Multi-locus phylogeny of the tribe Tragelaphini (Mammalia, Bovidae) and species delimitation in bushbuck: Evidence for chromosomal speciation mediated by interspecific hybridization

Abstract

The bushbuck is the most widespread bovid species in Africa. Previous mitochondrial studies have revealed a polyphyletic pattern suggesting the possible existence of two distinct species. To assess this issue, we have sequenced 16 nuclear genes and one mitochondrial fragment (cytochrome b gene + control region) for most species of the tribe Tragelaphini, including seven bushbuck individuals belonging to the two divergent mtDNA haplogroups, Scriptus and Sylvaticus. Our phylogenetic analyses show that the Scriptus lineage is a sister-group of Sylvaticus in the nuclear tree, whereas it is related to Tragelaphus angasii in the mitochondrial tree. This mito-nuclear discordance indicates that the mitochondrial genome of Scriptus was acquired by introgression after one or several past events of hybridization between bushbuck and an extinct species closely related to T. angasii. The division into two bushbuck species is supported by the analyses of nuclear markers and by the karyotype here described for T. scriptus (2n = 57 M/58F), which is strikingly distinct from the one previously found for T. sylvaticus (2n = 33 M/34F). Molecular dating estimates suggest that the two species separated during the Early Pleistocene after an event of interspecific hybridization, which may have mediated massive chromosomal rearrangements in the common ancestor of T. scriptus.

Mitogenomics of historical type specimens of Australasian turtles: clarification of taxonomic confusion and old mitochondrial introgression

“…the complete replacement of the original mitochondrial genome with that of another species through introgressive hybridization, is much rarer. Cases have been described for insects 103 , freshwater fishes 104–106 , newts 107 , frogs 108–111 , turtles 97,100–102 , lizards 112 , snakes 113 , and bovids 114–117 , with the oldest case (12 Ma) referring to emydid turtles 100 .…”

A comparative approach for species delimitation based on multiple methods of multi-locus DNA sequence analysis: A case study of the genus Giraffa (Mammalia, Cetartiodactyla)

“…Indeed, the maternal inheritance of the mtDNA genome can be misleading for species delimitation in mammals, because females and males have usually different dispersal behaviours (female philopatry versus male dispersal) [5,6], and because interspecific hybrid females are generally fertile, whereas hybrid males are often sterile (Haldane's rule), facilitating mitochondrial introgression between closely related species [7][8][9]. To overcome these limitations, most recent taxonomic studies dealing with the delimitation between cryptic mammal species have focused on multi-locus datasets [10][11][12], as the use of multiple independent DNA markers has been shown to provide a strong and reliable signal for deciphering relationships among closely related taxa [13,14]. However, interpreting the results from multi-locus datasets can be difficult, especially when the DNA markers show low genetic variation or conflicting relationships between them.…”

“…The comparison between the mtDNA tree based on 82 giraffe haplotypes and the nuclear tree reconstructed from 21 introns sequenced for 137 giraffes reveals a robust conflict for the evolutionary history drawn from maternal and biparental markers (Fig 1). Some mito-nuclear conflicts can be simply explained by recent hybridization between sympatric or parapatric taxa (species or subspecies), resulting in the transfer of the mitochondrial genome from one taxa to the other, a process referred to as mitochondrial introgression [6][7][8][9][10][11].…”

A conservative approach for species delimitation based on multi-locus DNA sequences: a case study of the genusGiraffa(Mammalia, Cetartiodactyla)

“…Indeed, the maternal inheritance of the mtDNA genome can be misleading for species delimitation because females and males have generally different dispersal behaviours (female philopatry versus male dispersal) [5,6], and because interspecific hybrid females are generally fertile, whereas hybrid males are often sterile (Haldane’s rule), facilitating mitochondrial introgression between closely related species [7–9]. To overcome these limitations, most recent taxonomic studies dealing with the delimitation between cryptic mammal species have focused on multi-locus datasets [10–12], as the use of multiple independent DNA markers has been shown to provide a strong and reliable signal for deciphering relationships among closely related taxa [13–14]. However, interpreting the results from multi-locus datasets can be difficult, especially when the DNA markers show low genetic variation or conflicting relationships between them.…”