Cytological evidence of constant tetraploidy in the bisexual South American frog Odontophrynus americanus

Polyploidy breaks speciation barriers in Australian burrowing frogs Neobatrachus

Polyploidy has played an important role in evolution across the tree of life but it is still unclear how polyploid lineages may persist after their initial formation. While both common and well-studied in plants, polyploidy is rare in animals and generally less understood. The Australian burrowing frog genus Neobatrachus is comprised of six diploid and three polyploid species and offers a powerful animal polyploid model system. We generated exome-capture sequence data from 87 individuals representing all nine species of Neobatrachus to investigate species-level relationships, the origin and inheritance mode of polyploid species, and the population genomic effects of polyploidy on genus-wide demography. We describe rapid speciation of diploid Neobatrachus species and show that the three independently originated polyploid species have tetrasomic or mixed inheritance. We document higher genetic diversity in tetraploids, resulting from widespread gene flow between the tetraploids, asymmetric inter-ploidy gene flow directed from sympatric diploids to tetraploids, and isolation of diploid species from each other. We also constructed models of ecologically suitable areas for each species to investigate the impact of climate on differing ploidy levels. These models suggest substantial change in suitable areas compared to past climate, which correspond to population genomic estimates of demographic histories. We propose that Neobatrachus diploids may be suffering the early genomic impacts of climate-induced habitat loss, while tetraploids appear to be avoiding this fate, possibly due to widespread gene flow. Finally, we demonstrate that Neobatrachus is an attractive model to study the effects of ploidy on the evolution of adaptation in animals.

Whole-genome duplication and hemoglobin differentiation traits between allopatric populations of Brazilian Odontophrynus americanus species complex (Amphibia, Anura)

Two allopatric populations of Brazilian diploid and tetraploid Odontophrynus americanus species complex, both from São Paulo state, had their blood hemoglobin biochemically analyzed. In addition, these specimens were cytogenetically characterized. Biochemical characterization of hemoglobin expression showed a distinct banding pattern between the allopatric specimens. Besides this, two distinct phenotypes, not linked to ploidy, sex, or age, were observed in adult animals of both populations. Phenotype A exhibits dark-colored body with small papillae, ogival-shaped jaw with reduced interpupillary distance and shorter hind limbs. Phenotype B shows yellowish-colored body with larger papillae, arch-shaped jaw with broader interpupillary distance and longer hind limbs. Intermediate phenotypes were also found. Considering the geographical isolation of both populations, differences in chromosomal secondary constrictions and distinct hemoglobins banding patterns, these data indicate that 2n and 4n populations represent cryptic species in the O. americanus species complex. The observed phenotypic diversity can be interpreted as population genetic variability. Eventually future data may indicate a probable beginning of speciation in these Brazilian frogs. Such inter- and intrapopulational differentiation/speciation process indicates that O. americanus species complex taxonomy deserves further evaluation by genomics and metabarcoding communities, also considering the pattern of hemoglobin expression, in South American frogs.

Naturally occurring triploids in contact zones between diploid/tetraploid Odontophrynus cordobae and O. americanus (Anura, Odontophrynidae)

Polyploidization plays an important role in speciation and evolution in anurans. However, a few stable triploid populations and some isolated triploid individuals have been reported. Here, we report the discovery of naturally occurring triploids in contact zones between diploidOdontophrynus cordobaeand tetraploidO. americanusfrom Central Argentina, and propose values of erythrocyte area for the distinction of ploidy levels. A total of 101 individuals from three contact zones were studied and ploidy of each specimen was identified by mean chromosome count and erythrocyte size. Twenty three adult triploid specimens (males: ; females: ) from two contact sites were identified (percentage of individuals per ploidy level: site S2, %, %, %; site S3: %, %, %). The limit values of erythrocyte nuclear area used to distinguish between different ploidy levels were 23.62 μm2(probability to be assigned to a respective ploidy level = 94.78%) for separating diploids and triploids and 27.67 μm2(98.62%) for triploids and tetraploids. The high number of adult triploids occurring in more than one contact site betweenO. cordobaeandO. americanusindicates that is not an isolated event. However, further studies are necessary to provide a hypothesis on the origin and evaluate the possible maintenance of triploids in syntopy withO. cordobaeandO. americanus.

Polyploidy in Amphibia

This review summarizes the current status of the known extant genuine polyploid anuran and urodelan species, as well as spontaneously originated and/or experimentally produced amphibian polyploids. The mechanisms by which polyploids can originate, the meiotic pairing configurations, the diploidization processes operating in polyploid genomes, the phenomenon of hybridogenesis, and the relationship between polyploidization and sex chromosome evolution are discussed. The polyploid systems in some important amphibian taxa are described in more detail.

Enigmatic orthology relationships between Hox clusters of the African butterfly fish and other teleosts following ancient whole-genome duplication

Numerous ancient whole-genome duplications (WGD) have occurred during eukaryote evolution. In vertebrates, duplicated developmental genes and their functional divergence have had important consequences for morphological evolution. Although two vertebrate WGD events (1R/2R) occurred over 525 Ma, we have focused on the more recent 3R or TGD (teleost genome duplication) event which occurred approximately 350 Ma in a common ancestor of over 26,000 species of teleost fishes. Through a combination of whole genome and bacterial artificial chromosome clone sequencing we characterized all Hox gene clusters of Pantodon buchholzi, a member of the early branching teleost subdivision Osteoglossomorpha. We find 45 Hox genes organized in only five clusters indicating that Pantodon has suffered more Hox cluster loss than other known species. Despite strong evidence for homology of the five Pantodon clusters to the four canonical pre-TGD vertebrate clusters (one HoxA, two HoxB, one HoxC, and one HoxD), we were unable to confidently resolve 1:1 orthology relationships between four of the Pantodon clusters and the eight post-TGD clusters of other teleosts. Phylogenetic analysis revealed that many Pantodon genes segregate outside the conventional "a" and "b" post-TGD orthology groups, that extensive topological incongruence exists between genes physically linked on a single cluster, and that signal divergence causes ambivalence in assigning 1:1 orthology in concatenated Hox cluster analyses. Out of several possible explanations for this phenomenon we favor a model which keeps with the prevailing view of a single TGD prior to teleost radiation, but which also considers the timing of diploidization after duplication, relative to speciation events. We suggest that although the duplicated hoxa clusters diploidized prior to divergence of osteoglossomorphs, the duplicated hoxb, hoxc, and hoxd clusters concluded diploidization independently in osteoglossomorphs and other teleosts. We use the term "tetralogy" to describe the homology relationship which exists between duplicated sequences which originate through a shared WGD, but which diploidize into distinct paralogs from a common allelic pool independently in two lineages following speciation.

Karyotypic differentiation via 2n reduction and a finding of a case of triploidy in anurans of the genus Engystomops (Anura, Leiuperidae)

The genus Engystomops is divided into two groups, namely the Duovox clade and the Edentulus clade. The species of Edentulus clade have karyotypes with 2n = 22, while E. pustulatus and E. puyango, which belong to Duovox clade, have 2n = 20. To investigate if 2n = 20 is a synapomorphy of Duovox clade, we cytogenetically analyzed all the species of this group, except for E. puyango, in the present study. All of them had 2n = 20, differing from the species of Edentulus clade. Since the species already karyotyped of the genus Physalaemus, which is considered to be the sister group of Engystomops, also have 2n = 22, we conclude that the 2n reduction is a synapomorphy of Duovox clade. Despite the karyotypes of all the species of Duovox clade were very similar, they varied in the NOR pattern. In E. coloradorum, an additional NOR was found in one homologue of the chromosome pair 10 exclusively in all females, indicating that this could possibly be a sexual pair of the ZZ/ZW system. Also in this species, it was found the first case of natural polyploidy of the genus Engystomops.

Molecular evolution of ribosomal intergenic spacers in Odontophrynus americanus 2n and 4n (Amphibia: Anura)

Ribosomal intergenic spacers (IGSs) of Odontophrynus americanus 2n and 4n were cloned, restriction mapped, and partially sequenced. Three distinct regions, namely alpha, beta, and delta, were identified in the IGSs. The alpha and beta regions flanked the 28S and 18S rRNA genes, respectively, conserving an identical restriction pattern at each ploidy level. The delta region, located between alpha and beta, was highly variable in size and restriction pattern, enclosing different BamHI subrepeats (B-SR), 87- to 530-bp-long. Sequence analysis showed that B-SRs were composed mainly of different arrangements of similar blocks of sequences. Another family of repetitive sequences was found in the delta region, clustered inside large BamHI fragments. These subrepeats are 189-bp-long and, although very similar in diploid and tetraploid IGSs, show a pattern of concerted evolution. A hypothetical functional role for the 189-bp repeats is discussed in view of their predicted secondary structure and presence of potential E2 binding sites inside diploid subrepeats. Although the same structural elements were present both in diploid and tetraploid IGSs, the higher level of repeatability of tetraploid IGSs suggests that common ancestor sequences have undergone several rounds of amplification after O. americanus polyploidy.

Aspects of gene regulation in the diploid and tetraploid Odontophrynus americanus (Amphibia, Anura, Leptodactylidae)

Erythropoietic and hemoglobin DNA transcriptional activities were analyzed in the diploid and the tetraploid Odontophrynus americanus. Flow cytometric analyses of DNA, RNA and mitochondrial contents showed increased genic activity in both diploid and tetraploid animals during erythropoiesis in vivo elicited by pretreatment phenylhydrazine. Generally, higher values were seen in immature tetraploid erythroid cells. On the 10th day of recovery from anemia, large amounts of messenger RNA were found in both specimens. Based on the mitochondrial content, the tetraploid cells had more intense energy metabolism than the diploid cells. Diploid O. americanus had about three times more erythroid cells than tetraploid specimens, indicating that there were differences in the regulatory mechanisms of erythroid cells. Hematological parameters showed that tetraploid cells had 30% more hemoglobin than the diploid, suggesting a regulatory mechanism of hemoglobin synthesis at the transcriptional level. Cytoplasmic inclusions resembling Heinz bodies were found in both types of cells. In the tetraploid cells they were previously found associated with RNA or RNP, suggesting that other regulatory system which controls the accumulation of nontranslated RNA transcribed in excess must be present. These differences at the physiological and molecular levels during erythropoiesis reinforce the hypothesis that speciation is occurring between diploid and tetraploid O. americanus.

A second case of multivalent meiotic configurations in diploid species of Anura

We analyzed the meiotic chromosomes of specimens from the two karyological groups of Physalaemus petersi (Jiménez de la Espada, 1872) described in the literature. Multivalent configurations (rings or chains) were observed in both groups. This meiotic organization resulted from the terminal association of non-homologous chromosomes, and an analysis of C-banded multivalents indicated no involvement of heterochromatic regions in these associations. A possible explanation for such meiotic configurations is the occurrence of heterozygous translocations. Thus, multivalents may indicate the involvement of translocation events in the karyotypic evolution of P. petersi.

Gene duplication and the uniqueness of vertebrate genomes circa 1970-1999

In this article I review research undertaken over the past 30 years into the role that gene duplication played in shaping vertebrate genomes. I discuss early karyotype studies that pointed to a relative stability of mammalian and avian genomes, the discovery and possible evolutionary significance of enormous genomes in urodele amphibians and lungfish, genome compaction in certain specialised bony fish, evidence for two rounds of total genome doubling in early vertebrate evolution and the fate of duplicated genes in polyploid fish.

Gen(om)e duplications in the evolution of early vertebrates

Phylogenetic analyses and sequence surveys of developmental regulator gene families indicate that two large-scale gene duplications, most likely genome duplications, occurred in ancestors of vertebrates. Relaxed constraints allowed duplicated and thus redundant genes to diverge in a two stage mechanism. Neutral changes dominated at first but then positively selected regulatory changes evolved the novel and increasingly complex vertebrate developmental program.

Comparative study of immature erythroid cells of the diploid Bufo ictericus and the tetraploid Odontophrynus americanus (Amphibia, Anura): ultrastructural cytochemical detection of nucleic acids and polysaccharides, and mapping of the element phosphorus

In the present study, we used ultrastructural cytochemistry to analyze the distribution of nuclear and cytoplasmic nucleic acids and polysaccharides, and electron spectroscopic imaging to map the element phosphorus in immature erythroid cells taken from two amphibians, the diploid Bufo ictericus and the tetraploid Odontophrynus americanus. In the cytoplasm of cells from the tetraploid species, we detected numerous inclusions containing a material that was similar to the dispersed chromatin seen in the nucleus of these cells. The RNase-gold complex labeled both the dispersed nuclear chromatin and the cytoplasmic inclusions. The Thiéry technique showed that glycoconjugates were present in all the membranous complexes of the erythroid cells of both types of amphibians under study, although they were absent within or around the cytoplasmic RNA inclusions. Electron spectroscopic imaging revealed the presence of phosphorus in these inclusions. These data suggest that an increase in RNA synthesis occurs in tetraploid amphibian cells, probably as a result of an alteration in the mechanisms of gene regulation.

High levels of chromosome instability in polyploids of Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae was used to study the genetic consequences of polyploidy in a unicellular organism. Isogenic diploid (2N), triploid (3N) and tetraploid (4N) strains with a genetically marked chromosome VII (cyh2-leu1-CEN7-ade6) were constructed and were used to follow the loss of one, two or three chromosome VII's during mitosis. We found that as ploidy increased, the frequency of loss of a single chromosome VII increased: Loss of one copy of chromosome VII occurred at a rate nearly 30-fold higher in triploids and approximately 1000-fold higher in tetraploids than in the diploid. Loss of two or three copies occurred at an even greater frequency. These findings suggest either that aneuploidy (3N-1, 3N-2, 4N-1, 4N-2, 4N-3) increases genome instability or that multiple chromosome loss events occur at high frequency. Polyploidy appears to dramatically increase chromosome loss, presumably due to the inability of the cell to undergo proper chromosome segregation. The biological significance and possible causes for the instability of polyploidy in unicellular organisms such as yeast are discussed.

Restriction endonuclease mapping of ribosomal RNA genes: sequence divergence and the origin of the tetraploid treefrog Hyla versicolor

Hyla chrysoscelis (2n = 24) and H. versicolor (2n = 48) are a diploid-tetraploid species pair of treefrogs. Restriction endonuclease mapping of ribosomal RNA (rRNA) gene repeat units of diploids collected from eastern and western populations reveals no differences within rRNA gene coding regions but distinctive differences within the nontranscribed spacers. A minimum of two physical maps is required to construct an rRNA gene map for the tetraploid, whose repeat units appear to be a composite, with about 50% of the elements resembling the "western" diploid population and about 50% resembling the "eastern" population. These results imply that this population of the tetraploid species may have arisen from a genetically hybrid diploid. Alternatively, the dual level of sequence heterogeneity in H. versicolor may reflect some type of gene flow between the two species. The coding region of the rRNA genes in the tetraploid differs from that in either diploid in about 20% of all repeat units, as exemplified by a BamHI site located near the 5' terminus of the 28 S rRNA gene. If the 20% variant class of 28 S rRNA gene coding sequences is expressed, then there must be two structural classes of ribosomes; if only the 80% sequence class is expressed, then a genetic control mechanism must be capable of distinguishing between the two different sequence variants. It is postulated that the 20% variant sequence class may be correlated with a partial functional diploidization of rRNA genes in the tetraploid species.

Chromosome banding in Amphibia. IX. The polyploid karyotypes of Odontophrynus americanus and Ceratophrys ornata (Anura, Leptodactylidae)

The somatic and meiotic chromosomes of the South American leptodactylid toads Odontophrynus americanus, Ceratophyrys ornata, and C. cranwelli were analysed both with conventional staining and differential banding techniques. The karyotypes of O. americanus were tetraploid; those of C. ornata octaploid. Ceratophrys cranwelli is a diploid species whose karyotype displays great similarities with that of C. ornata. The high frequency of multivalent pairing configurations in the meioses of O. americanus and C. ornata indicate that these animals were of autopolyploid origin. The conventionally stained somatic chromosomes of O. americanus can be arranged into sets of four similar chromosomes (quartets); those of C. ornata, into sets of eight similar chromosomes (octets). The banding patterns revealed heterogeneity within some quartets of O. americanus, dividing each of them into two pairs of homologous chromosomes. In analogy, some octets of C. ornata can be subdivided into two quartets of chromosomes with homologous bands. These structural heterogeneities within the quartets and octets are interpreted as a "diploidization" of the polyploid karyotypes. Diploidization leads to genomes that are polyploid with respect to the amount of genetic material and diploid with respect to chromosomal characteristics and the level of gene expression. In tetraploid O. americanus, the number of nucleolus organizer regions (NORs) and their DNA content is proportional to the degree of ploidy. In contrast, up to eight NORs have been deleted in the octoploid C. ornata. These NOR losses are discussed as a possible reason for the reduction of genetic activity in polyploid genomes.

Yolk proteins and their plasmatic precursor in the tetraploid Odontophrynus americanus (Amphibia, Anura)

The vitellogenin of Odontophrynus americanus is a large (426.5 kDa) plasmatic protein. The vitellogenin is composed of two different phosphoglycopeptides: VTG1 = 207.5 kDa and VTG2 = 202.4 kDa. The vitellins originating from the partial proteolysis of the plasmatic vitellogenin on the ovary cells are composed of lipovitellins and phosphoproteins. Lipovitellin 1 has two glycopeptides with different amino acid sequences as determined by peptide mapping (LV1 alpha, 104.6 kDa; and LV1 beta, 92.6 kDa). Lipovitellin 2 is composed of three kinds of polypeptides (LV2 alpha, 31.7 kDa; LV2 beta, 29.7 kDa; LV2 gamma, 27.8 kDa). There are three phosphopeptides in the yolk: phosvitin (PV, 37.4 kDa) and phosvettes 1 (PVT1, 27.7 kDa) and 2 (PVT2, 26.1 kDa).

Ribosomal RNA structure in the diploid and phylogenetically polyploid amphibian species Hyla and Odontophrynus

Ribosomal RNA of the diploid amphibian species Hyla chrysoscelis and Odontophrynus americanus is structurally modified by hidden breaks. Phylogenetically polyploid related species like the tetraploid Hyla versicolor, the tetraploid Odontophrynus americanus and the octoploid Ceratophrys ornata do not show hidden breaks in ribosomal RNA. Structural modifications of rRNA molecules in diploid amphibians has no detectable effect on the ribosomal activity in vitro.

Towards an understanding of the molecular mechanisms regulating gene expression during diploidization in phylogenetically polyploid lower vertebrates

Polyploidization and regional gene duplication have occurred frequently during vertebrate evolution, providing the genetic material necessary for creating evolutionary novelties. Mammals, including man, can be regarded as diploid species with a polyploid history of evolution. Polyploidization steps during the phylogeny of mammals probably took place in the genomes of amphibian- or fish-like mammalian ancestors. The polyploid status has subsequently been shaped by the process of diploidization, leading to genomes that are polyploid with respect to the amount of genetic material and the number of gene copies, and diploid with respect to the level of gene expression and chromosomal characteristics. Phylogenetically tetraploid amphibian and teleost species together with their diploid close relatives can be used as a model system to study the effect of polyploidization and the mechanisms of diploidization of a parallel event during early mammalian evolution. Experimental evidence permits the assumption that the diploidization of gene expression in tetraploid cyprinid fish may be functionally correlated with structural modifications of the ribosomal components, RNA and protein. These findings are discussed in the light of reduced protein synthesis in diploidized tetraploid species and a mechanism to explain diploidization during mammalian evolution.

Adaptative features of ectothermic enzymes. III--Studies on phosphoglucose isomerase (PGI) from five species of tropical fishes of the superorder Ostariophysi

1. The electrokinetic and thermostability properties of phosphoglucose isomerase (PGI) in five species of tropical fish (Ostariophysi)-Leporinus friderici, L. silverstrii, Schizodon nasuttus, Hypostomus sp and Pimelodus maculatus--have been studied in order to study the adaptative nature of protein heterogeneity found in ectotherms. 2. Unlike most diploid fishes, the PGI of these species seemed to be encoded by three, four or five loci. 3. The subunits encoded by these loci occurred at different levels in the different tissues and organs analyzed. 4. Genetic variants at the three PGI loci were detected in two species of the family Anostomidae (L. friderici and S. nasuttus). In the family Pimelodidae, P. Maculatus showed a genetic variant as the Pgi-1 locus. 5. The product of these loci could be separated in three PGI regions based on their electrophoretic mobility, tissue distribution and thermostability properties. 6. The more anodal region (including isozymes and allozymes) was more thermolabile then the less anodal one, which is predominant in a single tissue-skeletal muscle.

Escape efficiency of diploid and polyploid frogs: a comparison of Odontophrynus cultripes (2n = 22) and O. americanus (4n = 44)

The escape efficiency of two closely related species of frogs, Odontophrynus cultripes (2n = 22) and the tetraploid O. americanus (4n = 44), were compared in a shuttle box and under simulated naturalistic conditions. O. americanus was generally superior to O. cultripes, and females tended to outperform males within both species. The relative inefficiency of O. Cultripes escape behavior was examined in light of the animals' having an elaborate, passive defense mechanism in the form of well marked venom glands. Escape efficiency was highly variable in both species. Possessing twice the amount of DNA, the tetraploid behavioral variation was paradoxically less than that of the diploid, but compatible with what has been found for morphological characters in other organisms.

Polyploidy in the australian leptodactylid frog genus Neobatrachus

Karyotypic analysis of six species of the Australian leptodactylid frog genus Neobatrachus showed that N. pictus, N. centralis, N. pelobatoides and N. wilsmorei are diploid (2n = 24) while N. sudelli and N. sutor are tetraploid (4n = 48). Polyploidy has not been reported previously among Australian anurans. Idiograms of the six species indicate that they are similar to the other Australian leptodactylids so far discribed. DNA values of the tetraploids are approximately double the values for diploids. Tetraploid nuclear and cell sizes are greater compared with diploids but total body size shows no increase. At diakinesis in primary spermatocytes of tetraploids, mainly tetravalents together with a few bivalents are present. Silver straining of metaphase spreads clearly demonstrates the location of NORs at the secondary constrictions and their frequent association in the tetraploid N. sutor. Nucleolar number in interphase nuclei provides a reliable guide for distinguishing tetraploid from diploid frogs in the absence of chromosome analysis and can be determined for both living and preserved specimens. The possible origins and relationships of the tetraploid species are discussed.

Non-repetitive DNA sequence divergence in phylogenetically diploid and tetraploid teleostean species of the family cyprinidae and the order isospondyli

Non-repetitive DNA of anciently tetraploid teleostean species was analysed for the presence of duplicated sequences. Closely related diploid species were investigated in comparison. From the reassociation kinetics of total nuclear DNA, rate constants and fraction sizes of classes of repetitive and non-repetitive sequences were determined. DNA fractions enriched in the slowest renaturing sequence class were determined. DNA fractions enriched in the slowest renaturing sequence class were prepared and subjected to reassociation. The rate constants of these reactions were compared with the values expected for single-copy DNA from analytical genome size determinations. From reassociated DNA enriched in non-repetitive sequences also the melting temperatures were determined as a measure of internal base sequence heterogeneity. It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallus are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regard to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls (Rutilus rutilus, Clupea harengus and Sprattus sprattus). The tetraploid species Salmo irideus, Salvelinus fontinalis and Coregonus lavaretus appear as very recent tetraploids with regard to these criteria. The significance of the results for estimating the time of occurrence of polyploidisation events in these taxa is discussed.

Circles in spermatocyte chromatin loops. Electron microscopy and AgAs-NORs studies

We describe the production of circles in chromomeric loops during the pachytene stage of the spermatocytes. These circles are found attached to chromatin or already free in the nucleoplasm. Each circle measures an average of 3700 A in circunference. We suggest that such circles might indicate the presence of tandem repetitions.

Chromatin ultrastructure of lower vertebrates

Meiotic and mitotic chromosomes from amphibians and snakes were studied by electron microscopy. By using water spreading, preceded by a mild NaCl pretreatment, we showed: 1. 'Beads on a string' arrangement of the chromatin fibres; 2. The presence of loops at pachytene chromomeres as well as during metaphase of both mitosis and first meiosis; 3. Transcriptional activity for non-ribosomal RNA on peripheral loops during the middle pachytene.

Tetraploid origin of the karyotype of catostomid fishes

Catostomid fishes appear to have 2n(-->4n?) approximately 100 chromosomes. The Cyprinidae, from which catostomids probably diverged before the Eocene, usually have 2n = 48 or 50 chromosomes. Preliminary cytophotometric measurements indicate an approximate doubling of DNA content of cells among catostomids.

Polyploidy in the common tree toad Hyla versicolor Le Conte

A karyotype of the first known naturally occurring anuran polyploid in North America is described. Hyla versicolor, the common tree toad, is tetraploid (2n-->4n=48). Individual chromosmes representing, each set of four of the Hyla versicolor karyotype correspond closely with those of the diploid (2n = 24) Hyla andersonii karyotype.