Difficult climate-adaptive decisions in forests as complex social-ecological systems.

Climate change threatens the social, ecological, and economic benefits enjoyed by forest-dependent communities worldwide. Climate-adaptive forest management strategies such as genomics-based assisted migration (AM) may help protect many of these threatened benefits. However, such novel technological interventions in complex social-ecological systems will generate new risks, benefits, and uncertainties that interact with diverse forest values and preexisting risks. Using data from 16 focus groups in British Columbia, Canada, we show that different stakeholders (forestry professionals, environmental nongovernmental organizations, local government officials, and members of local business communities) emphasize different kinds of risks and uncertainties in judging the appropriateness of AM. We show the difficulty of climate-adaptive decisions in complex social-ecological systems in which both climate change and adaptation will have widespread and cascading impacts on diverse nonclimate values. Overarching judgments about AM as an adaptation strategy, which may appear simple when elicited in surveys or questionnaires, require that participants make complex trade-offs among multiple domains of uncertain and unknown risks. Overall, the highest-priority forest management objective for most stakeholders is the health and integrity of the forest ecosystem from which all other important forest values derive. The factor perceived as riskiest is our lack of knowledge of how forest ecosystems work, which hinders stakeholders in their assessment of AM's acceptability. These results are further evidence of the inherent risk in privileging natural science above other forms of knowledge at the science-policy interface. When decisions are framed as technical, the normative and ethical considerations that define our fundamental goals are made invisible.

Reforestation of high elevation pines: Direct seeding success depends on seed source and sowing environment.

Forest persistence in regions impacted by increasing water and temperature stress will depend upon species' ability to either rapidly adjust to novel conditions or migrate to track ecological niches. Predicted, rapid climate change is likely to outpace the adaptive and migratory capacity of long-lived isolated tree species, and reforestation may be critical to species' persistence. Facilitating persistence both within and beyond a species' range requires identification of seed lots best adapted to the current and future conditions predicted with rapid climate change. We evaluate variation in emergent seedling performance that leads to differential survival among species and populations for three high elevation five-needle pines. We paired a fully reciprocal field common garden experiment with a greenhouse common garden study to (1) quantify variation in seedling emergence and functional traits, (2) ask how functional traits affect performance under different establishment conditions, and (3) evaluate whether trait and performance variation demonstrates local adaptation and plasticity. Among study species-limber, Great Basin bristlecone, and whitebark pines-we found divergence in emergence and functional traits, though soil moisture was the strongest driver of seedling emergence and abundance across all species. Generalist limber pine had a clear emergence advantage as well as traits associated with drought adaptation, while edaphic specialist bristlecone pine was characterized by low emergence yet high early survival once established. Despite evidence for edaphic specialization, soil characteristics alone did not explain bristlecone success. Across species, trait-environment relationships provided some evidence for local adaptation in drought-adapted traits, but we found no evidence of local adaptation in emergence or survival at this early life stage. For managers looking to promote persistence, sourcing seed from drier environments is likely to impart greater drought resistance into reforestation efforts through strategies such as greater root investment, increasing the probability of early seedling survival. This research demonstrates, through a rigorous reciprocal transplant experimental design, that it may be possible to select climate- and soil-appropriate seed sources for reforestation. However, planting success will ultimately rely on a suitable establishment environment, requiring careful consideration of interannual climate variability for management interventions in these climate and disturbance-impacted tree species.

Genetic rescue remains underused for aiding recovery of federally listed vertebrates in the United States.

Restoring gene flow among fragmented populations is discussed as a potentially powerful management strategy that could reduce inbreeding depression and cause genetic rescue. Yet, examples of assisted migration for genetic rescue remain sparse in conservation, prompting several outspoken calls for its increased use in genetic management of fragmented populations. We set out to evaluate the extent to which this strategy is underused and to determine how many imperiled species would realistically stand to benefit from genetic rescue, focusing on federally threatened or endangered vertebrate species in the United States. We developed a "genetic rescue suitability index (GR index)" based on concerns about small population problems relative to risks associated with outbreeding depression and surveyed the literature for 222 species. We found that two-thirds of these species were good candidates for consideration of assisted migration for the purpose of genetic rescue according to our suitability index. Good candidate species spanned all taxonomic groups and geographic regions, though species with more missing data tended to score lower on the suitability index. While we do not recommend a prescriptive interpretation of our GR index, we used it here to establish that assisted migration for genetic rescue is an underused strategy. For example, we found in total, "genetic rescue" was only mentioned in 11 recovery plans and has only been implemented in 3 of the species we surveyed. A potential way forward for implementation of this strategy is incorporating genetic rescue as a priority in USFWS recovery documentation. In general, our results suggest that although not appropriate for all imperiled species, many more species stand to benefit from a conservation strategy of assisted migration for genetic rescue than those for which it has previously been considered or implemented.

Do southern seed or soil microbes mitigate the effects of warming on establishing prairie plant communities?

Restoration in this era of climate change comes with a new challenge: anticipating how best to restore populations to persist under future climate conditions. Specifically, it remains unknown whether locally adapted or warm-adapted seeds best promote native plant community restoration in the warmer conditions predicted in the future and whether local or warm-adapted soil microbial communities could mitigate plant responses to warming. This may be especially relevant for biomes spanning large climatic gradients, such as the North American tallgrass prairie. Here, we used a short-term mesocosm experiment to evaluate how seed provenances (Local Northern region, Non-local Northern region, Non-local Southern region) of 10 native tallgrass prairie plants (four forbs, two legumes, and four grasses) responded to warmer conditions predicted in the future and how soil microbial communities from those three regions influenced these responses. Warming and seed provenance affected plant community composition and warming decreased plant diversity for all three seed provenances. Plant species varied in their individual responses to warming, and across species, we detected no consistent differences among the three provenances in terms of biomass response to warming and few strong effects of soil provenance. Our work provides evidence that warming, in part, may reduce plant diversity and affect restored prairie composition. Because the southern provenance did not consistently outperform others under warming and we found little support for the "local is best" paradigm currently dominating restoration practice, identifying appropriate seed provenances to promote restoration success both now and in future warmer environments may be challenging. Due to the idiosyncratic responses across species, we recommend that land managers compare seeds from different regions for each species to determine which seed provenance performs best under warming and in restoration for tallgrass prairies.

The immediate costs and long-term benefits of assisted gene flow in large populations.

With the genetic health of many plant and animal populations deteriorating due to climate change outpacing adaptation, interventions, such as assisted gene flow (AGF), may provide genetic variation necessary for populations to adapt to climate change. We ran genetic simulations to mimic different AGF scenarios in large populations and measured their outcomes on population-level fitness to determine circumstances in which it is worthwhile to perform AGF. In the absence of inbreeding depression, AGF was beneficial within a few generations only when introduced genotypes had much higher fitness than local individuals and traits affecting fitness were controlled by a few genes of large effect. AGF was harmful over short periods (e.g., first ∼10-20 generations) if there was strong outbreeding depression or introduced deleterious genetic variation. When the adaptive trait was controlled by many loci of small effect, the benefits of AGF took over 10 generations to realize-potentially too long for most climate-related management scenarios. The genomic integrity of the recipient population typically remained intact following AGF; the amount of genetic material from the donor population usually constituted no more of the recipient population's genome than the fraction of the population introduced. Significant genomic turnover (e.g., >50% replacement) only occurred when the selective advantage of the adaptive trait and translocation fraction were extremely high. Our results will be useful when adaptive management is used to maintain the genetic health and productivity of large populations under climate change.

Con el deterioro de la salud genética de muchas poblaciones de plantas y animales debido a la ventaja que le lleva el cambio climático a la adaptación, algunas intervenciones, como el flujo génico asistido (FGA), pueden proporcionar la variación genética necesaria para que las poblaciones se adapten al cambio climático. Simulamos diferentes escenarios de FGA aplicado en poblaciones grandes y medimos los resultados en la aptitud a nivel poblacional para determinar las circunstancias en las que merece la pena realizar FGA. Cuando no hubo depresión endogámica, el FGA produjo un beneficio en pocas generaciones sólo cuando se introdujeron genotipos que tenían una aptitud mucho mayor que los individuos locales y cuando unos cuantos genes de gran efecto controlaron los rasgos que afectaban a la aptitud. El flujo génico asistido fue dañino en periodos cortos (p.ej.: las primeras 10-20 generaciones) si existía una fuerte depresión exogámica o una variación genética deletérea introducida. Cuando muchos loci de pequeño efecto controlaron el rasgo adaptativo, los beneficios del FGA tardaron más de 10 generaciones en aparecer - un tiempo potencialmente muy largo para la mayoría de la gestión relacionada con el clima. La integridad genómica de la población receptora casi siempre permaneció intacta después del FGA; es decir, la cantidad de material genético de la población donante generalmente no constituyó más que la fracción de población introducida en el genoma de la población receptora. La rotación genómica significativa (p.ej.: reemplazos >50%) sólo ocurrió cuando la ventaja selectiva del rasgo adaptativo y la fracción de reubicación fueron extremadamente elevadas. Nuestros resultados serán útiles cuando se use la gestión adaptativa para mantener la salud genética y la productividad de las poblaciones grandes bajo el cambio climático.

Evaluating unintended consequences of intentional species introductions and eradications for improved conservation management.

Increasingly intensive strategies to maintain biodiversity and ecosystem function are being deployed in response to global anthropogenic threats, including intentionally introducing and eradicating species via assisted migration, rewilding, biological control, invasive species eradications, and gene drives. These actions are highly contentious because of their potential for unintended consequences. We conducted a global literature review of these conservation actions to quantify how often unintended outcomes occur and to elucidate their underlying causes. To evaluate conservation outcomes, we developed a community assessment framework for systematically mapping the range of possible interaction types for 111 case studies. Applying this tool, we quantified the number of interaction types considered in each study and documented the nature and strength of intended and unintended outcomes. Intended outcomes were reported in 51% of cases, a combination of intended outcomes and unintended outcomes in 26%, and strictly unintended outcomes in 10%. Hence, unintended outcomes were reported in 36% of all cases evaluated. In evaluating overall conservations outcomes (weighing intended vs. unintended effects), some unintended effects were fairly innocuous relative to the conservation objective, whereas others resulted in serious unintended consequences in recipient communities. Studies that assessed a greater number of community interactions with the target species reported unintended outcomes more often, suggesting that unintended consequences may be underreported due to insufficient vetting. Most reported unintended outcomes arose from direct effects (68%) or simple density-mediated or indirect effects (25%) linked to the target species. Only a few documented cases arose from more complex interaction pathways (7%). Therefore, most unintended outcomes involved simple interactions that could be predicted and mitigated through more formal vetting. Our community assessment framework provides a tool for screening future conservation actions by mapping the recipient community interaction web to identify and mitigate unintended outcomes from intentional species introductions and eradications for conservation.

Evaluación de las Consecuencias Involuntarias de las Introducciones y Erradicaciones Intencionales de Especies para el Manejo Mejorado de la Conservación Resumen Actualmente se despliegan estrategias cada vez más intensas para mantener la biodiversidad y la función del ecosistema como respuesta a las amenazas antropogénicas mundiales, incluyendo la introducción y erradicación intencionales de especies por medio de la migración asistida, el retorno a la vida silvestre, el control biológico, la erradicación de especies invasoras y la genética dirigida. Estas acciones son muy polémicas por el potencial que tienen para generar consecuencias involuntarias. Realizamos una revisión de la literatura mundial sobre estas acciones de conservación para cuantificar cuán seguido ocurren las consecuencias involuntarias y cuáles son sus causas subyacentes. Para evaluar los resultados de conservación, desarrollamos un marco de trabajo de evaluación comunitaria para mapear sistemáticamente el rango de posibles interacciones para 111 estudios de caso. Con la aplicación de esta herramienta cuantificamos el número de tipos de interacción consideradas en cada estudio y documentamos la naturaleza y la fuerza de los resultados involuntarios. Se reportaron los resultados voluntarios en 51% de los casos, una combinación de resultados voluntarios e involuntarios en 26% de los casos y estrictamente los resultados involuntarios en el 10% de los casos. Por lo tanto, los resultados involuntarios fueron reportados en el 36% de todos los casos evaluados. En la evaluación general de los resultados de conservación (sopesando los efectos voluntarios y. los involuntarios), algunos efectos involuntarios fueron bastante inocuos en relación con el objetivo de conservación, mientras que otros resultaron en consecuencias involuntarias severas para las comunidades receptoras. Los estudios que evaluaron un mayor número de interacciones comunitarias con la especie objetivo reportaron resultados involuntarios con mayor frecuencia, lo que sugiere que las consecuencias involuntarias pueden estar subvaloradas debido al escrutinio insuficiente. La mayoría de los resultados involuntarios reportados surgieron de los efectos directos (68%) o de los efectos indirectos o mediados por la densidad (25%) vinculados con la especie diana. Solamente unos cuantos casos documentados surgieron de interacciones más complejas (7%). Por lo tanto, la mayoría de los resultados involuntarios involucran interacciones simples que podrían ser pronosticadas y mitigadas por medio de un escrutinio más formal. Nuestro marco de trabajo de evaluación comunitaria proporciona una herramienta para la revisión de las acciones de conservación en el futuro mediante el mapeo de la red de interacciones entre comunidades receptoras y para la mitigación de los resultados involuntarios surgidos de las introducciones y erradicaciones intencionales de especies a favor de la conservación.

Of mutualism and migration: will interactions with novel ericoid mycorrhizal communities help or hinder northward Rhododendron range shifts?

Rapid climate change imperils many small-ranged endemic species as the climate envelopes of their native ranges shift poleward. In addition to abiotic changes, biotic interactions are expected to play a critical role in plant species' responses. Below-ground interactions are of particular interest given increasing evidence of microbial effects on plant performance and the prevalence of mycorrhizal mutualisms. We used greenhouse mesocosm experiments to investigate how natural northward migration/assisted colonization of Rhododendron catawbiense, a small-ranged endemic eastern U.S. shrub, might be influenced by novel below-ground biotic interactions from soils north of its native range, particularly with ericoid mycorrhizal fungi (ERM). We compared germination, leaf size, survival, and ERM colonization rates of endemic R. catawbiense and widespread R. maximum when sown on different soil inoculum treatments: a sterilized control; a non-ERM biotic control; ERM communities from northern R. maximum populations; and ERM communities collected from the native range of R. catawbiense. Germination rates for both species when inoculated with congeners' novel soils were significantly higher than when inoculated with conspecific soils, or non-mycorrhizal controls. Mortality rates were unaffected by treatment, suggesting that the unexpected reciprocal effect of each species' increased establishment in association with heterospecific ERM could have lasting demographic effects. Our results suggest that seedling establishment of R. catawbiense in northern regions outside its native range could be facilitated by the presence of extant congeners like R. maximum and their associated soil microbiota. These findings have direct relevance to the potential for successful poleward migration or future assisted colonization efforts.

Current Conservation Regimes and the Road to Laws on Assisted Migration.

The negative impact of climate change on biodiversity will continue to escalate rapidly. While some species will naturally migrate to more suitable areas or adapt to the new climatic environmental conditions in different fashions, for others doing so may prove to be problematic or impossible. Against this backdrop, scientists and environmentalists have proposed implementing plans for Assisted Migration (AM)-meaning the translocation of plants and animals to areas outside their natural habitats to conserve their species under the new emerging climatic conditions. This article seeks to identify legal approaches towards AM considering not only possible benefits from using this tool but also a necessity to minimize related risks. With regard to its stated purpose, this article also compares legal and policy documents relevant to AM issues from the United States, Australia, and the European Union. In conclusion, we have found, and this article shows, that while existing legal and policy documents leave room for manoeuvreing in regard to climate-related translocations and even sometimes explicitly mention AM as a possible tool for conservation, there exists a need for the further development of concrete legal mechanisms and their balancing with the predominant ideas and goals brought about by the necessity to protect native biota.

Importance of species translocations under rapid climate change.

Species that cannot adapt or keep pace with a changing climate are likely to need human intervention to shift to more suitable climates. While hundreds of articles mention using translocation as a climate-change adaptation tool, in practice, assisted migration as a conservation action remains rare, especially for animals. This is likely due to concern over introducing species to places where they may become invasive. However, there are other barriers to consider, such as time-frame mismatch, sociopolitical, knowledge and uncertainty barriers to conservationists adopting assisted migration as a go-to strategy. We recommend the following to advance assisted migration as a conservation tool: attempt assisted migrations at small scales, translocate species with little invasion risk, adopt robust monitoring protocols that trigger an active response, and promote political and public support.

Importancia de las Reubicaciones de Especies bajo el Cambio Climático Acelerado Resumen Las especies que no pueden adaptarse o mantener el ritmo del cambio climático probablemente requieran de la intervención humana para mudarse a climas más adecuados. Mientras que cientos de artículos mencionan el uso de las reubicaciones como una herramienta de adaptación al cambio climático, en la práctica, la migración asistida todavía es rara como una acción de conservación, especialmente para animales. Lo anterior probablemente se debe a la preocupación que existe por la introducción de especies a sitios en los que podrían volverse invasoras. Sin embargo, existen otras barreras que deberían considerarse, como aquellas ocasionadas por el desfase en el marco temporal, cuestiones sociopolíticas, de conocimiento o de incertidumbre para los conservacionistas que adoptan a la migración asistida como la estrategia de cajón. Recomendamos lo siguiente para que la migración asistida avance como herramienta de conservación: intentar realizar migraciones asistidas a pequeñas escalas, reubicar especies con poco riesgo de invasión, adoptar protocolos de monitoreo robustos que generen una respuesta activa y promover el apoyo público y político.

Augmenting coral adaptation to climate change via coral gardening (the nursery phase).

Unceasing climate change and anthropogenic impacts on coral reefs worldwide lead the needs for augmenting adaptive potential of corals. Currently, the most successful approach for restoring degraded reefs is 'coral gardening', where corals are farmed in underwater nurseries, then outplanted to damaged reefs. Dealing with enhanced coral adaptation, the 'coral gardening' approach is conceptually structured here within a hierarchical list of five encircling tiers that include all restoration activities, focusing on the nursery phase. Each tier encompasses all the activities performed in the levels below it hierarchically. The first is the 'coral mariculture' tier, followed by the 'ecological engineering' tier. The third is the adaptation-based reef restoration (ABRR) tier, preceding the fourth ('ecosystem seascape') and the fifth ('ecosystem services') tiers. The ABRR tier is further conceptualized and its constituent five classes (phenotypic plasticity, assisted migration, epigenetics, coral chimerism, holobiont modification) are detailed. It is concluded that the nursery phase of the 'gardening' tenet may further serve as a platform to enhance the adaptation capacities of corals to climate change through the five ABBR classes. Employing the 'gardening' tiers in reef restoration without considering ABRR will scarcely be able to meet global targets for healthy reef ecosystems in the future.

Perceived Barriers to the Use of Assisted Colonization for Climate Sensitive Species in the Hawaiian Islands.

Conservation actions to safeguard climate change vulnerable species may not be utilized due to a variety of perceived barriers. Assisted colonization, the intentional movement and release of an organism outside its historical range, is one tool available for species predicted to lose habitat under future climate change scenarios, particularly for single island or single mountain range endemic species. Despite the existence of policies that allow for this action, to date, assisted colonization has rarely been utilized for species of conservation concern in the Hawaiian Islands. Given the potential for climate driven biodiversity loss, the Hawaiian Islands are a prime location for the consideration of adaptation strategies. We used first-person interviews with conservation decision makers, managers, and scientists who work with endangered species in the Hawaiian Islands to identify perceived barriers to the use of assisted colonization. We found that assisted colonization was often not considered or utilized due to a lack of expertize with translocations; ecological risk and uncertainty, economic constraints, concerns regarding policies and permitting, concerns with public perception, and institutional resistance. Therefore, conservation planners may benefit from decision tools that integrate risk and uncertainty into decision models, and compare potential outcomes among conservation actions under consideration, including assisted colonization. Within a decision framework that addresses concerns, all conservation actions for climate sensitive species, including assisted colonization, may be considered in a timely manner.

Suitable climatic habitat changes for Mexican conifers along altitudinal gradients under climatic change scenarios.

The high biodiversity of the Mexican montane forests is concentrated on the Trans-Mexican Volcanic Belt, where several Protected Natural Areas exist. Our study examines the projected changes in suitable climatic habitat for five conifer species that dominate these forests. The species are distributed sequentially in overlapping altitudinal bands: Pinus hartwegii at the upper timberline, followed by Abies religiosa, the overwintering host of the Monarch butterfly at the Monarch Butterfly Biosphere Reserve, P. pseudostrobus, the most important in economic terms, and P. devoniana and P. oocarpa, which are important for resin production and occupy low altitudes where montane conifers merge with tropical dry forests. We fit a bioclimatic model to presence-absence observations for each species using the Random Forests classification tree with ground plot data. The models are driven by normal climatic variables from 1961 to 1990, which represents the reference period for climate-induced vegetation changes. Climate data from an ensemble of 17 general circulation models were run through the classification tree to project current distributions under climates described by the RCP 6.0 watts/m2 scenario for the decades centered on years 2030, 2060 and 2090. The results suggest that, by 2060, the climate niche of each species will occur at elevations that are between 300 to 500 m higher than at present. By 2060, habitat loss could amount to 46-77%, mostly affecting the lower limits of distribution. The two species at the highest elevation, P. hartwegii and A. religiosa, would suffer the greatest losses while, at the lower elevations, P. oocarpa would gain the most niche space. Our results suggest that conifers will require human assistance to migrate altitudinally upward in order to recouple populations with the climates to which they are adapted. Traditional in situ conservation measures are likely to be equivalent to inaction and will therefore be incapable of maintaining current forest compositions.

Assisted migration across fixed seed zones detects adaptation lags in two major North American tree species.

Boreal forests are experiencing dramatic climate change, having warmed 1.0°-1.9°C over the last century. Yet forest regeneration practices are often still dictated by a fixed seed zone framework, in which seeds are both harvested from and planted into predefined areas. Our goal was to determine whether seedlings sourced from southern seed zones in Minnesota USA are already better adapted to northerly seed zones because of climate change. Bur oak (Quercus macrocarpa) and northern red oak (Quercus rubra) seedlings from two seed zones (i.e., tree ecotypes) were planted into 16 sites in two northern seed zones and measured for 3 yr. Our hypotheses were threefold: (1) tree species with more southern geographic distributions would thrive in northern forests where climate has already warmed substantially, (2) southern ecotypes of these species would have higher survival and growth than the northern ecotype in northern environments, and (3) natural selection would favor seedlings that expressed phenotypic and phenological traits characteristic of trees sourced from the more southern seed zone. For both species, survival was high (>93%), and southern ecotypes expressed traits consistent with our climate adaptation hypotheses. Ecotypic differences were especially evident for red oak; the southern ecotype had had higher survival, lower specific leaf area (SLA), faster height and diameter growth, and extended leaf phenology relative to the northern ecotype. Bur oak results were weaker, but the southern ecotype also had earlier budburst and lower SLA than the northern ecotype. Models based on the fixed seed zones failed to explain seedling performance as well as those with continuous predictors (e.g., climate and geographical position), suggesting that plant adaptations within current seed zone delineations do align with changing climate conditions. Adding support for this conclusion, natural selection favored traits expressed by the more southern tree ecotypes. Collectively, these results suggest that state seed sourcing guidelines should be reexamined to permit plantings across seed zones, a form of assisted migration. More extensive experiments (i.e., provenance trails) are necessary to make species-specific seed transfer guidelines that account for climate trends while also considering the precise geographic origin of seed sources.

Public trust and knowledge in the context of emerging climate-adaptive forestry policies.

Effective governance of public forests depends, in part, on public support for changes in forest management, particularly those responding to changes in socio-ecological conditions driven by climate change. Trust in managing authorities and knowledge about forest management have proven influential in shaping public support for policy across different forest managemen contexts. However, little is known about the relationship between public trust and knowledge as it relates to policy support for emerging management strategies for climate adaptation in forests. We use the example of genomics-based assisted migration (within and outside of natural range) in British Columbia's (BC) forests to examine the relative roles of and interactions between trust in different forestry actors and knowledge of forestry in shaping public support for this new and potentially controversial management alternative. Our results, based on an online survey (n = 1953 BC residents), reveal low public trust in governments and the forest industry combined with low levels of public knowledge about forest management. We find that individuals who are more trusting of decision-makers and other important forestry actors hold higher levels of support for assisted migration. Higher levels of forestry knowledge are linked with support for assisted migration within native range, whereas no knowledge effect is observed for assisted migration outside of native range. We discuss the implications of these observations and provide recommendations to more fully engage with the challenges of low levels of trust and knowledge in this context.

Evolutionary history and biogeography of Mandragora L. (Solanaceae).

Mandragora L. (Solanaceae) is the only genus of the tribe Mandragoreae, one of the two tribes of the cosmopolitan nightshade family, which occur exclusively in Eurasia and northern Africa. The genus occurs discontinuously in the Mediterranean region, Turanian region, and on the Tibetan Plateau, representing a classical disjunction pattern in the biogeography of the Old World flora. In this study, we reconstructed the genus phylogeny using AFLP, eight plastid DNA regions and one nuclear (ITS) gene, and evaluated the taxonomic value of quantitative traits time to flowering, fruit and seed size. We also analyzed the evolutionary history of the genus based on a phylogenetic framework and dating inferred from a combined data set of seven plastid regions with one fossil calibration point. Our data suggest that Mandragora originated in the Eocene, apparently along the Tethyan coast in broadleaf deciduous mesophytic forests that covered most of the Mediterranean region at that time. The Mediterranean-Turanian clade diverged from the Tibetan Plateau clade about 20.5 million years ago (Ma) as a result of the plateau uplift which probably was enhanced by aridification in the interior of Eurasia. A second split within the genus occurred about 11.1 Ma and resulted in Western Mediterranean and Near East-Turanian clades. Mandragora turcomanica was found to have very closely related evolutionary history with plants from the Near East indicating a possible ancient human assisted migration from Israel to Persia in historic times. In the Tibetan Plateau area, the morphologically distinctive M. chinghaiensis is nested within the M. caulescens clade indicating a very recent diversification within this lineage.

Climate-based seed transfer of a widespread shrub: population shifts, restoration strategies, and the trailing edge.

Genetic resources have to be managed appropriately to mitigate the impact of climate change. For many wildland plants, conservation will require knowledge of the climatic factors affecting intraspecific genetic variation to minimize maladaptation. Knowledge of the interaction between traits and climate can focus management resources on vulnerable populations, provide guidance for seed transfer, and enhance fitness and resilience under changing climates. In this study, traits of big sagebrush (Artemisia tridentata) were examined among common gardens located in different climates. We focus on two subspecies, wyomingensis and tridentata, that occupy the most imperiled warm-dry spectrum of the sagebrush biome. Populations collected across the sagebrush biome were recorded for flower phenology and survival. Mixed-effects models examined each trait to evaluate genetic variation, environmental effects, and adaptive breadth of populations. Climate variables derived from population-source locations were significantly associated with these traits (P < 0.0001), explaining 31% and 11% of the flower phenology and survival variation, respectively. To illustrate our model and assess variability in prediction, we examine fixed and focal point seed transfer approaches to map contemporary and climate model ensemble projections in two different regions of the sagebrush biome. A comparison of seed transfer areas predicts that populations from warmer climates become more prevalent, replacing colder-adapted populations by mid-century. However, these warm-adapted populations are often located along the trailing edge, margins of the species range predicted to be lost due to a contraction of the climatic niche. Management efforts should focus on the collection and conservation of vulnerable populations and prudent seed transfer to colder regions where these populations are projected to occur by mid-century. Our models provide the foundation to develop an empirical, climate-based seed transfer system for current and future restoration of big sagebrush.

An experimental test of alternative population augmentation scenarios.

Human land use is fragmenting habitats worldwide and inhibiting dispersal among previously connected populations of organisms, often leading to inbreeding depression and reduced evolutionary potential in the face of rapid environmental change. To combat this augmentation of isolated populations with immigrants is sometimes used to facilitate demographic and genetic rescue. Augmentation with immigrants that are genetically and adaptively similar to the target population effectively increases population fitness, but if immigrants are very genetically or adaptively divergent, augmentation can lead to outbreeding depression. Despite well-cited guidelines for the best practice selection of immigrant sources, often only highly divergent populations remain, and experimental tests of these riskier augmentation scenarios are essentially nonexistent. We conducted a mesocosm experiment with Trinidadian guppies (Poecilia reticulata) to test the multigenerational demographic and genetic effects of augmenting 2 target populations with 3 types of divergent immigrants. We found no evidence of demographic rescue, but we did observe genetic rescue in one population. Divergent immigrant treatments tended to maintain greater genetic diversity, abundance, and hybrid fitness than controls that received immigrants from the source used to seed the mesocosms. In the second population, divergent immigrants had a slightly negative effect in one treatment, and the benefits of augmentation were less apparent overall, likely because this population started with higher genetic diversity and a lower reproductive rate that limited genetic admixture. Our results add to a growing consensus that gene flow can increase population fitness even when immigrants are more highly divergent and may help reduce uncertainty about the use of augmentation in conservation.

Species distribution models may misdirect assisted migration: insights from the introduction of Douglas-fir to Europe.

Species distribution models (SDMs), which statistically relate species occurrence to climatic variables, are widely used to identify areas suitable for species growth under future climates and to plan for assisted migration. When SDMs are projected across times or spaces, it is assumed that species climatic requirements remain constant. However, empirical evidence supporting this assumption is rare, and SDM predictions could be biased. Historical human-aided movements of tree species can shed light on the reliability of SDM predictions in planning for assisted migration. We used Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a North American conifer introduced into Europe during the mid-19th century, as a case-study to test niche conservatism. We combined transcontinental data sets of Douglas-fir occurrence and climatic predictors to compare the realized niches between native and introduced ranges. We calibrated a SDM in the native range and compared areas predicted to be climatically suitable with observed presences. The realized niches in the native and introduced ranges showed very limited overlap. The SDM calibrated in North America had very high predictive power in the native range, but failed to predict climatic suitability in Europe where Douglas-fir grows in climates that have no analogue in the native range. We review the ecological mechanisms and silvicultural practices that can trigger such shifts in realized niches. Retrospective analysis of tree species introduction revealed that the assumption of niche conservatism is erroneous. As a result, distributions predicted by SDM are importantly biased. There is a high risk that assisted migration programs may be misdirected and target inadequate species or introduction zones.

Phenological mismatch and the effectiveness of assisted gene flow.

The persistence of narrowly adapted species under climate change will depend on their ability to migrate apace with their historical climatic envelope or to adapt in place to maintain fitness. This second path to persistence can only occur if there is sufficient genetic variance for response to new selection regimes. Inadequate levels of genetic variation can be remedied through assisted gene flow (AGF), that is the intentional introduction of individuals genetically adapted to localities with historic climates similar to the current or future climate experienced by the resident population. However, the timing of reproduction is frequently adapted to local conditions. Phenological mismatch between residents and migrants can reduce resident × migrant mating frequencies, slowing the introgression of migrant alleles into the resident genetic background and impeding evolutionary rescue efforts. Focusing on plants, we devised a method to estimate the frequency of resident × migrant matings based on flowering schedules and applied it in an experiment that mimicked the first generation of an AGF program with Chamaecrista fasciculata, a prairie annual, under current and expected future temperature regimes. Phenological mismatch reduced the potential for resident × migrant matings by 40-90%, regardless of thermal treatment. The most successful migrant sires were the most resident like in their flowering time, further biasing the genetic admixture between resident and migrant populations. Other loci contributing to local adaptation-heat-tolerance genes, for instance-may be in linkage disequilibrium with phenology when residents and migrants are combined into a single mating pool. Thus, introgression of potentially adaptive migrant alleles into the resident genetic background is slowed when selection acts against migrant phenology. Successful AGF programs may require sustained high immigration rates or preliminary breeding programs when phenologically matched migrant source populations are unavailable.

Drought tolerance and growth in populations of a wide-ranging tree species indicate climate change risks for the boreal north.

Choosing drought-tolerant planting stock in reforestation programs may help adapt forests to climate change. To inform such reforestation strategies, we test lodgepole pine (Pinus contorta Doug. ex Loud. var latifolia Englm.) population response to drought and infer potential benefits of a northward transfer of seeds from drier, southern environments. The objective is addressed by combining dendroecological growth analysis with long-term genetic field trials. Over 500 trees originating from 23 populations across western North America were destructively sampled in three experimental sites in southern British Columbia, representing a climate warming scenario. Growth after 32 years from provenances transferred southward or northward over long distances was significantly lower than growth of local populations. All populations were affected by a severe natural drought event in 2002. The provenances from the most southern locations showed the highest drought tolerance but low productivity. Local provenances were productive and drought tolerant. Provenances from the boreal north showed lower productivity and less drought tolerance on southern test sites than all other sources, implying that maladaptation to drought may prevent boreal populations from taking full advantage of more favorable growing conditions under projected climate change.