Karyotype Evolution in the Horseshoe Bat <b><i>Rhinolophus sedulus</i></b> by Whole-Arm Reciprocal Translocation (WART)

Abstract

Robertsonian (centric) fusion or fission is one of the predominant modes of chromosomal rearrangement in karyotype evolution among mammals. However, in karyotypes composed of only bi-armed chromosomes, creation of new chromosomal arm combinations in one step is possible only via whole-arm reciprocal translocation (WART). Although this type of rearrangement has often been proposed to play an important role in chromosomal evolution, direct observations of WARTs remained rare, and, in most cases, were found in hybrids of chromosomal races in the genera Mus and Sorex. For the first time, we present the karyotype of the horseshoe bat species Rhinolophus sedulus (2n = 28, FNa = 52), where a WART between 2 metacentric autosomes was detected by G-banding and confirmed by FISH with painting probes of the vespertilionid bat Myotis myotis. Among the 6 specimens analyzed, 2 showed the heterozygous condition of the WART, 1 showed the presumed ancestral, and 3 specimens showed the derived homozygous state. As the existence of a hybrid zone at the sampling locality is thought to be rather improbable, the WART may indicate ongoing karyotype evolution in this taxon.

Chromosomal Evolution in Chiroptera

“…However, it should be considered that it is the most easily detectable type of rearrangement. Conservation of chromosomal arm architecture is also facilitated by rarely described whole arm reciprocal translocations (WARTs) [ 100 ]. Further reduction of the diploid numbers in all-metacentric karyotypes is due to tandem fusions.…”

“…In addition to currently known 13 species with 62 chromosomes (Asian clade), a high diversity of chromosomal numbers was identified in Asian rhinolophids. A morphologically clearly defined group is the R. trifoliatus clade with 2n between 28 ( R. sedulus ) and 52 ( R. formosae ) and extremely high rates of chromosomal changes which led to the detection of cryptic species in the “ R. luctus complex” [ 100 , 101 , 102 ]. The second group of Asian Rhinolophus species with chromosomal numbers from 36 to 56 consists of R. pearsoni , R. rouxi and related species.…”

“…Arm combinations in R. trifoliatus equal those of R. morio . Data extracted from literature [ 62 , 74 , 75 , 99 , 100 , 101 , 102 ].…”

Chromosome Changes in Soma and Germ Line: Heritability and Evolutionary Outcome

“…Apparently, it arises in different breeding lines; furthermore, this translocation was also shown in the ancestral form, which indicates the karyotype prone to such a rearrangement [130][131][132]. In cases of partial or monobrachial homology, or in cases of numerous Rbs, the synapsis might be prolonged, leading to meiotic failure in some cells and decreasing fertility [133][134][135][136]. Examples of bats, shrews, mole voles, mice, and rock-wallabies demonstrate the restriction of the gene flow due to monobrachial homology, presumably resulting in speciation [137][138][139][140][141][142][143].…”

Surprising Genetic Diversity inRhinolophus luctus(Chiroptera: Rhinolophidae) from Peninsular Malaysia: Description of a New Species Based on Genetic and Morphological Characters

“…Further, according to the differing diploid number of 52 (Ando et al, 1980(Ando et al, , 1983, the former R. luctus subspecies formosae is now treated as a separate species (Yoshi yuki and Harada, 1995). The only species from the trifoliatus group for which a differentially stained karyotype has been published is the smallest species of the clade, R. sedulus, with a diploid number of 2n = 28 (Volleth et al, 2014).…”