Chromosome painting among Proboscidea, Hyracoidea and Sirenia: support for Paenungulata (Afrotheria, Mammalia) but not Tethytheria

Abstract

Despite marked improvements in the interpretation of systematic relationships within Eutheria, particular nodes, including Paenungulata (Hyracoidea, Sirenia and Proboscidea), remain ambiguous. The combination of a rapid radiation, a deep divergence and an extensive morphological diversification has resulted in a limited phylogenetic signal confounding resolution within this clade both at the morphological and nucleotide levels. Cross-species chromosome painting was used to delineate regions of homology between Loxodonta africana (2nZ56), Procavia capensis (2nZ54), Trichechus manatus latirostris (2nZ48) and an outgroup taxon, the aardvark (Orycteropus afer, 2nZ20). Changes specific to each lineage were identified and although the presence of a minimum of 11 synapomorphies confirmed the monophyly of Paenungulata, no change characterizing intrapaenungulate relationships was evident. The reconstruction of an ancestral paenungulate karyotype and the estimation of rates of chromosomal evolution indicate a reduced rate of genomic repatterning following the paenungulate radiation. In comparison to data available for other mammalian taxa, the paenungulate rate of chromosomal evolution is slow to moderate. As a consequence, the absence of a chromosomal character uniting two paenungulates (at the level of resolution characterized in this study) may be due to a reduced rate of chromosomal change relative to the length of time separating successive divergence events.

Paleocene emergence of elephant relatives and the rapid radiation of African ungulates

“…60 mys) and a rapid paenungulate radiation at the CretaceousTertiary (KT) transition, which is also supported by the latest genomic studies (26)(27)(28). Rapid paenungulate radiation and fossil gaps may explain poorly resolved interordinal relationships.…”

Chromosomal evolution in tenrecs (Microgale and Oryzorictes, Tenrecidae) from the Central Highlands of Madagascar

“…In contrast, 12 chromosomal changes detected in M. thomasi and between 6 and 13 (depending on which matrix is considered) in M. cowani punctuate the õ9.9 Myr that separate these two species from the Microgale ancestor ( Figure 5), mimicking the karyotypic megaevolution of certain bat species (Baker & Bickham 1980). Although these rates are lower than those observed in several mammals (e.g., Britton-Davidian et al 2000, Wang & Lan 2000, Dobigny et al 2005, they are clearly accelerated with respect to most Afrotheria, the only exception being within the Sirenia where at least four chromosomal changes separate Trichechus inunguis and T. manatus, taxa that are thought to have diverged 1Y4 Myr ago (Pardini et al 2007). Chromosomal mutation rates depend on many factors including population dynamics, life history and genomic traits of the species concerned.…”

Molecular Cytogenetic Characterization of the Genome Organization of the 6-Banded Armadillo <i>(Euphractus sexcinctus)</i>

“…Previous studies have shown that Afrotheria with disparate morphological characters are united by shared derived syntenic associations such as HSA 3/21/5 and 1/19p [Frönicke et al, 2003;Yang et al, 2003;Robinson et al, 2004;Kellogg et al, 2007;Pardini et al, 2007]. Interestingly, based on the combined analysis of comparative chromosome maps among the 2-toed sloth ( C. didactylus , CDI), tree anteater ( T. tetradactyla , TTE) and human, Yang et al [2006] proposed that 2 derived segmental associations (HSA 2/8 and 7a/10p) existing in the genomes of C. didactylus and T. tetradactyla could be regarded as the cytogenetic signatures for Xenarthra.…”