Northwest Science - Accepted Articles and Notes
Northwest Science 98(4)
Environmental DNA sampling identifies different nonnative and native salmonid species assemblages in two eastern Oregon wilderness areas - Ben C. Wiley, Kellie J. Carim, Kathleen G. O’Malley
Wilderness areas often provide critical habitat for native fishes. However, remoteness of wilderness areas can limit fish monitoring efforts, such that changes in nonnative and native fish distributions may not be detected and management responses may be delayed. Environmental DNA (eDNA) sampling offers a non-invasive and efficient method to monitor aquatic species across remote waterways. We used eDNA sampling and species-specific qPCR analysis to assess distributions of nonnative brook trout (Salvelinus fontinalis) and native bull trout (S. confluentus) and Columbia River redband trout (Oncorhynchus mykiss gairdneri) across sections of Monument Rock and Strawberry Mountain Wilderness Areas in eastern Oregon. In Monument Rock, we did not detect brook trout or bull trout eDNA, supporting previous findings of brook trout non-invasion and bull trout extirpation. Redband trout eDNA was detected at 29 of 34 sites despite recent environmental disturbances. Environmental DNA from all species was detected in Strawberry Mountain. Brook trout eDNA was detected at 10 of 17 sites, indicating upstream expansion of this nonnative species in Meadow Fork Big Creek. Bull trout eDNA was detected at seven sites and redband trout eDNA was detected at four sites, confirming native salmonid persistence despite decades of co-occurrence with brook trout. Brook trout eDNA concentrations were highest in samples closer to High Lake where the species was first introduced, while native salmonid eDNA concentrations were higher at locations further from the lake. This study provides baseline distributions for these species and a framework for using eDNA sampling to monitor fish distributions in remote areas.
Western oak mistletoe (Phoradendron villosum subsp. villosum) on non-native urban trees of western Oregon - David C. Shaw, Max Bennett, Don Goheen, Alan Kanaskie, Scott Altenhoff
Western oak mistletoe (Phoradendron villosum subsp. villosum) (WOM) occurs on native oaks (Quercus spp., Fagaceae) from Baja California, Mexico to the northern Willamette Valley, Oregon, USA. A variety of other native and non-native hardwoods within its native range are also hosts. We used the diverse urban forests of western Oregon (Salem, Corvallis, Eugene, Medford, Central Point, Rogue River, and Ashland) as a natural laboratory to investigate the host range of WOM and to assess the effects of WOM on tree health. During the leaf-off period of deciduous hardwood trees, we surveyed these urban forests for the occurrence of WOM in crowns of non-native trees. We collected data on tree species, tree size, height, mistletoe abundance, and tree condition. We observed WOM in 227 non-native trees, of which 85 percent were pin oak (Q. palustris) or northern red oak (Q. rubra), 12 percent were other oak species, and only 3 percent were individuals of non-oak species, despite the fact that non-oak genera represented from 81 to 96 percent of the urban trees in four cities with tree inventories. WOM tended to occur in larger trees which is consistent with the literature. We found no observable effects of mistletoe infestation on tree condition. The decision to manage WOM should involve oaks only, and depends on whether tree owners are concerned about potential negative effects of heavy infestations on tree health or desire increased biodiversity. Urban forest managers could also consider alternatives to red oak group species if WOM is abundant in the area.
The complete pre-print version of this article is available here.
Ecological, demographic, and physical characteristics of Sierra Nevada red foxes in the Oregon Cascades - Jamie L. Bowles, Corey Heath, Tim L. Hiller
Little is known about the montane subspecies, Sierra Nevada red fox Vulpes vulpes necator (SNRF). The SNRF is a habitat specialist putatively limited to sky islands of alpine and subalpine meadows and parklands in the Cascades of Oregon and California, and the Sierra Nevada of California. Populations in California have experienced substantial range contractions for unknown reasons in recent decades, complicating research and management, whereas populations in Oregon are more widespread, thereby allowing for accumulation of basic knowledge with conservation and management benefits. We collected data on radiomarked SNRF in Oregon during 2016–2020. Using a biased random bridge approach, SNRF showed patterns of larger areas used during the breeding (e.g., 95% utilization distribution, x̄ = 138.3 km2; n = 10) vs. nonbreeding (x̄ = 79.5 km2; n = 12) season. Based on selection ratios to assess second-order cover selection, SNRF most strongly selected for parkland and meadow (alpine and subalpine), woodland (alpine and subalpine), grassland (alpine and subalpine), forest (hemlock dominated), and rock (volcanic, other), regardless of season. For third-order selection, SNRF often strongly selected for developed land-cover types, potentially associated with anthropogenic food sources. The most common cause of mortality was potential predation (3 of 7 foxes), and mean annual survival probability was 0.69. Given that SNRF are generally limited to sensitive, linear-shaped alpine and subalpine areas primarily on federal lands, multi-agency coordination for management decisions are necessary to address or mitigate impacts from humans, including impacts from increasing levels of recreational use and development.