Reproductive character displacement in Magicicada -decim calling songs.
|M. tredecim||M. neotredecim||M. neotredecim||M. septendecim|
In 1998, while studying Brood XIX in northern Arkansas, periodical cicada choruses with two peak acoustical frequencies (ca. 1.1 and ca. 1.7 kHz;) were found within the "anomalous zone" reported by Martin and Simon, in which two mtDNA haplotypes of 13-year M. -decim could be found. The high-pitched cicadas that we found corresponded to the northern haplotype (A) and the low-pitched cicadas corresponded to the southern haplotype (B). A series of playback experiments demonstrated that the two types of 13-year M. -decim were reproductively isolated, so the northern type (mtDNA lineage A) was named M. neotredecim while the southern type retained the name M. tredecim
Where M. neotredecim and M. tredecim overlap, they exhibit a pattern of reproductive character displacement in calling song pitch and female pitch preferences. Within the zone of displacement, the dominant male call pitch of M. neotredecim is 1.7 kHz, while outside the contact zone, its call pitch is ca. 1.4 kHz, identical to that of its putative ancestor, M. septendecim.