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Latest Publications

Latest Publications

  • U.S. Geological Survey (James Hatten), 2022
    An ArcGIS Online (AGOL) page containing historical and predictive maps develop by the USGS for the southwestern willow flycatcher habitat across the southwestern United States. The model outputs a range of probabilities for suitable and less suitable habitat in 20% probability classes. See the 2021 Southwestern Willow Flycatcher Habitat Viewer User's Manual for tips on changing base map layers, toggling through data layers, utilizing tools to compare different datasets, and locating the metadata for the provided layers.
    Recovery of a native tree following removal of an invasive competitor with implications for endangered bird habitat. 
    Goetz, A., Moffit, I. and Sher, A.A., 2022. Biological Invasions, pp.1-25.
    What site conditions are associated with greater recovery and overall higher cover of willows? Goetz et al. performed a meta-analysis of tamarisk removal and willow (Salix) recovery across the southwest, compiling data from 260 sites where tamarisk was subject to active removal and/or biocontrol and 132 reference sures. Cut-stump method with biological control was the most effective method to improve native species dominance. Tamarisk removal approach for increasing native species dominance Overall they suggest that removal of tamarisk can best improve SWFL habitat when sites are selected based on their suitability of willow habitat.
    Fitness and host use remain stable in a biological control agent after many years of hybridization
    Clark, E.I., Stahlke, A.R., Gaskin, J.F., Bean, D.W., Hohenlohe, P.A., Hufbauer, R.A. and Bitume, E.V., 2022. Biological Control, p.105102.
    Does hybridization among tamarisk beetles change the risk of non-target attack in the field? Clark et al. study the consequences of hybridization in  tamarisk beetles (Diorhabda). They paired laboratory phenotyping with genomics to assess changes in risk of non-target attack and body size and fecundity. Body size and early fecundity were similar in pure and hybrid females, indicating that hybridization is not detrimental to insect fitness or the biocontrol program and may provide variation that allows populations to become locally adapted. Host use of hybrids was very similar to that of pure species, although some hybrid individuals had increased preference for Frankenia salina, a native non-target species. Overall, hybridization has likely not been detrimental to the efficacy and safety of the Diorhabda biocontrol program, but possible impacts on F. salina should be monitored, considering ongoing hybridization and evolution in the field.

    Evolution of reproductive life-history and dispersal traits during the range expansion of a biological control agent

    Clark, E. I.Bitume, E. V.Bean, D. W.Stahlke, A. R.Hohenlohe, P. A., & Hufbauer, R. A. 2022. Evolutionary Applications, 001– 11
    Clark et al. evaluated theoretical predictions for evolution of reproductive life-history and dispersal traits in the range expansion of the tamarisk biological control agent, Diorhabda carinulata, or northern tamarisk beetle. With experiments run on field-collected populations, they found that females at the expansion front had increased fecundity and body mass, and reduced age at first reproduction; and that dispersal increased at the expansion front in males, especially when unmated and reared at low density. An increase in both reproductive output and dispersal ability in some contexts at the edge and low genetic load may enable an accelerating expansion front and will likely contribute to the establishment and persistence of the northern tamarisk beetle.
    Monitoring Tamarix Changes Using WorldView-2 Satellite Imagery in Grand Canyon National Park, Arizona
    Bransky N, Sankey T, B. Sankey J, Johnson M, Jamison L. Remote Sensing. 2021; 13(5):958.
    Branksey et al. used a Spectral Angle Mapper (SAM) supervised classification method with WorldView-2 (2 m spatial resolution) multispectral images from May and August of 2019 to map healthy tamarisk, canopy dieback, and defoliated tamarisk over a 48 km segment of the Colorado River in the topographically complex Grand Canyon National Park. They found that 47.5% of the healthy tamarisk detected in May 2019 had been defoliated by August 2019 and 29.5% of healthy tamarisk canopy declined between 2009 and 2019. Tamarisk beetle impacts are continuing to accumulate even though land managers have noted the presence of the beetles in this reach of the river since 2012.

    River channel response to invasive plant treatment across the American Southwest

    Wieting, C, Friedman, JM, Rathburn, S. Earth Surf. Process. Landforms. 2022. Accepted Author Manuscript.

    To what extent has invasive riparian vegetation (IRV) treatment reversed channel narrowing and reduced dynamism trends? Paired treated and untreated reaches at 15 sites along 13 rivers were compared before and after treatment using repeat aerial imagery to assess long-term (~10 year) channel change due to treatment on a regional scale across the Southwest U.S. Wieting et al. found that IRV treatment significantly increased channel width and floodplain destruction. They argue that geomorphic processes should be considered in restoration planning according to the restoration goal because they drive aquatic habitat and vegetation dynamics, and because of the potential for damage to downstream infrastructure.
    Hybridization and range expansion in tamarisk beetles (Diorhabda spp.) introduced to North America for classical biological control
    Stahlke, A. R., Bitume, E. V., Özsoy, Z. A., Bean, D. W., Veillet, A., Clark, M. I., Clark, E. I., Moran, P., Hufbauer, R. A., & Hohenlohe, P. A. 2022. Evolutionary Applications, 15, 60– 77.
    Stahlke et al. developed a reference genome for tamarisk beetles (Diorhabda spp.) and reference panel of all four introduced parental species to monitor range expansion and hybridization across N. America. They found a substantial genetic bottleneck among D. carinulata in N. America, although populations continue to establish and spread, possibly due to aggregation behavior. Among hybrids, they found that D. carinata, D. elongata, and D. sublineata hybridize in the field, especially in eastern New Mexico, with D. carinata × D. sublineata hybrids being the most abundant. Genetic diversity was greater at sites with hybrids, highlighting potential for increased ability to adapt and expand.

    Gaffke, A.M., Dudley, T.L., Bean, D.W., Drus, G.M., Johnson, M.J., Knutson, A.E., Weaver, D.K., Sing, S.E., Orr, B.K. and Thompson, D.C., 2022. [Chapter 28]. In: Van Driesche, RG; Winston, RL; Perring, TM; Lopez, VM, eds. Contributions of Classical Biological Control to the US Food Security, Forestry, and Biodiversity. FHAAST-2019-05. Morgantown, WV: US Department of Agriculture, Forest Service. p. 329-355., pp.329-355. 

    A book chapter reviewing the history and outcomes of the tamarisk biocontrol program.

    Long et al., 2021
    A study subjecting tamarisk from two distinct populations originating from areas with greatly varying soil salinities to a range of different salinities. Results showed dramatic differences between growth with the low salinity population accumulating 72% more biomass when grown at 4 ppt compared to 16 ppt, while the high salinity population produced 50% more biomass when grown at 16 ppt. Additionally, the high salinity population had a lower turgor loss point and exhibited greater stomatal control relative to the low salinity population. These results of local adaptation to increased salinity could have implications for continued tamarisk dominance in aridland riparian ecosystems where drought or water management may lead to increased soil salinities. 
    Jeplawy et al., 2021
    A common garden study of six distinct Fremont cottonwood populations across an elevation gradient and covering a range of genomic variation to determine responses to different heat conditions. The common gardens had mean annual temperatures of 11, 17, and 23°C and all received regular watering throughout the growing season. Results found that all genotypes in the hottest garden produced comparatively small leaves that decomposed quickly and supported lower abundances of aquatic invertebrates, whereas the same genotypes in the coldest garden produced litter with distinct morphologies and decomposition rates.
    Henry et al., 2021
    This study employs functional diversity metrics and guilds—suites of species with similar traits—to assess the influence of an invasive tree (Tamarix spp.) on riparian plant communities in the southwestern United States. Nine distinct guilds were identified with a gradient of functional diversity related to both tamarisk cover and environmental conditions. The identified guilds can be correlated to specific site conditions and can be used to anticipate plant community response to restoration efforts and in selecting appropriate species for revegetation.
    Long et al., 2021
    Researchers looked at non-structural carbohydrate storage in different genotypes of Tamarix from an experimental common garden. Results suggest that Tamarix from colder locations cope with freeze events by maintaining large storage pools to support tissue regrowth, but with the trade-off of overall reduced growth and reproduction.
    Bush et al., 2021
    A common garden experiment to compare the stomatal sensitivity, sap flux, and canopy transpiration of different tamarisk populations. Results showed that higher-elevation tamarisk populations that are adapted to freezing tolerated drought conditions much better than low-elevation populations. Root area to leaf area ratios were also higher in the highest elevation population. Results indicate that rapid changes in ecohydrologic conditions may result in some Tamarix populations becoming maladapted sooner to reductions in available water than others in the western US
    Saunders et al., 2021
    An insightful look at several case studies from conservation practitioners and ornithological social scientists to highlight six core principles of translational ecology - an intentional approach in which researchers and practitioners from multiple disciplines collaborate on conservation management. The authors demonstrate how implementing collaboration, engagement, communication, commitment, process, and decision-framing can lead to improved conservation decision-making and delivery of outcomes applicable to specific management decisions. Finally, they recommend strategies for building a stronger translational ecology culture to further improve the integration of these principles into avian conservation decisions.
    Long et al., 2021
    A two-part study looking at how changes in soil salinity affect tamarisk growth and how beetle-induced defoliation affects tamarisk growing in soils with different salinities. Results showed that tamarisk plants grow better in soils with a similar salinity to their own origin site and that lower salinity does not benefit tamarisk plants adapted to higher saline conditions. Tamarisk beetles caused a significantly greater reduction in total biomass in the high salinity plants than the low salinity ones (averages of 63% and 32% respectively), likely due to increased water stress and reduced resources to enable regrowth. Although plants compensated for herbivory by regrowing foliage over three defoliation events and maintained similar leaf biomass through regrowth, they ultimately had a reduced basal area and 62% lower root biomass compared to the controls. Thus, herbivory caused a shift in plant allocation of resources from overall growth to compensation, reducing root and stem investment.
    Gonzalez et al., 2020
    A look at beetle-occupied tamarisk sites 11-13 years after initial occupancy to determine long-term vegetative community response. Study found that Tamarix cover across sites initially declined an average of ca. 50% in response to the beetle, but then recovered. Changes in the associated plant community were small but supported common management goals, including a 47% average increase in cover of a native shrub (Salix exigua), and no secondary invasions by other non-native plants.
    Gaffke et al., 2020
    Development of a novel repellant compound for the potential management of tamarisk beetle, specifically the Northern species. Repellant has been shown to be effective on reproductive adults and alter the behaviors of 1st and 2nd instar larvae. Continued development and field deployment of this repellent compound may provide a new tool for the management of D. carinulata.



    • Invasive species disturb ecosystems and threaten biodiversity. Invasive species management, such as biological control, can cause additional disturbances, so quantifying how native species respond to invasive control is important
    to inform best management practices
    • We quantifed southwestern bird communities in sites that varied in the amount of the non-native plant tamarisk (Tamarix spp.), before and after biological control efforts
    • Following biocontrol, we found significant differences in community composition and diversity, and several bird species declined by ≥30%
    • Bird declines were ameliorated in the presence of native vegetation, consistent with the hypothesis that tamarisk biocontrol decreases prey availability and alters microclimate
    • We recommend land managers monitor areas dominated by tamarisk after biocontrol, and if re-establishment of native vegetation is slow or lacking, consider the feasibility of active restoration

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