Monito del monte
|Monito del monte|
|Map of Dromiciops gliroides distribution|
The monito del monte (Spanish for "little bush monkey"), Dromiciops gliroides, also called chumaihuén in Mapudungun, is a diminutive marsupial native only to southwestern South America (Chile and Argentina). It is the only extant species in the ancient order Microbiotheria, and the sole New World representative of the superorder Australidelphia (all other New World marsupials are members of Ameridelphia). The species is nocturnal and arboreal, and lives in thickets of South American mountain bamboo in the Valdivian temperate rain forests of the southern Andes, aided by its partially prehensile tail. It eats primarily insects and other small invertebrates, supplemented with fruit.
Phylogeny and biogeography
It has long been suspected that South American marsupials were ancestral to those of Australia, consistent with the fact that the two continents were connected via Antarctica in the early Cenozoic. Australia’s earliest known marsupial is Djarthia, a primitive mouse-like animal that lived about 55 million years ago. Djarthia had been identified as the earliest known australidelphian, and this research suggested that the monito del monte was the last of a clade which included Djarthia. This implied that the ancestors of the Monito del Monte might have reached South America via a back-migration from Australia. The time of divergence between the Monito del Monte and Australian marsupials was estimated to have been 46 million years ago. However, in 2010, analysis of retrotransposon insertion sites in the nuclear DNA of a variety of marsupials, while confirming the placement of the Monito del Monte in Australidelphia, showed that its lineage is the most basal of that superorder. The study also confirmed that the most basal of all marsupial orders are the other two South American lineages (Didelphimorphia and Paucituberculata, with the former probably branching first). This indicates that Australidelphia arose in South America (along with the ancestors of all other living marsupials), and probably reached Australia in a single dispersal event after Microbiotheria split off.
Body length is 11–12.5 cm. Tail length is 9–10 cm.
The monito del monte normally reproduces in the spring and can have a litter size varying anywhere from one to four young. The females have a pseudovagina, and a fur-lined pouch containing four mammae. When the young are mature enough to leave the pouch they are nursed in a nest, and then carried on the mother’s back. The young remain in association with the mother after weaning. Males and females both reach sexual maturity after 2 years. 
Monitos del monte mainly live in trees, where they construct spherical nests of water resistant colihue leaves. These leaves are then lined with moss or grass, and placed in well protected areas of the tree. The nests are sometimes covered with grey moss as a form of camouflage. These nests provide the monito del monte with some protection from the cold, both when it is active and when it hibernates. It stores fat in the base of its tail for winter hibernation. It lives in the dense, humid forests of highland Chile and Argentina.
Role as a seed disperser
A study performed in the temperate forests of southern Argentina showed a mutualistic seed dispersal relationship between D. gliroides and Tristerix corymbosus, also known as the Loranthacous mistletoe. The monito del monte is the single dispersal agent for this plant, and without it the plant would likely become extinct. The monito del monte eats the fruit of T. corymbosus, and thus disperses the seeds. Scientists speculate that the coevolution of these two species could have begun 60–70 million years ago.
- Gardner, A. L. (2005). "Order Microbiotheria". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 21. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Diaz, M. & Teta, P. (2008). Dromiciops gliroides. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 28 December 2008. Database entry includes justification for why this species is listed as near threatened
- "Monito del monte (Dromiciops gliroides)". EDGE of Existence programme. Zoological Society of London. 2006-08-09. Retrieved 2009-07-05.
- Beck, Robin M. D.; Godthelp, Henk; Weisbecker, Vera; Archer, Michael; Hand, Suzanne J. (2008-03-26). Hawks, John, ed. "Australia's Oldest Marsupial Fossils and their Biogeographical Implications". PLoS ONE (Public Library of Science) 3 (3): e1858. doi:10.1371/journal.pone.0001858. PMC 2267999. PMID 18365013. Retrieved 2009-07-08.
- Schiewe, Jessie (2010-07-28). "Australia's marsupials originated in what is now South America, study says". LATimes.Com. Los Angeles Times. Retrieved 2010-08-01.
- Inman, M. (2010-07-27). "Jumping Genes Reveal Kangaroos' Origins". PLoS Biology (Public Library of Science) 8 (7): e1000437. doi:10.1371/journal.pbio.1000437. PMC 2910652. PMID 20668663.
- Nilsson, M. A.; Churakov, G.;, Sommer, M.; Van Tran, N.; Zemann, A.; Brosius, J.; Schmitz, J. (2010-07-27). Penny, David, ed. "Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions". PLoS Biology (Public Library of Science) 8 (7): e1000436. doi:10.1371/journal.pbio.1000436. PMC 2910653. PMID 20668664.
- Spotorno, Angel E.; Marin, Juan C.; Yevenes, Marco; Walker, Laura I.; Donoso, Raul Fernandez; Pinchiera, Juana; Barrios, M. Soleda; Palma, R. Eduardo (December 1997). "Chromosome Divergences Among American Marsupials and the Australian Affinities of the American Dromiciops". Journal of Mammalian Evolution (Springer) 4 (4): 259–269. doi:10.1023/A:1027374514503. Retrieved 2009-07-09.
- Brugni, Norma; Flores, Veronica R. (September 2007). "Allassogonoporus dromiciops n. sp. (Digenea: Allassogonoporidae) from Dromiciops gliroides (Marsupialia: Microbiotheriidae) in Patagonia, Argentina". Systematic Parasitology (Springer) 68 (1): 45–48. doi:10.1007/s11230-006-9083-1. PMID 17401634. Retrieved 2009-07-10.
- Lidicker, Jr., William Z., Michael T. Ghiselin (1996). Biology. Menlo Park, California: The Benjamin/Cummings Publishing Company.
- Macdonald, David (1995). Encyclopedia of Mammals. New York City: Facts on File.
- Nowak, Ronald M., Chris R. Dickman (2005). Walker's Marsupials of the World. JHU Press.
- Lord, Rexford D. (2007). Mammals of South America. JHU Press.
- Garcia, Daniel; Rodríguez-Cabal, Mariano A.; Amico, Guillermo C. (March 2009). "Seed dispersal by a frugivorous marsupial shapes the spatial scale of a mistletoe population". Journal of Ecology (British Ecological Society) 97 (2): 217–229. doi:10.1111/j.1365-2745.2008.01470.x. Retrieved 2009-07-10.
- Amico, Guillermo C.; Rodriguez-Cabal, Mariano A.; Aizen, Marcelo A. (January–February 2009). "The potential key seed-dispersing role of the arboreal marsupial Dromiciops gliroides". Acta Oecologica (Elsevier) 35 (1): 8–13. doi:10.1016/j.actao.2008.07.003.