Article Review: Komodo Dragon and Invasive Prey

Invasive Toxic Prey May Imperil the Survival of an Iconic Giant Lizard, the Komodo Dragon

BEATA UJVARI, HEE-CHANG MUN, ARTHUR D. CONIGRAVE, CLAUDIO CIOFI and THOMAS MADSEN

Journal of Pacific Conservation Biology (From EBISCO)

 

                                                                                                                                                                               

Link to primary source article: http://eds.b.ebscohost.com.nuncio.cofc.edu/eds/pdfviewer/pdfviewer?sid=3bc661bd-633b-4cad-b467-0babf75a1613%40sessionmgr111&vid=3&hid=127

Humans introducing a new species to an environment where they have not yet been has been proven to cause ill effects on other populations of plants and animals. This article relates the effects that a specific family of toad, Bufonidae, has had on large bodied lizards in Australia to the largest lizard in the world, the Komodo dragon. The article cited five older research papers that had shown the Bufonidae family as secreting toxic steroid rings that are extremely harmful to predators when ingested. The authors set the scene for the study by informing the reader that since the introduction of the invasive species of the South American Cane Toad to Australia, the large Australian predator populations have had a 95% increase in mortality rate. This study did blood tests on the Komodo dragon with its closest known relative, the Australian lace monitor, varius, which is susceptible to the toad’s toxins, to determine whether or not the Komodo dragon would be affected by the toxins in the same way. The five blood samples collected from three Komodo dragons were used to sequence a subunit of the sodium potassium-ATPase gene, and compare it to the existing data from the lace monitor, as well as other species of large lizards. Table 2, shows the results of the testing, and shows that the Australian lizards and Komodo dragons coded for the same 12 amino acids, while the Komodo dragon differed from the Asian-African varanids by 3 sequences. The author stated that the clear similarities between the Komodo dragon and Australian varanids support the theory that the dragons would be highly susceptible to the toxins of these toads, like the black-spined toad (Bufo vielanostidus), which has settled on islands very close to the few that Komodo dragons inhabit. If the toads were able to migrate into the territory of the Komodo dragon, it could prove disastrous for the already endangered species of lizard.

We have learned about phylogenies of reptiles and how genetic testing can show, with certainty, how closely related different species are, and what types of traits they may share due to 

their lineage. We have also discussed the harmful roles that invasive species can play in the overall health of an ecosystem. This article adds to our understanding of reptiles and amphibians because it discusses species that we did not touch on in class. It also introduces the specific types of genetic testing you can do to relate species. The authors show that predator prey dynamics in one area can be completely different, even in similar species. For example, the Asian-African varanids were immune to the toad’s toxins due to minor differences in amino acid sequencing that they most likely developed by evolving concurrently with the toxic toads. The Komodo dragons and Australian lizards do not have this mutation, and will decrease in numbers dramatically by preying on the toads. Finally, the article shows that invasive species are not always caused by human intervention. The black spiny toads have not been placed in the habitat of the Komodo dragon, but are slowly migrating closer and closer to the islands.

This work is interesting because of the genetic testing done to determine the susceptibility of the Komodo dragons as well as how species that are closely related can have completely different reactions to ingesting the same prey due to minor differences in gene sequences. It is important because the Komodo dragon is the largest living lizard, and a great boost to the economy of local islands for eco-tourism. The local workers need to know that if the toads invade the islands, it could spell the end for the Komodo dragons, as well as their main source of income. The conservation of this species is of great importance for ecological, as well as financial reasons.