A researcher studying a cricket species finds that individuals on either side of a large river have different call frequencies on average. The following statements were made:

A. The different call frequencies may signal incipient speciation
B. The change in call frequency can lead to allopatric speciation
C. Individuals of one population transplanted to the other population (across the river) may have lower chance of finding mates than residents
D. Call frequencies have changed from ultrasound across the river

If the call helps attract mates which of the above statements are correct?

Correct option is A

Explanation-

Analyzing each statement-

A. The different call frequencies may signal incipient speciation - CORRECT
“Incipient speciation” means the early stages of speciation. If call frequency differences reduce mating between the two populations, it may lead to reproductive isolation, a key driver of speciation.
B. The change in call frequency can lead to allopatric speciation - CORRECT
Allopatric speciation occurs when a physical barrier (like a river) separates populations. If call differences reduce mating across the river, reproductive isolation may evolve, promoting allopatric speciation.
C. Individuals of one population transplanted to the other population (across the river) may have lower chance of finding mates than residents - CORRECT
If mating calls differ significantly, transplanted individuals may not be recognized or preferred as mates by the opposite population, reducing their mating success.
D. Call frequencies have changed from ultrasound to infrasound across the river - INCORRECT
This is an extreme and biologically implausible change. Such drastic shifts in frequency (from ultrasound to infrasound) would likely result in complete communication breakdown, and are not supported by typical patterns of acoustic divergence in insects like crickets.

Final Answer:
A, B, and C (Option a)