Karyotypic Evolution in Malagasy Flying Foxes (Pteropodidae, Chiroptera) and Their Hipposiderid Relatives as Determined by Comparative Chromosome Painting

Abstract

Pteropodidae and Hipposideridae are 2 of the 9 chiropteran families that occur on Madagascar. Despite major advancements in the systematic study of the island's bat fauna, few karyotypic data exist for endemic species. We utilized G- and C-banding in combination with chromosome painting with Myotismyotis probes to establish a genome-wide homology among Malagasy species belonging to the families Pteropodidae (Pteropus rufus 2n = 38; Rousettus madagascariensis, 2n = 36), Hipposideridae (Hipposideros commersoni s.s., 2n = 52), and a single South African representative of the Rhinolophidae (Rhinolophus clivosus, 2n = 58). Painting probes of M. myotis detected 26, 28, 28, and 29 regions of homology in R. madagascariensis, P. rufus, H. commersoni s.s, and R. clivosus, respectively. Translocations, pericentric inversions, and heterochromatin additions were responsible for karyotypic differences amongst the Malagasy pteropodids. Comparative chromosome painting revealed a novel pericentric inversion on P. rufus chromosome 4. Chromosomal characters suggest a close evolutionary relationship between Rousettus and Pteropus. H. commersoni s.s. shared several chromosomal characters with extralimital congeners but did not exhibit 2 chromosomal synapomorphies proposed for Hipposideridae. This study provides further insight into the ancestral karyotypes of pteropodid and hipposiderid bats and corroborates certain molecular phylogenetic hypotheses.

Chromosomal Evolution in Chiroptera

“…In total, 13 species have been studied with G-banding. FISH analyses were undertaken for 5 species from 4 genera (2n in parentheses), i.e., Cynopterus (34), Eonycteris (36), Rousettus (36), and Pteropus (38) [ 62 , 68 , 74 , 75 , 97 ].…”

“…However, detailed morphological studies [ 111 ] and DNA sequence analyses revealed that both genera are in fact distantly related [ 3 ]. In contrast, the molecular hypothesis of a close relationship between Eonycteris and Rousettus (subfamily Rousettinae) is also supported by karyotype similarities [ 97 ]. The karyotype of M. sobrinus , based on the analysis of one male and one female from Peninsular Malaysia (Ulu Gombak, Selangor), consists of 2n = 34 and FN = 60.…”

“…However, structural differences were found in the elements homologous to Myotis chromosomes (MMY) 16/17, 20, 24, and the element homologous to the proximal region of MMY7 (named 7i). In Pteropus , which displays the highest chromosome number of the mentioned genera (2n = 38), these elements represent individual chromosomes, partly altered by terminal heterochromatin additions [ 97 ]. The 2n reduction from 38 to 34 in Macroglossus , unlike in Eonycteris and Rousettus , is not the result of a terminal fusion of the MMY homologs 24 and 16/17 [ 62 , 75 , 97 ].…”

“…In Pteropus , which displays the highest chromosome number of the mentioned genera (2n = 38), these elements represent individual chromosomes, partly altered by terminal heterochromatin additions [ 97 ]. The 2n reduction from 38 to 34 in Macroglossus , unlike in Eonycteris and Rousettus , is not the result of a terminal fusion of the MMY homologs 24 and 16/17 [ 62 , 75 , 97 ]. Instead, the 2n reduction in Macroglossus is the result of centric fusions of MMY24 and MMY7i on one hand (MSO14) and a tandem fusion of MMY20 and MMY16/17 homologous chromosomes (MSO13).…”

“…Further, the ancestral acrocentric shape of MMY7i has been changed in Eonycteris and Rousettus , resulting in a small metacentric chromosome. As a consequence, the fusion chromosome 24-16/17 found in Eonycteris and Rousettus has to be considered as derived and as an independent event from a similar fusion in Hipposideros [ 97 ].…”