Species Status Assessment for Graptopetalum Bartramii

Species Status Assessment Report for Graptopetalum bartramii Bartram’s stonecrop April 2018 Southwest Region United States Fish and Wildlife Service Arizona Ecological Services Office Tucson, Arizona i This document was prepared by Julie Crawford, Arizona Ecological Services Office and Hayley Dikeman, Southwest Regional Office. We thank Angela Anders, Southwest Regional Office, for reviews of drafts. Valuable input was provided by George Ferguson, University of Arizona; Steve Buckley, National Park Service; George Montgomery, formerly of the Arizona Sonora Desert Museum; Jessica Simms, National Park Service; Angela Barclay, National Forest Service, and Kathryn Kennedy, National Forest Service. ii Suggested reference: United States Fish and Wildlife Service. 2018. Species status assessment report for Graptopetalum bartramii (Bartram’s stonecrop). United States Fish and Wildlife Service Arizona Ecological Services Office, Tucson, Arizona. 117 pp. + 2 appendices. iii Species Status Assessment Report for Graptopetalum bartramii Bartram’s stonecrop Prepared by the United States Fish and Wildlife Service EXECUTIVE SUMMARY This species status assessment reports the results of the comprehensive status review for Graptopetalum bartramii (Bartram’s stonecrop) through an analytical approach assessing the species needs, current status, and future status of a species using the best available information, and provides a thorough account of the species’ overall viability. For the purpose of this assessment, we generally define viability as the ability of G. bartramii to sustain populations in natural systems over time. The SSA Framework uses the conservation biology principles of resiliency, redundancy, and representation (collectively known as the “3Rs”) as a lens to evaluate the current and future condition of the species. Graptopetalum bartramii is a succulent of the Crassulaceae or stonecrop family. The species typically occurs on rocky outcrops in deep, narrow canyons in heavy cover of litter and shade; and typically within 10 meters (m; 32.8 feet (ft)) of streambeds, springs, or seeps. It is known to have historically occurred in 33 separate populations within 13 isolated sky island mountain ranges, 10 in southern Arizona and 3 in northern Mexico. We are aware of four populations that have become extirpated in the United States in recent years, and a fifth, which has contracted in size. In three instances, extirpation was associated with the drying of habitat, which rendered it no longer suitable for the species to persist; we do not know the cause of extirpation in the fourth instance. Currently, there are 29 extant populations across 12 mountain ranges in the United States and Mexico. We are aware of 3,726 adult individuals across the entire range within the United States, including an assumed 10 plants from one U.S. population that has not been revisited, but presumed to be small (Thomas Canyon). Similarly, the three populations in Mexico have not been revisited and no counts ever made at these sites. We assume a small number of plants (10) at each of these locations, for a total of 3,756 across the entire range of the species. We also assume habitat, where these populations grow, to be in Low condition. Graptopetalum bartramii needs multiple resilient populations. Resilient populations are those able to withstand stochastic events arising from spatially and temporally random factors, and that are distributed widely across its range, to maintain its persistence into the future and to avoid extinction. Several factors influence the resiliency of a population in response to stochastic events. These factors are: • Abundance – populations large enough that local stochastic events do not eliminate all individuals, allowing the overall population to recover from any one event • Subpopulations – multiple subpopulations per population so that local stochastic events do not eliminate the entire population • Recruitment – the number of seedlings exceeds the number of dead or dying individuals • Riparian elements – typically located within 10 m (32.8 ft) of a water source, which is presumed to increase humidity iv • Precipitation – to maintain soil moisture, cooler temperatures, and humidity in the microenvironment • Shade – litter and deep shade from rock walls and / or overstory vegetation which is presumed to increase humidity • Substrate – crevices in solid bedrock or in shallow soil pockets • Pollinators – sufficient to ensure seed production, as the species does not reproduce vegetatively To assess the population resiliency levels for current condition, we used the first six population and habitat factors listed above, as they are the primary factors influencing G. bartramii. These include all of the above factors except substrate and pollinators. We did not include these last two because they do not appear to be limiting factors for this species. For each of the six population and habitat factors we developed condition categories (High, Moderate, Low, and Extirpated) to assess the condition of each factor for each population, in order to determine overall population resiliency. Tables ES–1 and ES-2 provide our assessment of the current and future conditions of G. bartramii populations. To assess current condition of the species, we considered representation and redundancy. Representation is the ability to adapt to changing environmental conditions as measured by the breadth of genetic or environmental diversity within and among populations. Redundancy is the ability of a species to withstand catastrophic events, measured by the number of populations, their resiliency, and their distribution and connectivity. Genetic analysis of this species has not been conducted within or among populations or sky islands. However, sky island populations on different mountain ranges are widely separated (ranging from roughly 14 to 42 km (8.7 to 26 mi) apart), making cross- pollination highly unlikely, and most of the populations contain small numbers of individuals. Currently, there are 29 populations across 12 mountain ranges, with lack of connectivity among mountain ranges. To evaluate the biological status of G. bartramii into the future, we assessed a range of conditions over 10 and 40 years to allow us to consider the species’ resiliency, redundancy, and representation. Our analysis of the past, current, and future influences on what G. bartramii needs for long term viability revealed that there are a number of stressors to this species including two primary stressors, related to habitat changes, which pose the greatest risk to future viability of the species. A stressor is a chemical or biological agent, environmental condition, external stimulus or an event that causes stress to an organism, and risk is the possibility of the stressor impacting the organism. These stressors include 1) groundwater extraction and drought that may reduce nearby water levels and humidity within G. bartramii habitat, and 2) altered fire regimes leading to erosion of G. bartramii habitat, sedimentation that could cover individuals, and loss of overstory shade trees. These stressors play a large role in the future viability of G. bartramii, especially for smaller populations. If populations lose resiliency, they are more vulnerable to extirpation, with resulting losses in representation and redundancy. Each population faces varying levels of risk into the future from natural and anthropogenic stressors including the following: • Loss of water in nearby drainages from mining and drought • Erosion, sedimentation, and burial from mining, livestock, wildlife, recreation trails and roads, cross border violators, and post-wildfire runoff v • Trampling from humans, wildlife, and livestock • High severity wildfires ignited from recreationists, cross border violators, and lightning • Loss of shade from mining, drought, insect predation, flooding, and wildfire • Higher frequencies of freezing and flooding events from current and future climate change • Loss of seedling, immature, and adult plants, and reproduction from current and future drought • Predation of individuals and shade trees • Illegal collection Given our uncertainty regarding the species’ persistence in Mexico and the future of nearby water and shade that create a humid microhabitat within populations, we have forecasted what G. bartramii may have in terms of resiliency, redundancy, and representation under four future plausible scenarios (Table ES–1 and 2). Under scenario 1 – Continuation - We would expect the viability of G. bartramii to be characterized by a loss of resiliency, representation, and redundancy at the level that is currently occurring. At the 10-year time step, no populations would be in High condition, 4 populations (12 percent) would be in Moderate condition, 23 populations (70 percent) would be in Low condition and more susceptible to loss, and 6 populations (18 percent) would be extirpated. Within Scenario 1 we assume impacts from drought, climate change, and other stressors continue as in the near past. We think this is highly likely to occur within the 10-year time step with decreasing likelihood at future timesteps. This expectation is based on climate change projections portraying emissions increases, resulting in increased impacts to the species. Under scenario 2 – Conservation – We would expect the viability of G. bartramii to be characterized by higher levels of resiliency, representation, and redundancy than it exhibits under the current condition. However, because current stressors

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