Karyotypic diversity within the genus Makalata (Echimyidae: Echimyinae) of Brazilian Amazon: Chromosomal evidence for multiple species

Abstract

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.

A molecular and chromosomic meta‐analysis approach and its implications for the taxonomy of the genusMakalataHusson, 1978 (Rodentia, Echimyidae) including an amended diagnosis forM. macrura(Wagner, 1842)

“…In this study, we examined and sequenced topotypical Figure 2 of M. macrura and were able to clearly associate them with Wagner's original description (1842). The identification of the karyotype obtained by Pereira et al (2020) for the upper Rio Tapajós region was also confirmed as M . macrura .…”

“…didelphoides with this cytotype (Table 4). According to Table 4, karyotypes from the Barcelos region, in the middle Negro River, associated with M. macrura (subclade F of the present study), as well as those from Caracaraí, Roraima (probably a fifth potential species with morphology similar to didelphoides and synonyms, since the karyotype is quite different from those associated with the other subclades that emerged in our analysis with similar morphology—G, K, J, or N), and the state of Tocantins (probably subclade N of the present study), identified as M. didelphoides are not supported (see Table 4; Pereira et al, 2020). Sequencing all holotypes from the Guiana Shield is a fundamental step toward establishing proper names for specimens from this biogeographical region.…”

“…The specimens karyotyped and deposited in the mammal collection of the Federal University of Paraíba (UFPB 956, 990) have a morphology similar to didelphoides and their synonyms, and Silva et al (2013) associated the name didelphoides with populations from Amapá state with karyotype 2 n = 70 based on personal communication. However, this karyotype was later described by Pereira et al (2020) presenting 2 n = 72 and FN = 128.…”

“…We reevaluated the recent meta‐analysis carried out by Pereira et al (2020) performing the necessary adjustments (Table 4). Chromosome preparations in the present study were obtained by direct bone marrow extraction, according to Ford and Hamerton (1956).…”

“…The second karyotype was described from a voucher from the Samuel Hydroelectric Power Plant, Jamari River, in the state of Rondonia, also associated with M. armata , presenting 2 n = 70/FN = 120 (Ventura et al, 2008). Recently, Pereira et al (2020) published two additional karyotypes: 2 n = 66/FN = 124 in Abaetetuba, state of Para, Brazil, identified only at generic level, Makalata sp. ; and 2 n = 72/FN = 128 from Porto Grande, state of Amapá, Brazil, associating it with M. didelphoides .…”