Acoustic characteristics of eight common Chinese anurans during the breeding season

Anurans often have species-specific vocalizations. To quantify and compare the characteristics of anuran calls in Gutianshan National Nature Reserve, Zhejiang Province, we recorded the advertisement calls of eight species belonging to four families (Ranidae, Microhylidae, Megophryidae and Bufonidae) from June to September 2012 using Sony ICD-FX8 IC recorders. All recordings were analyzed using the "Praat" software. Five acoustics parameters were measured, including temporal traits (call duration, number of notes or pulse number/call) and spectral traits (fundamental frequency, the first three formants and dominant frequency). The characteristic parameters of Microhyla ornate and Fejervarya limnocharis calls were different as were the calls of some populations of the same species recorded in different regions. The advertisement calls of the eight species were specific. Our study has provided a useful reference for identifying the calls of some common Chinese anurans.     

Geographical variation in male advertisement calls and female preference of the wide‐ranging canyon treefrog,Hyla arenicolor

We surveyed the geographical variation in male advertisement calls of the wide‐ranging canyon treefrog, Hyla arenicolor, and found large call differences among geographically distant lineages that had been characterized by a recent phylogeographical study. To test whether these call differences were biologically relevant and could allow reproductive isolation of different lineages should they come into secondary contact, we assessed female preference in a lineage occurring in southern Utah and north‐western Arizona, USA. These females exhibited a strong preference for their own lineage's call type over the calls of two Mexican lineages, but not over the calls from the geographically nearest lineage. We also identified traits that female frogs probably use to discriminate between lineage‐specific advertisement calls. Our behavioural results, together with recent molecular estimates of phylogenetic relationships among lineages, will guide future work addressing the evolutionary forces that have led to this biologically significant variation in male sexual signals. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

The evolution of release and advertisement calls in green toads (Bufo viridis complex)

In the present paper we tested the hypothesis that differences in the acoustic communication system of diploid and tetraploid green toads ( Bufo viridis complex) might be due to selection for reproductive character displacement. We recorded two acoustic signals of the toad repertoire − the advertisement call (a long range mate-attracting signal) and the release call (a short-range signal mediating male–male interactions) − from six sympatric Central Asian populations (three diploid and three tetraploid populations) as well as from three allopatric diploid populations from Italy, and compared their patterns of variation with the pattern of among-population genetic distances. Although release and advertisement calls share the same morpho-physiological constraints, they show significantly different patterns of variation. Release calls vary congruently with the pattern of genetic distances, suggesting that mutation and genetic drift have been the major forces responsible for their change both in time and space. By contrast, the pattern of advertisement-call variation is not consistent with the phylogeny of the group, because the advertisement calls of Asian diploid and tetraploid populations differ from each other more than their genetic distances would predict. These results strongly support the hypothesis that selection acted on the advertisement calls of either or both Asian taxa , possibly, to favour reproductive isolation.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77, 379–391.     

REINFORCEMENT AND REPRODUCTIVE CHARACTER DISPLACEMENT IN GASTROPHRYNE CAROLINENSIS AND G. OLIVACEA (ANURA: MICROHYLIDAE): A REEXAMINATION

Tape-recorded advertisement calls of Gastrophryne carolinensis and G. olivacea, obtained in Texas and southern Louisiana, were analyzed by means of an analogue audiospectrograph. Samples were grouped into four areas: allopatric and sympatric for G. carolinensis, and combined adjacent allopatric/shallow sympatric, and sympatric for G. olivacea. Three attributes of the advertisement call (call duration, pulse rate, and dominant frequency) were investigated, with water temperature at the calling site as the independent variable. Values for dominant frequency do not overlap between species, across the full range of recording temperatures, and those of sympatric G. carolinensis are displaced away from those of both groups of G. olivacea (which are very similar)—thus indicating a pattern of geographic variation consistent with reproductive character displacement. There is considerable overlap in the values for duration and for pulse rate of each species when considered alone, but there is only slight overlap of the scatters of points for the pairs of values. For both species, no consistent patterns of correlation were detected between the three attributes of the call and the snout–vent length of the emitter, thus reducing the likelihood that the divergence in calls is due to pleiotropic effects of body size.     

Patterns of variability are consistent across signal types in the treefrog Dendropsophus ebraccatus

Animal signal characteristics vary at multiple levels, and this variation can be related to the selective forces acting on signal structure. However, the effectiveness of selection acting on any one signal type may depend on selective forces acting on the same characteristics in other signal types, particularly if the signals share a common physical production mechanism. In anurans, signal variability has been related to the potential for various forms of selection by female choice on the characteristics of male advertisement calls. The significance of variability in the characteristics of another vocalization type, the aggressive call, is less well understood. In the present stiudy, within‐ and between‐male variability was measured in several characteristics of both advertisement and aggressive calls in the treefrog Dendropsophus ebraccatus. Many characteristics of both call types were repeatable within males. Fine‐temporal and spectral characteristics generally had low variation within males, whereas gross‐temporal characteristics were more variable. Unexpectedly, there were strong correlations between both measures of variability and mean values of the call characteristics of advertisement and aggressive calls. Thus, despite potentially conflicting selection pressures acting on advertisement and aggressive calls, the characteristics of individuals' calls were consistent across these two signal types. The potential forces responsible for consistency across call types are discussed, including morphological constraints and behavioural syndromes that act across different signalling contexts. In general, it is argued that measurements of variability made across multiple signal types, as in the present study, can provide important insights into the evolution of signal structure in organisms with complex signal repertoires. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 131–145.     

Intraspecific variation in advertisement call characteristics and acoustic strategies among male forest green tree frogs

Frogs are a representative taxon that use advertisement calls to aid in reproduction. In most frog species, calls vary with body size, and allometric constraints between body size and call frequency have been widely reported among anuran species. Although this variation is an important driver of sexual selection in frogs, male advertisement call strategies may also vary according to body size. In this study, we conducted playback experiments on the male forest green tree frog (Zhangixalus arboreus) to determine whether male advertisement call characteristics and strategies vary according to body size and the amplitude of intraspecific chorus noise. The results indicated that the calls of larger individuals are louder and lower than those of smaller ones, who call more frequently; moreover, the calls become lower, and the number of calls decreases, as noise levels increase. These findings suggest that forest green tree frog emits lower calls or refrains from calling when chorus noise increases, and that intraspecific variation in advertisement call characteristics can induce different strategies in response to chorus noise. Because advertisement call variation with body size is common among frog species, intraspecific variation in male advertisement call strategies may also be a common phenomenon.     

Intraspecific genome size variation and morphological differentiation of Ranunculus parnassifolius (Ranunculaceae), an Alpine–Pyrenean–Cantabrian polyploid group

The aim of this study was to assess genome size variation and multivariate morphometric analyses to ascertain cytotype distribution patterns and the morphological differentiation within the Ranunculus parnassifolius group in the Pyrenees and the Alps. Although divergences in nuclear DNA content among different species within a genus are widely acknowledged, intraspecific variation is still a somewhat controversial issue. Holoploid and monoploid genome sizes (C‐ and Cx‐values) were determined using propidium iodide flow cytometry in 125 plants of R. parnassifolius s.l. distributed across four European countries. Three different DNA ploidy levels were revealed in the study area: diploid (2n ～ 2x, 57.14%), triploid (2n ～ 3x, 1.19%), and tetraploid (2n ～ 4x, 41.67%). The mean population 2C‐values ranged from 8.15 pg in diploids to 14.80 pg in tetraploids, representing a ratio of 1 : 1.8. Marked intraspecific/interpopulation differences in nuclear DNA content were found. Diploid populations prevail in the Pyrenees, although tetraploid cytotypes were reported throughout the distribution area. In general, mixed‐cytotype populations were not found. The Spearman correlation coefficient did not reveal significant correlations between genome size and altitude, longitude, or latitude. Morphometric analyses and cluster analyses based on genome size variation revealed the presence of three major groups, which exhibited a particular biogeographical pattern. A new cytotype, DNA triploid, was found for the first time. Tetraploid populations showed constant nuclear DNA levels, whereas diploid populations from the Pyrenees, in which introgressive hybridization is suggested as a presumable trigger for genome size variation, did not. Scenarios for the evolution of geographical parthenogenesis in R. parnassifolius s.l. are discussed. Finally, the different levels of effectiveness between plant and animal reference standards are analysed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 251–271.     

Vocalisation and its association with androgens and corticosterone in a night frog (Nyctibatrachus humayuni) with unique breeding behaviour

In anurans, vocalisation is used to communicate within and between the sexes during reproduction. Knowledge of vocal repertoire and its diversity is essential in understanding its significance in sexual selection. In this context, we studied the vocal behaviour of Nyctibatrachus humayuni and quantified the urinary metabolites of androgens and corticosterone to understand the associations among hormones, body condition index and vocalisation. Our results show that males of N. humayuni produce an amplitude‐modulated call consisting of a train of pulses. Interestingly, a high degree of inter‐individual variation was observed in the call parameters. The dominant frequency and pulse interval were negatively correlated with male body size, whereas pulse duration and pulse duty cycle were positively correlated with it. Dominant frequency was negatively correlated with androgens and corticosterone, whereas pulse interval was negatively correlated with corticosterone. Further, pulse duty cycle, pulse duration and pulses per call were positively associated with corticosterone. Surprisingly, none of the acoustic parameters was associated with male body temperature and body condition. A significant variation was evident in the vocal effort, dominant frequency and amplitude of advertisement calls produced under different social situations. Calls produced during territory establishment had lower dominant frequency but higher vocal effort, whereas those produced during courtship had higher amplitude and vocal effort than the calls produced in the absence of a competitor/female. Our results suggest that greater inter‐male variability in the advertisement call of N. humayuni could be important in female choice as it may help females to assess the quality of a male. Further, androgens and corticosterone could be important in modulating crucial parameters of the advertisement call.     

Genome size and chromosome number in the New Zealand species of Schoenus (Cyperaceae)

Schoenus (Cyperaceae) has holocentric chromosomes. Chromosome numbers were counted and nuclear DNA amounts were measured for all the New Zealand species of the genus. Chromosome numbers ranged from 2n = 8 to c. 2n = 90. Two chromosome races, with 2n = 28 and 2n = 56, were found in S. pauciflorus. Flow cytometry using propidium iodide‐stained nuclei was used to measure genome size. A 14.8‐fold variation in 2C DNA content was found, with values ranging from 1.33 to 19.71 pg/2C nucleus. Phylogenetic trees based on sequence variation in the internal transcribed spacer (ITS) region of the 45S ribosomal DNA locus were constructed using several phylogenetic models to reveal possible evolutionary relationships among the New Zealand Schoenus spp. and a sample of Australian Schoenus spp. Analysis revealed heterogeneity of chromosome number, size and DNA C value within clades. Meiosis in four species showed only bivalent formation at metaphase I. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 555–564.     

Advertisement Call Variation in the Golden Rocket Frog (Anomaloglossus beebei): Evidence for Individual Distinctiveness

Individual distinctiveness in acoustic signals can allow receivers to respond appropriately to different individuals. The aim of this research was to examine signal variation and to investigate the relative importance of different acoustic properties for coding individual distinctiveness in the advertisement calls of male golden rocket frogs (Anomaloglossus beebei). We examined patterns of within‐individual and among‐individual variability in 760 advertisement calls of 40 males as well as repeatability in 16 additional males that were recorded on two different occasions. We examined eight call properties, and all properties exhibited significant among‐individual variation and moderate to high repeatability across days. We employed discriminant function analysis to examine individual distinctiveness statistically. These analyses assigned 79% of calls to the correct individual. Fine temporal properties, including pulse duration, pulse rate, and pulse interval, as well as the spectral property of dominant frequency, contributed most toward discrimination among individuals. These results indicate that individual male golden rocket frogs can be distinguished statistically by their advertisement calls. We use these findings to evaluate results of previous playback studies in A. beebei and to generate testable predictions regarding the potential for specific call properties to function in mate selection and social recognition.     

Wild and agronomically important Agave species (Asparagaceae) show proportional increases in chromosome number,genome size,and genetic markers with increasing ploidy

Agave (Asparagaceae) includes cultivated and wild varieties of henequen used for hard fibre production. As part of a breeding programme to improve Agave production, species with different ploidy levels were genetically characterized: two diploids [A. tequiliana Weber and the hybrid H11648 ((A. amaniensis Trel. & Nowell × A. angustifolia Haw.) × A. amaniensis)], a triploid (A fourcroydes Lem. var. kitam ki), a tetraploid (A. angustifolia var. letona), three pentaploids (A. fourcroydes var. sac ki, A. fourcroydes var. yaax ki, and A. sisalana Perrine), and two hexaploids (A. angustifolia var. chelem ki from two locations). Chromosome spreading was used to determine the chromosome number, flow cytometry was employed to measure the genome size, and fluorescent in situ hybridization was performed using 45S and 5S ribosomal DNA (rDNA) and the telomeric sequences (TTAGGG)_n and (TTTAGGG)_n as genetic markers. There were proportional increases with ploidy level of the following: (1) chromosome number (from diploid 2n = 2x = 60 to hexaploid 2n = 6x = 180), including the number of large and small chromosomes in the bimodal karyotype of Agave; (2) genome size, with a mean monoploid genome size (1Cx) of 7.5 pg (range, 7.36–7.61 pg); and (3) the number and distribution of 45S and 5S rDNA loci, with one locus of each per basic, monoploid genome. Thus there was complete additivity in genome structure with increasing ploidy, as reported in some angiosperm polyploids. However, as other analyses of polyploids have revealed a decrease in 1Cx values with increased ploidy, possible explanations for the observed genomic stability were considered. With the (TTAGGG)_n probe, the signal was localized at the telomeres, consistent with published data showing that many species in the order Asparagales have this type of telomere sequence. It is speculated that sporadic telomeric signals using the (TTTAGGG)_n probe are probably derived from either errors in telomerase activity or relic ancestral‐type telomeric sequences. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 215–222.     

A plant culture (BY‐2) widely used in molecular and cell studies is genetically unstable and highly heterogeneous

Nicotiana tabacum (tobacco, 2n = 4x = 48) is an allotetraploid with 24 S‐genome chromosomes (from a diploid related to N. sylvestris) and 24 T‐genome chromosomes (from a diploid related to N. tomentosiformis). The BY‐2 suspension cell culture, derived from N. tabacum cultivar Bright Yellow 2, has been used extensively for research in molecular and cell biology for almost 40 years; a Web of Knowledge search reveals that it has been used over 150 times since 2008 alone, largely for cell cycle and plant physiology studies. However, we show that this culture is unstable and, as with other long‐term cultures, exists as a community of cells with different karyotypes reflected in different chromosome numbers, morphologies and distributions of satellite repeats, At least one rearranged chromosome type was found in all cells investigated in detail. In comparison with N. tabacum, one satellite repeat, NTRS, has become dispersed across several chromosomes and there is complete homogenization of 35S rRNA genes towards T‐genome type rDNA units. Karyotype divergence should be considered when using BY‐2 cells for plant physiology or cell cycle/development studies in the future. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 459–471.     

Passive acoustic monitoring,development of disturbance calls and differentiation of disturbance and advertisement calls in the Argentine croaker Umbrina canosai (Sciaenidae)

Disturbance and advertisement calls of the Argentine croaker Umbrina canosai were recorded from coastal Uruguayan waters. Dissections indicate typical sciaenid extrinsic swimbladder muscles present exclusively in males. Disturbance calls were produced when captive U. canosai were startled, chased with a net or grabbed by the tail. Calls were unusual for sciaenids because each pulse consisted of multiple cycles. The number of cycles per pulse and dominant frequency did not change with U. canosai size, but pulse duration and interpulse interval increased. Advertisement calls were recorded from unseen choruses in the field and confirmed with captive individuals in a large tank. Advertisement calls were recorded throughout the known range of the species in Uruguay indicating a continuous belt of spawning populations. Tank recordings of the same individuals permitted explicit comparisons between the two calls. Advertisement call pulses averaged 2·4 more cycles (11·0–8·6) although pulses of both calls were basically similar as were durations and dominant frequencies. Pulse number, however, differed markedly, averaging 13·6 and 3·4 pulses for disturbance and advertisement calls respectively. Furthermore, disturbance calls were produced as a rapid series with an interpulse interval of 26–31 ms whereas advertisement call patterns were less stereotyped and ranged from <100 to 450 ms. Multicycle pulses distinguished U. canosai from other sympatric sciaenids.     

Advertisement calls of two anuran amphibians,Rana tigrina andTomopterna breviceps

Rana tigrina andTomopterna breviceps occur as sympatric species at Dharwad, India. Sexually mature males produce advertisement calls. The advertisement call of both the species consist of a number of calls produced in series forming a call group. Each call group ofRana tigrina comprises 10–40 calls, whereas that ofTomopterna breviceps consists 13–141 calls. Each call consists of a pulse group with variable number of pulses which lack pulse interval. Calls of both the species exhibit similarities in (i) call consisting of series of calls with a pulse group in each call, (ii) absence of pulse interval within the pulse group, (iii) the amplitude of the first pulse being always small, and (iv) the frequency spectrum beginning from 200 Hz. Based on the similarities in the spectral features of the calls, it is suggested that the two species may be closely related to each other.     

Genetic diversity patterns in Curcuma reflect differences in genome size

The relationships between genome size and the systematic and evolutionary patterns in vascular plants are equivocal, although a close relationship between genome size and evolutionary patterns has been previously reported. However, several studies have also revealed the dynamic nature of genome size evolution and its considerable ‘ups’ and ‘downs’. Thus, in this study, the phylogenetic relationships among three previously revealed genome size groups and among species of the highly polyploid genus Curcuma were evaluated using AFLP. Our results suggest two main lineages within Indian Curcuma reflecting evolution of genome size. The first one includes hexaploids and higher polyploids of the previously recognized genome size group I, and the second one includes mainly hexaploids of genome size groups II and III. Within genome size group I, relationships among species seem to be influenced by reticulate evolution and higher polyploids are likely to be of allopolyploid origin. Reproductive systems in Indian Curcuma vary considerably among ploidy levels and these differences considerably affect morphological and genetic variation. In general, clonally reproducing species are expected to exhibit low genotypic diversity, but, at the same time, species of allopolyploid origin are expected to maintain higher levels of heterozygosity compared with their progenitors. We investigated intra‐populational genetic variability in Curcuma spp. to evaluate whether mode of reproduction or ploidy represent the main factor influencing the degree of genetic diversity. We found that hexaploid species exhibited significantly higher genetic diversity than higher polyploids (9x, 15x). Our results suggest that this genetic diversity pattern is largely influenced by the mode of reproduction, as higher polyploids reproduce exclusively vegetatively, whereas hexaploids reproduce mainly sexually. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 388–401.     

FISH mapping of 35S and 5S rRNA genes in Artemisia subgenus Dracunculus (Asteraceae): changes in number of loci during polyploid evolution and their systematic implications

Fluorescence in situ hybridization (FISH) with 35S and 5S rDNA probes was used to characterize cytogenetically representatives of Artemisia subgenus Dracunculus and allied species and to explore their evolution following polyploidization. At the diploid level two rDNA loci were observed in most species belonging to the A. dracunculus complex, a pattern considered to be the ancestral state for diploid Artemisia. In contrast, representative species from the Eurasian grade which belong to the other major lineage of the subgenus had more heterogeneous rDNA profiles, with three to five loci at the diploid level. Divergent patterns of locus evolution were also detected in polyploids, with the number and distribution of rDNA loci broadly fitting the two main diversification lineages in the subgenus. In the polyploid complex of A. dracunculus, the number of rDNA loci was almost proportional to ploidy, although monoploid genome size was shown to decrease with increasing ploidy. However, in polyploids from the Eurasian grade we found a remarkable reduction in the number of rDNA sites, suggesting that these species might have experienced either a complete loss of loci or a significant reduction in the number of repeats following polyploid formation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013 , 171 , 655–666.     

Variation in Avian Vocalizations during the Non‐Breeding Season in Response to Traffic Noise

Low‐frequency traffic noise that leads to acoustic masking of vocalizations may cause birds to alter the frequencies or other components of their vocalizations in order to be heard by conspecifics and others. Altering parts of a vocalization may result in poorer vocal performance or the message contained in the vocalization being received incorrectly. During the winters of 2011–2012 and 2012–2013, we recorded and measured the ‘chick‐a‐dee’ call of Black‐capped Chickadees (Poecile atricapillus) and the ‘po‐ta‐to‐chip’ call of American Goldfinches (Spinus tristis) to determine whether components of the calls produced in areas of high traffic noise and low traffic noise differed in any way. We found that both chickadee and goldfinch calls had higher minimum frequencies in areas with high traffic‐noise than in low traffic‐noise areas. The maximum frequencies showed no differences in either species' calls. This suggests that chickadees and goldfinches alter the part of their calls that are acoustically masked by traffic noise in effort to better transmit the vocalization. These differences suggest that increasing anthropogenic noise may influence avian communication and that noise management should be included in conservation planning.     

Is genome downsizing associated with diversification in polyploid lineages of Veronica?

The study of genome size evolution in a phylogenetic context in related polyploid and diploid lineages can help us to understand the advantages and disadvantages of genome size changes and their effect on diversification. Here, we contribute 199 new DNA sequences and a nearly threefold increase in genome size estimates in polyploid and diploid Veronica (Plantaginaceae) (to 128 species, c. 30% of the genus) to provide a comprehensive baseline to explore the effect of genome size changes. We reconstructed internal transcribed spacer (ITS) and trnL‐trnL‐trnF phylogenetic trees and performed phylogenetic generalized least squares (PGLS), ancestral character state reconstruction, molecular dating and diversification analyses. Veronica 1C‐values range from 0.26 to 3.19 pg. Life history is significantly correlated with 1C‐value, whereas ploidy and chromosome number are strongly correlated with both 1C‐ and 1Cx‐values. The estimated ancestral Veronica 1Cx‐value is 0.65 pg, with significant genome downsizing in the polyploid Southern Hemisphere subgenus Pseudoveronica and two Northern Hemisphere subgenera, and significant genome upsizing in two diploid subgenera. These genomic downsizing events are accompanied by increased diversification rates, but a ‘core shift’ was only detected in the rate of subgenus Pseudoveronica. Polyploidy is important in the evolution of the genus, and a link between genome downsizing and polyploid diversification and species radiations is hypothesized. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 243–266.     

Dual Function of Chip Calls Depending on Changing Call Rate Related to Risk Level in Territorial Pairs of White‐Eared Ground‐Sparrows

Different mechanisms have been proposed for encoding information into vocalizations: variation of frequency or temporal characteristics, variation in the rate of vocalization production, and use of different vocalization types. We analyze the effect of rate variation on the dual function of chip calls (contact and alarm) produced by White‐eared Ground‐sparrows (Melozone leucotis). We conducted an acoustic playback experiment where we played back 1 min of four chip call rates (12, 36, 60, 84 calls/min). We measured the response of territorial pairs using behavioral responses, and fine structural features of calls produced in response to those playbacks. White‐eared Ground‐sparrows showed more intense behavioral responses to higher than lower call rate playbacks. Both individuals of the pair approached the source of the playback stimulus faster, produced the first vocalization faster, produced more vocalizations, and spent more time close to the stimulus in higher call rate than in lower call rate playbacks. Frequency and duration characteristics of calls (chip and tseet) were similar in response to all call rate playbacks. Our playback experiment elicited different intensity of behavioral responses, suggesting that risk‐based information is encoded in call rate. Our results suggest that variation in the rate of chip call production serves a dual function in this species; calls are used at lower rates for pair contact and at higher rates for alarm/mobbing signals.     

Parallel changes in mate-attracting calls and female preferences in autotriploid tree frogs

For polyploid species to persist, they must be reproductively isolated from their diploid parental species, which coexist at the same time and place at least initially. In a complex of biparentally reproducing tetraploid and diploid tree frogs in North America, selective phonotaxis--mediated by differences in the pulse-repetition (pulse rate) of their mate-attracting vocalizations--ensures assortative mating. We show that artificially produced autotriploid females of the diploid species (Hyla chrysoscelis) show a shift in pulse-rate preference in the direction of the pulse rate produced by males of the tetraploid species (Hyla versicolor). The estimated preference function is centred near the mean pulse rate of the calls of artificially produced male autotriploids. Such a parallel shift, which is caused by polyploidy per se and whose magnitude is expected to be greater in autotetraploids, may have facilitated sympatric speciation by promoting reproductive isolation of the initially formed polyploids from their diploid parental forms. This process also helps to explain why tetraploid lineages with different origins have similar advertisement calls and freely interbreed.