Comparative chromosome painting between the domestic pig <i>(Sus scrofa)</i> and two species of peccary, the collared peccary <i>(Tayassu tajacu)</i> and the white-lipped peccary <i>(T. pecari):</i> a phylogenetic perspective

Abstract

The Suidae and the Dicotylidae (or Tayassuidae) are related mammalian families, both belonging to the artiodactyl suborder Suiformes, which diverged more than 37 million years ago. Cross-species chromosome painting was performed between the domestic pig (Sus scrofa; 2n = 38), a representative of the Suidae, and two species of the Dicotylidae: the collared peccary (Tayassu tajacu; 2n = 30) and the white-lipped peccary (T. pecari; 2n = 26). G-banded metaphase chromosomes of the two peccaries were hybridized with whole chromosome painting probes derived from domestic pig chromosomes 1–18 and X. For both peccary species, a total of 31 autosomal segments that are conserved between pig and peccary could be identified. The painting results confirm conclusions inferred from G-band analyses that the karyotypes of the collared peccary and the white-lipped peccary are largely different. The karyotypic heterogeneity of the Dicotylidae contrasts with the relative homogeneity among the karyotypes of the Suidae. For this difference between the Dicotylidae and the Suidae, a number of explanations are being postulated: 1) the extant peccaries are phylogenetically less closely related than is usually assumed; 2) the peccary genome is less stable than the genome of the pigs; and 3) special (e.g. biogeographical or biosocial) circumstances have facilitated the fixation of chromosome rearrangements in ancestral dicotylid populations.

Chromosomal evolution and phylogenetic analyses in Tayassu pecari and Pecari tajacu (Tayassuidae): tales from constitutive heterochromatin

“…Thus, our data suggest that the radiation of the two species was extremely fast, and the great dissimilarity between the species is also in agreement with the results from the comparative chromosome data with pig probes (Bosma et al 2004;Adega et al 2006). The higher number of Cpositive heterochromatin classes/subclasses on P. tajacu autosomes suggests that this karyotype is more primitive, that is it did not go through a high level of homogenization due to concerted evolution of chromosomes.…”

“…The comparative chromosome painting results between the domestic pig and white-lipped and collared peccaries clearly revealed the high level of reshuffling between these two karyotypes (Bosma et al 2004;Adega et al 2006). Based on these two works, and on the assumption that the pres-ence of CH facilitates the occurrence of chromosomal rearrangements (Yunis and Yasmineh 1971;Peacock et al 1982;John 1988;Chaves et al 2004), we made a com-parative analysis between T. pecari and P. tajacu CH lo-calization and the breakpoints in each chromosome (figure 3).…”

“…The nomenclature used for the chromosomes of T. pecari is that of Bosma et al (2004), and for P. tajacu that of Adega et al (2006).…”

“…Pirtle 1967;Hufty et al 1973;Giannoni et al 1982a,b;Benirschke and Kumamoto 1989;Zijlstra et al 1997) of the peccaries Pecari tajacu (collared peccary) and Tayassu pecari (white-lipped peccary) are well known, and even molecular cytogenetic studies, such as rRNA gene assignments in T. pecari (Bosma et al 2004) and comparative chromosome painting with pig (Bosma et al 2004;Adega et al 2006) and sheep paint probes in both species (Adega et al 2006;and unpublished data) are available, but their CH was only analysed by classical C-banding techniques (Pirtle 1967;Benirschke and Kumamoto 1989).…”

“…Since these two species are related, and the syntenic regions as well as the chromosomal evolutionary rearrangements (relative to another suiform genome, the pig) are known (Bosma et al 2004;Adega et al 2006), it was possible to track the C-positive heterochromatin along the chromosomes of the two species, and hence to delineate a hypothesis on the evolutionary remodelling of heterochromatin in these species. Further, this approach is a contribution to the understanding of the chromosomal evolutionary process and phylogenetic relationships within this family.…”