Ever been told you are too picky when it comes to dating? That is ok, it is just sexual selection at work.
Matting often can be broken down into courting males and choosy females, each exhibiting specific behaviors. Males must be master communicators in order to pass along his genes. Spiders, specifically the Wolf spider (Gladicosa gulosa), are great models to study because sexual cannibalism increases the pressure of males’ needs to effectively court females. It is believed that male Wolf spiders give of specific sounds to attract a mate and approach females at different frequencies, however, the relationship between time of approach and sound is unknown along with their effects on copulation success.
In 2017 Researchers at the Uetz lab at the University of Cincinnati decided to further test how the specific aspects of sound such as amplitude, and latency affect copulation success. Researchers collected mature individuals from a deciduous forest in New Richmond, OH. Because all males and females were mature adults their past mating experiences was unknown. Researchers designed a plastic circular arena with a removable divider to conduct to trial pairings. During trial pairings, researchers placed the females on one side of the divider for 24 hours allowing them to deposit chemical mating cues. Then the females were removed for an hour and rewarded with a cricket and water before being placed in the opposite side of the arena under a glass vial blocking them from hearing and emitting sound along with chemical cues across the divider. Next, the males were placed on the side of the arena where the females left their chemical cues and the females were released from the vial. During this time the divider was still in place, however, this did not stop the transmission of auditory and chemical signals. After 10 minutes the divider was removed and the spiders were able to have a direct contact for another 10 minutes. Each trial was recorded using cameras and laser Doppler vibrometry in order to detailedly measure the sound vibrations and physical cues of the specimen. Finally, the vibratory and social signals were broken down and analyzed using a linear regression. Males produced stridulatory pulses and percussive strikes, which were found to be significantly related to the Wolf spiders mating success. Males who began their courtship sooner were found to be have had more successful courtships. Females were found to show many ranges of behavior however only tap was found to influence mating success. After the experiment, the spiders were euthanized.
The researchers discovered that as the amplitude of male stridulatory pulses increased so did the number of taps in response from females, thus showing that females preferred louder males. Researchers also discovered that males who began courtship immediately were often more likely to find a female mate. With new testing methods, one could test the males to see if the amplitude of the vibrations is the true reason. This allows for future studies to be more focused on the evolutionary relationship between the Wolf spiders and their other mating competitions. Because of female Wolf spiders’ specific choosiness over males, they are able to have a higher sexual fitness.
