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Difficulty: MediumAdaptive Radiation and Mechanisms of Speciation

Two closely related species of field crickets inhabit the same meadow and are capable of producing viable hybrids in laboratory settings. However, in nature, interbreeding never occurs because one species actively calls and mates at dawn while the other mates exclusively at dusk. Which type of reproductive isolating mechanism is maintaining speciation between these two populations?

  1. Temporal isolationAnswer
  2. B
    Geographical isolation
  3. C
    Mechanical isolation
  4. D
    Hybrid breakdown

Answer

Temporal isolation prevents gene flow between the two cricket populations because their reproductive activities occur at different times of the day (dawn versus dusk) despite sharing the same geographic habitat.
Temporal isolation is a pre-zygotic reproductive barrier that prevents interbreeding between sympatric species because they breed at different times of the day, seasons, or years. In this scenario, mating at dawn versus dusk ensures that mature gametes are never exchanged in nature.

Step-by-Step Solution

1
Analyze the environmental context and spatial distribution of the two populations.
Both species inhabit the exact same meadow, eliminating physical spatial barriers (geographical isolation).
Sympatric populations occupy overlapping geographic ranges.
2
Identify the precise barrier preventing interbreeding.
Mating activity is separated by time of day (dawn vs. dusk).
Different mating schedules act as a pre-zygotic barrier preventing gametes from meeting.
3
Classify the reproductive isolation mechanism.
Separation based on timing of reproductive behavior is defined as temporal isolation.
Temporal isolation prevents gene flow between populations due to differences in reproductive timing.

Key Concept

Pre-zygotic Reproductive Isolation Mechanisms (Temporal Isolation)
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Topics

Adaptive Radiation and Mechanisms of Speciation

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