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Abstract. 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.”

Abstract. 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.''

The evolution of 13-and 17-y periodical cicadas (Magicicada) is enigmatic because at any given location, up to three distinct species groups (Decim, Cassini, Decula) with synchronized life cycles are involved. Each species group is divided into one 13-and one 17-y species with the exception of the Decim group, which contains two 13-y species-13-y species are Magicicada tredecim, Magicicada neotredecim, Magicicada tredecassini, and Magicicada tredecula; and 17-y species are Magicicada septendecim, Magicicada cassini, and Magicicada septendecula. Here we show that the divergence leading to the present 13-and 17-y populations differs considerably among the species groups despite the fact that each group exhibits strikingly similar phylogeographic patterning. The earliest divergence of extant lineages occurred ∼4 Mya with one branch forming the Decim species group and the other subsequently splitting 2.5 Mya to form the Cassini and Decula species groups. The earliest split of extant lineages into 13-and 17-y life cycles occurred in the Decim lineage 0.5 Mya. All three species groups experienced at least one episode of life cycle divergence since the last glacial maximum. We hypothesize that despite independent origins, the three species groups achieved their current overlapping distributions because life-cycle synchronization of invading congeners to a dominant resident population enabled escape from predation and population persistence. The repeated life-cycle divergences supported by our data suggest the presence of a common genetic basis for the two life cycles in the three species groups.life-cycle shift | nurse brood | parallel evolution | speciation P eriodical cicadas (Magicicada) in the eastern United States represent one of the most spectacular life history and population phenomena in nature (1-10). These periodical cicadas spend most of their lives (13 y in the south, 17 y in the north) as underground juveniles except for a brief 2-to 4-wk period when adults emerge simultaneously in massive numbers. With few exceptions, at any given location, all of the periodical cicadas share the same life cycle and emerge on the same schedule, forming a single-year class referred to as a "brood." Surprisingly, each brood consists of multiple species from three species groups (Decim, Cassini, Decula).These three groups were considered to have diverged from each other allopatrically and to have later become sympatric and formed 13-and 17-y life cycles (2). The prolonged, primenumbered life cycles were hypothesized to have evolved in response to Pleistocene climatic cooling (9, 11) to avoid the adverse effect of low population density on mating success (9, 12, 13). Another view hypothesized that the long synchronized life cycles evolved in association with the predator avoidance strategy (2,4,8) and that this took place before both the glacial periods and the split of the three species groups (10) based on approximate genetic distances among species groups (8). To test these hypotheses, phylogenetic information about the r...

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One of the major tenets of the modern synthesis is that genetic differentiation among subpopulations is translated over time into genetic differentiation among species. Phylogeographic exploration is therefore essential to the study of speciation because it can reveal the presence of subpopulations that may go on to become species or that may already represent cryptic species. Acoustic species-specific mating signals provide a significant advantage for the recognition of cryptic or incipient species. Because the majority of species do not have such easily recognized premating signals, data from acoustically signaling species can serve as a valuable heuristic tool. Acoustic signals are also convenient tools for recognizing hybridization events. Here, we demonstrate that evidence of hybridization in the form of intermediate song phenotypes is present in many contact zones between species of the New Zealand grass cicadas of the Kikihia muta species complex and that recurring mitochondrial DNA (mtDNA) introgression has created misleading patterns that make it difficult to identify certain taxa using song or mtDNA alone. In one case, introgression appears to have occurred between allopatric taxa by dispersal of introgressed populations of an intermediary species ("hybridization by proxy"). We also present a comparison of mtDNA-tree- and song-based taxonomies obtained for the K. muta complex. We find that 12 mtDNA candidate species are identified using shifts in phylogenetic branching rate found by a single-threshold mixed Yule-coalescent lineage model, while only 7 candidate species are identified using songs. Results from the Yule-coalescent model are dependent on factors such as the number of modeled thresholds and the inclusion of duplicate haplotypes. Genetic distances within song species reach a maximum at about 0.028 substitutions/site when likely cases of hybridization and introgression are excluded. Large genetic breaks or "gaps" are not observed between some northern (warmer climate) song clades, possibly because climate-induced bottlenecks have been less severe. These results support ongoing calls for multimarker genetic studies as well as "integrative taxonomy" that combines information from multiple character sources, including behavior, ecology, geography, and morphology.

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.

A molecular phylogeny and a review of family-group classification are presented for 137 species (ca. 125 genera) of the insect family Cicadidae, the true cicadas, plus two species of hairy cicadas (Tettigarctidae) and two outgroup species from Cercopidae. Five genes, two of them mitochondrial, comprise the 4992 base-pair molecular dataset. Maximum-likelihood and Bayesian phylogenetic results are shown, including analyses to address potential base composition bias. Tettigarcta is confirmed as the sister-clade of the Cicadidae and support is found for three subfamilies identified in an earlier morphological cladistic analysis. A set of paraphyletic deep-level clades formed by African genera are together named as Tettigomyiinae n. stat. Taxonomic reassignments of genera and tribes are made where morphological examination confirms incorrect placements suggested by the molecular tree, and 11 new tribes are defined (Arenopsaltriini n. tribe, Durangonini n. tribe, Katoini n. tribe, Lacetasini n. tribe, Macrotristriini n. tribe, Malagasiini n. tribe, Nelcyndanini n. tribe, Pagiphorini n. tribe, Pictilini n. tribe, Psaltodini n. tribe, and Selymbriini n. tribe). Tribe Tacuini n. syn. is synonymized with Cryptotympanini, and Tryellina n. syn. is synonymized with an expanded Tribe Lamotialnini. Tribe Hyantiini n. syn. is synonymized with Fidicinini. Tribe Sinosenini is transferred to Cicadinae from Cicadettinae, Cicadatrini is moved to Cicadettinae from Cicadinae, and Ydiellini and Tettigomyiini are transferred to Tettigomyiinae n. stat from Cicadettinae. While the subfamily Cicadinae, historically defined by the presence of timbal covers, is weakly supported in the molecular tree, high taxonomic rank is not supported for several earlier clades based on unique morphology associated with sound production.