Boundaries and bacteria – identifying the mechanism for a parapatric boundary between two tick species.

HSF19059 | Amount: $85,233 | Project Leader: M Gardner | Project Period: Jul ’19 – Jul ‘22

A project undertaken at Flinders University, and supervised by A/Prof Mike Gardner.

Ticks are parasites that infest different vertebrates and some of these specialise in parasitising reptiles. There has been a long standing lizard survey that takes place in the Mid North of South Australia, started in 1982, to try and understand the reasons why a geographic boundary occurs between two tick species on sleepy lizards. One of the ticks occurs in the north east and the other in the south west of the site, but at the boundary some lizards have both ticks. Despite much research to understand why this boundary occurs, the answers have only ever related to the inability of the southern tick to survive off its host lizards in the hotter northern areas.

A sleepy lizard (Tiliqua rugosa) in researcher’s hand as part of the long-term survey work. A northern tick, Amblyomma limbatum, can be seen in the lizard’s ear.
The ear of a sleepy lizard (Tiliqua rugosa) in researcher’s hand as part of the long-term survey work. Several southern ticks, Bothriocroton hydrosauri, and northern ticks Amblyomma limbatum, can be seen in the lizard’s ear and surrounds.

No satisfactory explanation has been found as to why the northern tick could not survive further south, as early experiments showed the northern tick can survive and reproduce in more humid and in colder temperatures. This project investigated a new hypothesis which suggests that the range of the northern tick species is restricted due to the interactions of the northern tick and a bacterial species. We found preliminary results to support the hypothesis and the work will continue to more fully determine if this hypothesis is supported. If so, it will solve an over 40 year ecological mystery.