Date:
July 30, 2014
Source: PLoS ONE
Institutions Involved: Max Planck Institute for Ornithology,
University College Dublin, Tabachka Bat Research Station, MTA-ELTE-MTM Ecology
Research Group, Naturalia environnement, Tunis Superior Institute for
Biological Applied Sciences, and Max Planck Institute for Evolutionary Biology
Summary:
Research suggests that sexual selection plays a role in the
evolution of high frequency echolocation in bats, possibly against natural
selection, according to a study published on July 30, 2014 in the open-access
journal PLoS ONE by Sebastien J.
Puechmaille and his colleagues.
Animals
generally use echolocation, or acoustic signals, as a means of
communication. Unlike bird songs or frog calls, bats are very
interesting when studying the evolution of signaling systems because
echolocation is used for both foraging (food detection) and communication. While it was common belief that echolocation is
influenced by ecology through natural selection alone, Puechmaille et al.
investigated the role of echolocation calls with regards to sexual selection in
bats.
This
study was conducted using 90 Rhinolophus
mehelyi or Mehely’s horseshoe bat (75 females and 15 males) collected at
two caves in North-Eastern Bulgaria. This
bat species was an ideal choice because unlike other species of the
Rhinolophidae family that produce lower frequencies as they increase in body
size, R. mehelyi differ greatly by
producing frequencies higher than expected given their size. Attributing this piece of information to
sexual selection, researchers hypothesized that an individual’s echolocation
peak frequency should be related to its body size and condition, and therefore
indicate mate quality. They predicted
that females should prefer males with high frequency calls during the mating season. As a result, males with high peak frequency
should have a higher reproductive success, and therefore have higher
relatedness with other members of the colony (more relatives).
The
experiments were performed in a one cubic meter box, lined with sound-absorbing
foam. The bat was placed on a listening
perch (wooden basket) at an equidistant position from the two compartments, with
each containing a speaker. The set-up
was also equipped with infrared light, and an infrared-sensitive camera to
monitor the activity of the bat. The
assignment of low or high frequency playback to the left or right speaker was
randomized before testing each individual.
The
data demonstrated that echolocation peak frequency is representative of body
size and body condition, with the larger and heavier individuals have higher frequencies. It was found that the female bats are more
attracted to males with higher peak frequency during the mating season. This result is in accordance with the theory
of sexual selection that females prefer to mate with good quality males to produce
fitter offspring. Along with female mate
choice, the researchers had observed a significant positive correlation between
relatedness and peak frequency in male bats.
The
combination of behavioral, ecological, and genetic studies provided researchers
with the first documented evidence that female bats indeed choose their mate
based on echolocation frequency. The
ability of bats to precisely locate the source of acoustic signals even in
complete darkness further establishes the idea that echolocation is essential for
mating.
Citation:
Puechmaille,
S.J., I.M. Borissov, S. Zsebok, B. Allegrini, M. Hizem, S. Kuenzel, M.
Schuchmann, E.C. Teeling, and B.M. Siemers. 2014. Female Mate Choice Can Drive the Evolution of
High Frequency Echolocation in Bats: A Case Study with Rhinolophus mehelyi.
PLoS ONE 9(7): e103452.
I found it interesting how bats produce higher frequencies with increasing body size and weight. It was also fitting how you mentioned at the end that this study is supported since bats find mates in the dark.
ReplyDeleteI found it interesting that echolocation is used by bats as a measure of fitness. In fact, the parallel between natural selection and sexual selection related to echolocation is one that I have never read up on prior to this summary.
ReplyDeleteI found this study and write-up really interesting because it related to the main idea of the paper I researched, which is the sometimes antagonistic correlation between natural and sexual selection. I was also really fascinated in this particular study by the correlation between frequency and body size/weight. I had no idea that the two were related, but after reading your write-up, it makes sense that the two traits would go hand-in-hand, seeing as bigger bats might be considered the healthier and fitter kind, traits that a female would want to pass on to her offspring and also seeing as these bigger bats are the ones producing the higher frequencies that attract the females, proving -- like you said -- that echolocation is essential for bat mating.
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