Judges’ Queries and Presenter’s Replies

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Presentation Discussion

  • Icon for: Brian Drayton

    Brian Drayton

    Faculty
    May 21, 2012 | 09:56 p.m.

    Very interesting. I don’t know anything about this organism, but “nidicolous” suggests fairly slow dispersal — does Ornithodoros have a wide array of hosts? How does it interact with humans? And does the range of these ticks overlap with areas affected by bark-beetle die-back, which I would think would rapidly decrease acceptable habitat for the ticks?

  • Icon for: Tammi Johnson

    Tammi Johnson

    Presenter
    May 22, 2012 | 12:13 p.m.

    Hi Brian, great question! Unfortunately, almost nothing is known regarding the disperal capabilities of Ornithodoros ticks. O. hermsi has been shown to be a generalist feeder and is known to feed on numerous species of rodents including tree squirrels, ground squirrels, chipminks, voles and deer mice. These ticks have also been known to feed on birds and bats, which may serve as a dispersal mechanism for the ticks. Humans typically come in contact with these ticks in rustic settings such as mountain cabins. Undoubtably the range of O. hermsi and the range of the devastation caused by the pine beetles overlap. The beetle-killed trees may decrease habitat for some of the hosts of O. hermsi (tree squirrels), however, becuase so many rodents can potentially serve as hosts for O. hermsi, I am not sure that beetle kill will completely eliminate habitat for these ticks. I hope this helps to answer your questions. Thanks for asking!

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Icon for: Tammi Johnson

TAMMI JOHNSON

University of Montana
Years in Grad School: 6

The Potential Distribution of the Tick-borne Relapsing Fever Spirochete Borrelia hermsii and vector Ornithodoros hermsi in Western North America

An ecological niche model was created using the Maximum Entropy Species Distribution Model (Maxent) to estimate the probability of the predicted distribution of Ornithodoros hermsi, the soft tick vector for the relapsing fever spirochete Borrelia hermsii. The preference of coniferous forest habitats at a range of higher elevations and the preferred hosts for these ticks has been recognized for many years; however, the climatic factors driving the distribution are not well understood. Here we show that five climate variables combined contributed more than 75% to predicting the distribution of O. hermsi. Temperature extremes accounted for four of the five most important variables. Minimum temperature during the coldest month, mean temperature of the wettest month, maximum temperature during the warmest month and annual temperature range all contributed equally to the model. Predicted shifts in distribution of the tick were examined using climate change models for the year 2050. The geographic distributions with the highest probabilities of tick occurrence were predicted to decrease in all models for the year 2050.