Jonathan P. Rose

Contexts for change in alpine tundra

Because alpine tundra is responding to climate change, a need exists to understand the meaning of observed changes. To provide context for such interpretation, the relevance of niche and neutral theories of biogeography and the continuum and classification approaches to biogeographic description are assessed. Two extensive studies of alpine tundra, from the Indian Peaks area, Colorado and Glacier National Park, Montana, are combined. The data are ordinated to describe relations. The pattern that emerges is one of a continuum of vegetation, but with the distinctions one might expect from distant sites. The relationships of the similarity of vegetation on all possible pairs of sites to the environmental differences and geographic distances are analyzed using Mantel correlations. Because distance and environmental differences in climate between the two sites are correlated, partial correlations are weak but still significant. More advanced analyses are suggested for this environment prior to interpretation of monitoring efforts such as GLORIA.

Trapping Efficiency, Demography, and Density of an Introduced Population of Northern Watersnakes, Nerodia sipedon, in California

Abstract Northern Watersnakes, Nerodia sipedon, have been introduced into Californias Central Valley and pose an important new challenge for the management of biodiversity in the states already greatly distressed freshwater ecosystems. Nonnative watersnakes will likely compete with federally threatened Giant Gartersnakes, Thamnophis gigas, and prey on native amphibians and fish, including young salmonids, many of which are imperiled. We used three types of aquatic funnel traps and three different methods to estimate the abundance and density of N. sipedon in a small wetland in Roseville, California. Capture rates did not differ significantly among the three trap types but snakes captured in large box funnel traps were nearly 300 mm longer on average than those captured in minnow traps. Our estimates of the abundance of N. sipedon in our 2-ha trapping area were similar for the mark–recapture model, Leslie depletion curve, and the actual number of snakes removed over 57 days (112.4–119 individuals; approximately 56.2 snakes/ha). Extrapolating to the entire 6.2-ha aquatic area, the population likely numbered approximately 348 individuals. Several females were gravid, demonstrating successful reproduction by this species outside its native range. We caught more small N. sipedon compared with studies in its native range. This may be due to a sampling bias in our trapping methods but more likely reflects a population growing rapidly from a few initial founders with relatively fewer large adults. We recommend immediate action to prevent the spread and broader establishment of N. sipedon across the Central Valley of California.

Projecting Invasion Risk of Non-Native Watersnakes (Nerodia fasciata and Nerodia sipedon) in the Western United States

Species distribution models (SDMs) are increasingly used to project the potential distribution of introduced species outside their native range. Such studies rarely explicitly evaluate potential conflicts with native species should the range of introduced species expand. Two snake species native to eastern North America, Nerodia fasciata and Nerodia sipedon, have been introduced to California where they represent a new stressor to declining native amphibians, fish, and reptiles. To project the potential distributions of these non-native watersnakes in western North America, we built ensemble SDMs using MaxEnt, Boosted Regression Trees, and Random Forests and habitat and climatic variables. We then compared the overlap between the projected distribution of invasive watersnakes and the distributions of imperiled native amphibians, fish, and reptiles that can serve as prey or competitors for the invaders, to estimate the risk to native species posed by non-native watersnakes. Large areas of western North America were projected to be climatically suitable for both species of Nerodia according to our ensemble SDMs, including much of central California. The potential distributions of both N. fasciata and N. sipedon overlap extensively with the federally threatened Giant Gartersnake, Thamnophis gigas, which inhabits a similar ecological niche. N. fasciata also poses risk to the federally threatened California Tiger Salamander, Ambystoma californiense, whereas N. sipedon poses risk to some amphibians of conservation concern, including the Foothill Yellow-legged Frog, Rana boylii. We conclude that non-native watersnakes in California can likely inhabit ranges of several native species of conservation concern that are expected to suffer as prey or competing species for these invaders. Action should be taken now to eradicate or control these invasions before detrimental impacts on native species are widespread. Our methods can be applied broadly to quantify the risk posed by incipient invasions to native biodiversity.

Terrestrial Habitat use by Western Pond Turtles (Actinemys marmorata) in the Sierra Foothills

Abstract Western Pond Turtles (Actinemys marmorata) are endemic to western North America and are found in a diversity of aquatic habitats. To date, few studies have examined the ecology of populations in ephemeral or intermittent ponds. Here, we studied the terrestrial habitat requirements of Western Pond Turtles in an intermittent pond that dries in years with below-average rainfall. We tracked terrestrial movements of Western Pond Turtles in an ephemeral pond at the San Joaquin Experimental Range in Madera County, California, USA, in the western foothills of the Sierra Nevada. We used radiotelemetry in 2012–13 to record their terrestrial locations and timing of departure from, and return to, the pond. Also, we examined the terrestrial microhabitat turtles selected for aestivation and overwintering. Turtles began leaving the pond as it dried in the late spring and early summer, spending an average of 235 d out of water, and their return to the pond was correlated with increasing rainfall during late winter. The majority of terrestrial locations were concealed completely in litter or duff and 95% of terrestrial locations during the study occurred within 187 m of the pond edge. Turtles in our study generally exhibited terrestrial habitat use similar to that of populations in intermittent lotic systems such as the many snow-melt and rain-fed rivers in northern California. Our results reinforce the importance of terrestrial habitat in the life history of Western Pond Turtles and the context-dependence of their habitat needs.

A Herpetological Inventory of Naval Air Station Fallon, Churchill County, Nevada

Abstract. Much of the western United States is managed by state and federal agencies for multiple uses, including recreation, grazing, extraction, and defense. Biological inventories are integral to proper management and conservation of biodiversity on these lands. We surveyed for amphibians and reptiles occurring on Naval Air Station Fallon (NAS Fallon), Nevada, USA, using a variety of methods. We documented the presence of a majority of the amphibian and reptile species native to this region of the Great Basin. We found 5 species on NAS Fallon that are listed as Species of Conservation Priority by the Nevada Department of Wildlife: the Great Basin Spadefoot (Spea intermontana), Western Toad (Anaxyrus boreas boreas), Northern Desert Horned Lizard (Phrynosoma platyrhinos platyrhinos), Long-nosed Leopard Lizard (Gambelia wizlizenii), and Great Basin Collared Lizard (Crotaphytus bicinctores). However, we found no evidence of any narrowly distributed species of conservation concern, such as the Northern Leopard Frog (Lithobates pipiens) or Northern Rubber Boa (Charina bottae), that could have occurred on installation lands based on historical or recent observations in nearby areas. Our results indicate that this property, while primarily used for military training, can support a diverse, representative herpetofaunal community. Therefore, NAS Fallon should be considered a valuable part of the network of state and federally managed lands necessary for regional conservation planning in the face of future change. Our study also provides a baseline against which future inventories of this federally managed land can be compared.