M. neotredecim and its sister species, M. septendecim, are consistently distinguishable only in life cycle length. This species is similar to 13-year M. tredecim, but distinguishable in male song pitch, female song pitch preferences (Marshall and Cooley 2000), abdomen color, and mitochondrial DNA (mtDNA) lineage (Simon et al. 1998, Martin and Simon 1988, 1990). These findings are consistent with the theory that M. neotredecim evolved from populations of M. septendecim by a life cycle change (Martin and Simon 1988, 1990, Marshall and Cooley, 2000, Simon et al. 2000).
The two 13-year -decim species have a special geographic relationship — they are not sympatric (living together) across the entire 13-year range. M. neotredecim inhabits the midwestern part of the 13-year range, while M. tredecim inhabits the southern and southeastern part (see map below). The two species overlap only along a narrow region in northern Arkansas, western Kentucky, and southern Missouri, Illinois, and Indiana. By comparison, the three 17-year species are found together from Connecticut to Kansas, and the remaining 13-year species together inhabit most 13-year populations. Where M. neotredecim and M. tredecim overlap, M. neotredecim songs are much higher-pitched, while M. tredecim songs are slightly lower-pitched. This pattern of reproductive character displacement suggests that the songs have evolved to reduce wasteful sexual interactions between the species.
The photos show that M. neotredecim is extremely similar to 17-year M. septendecim in appearance. The dark bands on the underside of the abdomen are similar to those of M. septendecim. Again, the calling song of M. neotredecim is high-pitched only where it overlaps M. tredecim geographically; the samples below are taken from this overlap zone. Outside of that region, M. neotredecim songs are indistinguishable from those of M. septendecim.
Magicicada neotredecim songs:
The songs below are all high-pitched, displaced songs from the overlap zone.
Courship I song/ Calling song
Courtship II song
Courtship III song (fragment)
Reproductive Character Displacement
In 1998, while studying Brood XIX in northern Arkansas, we discovered periodical cicada choruses with two peak acoustical frequencies (ca. 1.1 and ca. 1.7 kHz;) within the “anomalous zone” reported by Martin and Simon, in which two mtDNA haplotypes (A and B) of 13-year M. -decim could be found. The high-pitched cicadas corresponded to the northern haplotype (A) and the low-pitched cicadas corresponded to the southern haplotype (B). We used a series of playback experiments to demonstrate that the two types of 13-year M. -decim were reproductively isolated. Thus, the northern type (mtDNA lineage A) was named M. neotredecim while the southern type (mtDNA lineage B) 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.
Cooley, J. R., C. Simon, D. C. Marshall, K. Slon, and C. Ehrhardt. 2001. Allochronic speciation, secondary contact, and reproductive character displacement in periodical cicadas (Hemiptera: Magicicada spp.): genetic, morphological, and behavioural evidence. Molecular Ecology 10:661-671.
Cooley, J. R., C. Simon, and D. C. Marshall. 2003. Temporal separation and speciation in periodical cicadas. Bioscience 53:151-157.
Martin, A., and C. Simon. 1988. Anomalous distribution of nuclear and mitochondrial DNA markers in periodical cicadas. Nature 336:237-239.
Martin, A., and C. Simon. 1990. Differing Levels of Among-Population Divergence in the Mitochondrial DNA of Periodical Cicadas Related to Historical Biogeography. Evolution 44:1066-1080.
Marshall, D. C., and J. R. Cooley. 2000. Reproductive Character Displacement and Speciation in Periodical Cicadas, with Description of a New Species, 13-Year Magicicada neotredecim. Evolution 54:1313-1325.
Simon, C., J. Tang, S. Dalwadi, G. Staley, J. Deniega, and T. R. Unnasch. 2000. Genetic Evidence for Assortative Mating between 13-Year Cicadas and Sympatric “17-Year Cicadas with 13-Year Life Cycles” Provides Support for Allochronic Speciation. Evolution 54:1326-1336.