Bimodal echolocation in pipistrelle bats: are cryptic species present?

Area of Science:

• Zoology
• Bioacoustics
• Evolutionary Biology

Background:

• The pipistrelle bat (Pipistrellus pipistrellus) is widespread and abundant in Europe.
• Traditionally, P. pipistrellus has been considered a single species across its European range.

Purpose of the Study:

• To investigate the acoustic and morphological variation within Pipistrellus pipistrellus populations in Britain and Europe.
• To determine if distinct 'phonic types' represent separate species or subspecies.

Main Methods:

• Analysis of echolocation call frequencies in British and European pipistrelle populations.
• Examination of morphological characteristics of bats belonging to different phonic types.
• Observation of roosting behavior and colony composition.

Main Results:

• Two distinct echolocation call frequency bands (averaging 46 kHz and 55 kHz) were identified in British pipistrelles.
• Roosting bats exclusively used one type of echolocation, with minimal mixing between colonies.
• Significant, though small, morphological differences were found between the two phonic types.
• Bimodal echolocation is common across Europe, with some areas showing sympatric occurrence of both types.

Conclusions:

• The data suggest that Pipistrellus pipistrellus may represent at least two cryptic sibling species.
• The findings support the hypothesis of sympatric speciation, potentially driven by disruptive selection on echolocation calls.