Cytogenetic analysis of Phyllomedusa distincta Lutz, 1950 (2n = 2x = 26), P. tetraploidea Pombal and Haddad, 1992 (2n = 4x = 52), and their natural triploid hybrids (2n = 3x = 39) (Anura, Hylidae, Phyllomedusinae)

Abstract

BackgroundNatural polyploidy has played an important role during the speciation and evolution of vertebrates, including anurans, with more than 55 described cases. The species of the Phyllomedusa burmeisteri group are mostly characterized by having 26 chromosomes, but a karyotype with 52 chromosomes was described in P. tetraploidea. This species was found in sintopy with P. distincta in two localities of São Paulo State (Brazil), where triploid animals also occur, as consequence of natural hybridisation. We analyse the chromosomes of P. distincta, P. tetraploidea, and their triploid hybrids, to enlighten the origin of polyploidy and to obtain some evidence on diploidisation of tetraploid karyotype.ResultsPhyllomedusa distincta was 2n = 2x = 26, whereas P. tetraploidea was 2n = 4x = 52, and the hybrid individuals was 2n = 3x = 39. In meiotic phases, bivalents were observed in the diploid males, whereas both bivalents and tetravalents were observed in the tetraploid males. Univalents, bivalents or trivalents; metaphase II cells carrying variable number of chromosomes; and spermatids were detected in the testis preparations of the triploid males, indicating that the triploids were not completely sterile. In natural and experimental conditions, the triploids cross with the parental species, producing abnormal egg clutches and tadpoles with malformations. The embryos and tadpoles exhibited intraindividual karyotype variability and all of the metaphases contained abnormal constitutions. Multiple NORs, detected by Ag-impregnation and FISH with an rDNA probe, were observed on chromosome 1 in the three karyotypic forms; and, additionally, on chromosome 9 in the diploids, mostly on chromosome 8 in the tetraploids, and on both chromosome 8 and 9 in the triploids. Nevertheless, NOR-bearing chromosome 9 was detected in the tetraploids, and chromosome 9 carried active or inactive NORs in the triploids. C-banding, base-specific fluorochrome stainings with CMA3 and DAPI, FISH with a telomeric probe, and BrdU incorporation in DNA showed nearly equivalent patterns in the karyotypes of P. distincta, P. tetraploidea, and the triploid hybrids.ConclusionsAll the used cytogenetic techniques have provided strong evidence that the process of diploidisation, an essential step for stabilising the selective advantages produced by polyploidisation, is under way in distinct quartets of the tetraploid karyotype.

Chromosome Banding in Amphibia. XXXIV. Intrachromosomal Telomeric DNA Sequences in Anura

“…Hence, in the specimens of Phyllomedusa distincta examined by Bruschi et al [2014], restricted het-ITSs are located in the heterochromatic centromeric regions of chromosomes 8 and 11, whereas in the individuals studied by Gruber et al [2013], these are found in the centromeric regions of chromosomes 6, 7 and 11 ( table 1 ). However, the possibility that these frogs actually belong to 2 different cryptic species should not be ignored.…”

“…An unexpected discovery was made by Gruber et al [2013] in P. tetraploidea . This tetraploid species (4n = 52) probably originated from the closely related diploid P. distincta (2n = 26) or, alternatively, from a common diploid ancestor of both species by autopolyploidy [Pombal and Haddad, 1992;Brunes et al, 2010].…”

The use of bioacoustics in anuran taxonomy: theory, terminology, methods and recommendations for best practice

“…In other cases, however, hybrids produce calls more similar to those of one of the parental species and sometimes, calls that include unique traits (e.g., in European water frogs of the genus Pelophylax; Wycherley et al 2002b) where call variation also is in line with genome dosage effects in triploid hybrids (Hoffmann & Reyer 2013). An additional example documented here is that of the leaf frogs, Phyllomedusa distincta and P. tetraploidea, which produce triploid hybrids (Haddad et al 1994;Gruber et al 2013). These frogs have very similar calls but subtle differences exist and the hybrids have intermediate number of notes (Fig.…”

“…Comparative spectrograms and oscillograms exemplifying the effect of hybridization on the call structure of anurans. The two tree frogs Phyllomedusa distincta (diploid) and P. tetraploidea (tetraploid) co-occur and hybridize in Ribeirão Branco, south of São Paulo state, Brazil, producing triploid hybrids (3n = 39) (Haddad et al 1994;Gruber et al 2013). Their advertisement calls are of similar structure and indistinguishable to the human ear, but have subtle quantitative differences (Student's t-Test = 11.06; p < 0.0001): 6-11 notes (7.8 ± 1.02; n = 31 calls from 3 males) in P. distincta, 8-17 notes (12.8 ± 2.4; n = 58 calls from 8 males) in P. tetraploidea (4n).…”

Comparative analysis based on replication banding reveals the mechanism responsible for the difference in the karyotype constitution of treefrogs Ololygon and Scinax (Arboranae, Hylidae, Scinaxinae)

“…In the present work our efforts were the use of replication banding after 5-bromodeoxiuridine treatment, an useful approach to identify homeologous chromosomes (Kasahara et al 2003, Silva et al 2004, Gruber et al 2007, Gazoni et al 2012, Gruber et al 2013). This methodology is very effective for comparative analyses in fishes, amphibians, and reptiles due to the difficulty in producing classical Q, G, and R banding patterns in the chromosomes of the ectothermic vertebrates (Sumner 2003).…”