Karyotypical Confirmation of Natural Hybridization between Two Manatee Species, Trichechus manatus and Trichechus inunguis.

Two species of manatees are found in Northern Brazil-the Antillean manatee (Trichechus manatus), which is found along the coast from Florida to Northeastern Brazil, and the Amazonian manatee (Trichechus inunguis), endemic to the Amazon drainage basin. These species show a sympatric distribution in the region of the Marajó Archipelago, an estuarine area surrounding the Amazon River mouth. There is evidence of the occurrence of interspecific hybrids in this area, based on mitochondrial DNA analyses, although the use of nuclear markers has not corroborated this proposal. Considering that these species show very distinct karyotypes, despite being closely related (2n = 48 in T. manatus and 2n = 56 in T. inunguis), hybrids would present distinct chromosome numbers. Based on this, we conducted cytogenetic analyses using classic and molecular techniques in three calves found stranded in the Marajó Island and Amapá coast. The results showed that one of them, morphologically classified as T. inunguis, presented the correspondent karyotype, with 2n = 56. However, the other two, which were phenotypically similar to T. manatus, showed 2n = 49. Despite the same diploid number, their G-banding patterns revealed some differences. The results of the distribution of some microsatellite sequences have also confirmed the heterozygosity of some chromosomal pairs in these two individuals. These results are the first indubitable confirmation of the occurrence of natural hybrids between T. manatus and T. inunguis, and also brings about some issues concerning the viability of hybrids, considering that these two individuals do not correspond to an F1 hybrid, but instead, both presented a possible F2 karyotype.

Karyotype asymmetry in Cuscuta L. subgenus Pachystigma reflects its repeat DNA composition.

Cuscuta is a cytogenetically diverse genus, with karyotypes varying 18-fold in chromosome number and 127-fold in genome size. Each of its four subgenera also presents particular chromosomal features, such as bimodal karyotypes in Pachystigma. We used low coverage sequencing of the Cuscuta nitida genome (subgenus Pachystigma), as well as chromosome banding and molecular cytogenetics of three subgenus representatives, to understand the origin of bimodal karyotypes. All three species, C. nitida, C. africana (2n = 28) and C. angulata (2n = 30), showed heterochromatic bands mainly in the largest chromosome pairs. Eighteen satellite DNAs were identified in C. nitida genome, two showing similarity to mobile elements. The most abundant were present at the largest pairs, as well as the highly abundant ribosomal DNAs. The most abundant Ty1/Copia and Ty3/Gypsy elements were also highly enriched in the largest pairs, except for the Ty3/Gypsy CRM, which also labelled the pericentromeric regions of the smallest chromosomes. This accumulation of repetitive DNA in the larger pairs indicates that these sequences are largely responsible for the formation of bimodal karyotypes in the subgenus Pachystigma. The repetitive DNA fraction is directly linked to karyotype evolution in Cuscuta.

Patterns of chromosomal variation in Mexican species of Aeschynomene (Fabaceae, Papilionoideae) and their evolutionary and taxonomic implications.

A cytogenetic analysis of sixteen taxa of the genus Aeschynomene Linnaeus, 1753, which includes species belonging to both subgenera Aeschynomene (Léonard, 1954) and Ochopodium (Vogel, 1838) J. Léonard, 1954, was performed. All studied species had the same chromosome number (2n = 20) but exhibited karyotype diversity originating in different combinations of metacentric, submetacentric and subtelocentric chromosomes, chromosome size and number of SAT chromosomes. The plasticity of the genomes included the observation in a taxon belonging to the subgenus Aeschynomene of an isolated spherical structure similar in appearance to the extra chromosomal circular DNA observed in other plant genera. By superimposing the karyotypes in a recent phylogenetic tree, a correspondence between morphology, phylogeny and cytogenetic characteristics of the taxa included in the subgenus Aeschynomene is observed. Unlike subgenus Aeschynomene, the species of Ochopodium exhibit notable karyotype heterogeneity. However the limited cytogenetic information recorded prevents us from supporting the proposal of their taxonomic separation and raise it to the genus category. It is shown that karyotype information is useful in the taxonomic delimitation of Aeschynomene and that the diversity in the diploid level preceded the hybridization/polyploidization demonstrated in the genus. The systematic implications of our results and their value can be extended to other Dalbergieae genera as knowledge about the chromosomal structure and its evolution increases.

Comparative Chromosome Painting in Two Brazilian Stork Species with Different Diploid Numbers.

Despite the variation observed in the diploid chromosome number of storks (Ciconiiformes, Ciconiidae), from 2n = 52 to 2n = 78, most reports have relied solely on analyses by conventional staining. As most species have similar macrochromosomes, some authors propose that karyotype evolution involves mainly fusions between microchromosomes, which are highly variable in species with different diploid numbers. In order to verify this hypothesis, in this study, the karyotypes of 2 species of storks from South America with different diploid numbers, the jabiru (Jabiru mycteria, 2n = 56) and the maguary stork (Ciconia maguary, 2n = 72), were analyzed by chromosome painting using whole chromosome probes from the macrochromosomes of Gallus gallus (GGA) and Leucopternis albicollis (LAL). The results revealed that J. mycteria and C. maguary share synteny within chromosome pairs 1-9 and Z. The syntenies to the macrochromosomes of G. gallus are conserved, except for GGA4, which is homologous to 2 different pairs, as in most species of birds. A fusion of GGA8 and GGA9 was observed in both species. Additionally, chromosomes corresponding to GGA4p and GGA6 are fused to other segments that did not hybridize to any of the macrochromosome probes used, suggesting that these segments correspond to microchromosomes. Hence, our data corroborate the proposed hypothesis that karyotype evolution is based on fusions involving microchromosomes. In view of the morphological constancy of the macrochromosome pairs in most Ciconiidae, we propose a putative ancestral karyotype for the family, including the GGA8/GGA9 fusion, and a diploid number of 2n = 78. The use of probes for microchromosome pairs should be the next step in identifying other synapomorphies that may help to clarify the phylogeny of this family.

Chromosomal Diversity of Thorny Catfishes (Siluriformes-Doradidae): A Case of Allopatric Speciation Among Wertheimerinae Species of São Francisco and Brazilian Eastern Coastal Drainages.

Wertheimerinae is a small subfamily of thorny catfish composed of two species found in eastern Brazilian coastal drainages: Wertheimeria maculata and Kalyptodoras bahiensis. According to molecular phylogenetic analysis, Franciscodoras marmoratus an endemic species of the São Francisco River is also a member of this subfamily. Even though both phylogenetic approaches suggest that this group is one of the oldest lineages of the Doradidae, a disagreement remains about the constitution of Wertheimerinae. Hence, cytogenetic analysis is important to understand the karyotypic evolution of thorny catfish and can be a useful cytotaxonomic tool to clarify the relationships between these species. All Wertheimerinae species, and F. marmoratus here analyzed, shared 2n = 58 chromosomes, karyotypic formulas (24m+12sm +8st +14a), and nucleolus organizer region (NOR) pattern (terminal 18S rDNA sites on pair 22). Differences were noted in heterochromatin and 5S rDNA site distribution. The chromosomal markers here applied added to the molecular data, reinforcing that these three species actually represent a well-resolved taxonomic unit. Our results represent one more evidence of the ancient connectivity between eastern coastal drainages and São Francisco River, whose separation represented an important event for the allopatric speciation that produced the current forms of Wertheimerinae subfamily.

Comparative cytogenetics and derived phylogenic relationship among Sitophilus grain weevils (Coleoptera, Curculionidae, Dryophthorinae).

Cytogenetic characteristics and genome size are powerful tools for species characterization and identification of cryptic species, providing critical insights into phylogenetic and evolutionary relationships. Sitophilus Linnaeus, 1758 grain weevils can benefit from such tools as key pest species of stored products and also as sources of archeological information on human history and past urban environments. Moreover, the phylogenetic relationship among these weevil species remains controversial and is largely based on single DNA fragment analyses. Therefore, cytogenetic analyses and genome size determinations were performed for four Sitophilus grain weevil species, namely the granary weevil Sitophilus granarius (Linnaeus, 1758), the tamarind weevil S. linearis (Herbst, 1797), the rice weevil S. oryzae (Linnaeus, 1763), and the maize weevil S. zeamais Motschulsky, 1855. Both maize and rice weevils exhibited the same chromosome number (2n=22; 10 A + Xyp). In contrast, the granary and tamarind weevils exhibited higher chromosome number (2n=24; 11 A + Xyp and 11 A + neo-XY, respectively). The nuclear DNA content of these species was not proportionally related to either chromosome number or heterochromatin amount. Maize and rice weevils exhibited similar and larger genome sizes (0.730±0.003 pg and 0.786±0.003 pg, respectively), followed by the granary weevil (0.553±0.003 pg), and the tamarind weevil (0.440±0.001 pg). Parsimony phylogenetic analysis of the insect karyotypes indicate that S. zeamais and S. oryzae were phylogenetically closer than S. granarius and S. linearis, which were more closely related and share a more recent ancestral relationship.

Cestrum strigilatum (Ruiz & Pavón, 1799) B chromosome shares repetitive DNA sequences with A chromosomes of different Cestrum (Linnaeus, 1753) species.

Species of Cestrum (Linnaeus, 1753) have shown large diversity in the accumulation and distribution of repetitive DNA families, and B chromosomes have been described in seven species. Some types of repetitive DNA were identified in A and B chromosomes in species of this plant group, such as AT-rich SSR, 35S and 5S rDNA, C-Giemsa and C-CMA/DAPI bands and retrotransposons. To increase our understanding of the relationships of A and B chromosomes, the B of C. strigilatum Ruiz & Pavón, 1799 was microdissected, amplified and hybridized in situ against chromosomes of this species, and in six other species of this genus. FISH signals were observed in whole the B of C. strigilatum, including stretches of A chromosomes, as well as in some A chromosomes of all tested species. A strong FISH signal was seen adjacent to the 5S rDNA in the proximal region of pair 8 of all species and, due to this, we have searched for 5S rDNA fragments in the microdissected B chromosome. PCR and sequencing data evidenced 5S rDNA deletion along evolutionary pathways of the B of C. strigilatum. Although A and B chromosomes displayed redundancy in the repetitive DNA families in different species, the B of C. strigilatum seemed to differ from those Bs of other Cestrum species by the loss of rDNA fractions. A possible origin of Bs in Cestrum was discussed.

A cytogenetic study of three parasitic wasp species (Hymenoptera, Chalcidoidea, Eulophidae, Trichogrammatidae) from Brazil using chromosome morphometrics and base-specific fluorochrome staining.

Chromosomes of three chalcid wasp species from Brazil, Palmistichus elaeisis Delvare et LaSalle, 1993, Trichospilus diatraeae Cherian et Margabandhu, 1942 (both belonging to the family Eulophidae) and Trichogramma pretiosum Riley, 1879 (Trichogrammatidae), were studied using chromosome morphometrics and base-specific fluorochrome staining. The present study confirmed that these species respectively have 2n = 12, 14 and 10. Chromomycin A3 / 4', 6-diamidino-2-phenylindole (CMA3/DAPI) staining revealed a single CMA3-positive and DAPI-negative band within haploid karyotypes of both Palmistichus elaeisis and Trichogramma pretiosum. This CG-rich band clearly corresponds to the nucleolus organizing region (NOR). Moreover, analogous multiple telomeric bands found on all chromosomes of Trichospilus diatraeae may also represent NORs. Certain features of karyotype evolution of the phylogenetic lineage comprising both Eulophidae and Trichogrammatidae are discussed. The results obtained during the present study demonstrate the importance of chromosome research on tropical parasitoids that remain poorly known in this respect.

A new species of Neotropical Drosophila (Diptera, Drosophilidae) belonging to the guarani group

Abstract Drosophila butantan sp. nov., a species belonging to the guarani group and closely related to Drosophila nigrifemur from Bolivia, is described based on a female, and some of its offspring, collected at the forest reserve of the Instituto de Biociências da Universidade de São Paulo, Cidade Universitária "Armando de Salles Oliveira", São Paulo City, state of São Paulo, Brazil. Although externally similar, the two apparently forest-dwelling species can be told apart by having distinct oviscapt valves and spermathecal introverts and tips. Accordingly, a proposal is made to also include D. nigrifemur, a previously unassigned species, in the guarani group. The two species seem to be also related to Drosophila alexandrei and Drosophila guaraja as indicated by their external morphology, their elongate spermathecae and the not so sharply pointed oviscapt valves. The karyotypes of the new species differ from those described for D. alexandrei and D. guaraja, while those of D. nigrifemur remain still unknown. Photomicrographs of the male and female imagines, in addition to drawings and photos of their terminalia, are also included.

Molecular characterization of KMT2A fusion partner genes in 13 cases of pediatric leukemia with complex or cryptic karyotypes.

In pediatric acute leukemias, reciprocal chromosomal translocations frequently cause gene fusions involving the lysine (K)-specific methyltransferase 2A gene (KMT2A, also known as MLL). Specific KMT2A fusion partners are associated with the disease phenotype (lymphoblastic vs. myeloid), and the type of KMT2A rearrangement also has prognostic implications. However, the KMT2A partner gene cannot always be identified by banding karyotyping. We sought to identify such partner genes in 13 cases of childhood leukemia with uninformative karyotypes by combining molecular techniques, including multicolor banding FISH, reverse-transcriptase PCR, and long-distance inverse PCR. Of the KMT2A fusion partner genes, MLLT3 was present in five patients, all with acute lymphoblastic leukemia, MLLT1 in two patients, and MLLT10, MLLT4, MLLT11, and AFF1 in one patient each. Reciprocal reading by long-distance inverse PCR also disclosed KMT2A fusions with PITPNA in one patient, with LOC100132273 in another patient, and with DNA sequences not compatible with any gene in three patients. The most common KMT2A breakpoint region was intron/exon 9 (3/8 patients), followed by intron/exon 11 and 10. Finally, multicolor banding revealed breakpoints in other chromosomes whose biological and prognostic implications remain to be determined. We conclude that the combination of molecular techniques used in this study can efficiently identify KMT2A fusion partners in complex pediatric acute leukemia karyotypes. Copyright © 2016 John Wiley & Sons, Ltd.

Two new Neotropical species of Drosophilinae (Diptera: Drosophilidae) from Uruguay

Two new species of Drosophilidae from Uruguay are described and illustrated: Drosophila montevidensis sp. nov. (Holotype male in MZSP: Facultad de Agronomía, Universidad de la República, Montevideo city, Department of Montevideo), and Scaptomyza pipinna sp. nov. (Holotype male in MZSP: Sarandí del Consejo, near north shore of Laguna de Castillos, Department of Rocha). The former species belongs to the D. tripunctata group and is sibling to Drosophila nappae Vilela, Valente & Basso-da-Silva, 2004, differing mainly in characters of the aedeagus. The latter is closely related to Scaptomyza striaticeps Wheeler & Takada, 1966, from which it can be distinguished by color and terminalia characters. The new Drosophila species was successfully cultured in a modified banana-agar medium which is provided. Photomicrographs of mitotic and meiotic chromosomes of D. montevidensis sp. nov. are also included.(AU)

Two new Neotropical species of Drosophilinae (Diptera: Drosophilidae) from Uruguay

Two new species of Drosophilidae from Uruguay are described and illustrated: Drosophila montevidensis sp. nov. (Holotype male in MZSP: Facultad de Agronomía, Universidad de la República, Montevideo city, Department of Montevideo), and Scaptomyza pipinna sp. nov. (Holotype male in MZSP: Sarandí del Consejo, near north shore of Laguna de Castillos, Department of Rocha). The former species belongs to the D. tripunctata group and is sibling to Drosophila nappae Vilela, Valente & Basso-da-Silva, 2004, differing mainly in characters of the aedeagus. The latter is closely related to Scaptomyza striaticeps Wheeler & Takada, 1966, from which it can be distinguished by color and terminalia characters. The new Drosophila species was successfully cultured in a modified banana-agar medium which is provided. Photomicrographs of mitotic and meiotic chromosomes of D. montevidensis sp. nov. are also included.

Cytogenetics and DNA barcoding of the Round-eared bats, Tonatia (Chiroptera: Phyllostomidae): a new karyotype for Tonatia bidens

There are two species of Neotropical Round-eared bats, Tonatia bidens Spix, 1823 and Tonatia saurophilaKoopman & Williams, 1951, which present highly similar morphological characteristics that can lead to errors of identification. Specimens originally identified as T. bidens have recently been reclassified as T. saurophila, and the onlykaryotype documented previously for these species was 2n = 16, FN = 20. In the present study, specimens of Tonatiacollected in the municipality of Barra do Garças, in the Brazilian state of Mato Grosso, were analyzed morphologically,using conventional cytogenetic techniques (C-banding, Ag-NOR, and CMA3), and through sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. In the specimens morphologically identified as T. bidens, the diploidnumber (2n) was 26, and the fundamental number (FN), 38, while in T. saurophila, 2n = 16 and FN = 20, which is thekaryotype also described previously for T. bidens. The dendograms obtained with sequences of the COI marker resultedin the formation of two distinct groups between T. bidens and T. saurophila, consistent with the two species, with a highsequence divergence value (14.22%). Distinct clades were also observed between T. bidens and the other phyllostominesanalyzed in this study, with T. bidens also close to Phyllostomus hastatus (14.18% of sequence divergence).(AU)

Cytogenetics and DNA barcoding of the Round-eared bats, Tonatia (Chiroptera: Phyllostomidae): a new karyotype for Tonatia bidens

There are two species of Neotropical Round-eared bats, Tonatia bidens Spix, 1823 and Tonatia saurophilaKoopman & Williams, 1951, which present highly similar morphological characteristics that can lead to errors of identification. Specimens originally identified as T. bidens have recently been reclassified as T. saurophila, and the onlykaryotype documented previously for these species was 2n = 16, FN = 20. In the present study, specimens of Tonatiacollected in the municipality of Barra do Garças, in the Brazilian state of Mato Grosso, were analyzed morphologically,using conventional cytogenetic techniques (C-banding, Ag-NOR, and CMA3), and through sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. In the specimens morphologically identified as T. bidens, the diploidnumber (2n) was 26, and the fundamental number (FN), 38, while in T. saurophila, 2n = 16 and FN = 20, which is thekaryotype also described previously for T. bidens. The dendograms obtained with sequences of the COI marker resultedin the formation of two distinct groups between T. bidens and T. saurophila, consistent with the two species, with a highsequence divergence value (14.22%). Distinct clades were also observed between T. bidens and the other phyllostominesanalyzed in this study, with T. bidens also close to Phyllostomus hastatus (14.18% of sequence divergence).

High chromosomal variation in wild horn fly Haematobiairritans (Linnaeus) (Diptera, Muscidae) populations.

The horn fly, Haematobiairritans is an obligate haematophagous cosmopolitan insect pest. The first reports of attacks on livestock by Haematobiairritans in Argentina and Uruguay occurred in 1991, and since 1993 it is considered an economically important pest. Knowledge on the genetic characteristics of the horn fly increases our understanding of the phenotypes resistant to insecticides that repeatedly develop in these insects. The karyotype of Haematobiairritans, as previously described using flies from an inbred colony, shows a chromosome complement of 2n=10 without heterochromosomes (sex chromosomes). In this study, we analyze for the first time the chromosome structure and variation of four wild populations of Haematobiairritans recently established in the Southern Cone of South America, collected in Argentina and Uruguay. In these wild type populations, we confirmed and characterized the previously published "standard" karyotype of 2n=10 without sex chromosomes; however, surprisingly a supernumerary element, called B-chromosome, was found in about half of mitotic preparations. The existence of statistically significant karyotypic diversity was demonstrated through the application of orcein staining, C-banding and H-banding. This study represents the first discovery and characterization of horn fly karyotypes with 2n=11 (2n=10+B). All spermatocytes analyzed showed 5 chromosome bivalents, and therefore, 2n=10 without an extra chromosome. Study of mitotic divisions showed that some chromosomal rearrangements affecting karyotype structure are maintained as polymorphisms, and multiple correspondence analyses demonstrated that genetic variation was not associated with geographic distribution. Because it was never observed during male meiosis, we hypothesize that B-chromosome is preferentially transmitted by females and that it might be related to sex determination.

The invasive spotted-wing Drosophila (Diptera, Drosophilidae) has been found in the city of São Paulo (Brazil)

The invasive spotted-wing Drosophila (Diptera, Drosophilidae) has been found in the city of São Paulo (Brazil). Drosophila suzukii (Matsumura, 1931), the cherry fly or spotted-wing Drosophila, a pest species from the Oriental and southeastern Palaearctic regions belonging to the melanogaster group, invaded the Nearctic and western countries of the Palaearctic regions late last decade (2008) and, more recently (2013), the southern Brazilian states of Rio Grande do Sul and Santa Catarina. Early in 2014 it was reared from blueberries produced in São Joaquim, state of Santa Catarina, that were bought at a São Paulo city grocery store. Despite being a cold-adapted species, after having arrived to the southeastern state of São Paulo, this invasive fly will probably expand its territory to other Brazilian states and South American countries through trade of cultivated soft skin small fruits, such as blueberries and strawberries, as well as naturally through the use of small wild fruits as breeding sites.

Cytogenetics of the Brazilian Bolitoglossa paraensis (Unterstein, 1930) salamanders (Caudata, Plethodontidae).

Plethodontid salamanders of genus Bolitoglossa constitute the largest and most diverse group of salamanders, including around 20% of living caudate species. Recent studies have indicated the occurrence of five recognized species in the Brazilian Amazon Rainforest. We present here the first cytogenetic data of a Brazilian salamander, which may prove to be a useful by contribution to the cytotaxonomy of the genus. Specimens were collected near the "type" locality (Utinga, Belém, PA, Brazil). Chromosomal preparations from duodenal epithelial cells and testes were subjected to Giemsa staining, C-banding and DAPI/CMA3 fluorochrome staining. All specimens showed a karyotype with 13 bi-armed chromosome pairs (2n = 26). Nucleolar Organizer Regions, evidenced by CMA3, were located distally on the long arm of pair 7 (7q). DAPI+ heterochromatin was predominantly centromeric, with some small pericentromeric bands. Although the C-banding patterns of other Bolitoglossa species are so far unknown, cytogenetic studies conducted in other Plethodontid salamanders have demonstrated that pericentromeric heterochromatin is a useful cytological marker for identifying interspecific homeologies. Species diversification is usually accompanied by chromosomal changes. Therefore, the cytogenetic characterization of Bolitoglossa populations from the middle and western Brazilian Amazon Basin could identify differences which may lead to the identification of new species.

Analyzing acute leukemia patients with complex MLL rearrangements by a sequential LDI-PCR approach.

Translocations involving MLL gene are common among children with acute leukemias. Most importantly, the presence of a given MLL fusion partner dictates the outcome of patients. Patients with complex MLL rearrangements, e.g. three-way translocations could be related to a poor clinical outcome. For this purpose, we characterize 5 childhood patients with three-way translocations involving MLL gene. By LDI-PCR we identified 15 out of 17 fusion alleles and determined the localization of these breakpoints. In all cases at least one functional MLL fusion allele was present. In addition, patients displayed a remaining 3'-MLL allele that allow in principle the expression of the MLL* protein variant.

Karyological analysis of Proechimys cuvieri and Proechimys guyannensis (Rodentia, Echimyidae) from central Amazon.

The aim was to characterize the karyotype of rodents of the genus Proechimys from three localities in the central Brazilian Amazon, in the search for new markers that might shed light on our understanding of the taxonomy and evolutionary history of this taxon. Two karyotypes were found, viz., 2n = 28, FN = 46 in individuals from the NRSP (Cuieiras River) and REMAN (Manaus), and 2n = 46, FN = 50 in individuals from the Balbina Hydroelectric Plant. While individuals with the karyotype with 2n = 28 chromosomes were morphologically associated with Proechimys cuvieri, their karyotype shared similarities with those of the same diploid number in two other regions. Although three karyotypes are described for Proechimys cuvieri, no geographic distribution pattern that defined a cline could be identified. Based on the morphological examination of voucher specimens and additional results from molecular analysis, the karyotype with 2n = 46 and FN = 50 could be associated with P. guyannensis.

A hybrid zone of the genus Ctenomys: A case study in southern Brazil.

We describe variation at microsatellite loci and the chromosomal polymorphisms of a hybrid population, and hybridizing populations of Ctenomys minutus (the minor tuco-tuco) from the coastal plain of Rio Grande do Sul, southern Brazil. Cytogenetic analysis and a survey of six microsatellite loci included 101 specimens of C. minutus from the parental populations (2n/AN = 42/74 and 48a/76) and their contact zone. Cytogenetic analysis recorded 26 different karyotypes exhibited by 50 individuals from the hybrid population. Of the 26 karyotypes, only 14% presented a parental-like configuration, and none had the combinations of 2n and AN expected for an F1 hybrid. The remaining karyotypes were alternative hybrid forms, with 2n varying from 42 to 46 and AN from 68 to 80. These results suggest chromosomal rearrangements are only of minor significance in the establishment of reproductive barriers for this species.