Amazonian mammal diversity is exceptionally high, yet new taxonomic discoveries continue to be made and many questions remain for understanding its diversification through time and space. Here we ...investigate the diversification of spiny rats in the genus Makalata, whose species are strongly associated with seasonally flooded forests, watercourses and flooded islands. We use a biogeographical approach based on a mitochondrial cytochrome b gene through divergence time estimation and reconstruction of ancestral areas and events. Our findings indicate an ancient origin of Makalata for the Guiana Shield and Eastern Amazonia as ancestral area. A first cladogenetic event led to a phylogeographic break into two broader clades of Makalata through dispersal, implying a pattern of western/Eastern Amazonian clades coinciding with the Purus Arch (middle Miocene). Most of subclades we infer originated between the late Pliocene to the early Pleistocene, with few recent exceptions in the early Pliocene through dispersal and vicariant events. The hypothesis of rivers as dispersal barriers is not corroborated for Makalata, as expected for mammalian species associated with seasonally flooded environments. We identify two key events for the expansion and diversification of Makalata species: the presence of geologically stable areas in the Guiana and Brazilian shields and the transition from lacustrine conditions in western Amazonia (Acre system) to a river system, with the establishment of the Amazon River transcontinental system and its tributaries. Our results are congruent with older geological scenarios for the Amazon basin formation (Miocene), but we do not discard the influence of recent dynamics on some speciation events and, mainly, on phylogeographic structuring processes.
Charadriiformes represent one of the largest orders of birds; members of this order are diverse in morphology, behavior and reproduction, making them an excellent model for studying evolution. It is ...accepted that the avian putative ancestral karyotype, with 2n = 80, remains conserved for about 100 million years. So far, only a few species of Charadriiformes have been studied using molecular cytogenetics. Here, we performed chromosome painting on metphase chromosomes of two species of Charadriidae, Charadrius collaris and Vanellus chilensis, with whole chromosome paint probes from Burhinus oedicnemus. Charadrius collaris has a diploid number of 76, with both sex chromosomes being submetacentric. In V. chilensi a diploid number of 78 was identified, and the Z chromosome is submetacentric. Chromosome painting suggests that chromosome conservation is a characteristic common to the family Charadriidae. The results allowed a comparative analysis between the three suborders of Charadriiformes and the order Gruiformes using chromosome rearrangements to understand phylogenetic relationships between species and karyotypic evolution. However, the comparative analysis between the Charadriiformes suborders so far has not revealed any shared rearrangements, indicating that each suborder follows an independent evolutionary path, as previously proposed. Likewise, although the orders Charadriiformes and Gruiformes are placed on sister branches, they do not share any signature chromosomal rearrangements.
Morphological, molecular and chromosomal studies in the genera Lonchothrix and Mesomys have contributed to a better understanding of taxonomic design, phylogenetic relationships and karyotypic ...patterns. Recent molecular investigations have shown a yet undescribed diversity, suggesting that these taxa are even more diverse than previously assumed. Furthermore, some authors have questioned the limits of geographic distribution in the Amazon region for the species M. hispidus and M. stimulax. In this sense, the current study sought to understand the karyotypic evolution and geographic limits of the genus Mesomys, based on classical (G- and C-banding) and molecular cytogenetic analysis (FISH using rDNA 18S and telomeric probes) and through the sequencing of mitochondrial genes Cytochrome b (Cytb) and Cytochrome Oxidase-Subunit I (CO using phylogeny, species delimitation and time of divergence, from samples of different locations in the Brazilian Amazon. The species M. stimulax and Mesomys sp. presented 2n = 60/FN = 110, while M. hispidus presented 2n = 60/FN = 112, hitherto unpublished. Molecular dating showed that Mesomys diversification occurred during the Plio-Pleistocene period, with M. occultus diverging at around 5.1 Ma, followed by Mesomys sp. (4.1 Ma) and, more recently, the separation between M. hispidus and M. stimulax (3.5 Ma). The ABGD and ASAP species delimiters support the formation of 7 and 8 potential species of the genus Mesomys, respectively. Furthermore, in both analyzes Mesomys sp. was recovered as a valid species. Our multidisciplinary approach involving karyotypic, molecular and biogeographic analysis is the first performed in Mesomys, with the description of a new karyotype for M. hispidus, a new independent lineage for the genus and new distribution data for M. hispidus and M. stimulax.
Cytogenetic studies show that there is great karyotypic diversity in order Testudines (2n = 26-68), and that this may be mainly attributed to the presence/absence of microchromosomes. Members of the ...Podocnemididae family have the smallest diploid numbers of this order (2n = 26-28), which may be a derived condition of the group. Diverse studies suggest that repetitive-DNA-rich sites generally act as hotspots for double-strand breaks and chromosomal reorganization. In this context, we used fluorescent in situ hybridization (FISH) to map telomeric sequences (TTAGGG)n, 45S rDNA, and the genes encoding histones H1 and H3 in two species of genus Podocnemis. We also observed conservation of the 45S rDNA and H1 histone sequences (probable case of conserved synteny), but multiple conserved and non-conserved clusters of H3 genes, which colocalized with the interstitial telomeric sequences in the Podocnemis genome. Our results suggest that fusions have occurred between macro and microchromosomes or between microchromosomes, leading to the observed reduction in diploid number in the family Podocnemididae.
Charadriidae comprise 142 valid species and the most recent checklist for the occurrence of this family in Brazil describes 11 species. There are few chromosomal studies in Charadriidae, most of them ...using a conventional approach. In Charadrius, only five species had their karyotypes described by classical cytogenetics, of which four have 2n = 76 (C. hiaticula, C. dubius, C. vociferou and C. collaris) and one 2n = 78 (C. alexandrinus alexandrinus). Among these species, only Charadrius collaris had the karyotype studied by chromosome painting, which allowed the identification of chromosomal homeologies with the karyotypes of Gallus gallus (GGA) and Burhinus oedicnemus (BOE). According to the literature, studies performed with BAC-FISH using probes from Gallus gallus and Taeniopygia guttata (TGU) libraries have shown interactions between macro and microchromosomes and micro inversions in chromosomes previously considered conserved. Other studies have shown the fusion of several microchromosomes, forming new macrochromosomes, leading to a decrease in the 2n of some species. The present study aims to deepen the chromosomal information in Charadrius collaris through the application of BAC-FISH with probes from the GGA and TGU libraries, in order to investigate possible rearrangements within the apparently conserved karyotype of this species, and thus better clarify the evolutionary history of the species. Charadrius collaris presented 2n = 76 and fundamental number (FN) equal to 94. Comparative mapping of BAC probes from GGA and TGU in Charadrius collaris revealed hybridization signals from 26 macrochromosome probes. Probes from microchromosomes 9 to 28 of GGA were also used and revealed 31 hybridization signals. The karyotype is well conserved, but it contains a paracentric and a pericentric inversion on the CCO1 chromosome, a paracentric and a pericentric inversion on the CCO4 and the separation of GGA4 into CCO4 and CCO8, demonstrating that the BAC-FISH approach allows for greater data resolution. More studies are needed to improve the understanding of chromosomal evolution within the order Charadriiformes and thus clarify whether these characteristics demonstrated here are specific traits for Charadrius collaris or if other species share these characteristics.
The genus Makalata is a taxonomically complex group of rodents on which few cytogenetic studies have been performed. Most of the published karyotypes were described based only on conventional ...chromosome staining. Here, we studied the karyotypes of Makalata from two Brazilian Amazonian states, Amapá and Pará, by Giemsa-staining, G- and C-banding, AgNO3-staining and FISH with 18S rDNA and telomeric sequences probes. We observed 2n = 66/FN = 124 in the Pará state population in Makalata sp; and 2n = 72/FN = 128 in the Amapá state population in M. didelphoides. Multiple chromosome rearrangements may have given rise to these karyotypes, which differ significantly from each other and from those reported in the literature. The chromosomal differences among the described Makalata karyotypes can act as a barrier to gene flow; since they are also associated with geographic barriers (e.g., rivers) and numerous molecular differences, they could be seen as evidence for reproductive isolation of populations from genus Makalata. Our data suggest that the genus is chromosomally diverse and the karyotypes may belong to different species. These karyotypes may prove useful as taxonomic markers for these rodents.
The genus Oecomys (Rodentia, Sigmodontinae) is distributed from southern Central America to southeastern Brazil in South America. It currently comprises 18 species, but multidisciplinary approaches ...such as karyotypic, morphological and molecular studies have shown that there is a greater diversity within some lineages than others. In particular, it has been proposed that O. paricola constitutes a species complex with three evolutionary units, which have been called the northern, eastern and western clades. Aiming to clarify the taxonomic status of O. paricola and determine the relevant chromosomal rearrangements, we investigated the karyotypes of samples from eastern Amazonia by chromosomal banding and FISH with Hylaeamys megacephalus (HME) whole-chromosome probes. We detected three cytotypes for O. paricola: A (OPA-A; 2n = 72, FN = 75), B (OPA-B; 2n = 70, FN = 75) and C (OPA-C; 2n = 70, FN = 72). Comparative chromosome painting showed that fusions/fissions, translocations and pericentric inversions or centromeric repositioning were responsible for the karyotypic divergence. We also detected exclusive chromosomal signatures that can be used as phylogenetic markers. Our analysis of karyotypic and distribution information indicates that OPA-A, OPA-B and OPA-C are three distinct species that belong to the eastern clade, with sympatry occurring between two of them, and that the "paricola group" is more diverse than was previously thought.
Rhipidomys
(Sigmodontinae, Thomasomyini) has 25 recognized species, with a wide distribution ranging from eastern Panama to northern Argentina. Cytogenetic data has been described for 13 species with ...12 of them having 2n = 44 with a high level of autosomal fundamental number (FN) variation, ranging from 46 to 80, assigned to pericentric inversions. The species are grouped in groups with low FN (46–52) and high FN (72–80). In this work the karyotypes of
Rhipidomys emiliae
(2n = 44, FN = 50) and
Rhipidomys mastacalis
(2n = 44, FN = 74), were studied by classical cytogenetics and by fluorescence
in situ
hybridization using telomeric and whole chromosome probes (chromosome painting) of
Hylaeamys megacephalus
(HME). Chromosome painting revealed homology between 36 segments of REM and 37 of RMA. We tested the hypothesis that pericentric inversions are the predominant chromosomal rearrangements responsible for karyotypic divergence between these species, as proposed in literature. Our results show that the genomic diversification between the karyotypes of the two species resulted from translocations, centromeric repositioning and pericentric inversions. The chromosomal evolution in
Rhipidomys
was associated with karyotypical orthoselection. The HME probes revealed that seven syntenic probably ancestral blocks for Sigmodontinae are present in
Rhipidomys
. An additional syntenic block described here is suggested as part of the subfamily ancestral karyotype. We also define five synapomorphies that can be used as chromosomal signatures for
Rhipidomys
.
Rodents of the genus Cerradomys belong to tribe Oryzomyini, one of the most diverse and speciose groups in Sigmodontinae (Rodentia, Cricetidae). The speciation process in Cerradomys is associated ...with chromosomal rearrangements and biogeographic dynamics in South America during the Pleistocene era. As the morphological, molecular and karyotypic aspects of Myomorpha rodents do not evolve at the same rate, we strategically employed karyotypic characters for the construction of chromosomal phylogeny to investigate whether phylogenetic relationships using chromosomal data corroborate the radiation of Cerradomys taxa recovered by molecular phylogeny. Comparative chromosome painting using Hylaeamys megacephalus (HME) whole chromosome probes in C. langguthi (CLA), Cerradomys scotii (CSC), C. subflavus (CSU) and C. vivoi (CVI) shows that karyotypic variability is due to 16 fusion events, 2 fission events, 10 pericentric inversions and 1 centromeric repositioning, plus amplification of constitutive heterochromatin in the short arms of the X chromosomes of CSC and CLA. The chromosomal phylogeny obtained by Maximum Parsimony analysis retrieved Cerradomys as a monophyletic group with 97% support (bootstrap), with CSC as the sister to the other species, followed by a ramification into two clades (69% of branch support), the first comprising CLA and the other branch including CVI and CSU. We integrated the chromosome painting analysis of Eumuroida rodents investigated by HME and Mus musculus (MMU) probes and identified several syntenic blocks shared among representatives of Cricetidae and Muridae. The Cerradomys genus underwent an extensive karyotypic evolutionary process, with multiple rearrangements that shaped extant karyotypes. The chromosomal phylogeny corroborates the phylogenetic relationships proposed by molecular analysis and indicates that karyotypic diversity is associated with species radiation. Three syntenic blocks were identified as part of the ancestral Eumuroida karyotype (AEK): MMU 7/19 (AEK 1), MMU 14 (AEK 10) and MMU 12 (AEK 11). Besides, MMU 5/10 (HME 18/2/24) and MMU 8/13 (HME 22/5/11) should be considered as signatures for Cricetidae, while MMU 5/9/14, 5/7/19, 5 and 8/17 for Sigmodontinae.
Ipê is a plant of the Bignoniaceae family. Among the compounds extracted from this tree, lapachol is notable because its structural modification allows the production of β-lapachone, which has ...anticancer properties. The objective of this work was to test this hypothesis at a cellular level in vitro and assess its potential safety for use. The following tests were performed: MTT cell viability assay, apoptotic index determination, comet assay, and micronucleus test. The results showed that β-lapachone had a high cytotoxic capacity for all cell lines tested: ACP02 (gastric adenocarcinoma cells), MCF7 (breast carcinoma cells), HCT116 (colon cancer cells) and HEPG2 (hepatocellular carcinoma cells). Regarding genotoxicity, the exposure of cells to sublethal doses of β-lapachone induced DNA damage (assessed by the comet assay) and nuclear abnormalities, such as nucleoplasmic bridges and nuclear buds (assessed by the micronucleus test). All tested cell lines responded similarly to β-lapachone, except for ACP02 cells, which were relatively resistant to the cytotoxic effects of the compound in the MTT test. Our results collectively indicate that although β-lapachone showed antiproliferative activity against cancer cell lines, it also caused harmful effects in these cells, suggesting that the use of β-lapachone in treating cancer should be carried out with caution.
PDF
