Butterfly Evolution: Why Only Some Males Are Able To Attract Females

Some species listen for mating calls, while others choose their better half based solely on physical attributes. Female butterflies, however search for males that smell just right, report researchers from the Smithsonian Institute.

Female butterflies use this screening process to ensure that they will reproduce successfully. That's a tough break for male butterflies, because not all males have scent-producing organs. When different species mate, certain genetic characteristics might get lost along the way. This is the case for some male butterflies who evolve without the scent-producing organs. A recent study, recently published in ZooKeys, explained that evolutionary losses such as this may occur when males are not living near their closest relatives, who would otherwise pass down the scent-producing organs. In other words, if there are fewer similar species in the same area to choose from, and males are not producing the right scent, female butterflies are subject to choosing more distant relatives to mate with. Therefore, less and less fragrant butterflies would evolve. 

To understand these evolutionary differences more, Dr. Robert Robbins, from the Smithsonian Institution, examined a small group of Latin American butterflies, known as the Oppia Hairstreak (Thereus oppia). According to a news release, he discovered that two new members of this group had scent pads, while their closest relatives did not. This suggests that scent pads were lost along two evolutionarily paths in this group, according to the researchers. The species that lacked the scent organs were also not surrounded by their closest relatives.

Dr. Robbins noted that he and his fellow researchers have seen evolutionary losses such as this in other species as well, and it is quite common. When a species evolves differently than its ancestors, it signifies habitat changes such as geographic isolation. This study help researchers better understand why some males evolve with the scent pads and other don't. 

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