured.
• Statistical analyses corrected for environmental variables like year and incubation temperature.

Main Results:

• High hatching success was observed, with a slight decrease at lower temperatures.
• Significant intraspecific variation in incubation time and embryonic heart rate was detected, suggesting intrinsic differences.
• Incubation time and embryonic heart rate were strongly correlated; faster heart rates correlated with shorter incubation times.
• Even after accounting for heart rate, lower temperatures led to longer development times, indicating environment-dependent resource allocation.

Conclusions:

• Intrinsic differences in embryonic development rates exist within the common tern population.
• Life-history trade-offs involving embryonic development time can be detected at the intraspecific level.
• The manifestation and resolution of these trade-offs are dependent on embryonic environmental conditions.