Comparative chromosome painting of four Siberian Vespertilionidae species with Aselliscus stoliczkanus and human probes

Chromosome-level genome assembly of the Stoliczka's Asian trident bat (Aselliscus stoliczkanus)

Stoliczka's Asian trident bat (Aselliscus stoliczkanus) is a small-bodied species and very sensitive to climate change. Here, we presented a chromosome-level genome assembly of A. stoliczkanus by combining Illumina sequencing, Nanopore sequencing and high-throughput chromatin conformation capture (Hi-C) sequencing technology. The genome assembly was 2.18 Gb in size with 98.26% of the genome sequences anchored onto 14 autosomes and two sex chromosomes (X and Y). The quality of the genome assembly is very high with a contig and scaffold N50 of 72.98 and 162 Mb, respectively, Benchmarking Universal Single-Copy Orthologs (BUSCO) score of 96.6%, and the consensus quality value (QV) of 47.44. A total of 20,567 genes were predicted and 98.8% of these genes were functionally annotated. Syntenic blocks between A. stoliczkanus and Homo sapiens, together with previous comparative cytogenetic studies, provide valuable foundations for further comparative genomic and cytogenetic studies in mammals. The reference-quality genome of A. stoliczkanus contributes an important resource for conservative genomics and landscape genomics in predicting adaptation and vulnerability to climate change.

Chromosomal Evolution in Chiroptera

Chiroptera is the second largest order among mammals, with over 1300 species in 21 extant families. The group is extremely diverse in several aspects of its natural history, including dietary strategies, ecology, behavior and morphology. Bat genomes show ample chromosome diversity (from 2n = 14 to 62). As with other mammalian orders, Chiroptera is characterized by clades with low, moderate and extreme chromosomal change. In this article, we will discuss trends of karyotypic evolution within distinct bat lineages (especially Phyllostomidae, Hipposideridae and Rhinolophidae), focusing on two perspectives: evolution of genome architecture, modes of chromosomal evolution, and the use of chromosome data to resolve taxonomic problems.

Two new cytotypes reinforce that Micronycteris hirsuta Peters, 1869 does not represent a monotypic taxon

Background

The genus Micronycteris is a diverse group of phyllostomid bats currently comprising 11 species, with diploid number (2n) ranging from 26 to 40 chromosomes. The karyotypic relationships within Micronycteris and between Micronycteris and other phyllostomids remain poorly understood. The karyotype of Micronycteris hirsuta is of particular interest: three different diploid numbers were reported for this species in South and Central Americas with 2n = 26, 28 and 30 chromosomes. Although current evidence suggests some geographic differentiation among populations of M. hirsuta based on chromosomal, morphological, and nuclear and mitochondrial DNA markers, the recognition of new species or subspecies has been avoided due to the need for additional data, mainly chromosomal data.

Results

We describe two new cytotypes for Micronycteris hirsuta (MHI) (2n = 26 and 25, NF = 32), whose differences in diploid number are interpreted as the products of Robertsonian rearrangements. C-banding revealed a small amount of constitutive heterochromatin at the centromere and the NOR was located in the interstitial portion of the short arm of a second pair, confirmed by FISH. Telomeric probes hybridized to the centromeric regions and weakly to telomeric regions of most chromosomes. The G-banding analysis and chromosome painting with whole chromosome probes from Carollia brevicauda (CBR) and Phyllostomus hastatus (PHA) enabled the establishment of genome-wide homologies between MHI, CBR and PHA.

Conclusions

The karyotypes of Brazilian specimens of Micronycteris hirsuta described here are new to Micronycteris and reinforce that M. hirsuta does not represent a monotypic taxon. Our results corroborate the hypothesis of karyotypic megaevolution within Micronycteris, and strong evidence for this is that the entire chromosome complement of M. hirsuta was shown to be derivative with respect to species compared in this study.

Chromosome evolution in bats as revealed by FISH: the ongoing search for the ancestral chiropteran karyotype

Chiroptera, the second largest order of mammals, comprises more than 1,000 species in 18 highly morphologically diverse families. Chromosome painting with human probes has been applied to 10 bat species from 8 families. Except for the combination 10/12pq/22q, all syntenic segmental associations proposed for the mammalian ancestor have been found in Chiroptera. Bat-specific painting probes, established from 4 species of 3 families, have been used in whole chromosome painting experiments in 29 species from 8 families. The results show that the prevailing mode of chromosomal evolution in bats is Robertsonian translocation with a large number of convergent events. Given our present knowledge of chiropteran karyotypes, only a few elements of the ancestral chiropteran karyotype can be reconstructed with confidence.