Marsupial Chromosome Evolution


Marsupial chromosomes were among the first mammalian chromosomes to be studied in the early twentieth century and have since been extensively characterised by multiple approaches. With relatively few and large chromosomes, marsupials have proven to be ideal subjects for studying how chromosomes have changed during marsupial evolution from a predicted ancestral marsupial karyotype consisting of just seven pairs of chromosomes. In this article, the current understanding of marsupial chromosome evolution is reviewed and the way two families of marsupials with different rates of chromosome evolution help to decipher the mechanisms involved in chromosome evolution is discussed. The family Dasyuridae is characterised by remarkable chromosome stability, whereas the family Macropodidae has experienced extensive chromosome shuffling. Comparisons of the differences in chromosome features between these two families may hold the key to understanding the role of chromosome rearrangements in speciation.

Key Concepts

  • Marsupials have large, relatively conserved karyotypes, making it possible to track the evolution of their chromosomes.
  • Chromosome numbers in marsupials range from 2n = 10 to 2n = 32.
  • Different marsupial karyotypes have evolved from a predicted ancestral marsupial with seven pairs of chromosomes (2n = 14).
  • All the members of the Dasyuridae family karyotyped to date have a 2n = 14 karyoytpe similar to that of the predicted ancestral marsupial.
  • Dasyurids have a unique telomere length dimorphism not found in any other species.
  • The family Macropodidae has a lot of karyotype diversity with chromosome numbers ranging from 2n = 10 to 2n = 24, evolving from a 2n = 22 ancestral macropod.
  • The Y chromosome of marsupials has been termed ‘minimal mammalian Y’.
  • X chromosomes in marsupials have experienced substantial rearrangement between species.

Keywords: marsupial; mammal; karyotype; comparative genomics; comparative cytogenetics; sex chromosomes; genome evolution; chromosome rearrangement

Figure 1. Arrangement of conserved chromosome segments (C1–C19) in different marsupials. All members of the family Dasyuridae have 2n = 14 karyotypes, with an arrangement of conserved segments similar to the Tasmanian devil and 2n = 14 marsupial ancestor. Examples of different chromosome arrangements observed in the family Macropodidae are shown, with the unadorned rock‐wallaby having a similar arrangement to the 2n = 22 macropod ancestor. Mya, millions of years ago.
Figure 2. The telomere length dimorphism on Tasmanian devil chromosomes. The intensity of the telomere signal (red) varies between chromosome homologues. Strong red signals correspond to long telomeres, whereas weaker signals correspond to short telomeres.
Figure 3. Chromosome rearrangements including fissions, inversions, fissions and centromere repositioning, resulting in a 2n = 22 macropod ancestor from a 2n = 14 marsupial ancestor.
Figure 4. Comparison of gene order between the X chromosomes of human, Tasmanian devil, Brazilian opossum and tammar wallaby. The yellow region of the human X chromosome is located on the autosomes in marsupials (not shown). The position of the noncoding RNA (RSX) involved in X chromosome inactivation is indicated on opossum X chromosome (its position is unknown on other marsupial X chromosomes). Each line indicates where a gene is located. Two lines ending at the same position indicate that the genes map to a similar position on the chromosome.


Bender HS, Murchison EP, Pickett HA, et al. (2012) Extreme telomere length dimorphism in the Tasmanian devil and related marsupials suggests parental control of telomere length. PLoS One 7: e46195.

Bulazel KV, Ferreri GC, Eldridge MDB and O'Neill RJ (2007) Species‐specific shifts in centromere sequence composition are coincident with breakpoint reuse in karyotypically divergent lineages. Genome Biology 8: R170.

Close RL and Bell JN (1997) Fertile hybrids in two genera of wallabies: Petrogale and Thylogale. Journal of Heredity 88: 393–397.

Close RL and Lowry PS (1990) Hybrids in marsupial research. Australian Journal of Zoology 37: 259–267.

De Leo AA, Guedelha N, Toder R, et al. (1999) Comparative chromosome painting between marsupial orders: relationships with a 2n = 14 ancestral marsupial karyotype. Chromosome Research 7: 509–517.

Deakin JE (2013) Marsupial X chromosome inactivation: past, present and future. Australian Journal of Zoology 61: 13–23.

Deakin JE, Bender HS, Pearse A‐M, et al. (2012a) Genomic restructuring in the Tasmanian devil facial tumour: chromosome painting and gene mapping provide clues to evolution of a transmissible tumour. PLoS Genetics 8: e1002483.

Deakin JE, Graves JAM and Rens W (2012b) The evolution of marsupial and monotreme chromosomes. Cytogenetic and Genome Research 137: 113–129.

Deakin JE, Delbridge ML, Koina E, et al. (2013) Reconstruction of the ancestral marsupial karyotype from comparative gene maps. BMC Evolutionary Biology 13: 258.

Deakin JE and Kruger‐Andrzejewska M (2016) Marsupials as models for understanding the role of chromosome rearrangements in evolution and disease. Chromosoma 125: 633–644.

Duke SE, Samollow PB, Mauceli E, et al. (2007) Integrated cytogenetic BAC map of the genome of the gray, short‐tailed opossum, Monodelphis domestica. Chromosome Research 15: 361–370.

Eldridge MDB and Close RL (1993) Radiation of chromosome shuffles. Current Opinion in Genetics and Development 3: 915–922.

Eldridge MDB and Johnston PG (1993) Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae): VIII. An investigation of the nonrandom nature of karyotypic change. Genome 36: 524–534.

Eldridge MDB, Johnston PG and Close RL (1992) Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia, Macropodidae). VI. Determination of the plesiomorphic karyotype: G‐banding comparison of Thylogale with Petrogale persephone, P. xanthopus, and P. l. lateralis. Cytogenetics and Cell Genetics 61: 29–33.

Eldridge MDB and Metcalfe CJ (2006) Marsupialia. In: O'Brien SJ, Menninger JC and Nash WG (eds) Atlas of Mammalian Chromosomes, pp 9–62. John Wiley & Sons, Inc.: Hoboken, NJ.

Farré M, Robinson TJ and Ruiz‐Herrera A (2015) An integrative breakage model of genome architecture, reshuffling and evolution. BioEssays 37: 479–488.

Foster JW and Graves JA (1994) An SRY‐related sequence on the marsupial X chromosome: implications for the evolution of the mammalian testis‐determining gene. Proceedings of the National Academy of Sciences of the United States of America 91: 1927–1931.

Glas R, Graves JAM, Toder R, et al. (1999) Cross‐species chromosome painting between human and marsupial directly demonstrates the ancient region of the mammalian X. Mammalian Genome 10: 1115–1116.

Grant J, Mahadevaiah SK, Khil P, et al. (2012) Rsx is a metatherian RNA with Xist‐like properties in X‐chromosome inactivation. Nature 487: 254–258.

Hayman D (1989) Marsupial cytogenetics. Australian Journal of Zoology 37: 331.

Hayman DL and Martin PG (1974) Mammalia I: Monotremata and Marsupialia. In: John B (ed.) Animal Cytogenetics, vol. 4: pp. 19–84. Chordata. Gebruder Borntraeger: Berlin and Stuttgart.

Ingles ED and Deakin JE (2015) Global DNA methylation patterns on marsupial and devil facial tumour chromosomes. Molecular Cytogenetics 8: 74.

Johnson RN, O'Meally D, Chen Z, et al. (2018) Adaptation and conservation insights from the koala genome. Nature Genetics 50: 1102–1111.

Kim J, Farre M, Auvil L, et al. (2017) Reconstruction and evolutionary history of eutherian chromosomes. Proceedings of the National Academy of Sciences of the United States of America 114: E5379–E5388.

Meredith RW, Westerman M, Case JA and Springer MS (2008) A phylogeny and timescale for marsupial evolution based on sequences for five nuclear genes. Journal of Mammalian Evolution 15: 1–36.

Metcalfe CJ, Bulazel KV, Ferreri GC, et al. (2007) Genomic instability within centromeres of interspecific marsupial hybrids. Genetics 177: 2507–2517.

Metcalfe CJ, Eldridge MDB, Toder R and Johnston PG (1998) Mapping the distribution of the telomeric sequence (T2AG3)n in the Macropodoidea (Marsupialia), by fluorescence in situ hybridization. I. The swamp wallaby, Wallabia bicolor. Chromosome Research 6: 603–610.

Mikkelsen TS, Wakefield MJ, Aken B, et al. (2007) Genome of the marsupial Monodelphis domestica reveals innovation in non‐coding sequences. Nature 447: 167–177.

O W‐S, Short RV, Renfree MB and Shaw G (1988) Primary genetic control of somatic sexual differentiation in a mammal. Nature 331: 716–717.

O'Neill RJ, Eldridge MDB, Toder R, et al. (1999) Chromosome evolution in kangaroos (Marsupialia: Macropodidae): cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype. Genome 42: 525–530.

O'Neill RJ, O'Neill MJ and Graves JA (1998) Undermethylation associated with retroelement activation and chromosome remodelling in an interspecific mammalian hybrid. Nature 393: 68–72.

Potter S, Bragg JG, Blom MP, et al. (2017) Chromosomal speciation in the genomics era: disentangling phylogenetic evolution of rock‐wallabies. Frontiers in Genetics 8: 1–18.

Reig OA, Gardner AL, Bianchi NO and Pattion JL (1977) The chromosomes of the Didelphidae (Marsupialia) and their evolutionary significance. The Biological Journal of the Linnean Society 9: 191–216.

Rens W and Ferguson‐Smith MA (2010) The conserved marsupial karyotype: chromosome painting and evolution. In: Deakin JE, Waters PD and Graves JAM (eds) Marsupial Genetics and Genomics, pp 37–53. Springer: Dordrecht.

Rens W, O'Brien PCM, Fairclough H, et al. (2003) Reversal and convergence in marsupial chromosome evolution. Cytogenetic and Genome Research 102: 282–290.

Rens W, O'Brien PCM, Yang F, et al. (1999) Karyotype relationships between four distantly related marsupials revealed by reciprocal chromosome painting. Chromosome Research 7: 461–474.

Rodríguez Delgado CL, Waters PD, Gilbert C, et al. (2009) Physical mapping of the elephant X chromosome: conservation of gene order over 105 million years. Chromosome Reseach 17: 917–926.

Rofe R (1978) G‐banded chromosomes and the evolution of Macropodidae. Australian Mammalogy 2: 53–63.

Rofe R and Hayman D (1985) G‐banding evidence for a conserved complement in Marsupialia. Cytogenetics and Cell Genetics 39: 40–50.

Sharman GB (1973) Chromosomes of non‐Eutherian Mammals. In: Chiarelli AN and Capanna E (eds) Cytotaxonomy and Vertebrate Evolution, pp 485–530. Academic Press: New York.

Sharman GB, Hughes RL and Cooper DW (1990) The chromosomal basis of sex differentiation in marsupials. Australian Journal of Zoology 37: 451–466.

Stammnitz MR, Coorens THH, Gori KC, et al. (2018) The origins and vulnerabilities of two transmissible cancers in Tasmanian devils. Cancer Cell 33: 607–619.e15.

Svartman M and Vianna‐Morgante AM (1998) Karyotype evolution of marsupials: from higher to lower diploid numbers. Cytogenetics and Cell Genetics 82: 263–266.

Toder R, O'Neill RJW, Wienberg J, et al. (1997) Comparative chromosome painting between two marsupials: origins of an XX/XY1Y2 sex chromosome system. Mammalian Genome 8: 418–422.

Toder R, Wakefield MJ and JA G (2000) The minimal mammalian Y chromosome – the marsupial Y as a model system. Cytogenetics and Cell Genetics 91: 285–292.

Tyndale‐Biscoe CH (2005) Life of Marsupials. CSIRO Publishing: Collingwood.

Westerman M, Meredith RW and Springer MS (2010) Cytogenetics meets phylogenetics: a review of karyotype evolution in diprotodontian marsupials. Journal of Heredity 101: 690–702.

Further Reading

Deakin JE (2012) Marsupial genome sequences: providing insight into evolution and disease. Scientifica 2012: 543176.

Deakin JE (2017) Implications of monotreme and marsupial chromosome evolution on sex determination and differentiation. General and Comparative Endocrinology 244: 130–138.

Deakin JE (2018) Chromosome evolution in marsupials. Genes 9: 72.

Deakin JE, Koina E, Waters PD, et al. (2008) Physical map of two tammar wallaby chromosomes: a strategy for mapping in non‐model mammals. Chromosome Research 16: 1159–1175.

Graves JA (2015) Weird mammals provide insights into the evolution of mammalian sex chromosomes and dosage compensation. Journal of Genetics 94: 567–574.

Graves JAM (2018) Weird animals, sex, and genome evolution. Annual Review of Animal Biosciences 6: 1–22.

Ingles ED and Deakin JE (2016) Telomere, species differences, and unusual telomeres in vertebrates: presenting challenges and opportunities to understand telomere dynamics. AIMS Genetics 3: 1–24.

Potter S and Deakin JE (2018) Cytogenetics: an important inclusion in the conservation genetics toolbox. Pacific Conservation Biology 24: 280–288.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Deakin, Janine E(May 2019) Marsupial Chromosome Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0028284]