Double the Bugs - Two cicada broods are set to emerge this summer, and our expert can explain the significance
It's coming this summer -and it'll be twice as big!
Two broods of cicadas are set to emerge this year, an event that last occurred more than 200 years ago and now has scientists, bug watchers, and fans of the loud and noisy (yet harmless) insects buzzing with anticipation.
Media coverage of this popular event put on by nature is also starting, and John R. Cooley, a cicada expert at UConn, offered his expertise on the impending emergence to MassLive:
This summer, some will get a chance to witness a phenomenon rarer — and probably louder — than Halley’s comet. For the first time in more than two centuries, two big groups of cicadas in the United States will emerge simultaneously from the ground. Cicadas, often called “heat bugs,” make their presence known throughout the country every summer by “singing” their loud song. But some of these large, flying insects only emerge from underground every so often, depending on their group, or brood. These “periodical” cicadas bury themselves in soil, where they spend most of their lives. This summer, millions of cicadas from broods XIX (emerging every 13 years) and XIII (every 17 years) will both crawl out from underground and fly across the south and Midwest looking for a mate, according to Cicadamania, a website dedicated to tracking the insects. The last time these two broods popped out of the ground at the same time was in 1803, Cicadamania reported – when the U.S. bought the Louisiana Territory from France. “You cannot possibly be unaware that periodical cicadas are out, because they’re out by the millions and millions, and they’re noisy, charismatic, active insects that are just everywhere,” John R. Cooley, an entomologist who studies cicadas at the University of Connecticut, told MassLive. “When you got them, you know it. And that’s what you can expect to see. That’s what any normal emergence looks like,” he continued. What folks will see are a whole lot of bugs that all look the same, as the ones that come out every decade-plus look the same as the ones that come out every year, Cooley said. Researchers are still exploring why some cicadas emerge periodically. One common theory is that their infrequent appearance helps them avoid predators and prevents enemies from synchronizing on their life cycle. But, Cooley said this theory is flawed since all cicadas have predators, but fewer than 10 species are periodical. Some of the cicada’s natural enemies include birds, moles and Cicada killer wasps, according to the University of California Integrated Pest Management Program. Another theory suggests the last ice age forced cicadas to evolve to have longer periodical life cycles. But, that theory is limited as many cicadas live near glacial areas – few of which are periodical, according to nature.com. “Science isn’t all about having the explanations,” Cooley said. “We just test hypotheses and there are a lot of hypotheses as to why these cicadas are the way they are, but none really stand up so far.” The emerging of cicadas is always a popular and trending topic, and if you have questions or are looking to cover, then let us help.
John R. Cooley is an Associate Professor in Residence at the University of Connecticut. He is an entomologist, author, and leading authority when it comes to cicadas. Simply click on his icon now to arrange a time to talk today.
Biography
As an undergraduate, John Cooley was fascinated by historical ecology and evolutionary biology. Inspired by Dr. Charles Remington, he developed a long-term interest in species, speciation, and secondary contact, especially the problem of whether populations merge or separate upon meeting. He completed a senior research project that was a simple molecular phylogeny of major insect orders.
As one of Richard D. Alexander's students, Cooley developed his interests in speciation, reproductive isolation, and mate choice. He studied both syrphid flies (genus Arctophilia) and periodic cicadas (genus Magicicada). He worked as a curatorial assistant in the insect division of the University of Michigan Museum of Zoology.
As a postdoctoral researcher under Dr. Chris Simon, he further developed the molecular biology skills first used as an undergraduate. He studied gene flow in a periodical cicada contact zone, the genetics of periodical cicada life cycle switching, and paternal leakage. He also contributed to ongoing systematic projects in the Simon lab and collected cicadas in North America, New Zealand, and Australia.
After finishing his postdoctoral research, Cooley taught at the University of Connecticut, Yale University, Wesleyan University, The Ohio State University, and the University of Rhode Island. For several years, he's been working on mapping species boundaries and using species distribution models to understand biogeography.
More than a trillion cicadas are expected to emerge this year. Will they in Connecticut?
CT Insider online
2025-04-15
While Brood XIV is expected in some parts of the southeast and midwest U.S., Brood XIV also expected on Cape Cod in Massachusetts and Long Island in New York, according to UConn's cicada map.
Connecticut, which has both annual and periodical cicadas, won't see the same level of activity as in neighboring states.
"We're at the edge of the distribution of these cicadas so its not prime territory," said John Cooley, associate professor-in-residence of Ecology and Evolutionary Biology at UConn. "So they're really going to be pretty restricted in where you see them in the state."
Cicadas will return to Kentucky this year. Here's where and when Brood XIV will emerge
Louisville Courier-Journal online
2025-03-26
Kentucky is expecting cicadas this year.
Other states that are expecting cicadas are Georgia, Maryland, Massachusetts, New Jersey, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia and West Virginia.
Kentucky and Tennessee probably will get the most cicadas this year, said John Cooley, an ecology and biology associate professor in residence at the University of Connecticut.
Cicadas set to bring the buzz to 13 states this year: When and where Brood XIV is emerging
USA Today print
2025-03-07
Kentucky and Tennessee probably will get the most cicadas this year, said John Cooley, an ecology and biology associate professor in residence at the University of Connecticut. There will also be large numbers in Georgia, the Carolinas and Pennsylvania, he said.
Is Brood XIV coming to Kentucky? Here's how to spot cicadas and when they might be in town
Louisville Courier Journal print
2025-01-23
John Cooley is an associate professor in residence in the Ecology and Evolutionary Biology department at the University of Connecticut. He said to find out where cicadas will emerge, he and other researchers look to past records.
The area with the most cicadas this year will likely be Kentucky and Tennessee. There will also be large numbers in Georgia, the Carolinas and Pennsylvania, he said.
Buzz, Chirp, Wee-Oo: The Sounds of Cicadas Are Back
The New York Times print
2024-05-17
For the 13-year-cycle cicada species, Brood XIX, which cover the most ground this year, John R. Cooley, a biology professor at the University of Connecticut, said some songs are similar to the 17-year-cycle insects.
In general, the songs of the Magicicada tredecula species are rhythmic frequency sweeps, while the songs of the Magicicada tredecassini species are a series of ticks followed by a frequency sweep, Professor Cooley said. He also noted that species can be active at different times of day.
Cicadas are coming to Massachusetts - but not this year
WBZ News - Boston tv
2024-04-19
Trillions of cicadas are set to emerge in the United States this spring. While the buzzing insects will not come out in New England in 2024, a unique group of cicadas is expected to appear in Massachusetts next year.
Professor John Cooley studies cicadas at the University of Connecticut.
"This year is not going to be a great year for cicada watchers out here in New England and the northeast," he explained to WBZ-TV's Paula Ebben. "Next year we get a true interesting thing that's going to happen."
Wide swath of US will get buggy as two cicada broods intrude
Reuters online
2024-04-02
The 17-year cycle Brood XIII is found in northern Illinois, eastern Iowa, southern Wisconsin and a few counties in northwestern Indiana. The 13-year cycle Brood XIX is distributed in Alabama, Arkansas, Georgia, Indiana, Illinois, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia.
"There's nowhere else in the world where it's possible to see anything at all like this, so I always counsel people to treat them with the respect and awe due to such remarkable creatures," said University of Connecticut evolutionary biologist John Cooley.
In historic year for cicadas, Illinois is ‘the epicenter of everything great’
Chicago Sun Times print
2024-03-14
When the cicadas emerge from their years feeding underground, one brood that emerges every 17 years will be centered in northern Illinois, while the 13-year brood will be found in the southern part of the state. The two converge near Springfield, but there aren’t likely to be many, if any, places where both broods can be found at once. Even so, you won’t know because the broods look and sound identical.
“If you look and you zero in on Springfield, Illinois, that’s where the two broods come close, but they don’t necessarily overlap,” according to John Cooley, who studies cicadas at the University of Connecticut, one of the top institutions for cicada research. “They come real close but there aren’t gonna be places that have double densities or anything like that.”
The World Hasn’t Seen Cicadas Like This Since 1803
The New York Times print
2024-01-19
John R. Cooley, a biology professor at the University of Connecticut, said his best advice for people living in the regions of the dual emergence is to let the bugs be.
“The forest is where they live,” he said. “They are a part of the forest. Don’t try to kill them. Don’t try to spray insecticide, all that kind of thing. That’s just going to end badly because there are more than you could possibly kill with insecticide, you’d end up killing everything.”
If you have delicate plants you want to protect, Professor Cooley said, use special netting created for that purpose.
Millions of cicadas coming out summer 2024 — will the bugs be in Mass.?
Mass Live online
2024-01-12
“You cannot possibly be unaware that periodical cicadas are out, because they’re out by the millions and millions, and they’re noisy, charismatic, active insects that are just everywhere,” John R. Cooley, an entomologist who studies cicadas at the University of Connecticut, told MassLive.
“When you got them, you know it. And that’s what you can expect to see. That’s what any normal emergence looks like,” he continued.
A group of Connecticut cicadas disappeared nearly 70 years ago. Scientists still search for answers.
WNPR radio
2022-07-25
On a hill overlooking the Fenton River Valley, John Cooley gestures to a horizon blanketed with trees. It’s the bucolic embodiment of New England’s forested landscape.
It’s also the scene of a mystery that’s puzzled scientists for nearly 70 years.
What happened to a group of periodical cicadas that used to live here?
“You would think this is perfect periodical cicada habitat; there’s no shortage of forest,” said John Cooley, a member of University of Connecticut’s Hartford teaching faculty who travels the country tracking and studying periodical cicadas.
Will Brood X emerge in New England? Here cicadas are snoozing until 2025 and 2030
USA Today online
2021-05-28
"Periodical cicadas are among the most unusual of insects, with long life cycles, infrequent, periodic mass emergences, striking appearance and noisy behaviors," writes UConn's John Cooley, who runs the Magicicada brood mapping project and studies cicada behavior and ecology.
Periodical cicadas spend nearly all of their lives underground, waiting to emerge, breed and lay eggs. After doing so, they die within just a few weeks. Following Brood X's emergence this year, their offspring will repeat the cycle and go back underground until 2038.
What is Brood X? When do cicadas come out in 2021? Answering your buggiest questions.
The Washington Post online
2021-05-12
People in other affected cities, such as Cincinnati and Philadelphia, will experience the insects as well, but New Yorkers may not. The last New York population, on Long Island, was nearly extinct in 2004. The sandy soil was never a good fit for cicadas, said John R. Cooley, who leads the Periodical Cicada Project at the University of Connecticut.
After 17 years underground, Brood X cicadas set to emerge in the coming weeks
WZZM Michigan tv
2021-04-26
"2021 is the year of periodic cicadas Brood X. These cicadas were eggs in 2004, went into the ground, have been developing for 17 years, and this is their year to come out," Cooley said. "They will come out, multiply into the adult form, spend a couple of weeks flying around, making a lot of noise, mating and laying eggs for the next generation."
These bugs are hard to miss, measuring an inch and a half in length and with mating calls reaching up to 96 decibels — that's as loud as a lawnmower or a train passing by.
"Individually they are not as loud as some of our summer cicadas. But the difference is there are an awful lot of these," Cooley said.
"It's a fun story for us, not for the cicadas," says UConn ecology and evolutionary biology researcher and adjunct faculty member John Cooley.
Though researchers have known about the fungus for around 100 years, Cooley and his colleagues David Marshall, a postdoc, and lab technician Kathy Hill have published new findings about the infection.
Billions of cicadas are emerging, from Cape Cod to north Georgia – here’s how and why we map them
The Conversation
Chris Simon and John Cooley
2025-05-22
If they’re in your area, you’ll know it from their loud droning, chirping and buzzing sounds. Cicadas from Brood XIV – one of the largest groups of cicadas that emerge from underground on a 13-year or 17-year cycle – are surfacing in May and June 2025 across 12 states. This large-scale biological event reaches from northern Georgia up into Indiana and Ohio and eastward through the mid-Atlantic, extending as far north as Long Island, N.Y. and Massachusetts.
Through mid-June, wooded areas will ring with cicadas’ loud mating calls. After mating, each female will lay hundreds of eggs inside small tree branches. Then the adult cicadas will die. When the eggs hatch six weeks later, new cicada nymphs will fall from the trees and burrow back underground, starting the cycle again.
Billions of cicadas are about to emerge from underground in a rare double-brood convergence
The Conversation
John Cooley and Chris Simon
2024-04-18
In the wake of North America’s recent solar eclipse, another historic natural event is on the horizon. From late April through June 2024, the largest brood of 13-year cicadas, known as Brood XIX, will co-emerge with a midwestern brood of 17-year cicadas, Brood XIII.
This event will affect 17 states, from Maryland west to Iowa and south into Arkansas, Alabama and northern Georgia, the Carolinas, Virginia and Maryland. A co-emergence like this of two specific broods with different life cycles happens only once every 221 years. The last time these two groups emerged together was in 1803, when Thomas Jefferson was president.
Gut microbiome insights from 16S rRNA analysis of 17-year periodical cicadas (Hemiptera: Magicicada spp.) Broods II, VI, and X
Scientific Reports
2022
Periodical cicadas (Hemiptera: Magicicada) have coevolved with obligate bacteriome-inhabiting microbial symbionts, yet little is known about gut microbial symbiont composition or differences in composition among allochronic Magicicada broods (year classes) which emerge parapatrically or allopatrically in the eastern United States. Here, 16S rRNA amplicon sequencing was performed to determine gut bacterial community profiles of three periodical broods, including II (Connecticut and Virginia, 2013), VI (North Carolina, 2017), and X (Maryland, 2021, and an early emerging nymph collected in Ohio, 2017).
Phylogeography of the endemic red-tailed cicadas of New Zealand (Hemiptera: Cicadidae: Rhodopsalta), and molecular, morphological and bioacoustical confirmation of the …
Zoological Journal of the Linnean Society
2022
Why do some genera radiate, whereas others do not? The genetic structure of present-day populations can provide clues for developing hypotheses. In New Zealand, three Cicadidae genera are depauperate [Amphipsalta (three species), Notopsalta (one species) and Rhodopsalta (three species)], whereas two have speciated extensively [Kikihia (~30 species/subspecies) and Maoricicada (~20 species/subspecies). Here, we examine the evolution of Rhodopsalta, the last New Zealand genus to be studied phylogenetically and phylogeographically. We use Bayesian and maximum-likelihood analyses of mitochondrial cox1 and nuclear EF1α gene sequences.
Advances in the evolution and ecology of 13-and 17-year periodical cicadas
Annual Review of Entomology
2022
Apart from model organisms, 13- and 17-year periodical cicadas (Hemiptera: Cicadidae: Magicicada) are among the most studied insects in evolution and ecology. They are attractive subjects because they predictably emerge in large numbers; have a complex biogeography shaped by both spatial and temporal isolation; and include three largely sympatric, parallel species groups that are, in a sense, evolutionary replicates. Magicicada are also relatively easy to capture and manipulate, and their spectacular, synchronized mass emergences facilitate outreach and citizen science opportunities.
Billions of cicadas may be coming soon to trees near you
The Conversation
John Cooley and Chris Simon
2021-03-16
A big event in the insect world is approaching. Starting sometime in April or May, depending on latitude, one of the largest broods of 17-year cicadas will emerge from underground in a dozen states, from New York west to Illinois and south into northern Georgia. This group is known as Brood X, as in the Roman numeral for 10.
For about four weeks, wooded and suburban areas will ring with cicadas’ whistling and buzzing mating calls. After mating, each female will lay hundreds of eggs in pencil-sized tree branches.
Documenting Single-Generation Range Shifts of Periodical Cicada Brood VI (Hemiptera: Cicadidae: Magicicada spp.)
Annals of the Entomological Society of America
2021
Historically, most North American periodical cicada (Hemiptera: Cicadidae: Magicicada spp. Davis 1925) distribution records have been mapped at county-level resolution. In recent decades, Magicicada brood distributions and especially edges have been mapped at a higher resolution, aided by the use of GIS technology after 2000. Brood VI of the 17-yr cicadas emerged in 2000 and 2017 and is the first for which detailed mapping has been completed in consecutive generations. Overlaying the records from the two generations suggests that in some places, Brood VI expanded its range slightly between 2000 and 2017, although the measured changes are close to the lower limit of detectability given the methods used.
Psychoactive plant-and mushroom-associated alkaloids from two behavior modifying cicada pathogens
Fungal Ecology
2019
Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but a few species keep insects alive while sporulating, which enhances dispersal. Transcriptomics- and metabolomics-based studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses. However, the mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina-infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora, which likely represent a single fungal species.
A GIS-Based Map of Periodical Cicada Brood XIII in 2007, with Notes on Adjacent Populations of Broods III and X (Hemiptera: Magicicada spp.)
American Entomologist, Volume 62, Issue 4, Winter 2016
John R. Cooley, Gene Kritsky, David C. Marshall, Kathy B. R. Hill, Gerry Bunker, M. L. Neckermann, Jin Yoshimura, James E. Cooley, Chris Simon
2016-12-06
The periodical cicadas (Magicicada spp.) of the eastern United States are known for their mass, synchronous emergences occurring every 13 or 17 years and for their extraordinarily high adult population densities (Forsythe 1976; Williams and Simon 1995). Up to four 13-year species emerge synchronously in southern and midwestern deciduous forests, while three 17-year species similarly inhabit northern and Great Plains states. The term “brood” refers to a set of populations, often geographically contiguous, that emerge on the same 13- or 17-year schedule. Regionally, periodical cicada emergences can occur out of phase; thus, in most years, a brood of periodical cicadas emerges somewhere in the eastern U.S. Broods are sequentially numbered I–XVII (17-year species) and XVIII–XXX (13-year species) with the start year of the sequence arbitrarily set at 1893; many year-classes are empty. Most existing brood maps consist largely of county-level records based on 19-century USDA records (Fig. 1; Marlatt 1923). Even though revisions have corrected some errors and distortions in these maps (Simon 1988; Kritsky 1992; Irwin and Coelho 2000; Cooley et al. 2009; Cooley et al. 2011; Cooley et al. 2013a; Cooley 2015; Cooley et al. 2015), older maps lack the fine detail needed to address many biogeographic questions (Stannard 1975; Simon 1988; Marshall 2001) and they miss some disjunct populations (Simon and Lloyd 1982; Cooley 2015; Cooley et al. 2015).
Developmental Plasticity of Life-Cycle Length in Thirteen-Year Periodical Cicadas (Hemiptera: Cicadidae)
Annals of the Entomological Society of America, Volume 104, Issue 3, 1 May 2011
David C. Marshall, John R. Cooley, Kathy B. R. Hill
2011-05-01
Speciation in periodical cicadas (Magicicada Davis) is closely tied to changes in life-cycle length, which presents a paradox because these organisms depend on emergence synchrony for survival. Recently proposed speciation models invoke developmental plasticity as a possible solution: Environmentally triggered “4-yr accelerations” occur in 17-yr cicadas, suggesting that canalization of induced plasticity could change 17-yr populations into temporally isolated 13-yr populations. However, the reverse shift, 13-yr cicadas emerging in 17 yr, has never been documented. We searched 4 yr after the normal emergence of a 13-yr brood (and in a year with no expected periodical cicada emergences anywhere) and found periodical cicadas active at 26 of 92 sites, with examples of all four 13-yr species. At one location, we found evidence of at least 1,724 cicadas per ha emerging. Few males were heard singing at most sites, so these off-schedule cicadas apparently did not survive long in the face of predation. We also found one 13-yr species singing 8 yr late within the range of a different 13-yr brood, suggesting an 8-yr delayed emergence or consecutive generations of 4-yr delayed cicadas. Developmental plasticity in life-cycle length seems to be similar in 13- and 17-yr cicadas—both types possess the ability to switch to the opposite life cycle and to emerge 1 yr early and/or late. The confirmation of a reverse life-cycle switch in 13- cicadas suggests improvements to theories of life-cycle evolution in Magicicada and strengthens the case for developmental plasticity in speciation.
Decoding Asymmetries in Reproductive Character Displacement
Proceedings of the Academy of Natural Sciences of Philadelphia
John R. Cooley
2007-06-01
Reproductive Character Displacement (RCD) has long been of interest to evolutionary biologists because of its association with speciation and reproductive isolation. Most studies of RCD focus on only a single species; however, when information about the evolutionary responses of two species is available, a possible pattern emerges: RCD often appears to be asymmetrical. Possible causes of displacement asymmetries are varied and include asymmetrical costs of hybridization, constraints, the effects of relative abundance, and extinction. Yet in spite of this variety, further study may show that asymmetries in RCD contain important clues about the interactions pf species in contact zones.
Reconstructing asymmetrical reproductive character displacement in a periodical cicada contact zone
Journal of Evolutionary Biology
John R. Cooley, David C. Marshall, Kathy B. R. Hill, Chris Simon
2006-01-09
Selection against costly reproductive interactions can lead to reproductive character displacement (RCD). We use information from patterns of displacement and inferences about predisplacement character states to investigate causes of RCD in periodical cicadas. The 13-year periodical cicada Magicicada neotredecim exhibits RCD and strong reproductive isolation in sympatry with a closely related 13-year species, Magicicada tredecim. Displacement is asymmetrical, because no corresponding pattern of character displacement exists within M. tredecim. Results from playback and hybridization experiments strongly suggest that sexual interactions between members of these species were possible at initial contact. Given these patterns, we evaluate potential sources of selection for displacement. One possible source is ‘acoustical interference’, or mate-location inefficiencies caused by the presence of heterospecifics. Acoustical interference combined with the species-specificity of song pitch and preference appears to predict the observed asymmetrical pattern of RCD in Magicicada. However, acoustical interference does not appear to be a complete explanation for displacement in Magicicada, because our experiments suggest a significant potential for direct sexual interactions between these species before displacement. Another possible source of selection for displacement is hybrid failure. We evaluate the attractiveness of inferred hybrid mating signals, and we examine the viability of hybrid eggs. Neither of these shows strong evidence of hybrid inferiority. We conclude by presenting a model of hybrid failure related to life cycle differences in Magicicada.
Temporal Separation and Speciation in Periodical Cicadas
BioScience, Volume 53, Issue 2
John R. Cooley, Chris Simon, David C. Marshall
2003-02-01
Speciation, the set of processes by which two populations of one species become distinct species, is an important topic in evolutionary biology. It is usually impractical to conduct experiments on how new species form, but occasionally the natural history of a species places it in a context that may be thought of as a “natural experiment” with regard to speciation. One such natural experiment involves the periodical cicadas of eastern North America, a group in which populations have become isolated in time and space. Some of these isolated populations appear to have evolved into distinct genetic lineages. A rare life-cycle switching event brought two such lineages into contact in the relatively recent past, and the two lineages are now behaving as distinct species. This natural experiment provides important insights into species differences and the processes that underlie species formation.
Holocene Climate Shifts, Life-Cycle Plasticity, and Speciation in Periodical Cicadas: A Reply to Cox and Carlton
Evolution, Vol. 57, No. 2
David C. Marshall, John R. Cooley, Chris Simon
2003-02-01
Periodical cicadas (Magicicada), with their unusual life-history mix of long prime-numbered life cycles, synchronized multispecies emergences every 13 or 17 years, and dependence on predator satiation via high adult population densities, present an especially intriguing speciation problem (Williams and Simon 1995). Each of the seven species is most closely related to a geographically adjacent counterpart with the alternative life cycle, suggesting that life-cycle changes may contribute to speciation in the genus. Allochrony, or isolation in time, has been of interest in speciation theory as a means by which populations may become genetically isolated without geographic isolation. However, to be plausible, allochronic speciation scenarios for Magicicada must account for the apparently ancient dependence on predator satiation-emergences of periodical cicadas appear un- likely to survive avian predators unless they number many thousands per hectare (Lloyd and Dybas 1966a; Karban 1982; Williams et al. 1993).
Allochronic speciation, secondary contact, and reproductive character displacement in periodical cicadas (Hemiptera: Magicicada spp.): genetic, morphological, and behavioural evidence
Molecular Ecology
J. R. Cooley, C. Simon, D. C. Marshall, K. Slon, C. Ehrhardt
2001-03-01
Periodical cicadas have proven useful in testing a variety of ecological and evolutionary hypotheses because of their unusual life history, extraordinary abundance, and wide geographical range. Periodical cicadas provide the best examples of synchronous periodicity and predator satiation in the animal kingdom, and are excellent illustrations of habitat partitioning (by the three morphologically distinct species groups), incipient species (the year classes or broods), and cryptic species (a newly discovered 13-year species, Magicicada neotredecim). They are particularly useful for exploring questions regarding speciation via temporal isolation, or allochronic speciation. Recently, data were presented that provided strong support for an instance of allochronic speciation by life-cycle switching. This speciation event resulted in the formation of a new 13-year species from a 17-year species and led to secondary contact between two formerly separated lineages, one represented by the new 13-year cicadas (and their 17-year ancestors), and the other represented by the pre-existing 13-year cicadas. Allozyme frequency data, mitochondrial DNA (mtDNA), and abdominal colour were shown to be correlated genetic markers supporting the life-cycle switching/allochronic speciation hypothesis. In addition, a striking pattern of reproductive character displacement in male call pitch and female pitch preference between the two 13-year species was discovered. In this paper we report a strong association between calling song pitch and mtDNA haplotype for 101 individuals from a single locality within the M. tredecim/M. neotredecim contact zone and a strong association between abdomen colour and mtDNA haplotype. We conclude by reviewing proposed mechanisms for allochronic speciation and reproductive character displacement.
Reproductive Character Displacement and Speciation in Periodical Cicadas, with Description of a New Species, 13-Year Magicicada neotredecim
Evolution
David C. Marshall, John R. Cooley
2000-08-01
Acoustic mate-attracting signals of related sympatric, synchronic species are always distinguishable, but those of related allopatric species sometimes are not, thus suggesting that such signals may evolve to "reinforce" premating species isolation when similar species become sympatric. This hypothesis predicts divergences restricted to regions of sympatry in partially overlapping species, but such "reproductive character displacement" has rarely been confirmed. We report such a case in the acoustic signals of a previously unrecognized 13-year periodical cicada species, Magicicada neotredecim, described here as a new species (see Appendix). Where M. neotredecim overlaps M. tredecim in the central United States, the dominant male call pitch (frequency) of M. neotredecim increases from approximately 1.4 kHz to 1.7 kHz, whereas that of M. tredecim remains comparatively stable. The average preferences of female M. neotredecim for call pitch show a similar geographic pattern, changing with the call pitch of conspecific males. Magicicada neotredecim differs from 13-year M. tredecim in abdomen coloration, mitochondrial DNA, and call pitch, but is not consistently distinguishable from 17-year M. septendecim; thus, like other Magicicada species, M. neotredecim appears most closely related to a geographically adjacent counterpart with the alternative life cycle. Speciation in Magicicada may be facilitated by life-cycle changes that create temporal isolation, and reinforcement could play a role by fostering divergence in premating signals prior to speciation. We present two theories of Magicicada speciation by life-cycle evolution: "nurse-brood facilitation" and "life-cycle canalization."
