The primary objective of this research was to determine whether native species of Castilleja and Pedicularis are naturally infected by Cronartium ribicola in whitebark pine ecosystems of the Oregon and Washington Cascade Range, USA. Secondary objectives were to monitor the phenology of aecial and telial hosts to determine whether there is sufficient time for C. ribicola to complete its life cycle within highelevation stands and to evaluate the variety of susceptible native host species within these genera through field and growth chamber inoculation. These objectives were approached through fieldwork in 2008 and 2009 in whitebark pine ecosystems at Mt. Rainier, Mt. Adams, Mt. Hood, Mt. Bachelor, Tumalo Mtn. and Crater Lake. Forty-nine observational study plots were established and monitored. Natural C. ribicola infection was detected on 84 Pedicularis racemosa plants and five Castilleja plants (C. applegatei, C. miniata and C. parviflora). Field observation provided evidence that there is sufficient time for C. ribicola to complete its life cycle on hosts within high-elevation whitebark pine stands. In 2009, 18 field inoculation plots were established at Mt. Rainier and Crater Lake. Field inoculation confirmed the susceptibility of two additional species within these genera, C. arachnoidea and P. bracteosa. All four Castilleja species inoculated in the growth chamber developed infection, with an overall infection incidence of 62% (167 out of 270 plants). The identity of the rust species on field specimens as C. ribicola was verified through PCR and sequencing of the ITS1-5.8S-ITS2 region of DNA. Improved understanding of the role of these newly recognized hosts in white pine blister rust epidemiology should be used to prioritize sites for the restoration of ecologically valuable whitebark pine.
Introduced mammalian predators threaten populations of endemic New Zealand skinks. Their effects on skink populations have been not often quantified on the mainland and are known primarily from skink population increases on islands from which mammals have been eradicated. Estimating skink population density with capture-recapture trapping is time-consuming and costly. Counting skinks in artificial retreats in specific weather conditions may be a useful and relatively quick way to index population density, but needs calibration for different habitats and species. In 2007 and 2009, we estimated the population density of small terrestrial skinks (McCann's skink Oligosoma maccanni, southern grass skink O. aff. polychroma clade 5 and cryptic skink O. inconspicuum), based on spatially explicit capture-recapture (SECR) in pitfall traps in three mammal-management treatments at Macraes Flat, Otago. The treatments were eradication of large predators and near-eradication of rodents inside a mammal-resistant fence, suppression of mammalian predator populations through continuous trapping (two locations within an extensive area), and no mammal management. We tested for relationships between the estimated population densities and dawn and late-morning counts of skinks in artificial retreats. Skink density (three species combined) ranged from c. 1200 per ha at the experimental control site to c. 4000 per ha at the fenced site. These treatment differences in skink density may be the combined effect of predator management and pre-existing differences due to habitat characteristics and farming practices. Skink counts done in late morning (2009) were related to estimated skink densities but did not differ significantly between treatments. Skink counts done at dawn (both years) were not related to densities. Counts, but not densities, were significantly higher at locations with a more northerly aspect. We recommend further investigation of the utility of skink counts in artificial retreats for monitoring skink density at this location, with careful control of ambient temperature during sampling, and of aspect, habitat and device placement.
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