Showing papers by "University of Maine published in 2007"

Expanding the utilization of sustainable plant products in aquafeeds: a review

Abstract: Continued growth and intensi¢cation of aquaculture production depends upon the development of sustainable protein sources to replace ¢sh meal in aquafeeds. This document reviews various plant feedstuis, which currently are or potentially may be incorporated into aquafeeds to support the sustainable production of various ¢sh species in aquaculture. The plant feedstuis considered include oilseeds, legumes and cereal grains, which traditionally have been used as protein or energy concentrates as well as novel products developed through various processing technologies. The nutritional composition of these various feedstuis are considered along with the presence of any bioactive compounds that may positively or negatively aiect the target organism. Lipid composition of these feedstuis is not speci¢cally considered although it is recognized that incorporating lipid supplements in aquafeeds to achieve proper fatty acid pro¢les to meet the metabolic requirements of ¢sh and maximize human health bene¢ts are important aspects. Speci¢c strategies and techniques to optimize the nutritional composition of plant feedstuis and limit potentially adverse eiects of bioactive compounds are also described. Such information will provide a foundation for developing strategic research plans for increasing the use of plant feedstuis in aquaculture to reduce dependence of animal feedstuis and thereby enhance the sustainability of aquaculture.

Phylogeny and classification of Rosaceae

Abstract: Phylogenetic relationships among 88 genera of Rosaceae were investigated using nucleotide sequence data from six nuclear (18S, gbssi1, gbssi2, ITS, pgip, and ppo) and four chloroplast (matK, ndhF, rbcL, and trnL-trnF) regions, separately and in various combinations, with parsimony and likelihood-based Bayesian approaches. The results were used to examine evolution of non-molecular characters and to develop a new phylogenetically based infrafamilial classification. As in previous molecular phylogenetic analyses of the family, we found strong support for monophyly of groups corresponding closely to many previously recognized tribes and subfamilies, but no previous classification was entirely supported, and relationships among the strongly supported clades were weakly resolved and/or conflicted between some data sets. We recognize three subfamilies in Rosaceae: Rosoideae, including Filipendula, Rubus, Rosa, and three tribes; Dryadoideae, comprising the four actinorhizal genera; and Spiraeoideae, comprising Lyonothamnus and seven tribes. All genera previously assigned to Amygdaloideae and Maloideae are included in Spiraeoideae. Three supertribes, one in Rosoideae and two in Spiraeoideae, are recognized.

A checklist for ecological management of landscapes for conservation

Abstract: The management of landscapes for biological conservation and ecologically sustainable natural resource use are crucial global issues. Research for over two decades has resulted in a large literature, yet there is little consensus on the applicability or even the existence of general principles or broad considerations that could guide landscape conservation. We assess six major themes in the ecology and conservation of landscapes. We identify 13 important issues that need to be considered in developing approaches to landscape conservation. They include recognizing the importance of landscape mosaics (including the integration of terrestrial and aquatic areas), recognizing interactions between vegetation cover and vegetation configuration, using an appropriate landscape conceptual model, maintaining the capacity to recover from disturbance and managing landscapes in an adaptive framework. These considerations are influenced by landscape context, species assemblages and management goals and do not translate directly into on-the-ground management guidelines but they should be recognized by researchers and resource managers when developing guidelines for specific cases. Two crucial overarching issues are: (i) a clearly articulated vision for landscape conservation and (ii) quantifiable objectives that offer unambiguous signposts for measuring progress.

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Abstract: A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

Dynamic clustered distribution of hemagglutinin resolved at 40 nm in living cell membranes discriminates between raft theories.

Abstract: Organization in biological membranes spans many orders of magnitude in length scale, but limited resolution in far-field light microscopy has impeded distinction between numerous biomembrane models. One canonical example of a heterogeneously distributed membrane protein is hemagglutinin (HA) from influenza virus, which is associated with controversial cholesterol-rich lipid rafts. Using fluorescence photoactivation localization microscopy, we are able to image distributions of tens of thousands of HA molecules with subdiffraction resolution (≈40 nm) in live and fixed fibroblasts. HA molecules form irregular clusters on length scales from ≈40 nm up to many micrometers, consistent with results from electron microscopy. In live cells, the dynamics of HA molecules within clusters is observed and quantified to determine an effective diffusion coefficient. The results are interpreted in terms of several established models of biological membranes.

Profile effects in early bilingual language and literacy

Abstract: Bilingual children’s language and literacy is stronger in some domains than others. Reanalysis of data from a broad-scale study of monolingual English and bilingual Spanish–English learners in Miami provided a clear demonstration of “profile effects,” where bilingual children perform at varying levels compared to monolinguals across different test types. The profile effects were strong and consistent across conditions of socioeconomic status, language in the home, and school setting (two way or English immersion). The profile effects indicated comparable performance of bilingual and monolingual children in basic reading tasks, but lower vocabulary scores for the bilinguals in both languages. Other test types showed intermediate scores in bilinguals, again with substantial consistency across groups. These profiles are interpreted as primarily due to the “distributed characteristic” of bilingual lexical knowledge, the tendency for bilingual individuals to know some words in one language but not the other and vice versa.

Eco-evolutionary conservation biology: contemporary evolution and the dynamics of persistence

Abstract: Summary 1 Natural and human mediated perturbations present challenges to the fate of populations but fuel contemporary evolution (evolution over humanly observable time-scales). Here we ask if such evolution is sufficient to make the difference between population extinction and persistence. 2 To answer this question requires a shift from the usual focus on trait evolution to the emergent ‘eco-evolutionary’ dynamics that arise through interactions of evolution, its fitness consequences and population abundance. 3 By combining theory, models and insights from empirical studies of contemporary evolution, we provide an assessment of three contexts: persistence of populations in situ, persistence of colonising populations, and persistence under gene flow and in metapopulations. 4 Contemporary evolution can likely rescue some, but not all, populations facing environmental change. Populations may fail partly because of the demographic cost of selection. 5 Contemporary evolution that initiates positive population growth, such as selective founding processes, may create a ‘persistence vortex’ that overcomes the problems of small populations. 6 Complex, even shifting, relationships between gene flow and adaptation may aid the persistence of subpopulations as well as the persistence and expansion of metapopulations. 7 An eco-evolutionary perspective suggests that we expand our focus beyond the acute problems of threatened populations and growing invasions, to consider how contemporary evolutionary mechanics contribute to such problems in the first place or affect their resolution.

Starch Fossils and the Domestication and Dispersal of Chili Peppers (Capsicum spp. L.) in the Americas

Abstract: Chili peppers (Capsicum spp.) are widely cultivated food plants that arose in the Americas and are now incorporated into cuisines worldwide. Here, we report a genus-specific starch morphotype that provides a means to identify chili peppers from archaeological contexts and trace both their domestication and dispersal. These starch microfossils have been found at seven sites dating from 6000 years before present to European contact and ranging from the Bahamas to southern Peru. The starch grain assemblages demonstrate that maize and chilies occurred together as an ancient and widespread Neotropical plant food complex that predates pottery in some regions.

The Differential Effect of Men and Women Entrepreneurs’ Human Capital and Networking on Growth Expectancies in Bulgaria:

Abstract: Based on expectancy theory and social psychology perspectives, this study looks at the differential effects of men and women entrepreneurs’ human capital and networking on their growth expectancies in the context of a transitional economy. Survey data from men and women new venture owners in Bulgaria (n = 544) suggest that growth expectancy among men is significantly and positively associated with outside advice achieved through networking. Among women entrepreneurs, growth expectancy is significantly and positively associated with perceived benefits from prior experience. A Chow test for coefficient differences reveals that the determinants of growth expectancy for women entrepreneurs are significantly different than those for men, rendering support for perspectives from social psychology, which suggest that women have different socialization experiences and, as a result, conceive of their new venture growth differently. Implications for managerial practice and public policy are discussed.

Evolutionary responses to climate change.

Abstract: In their paper Malcolm et al. (2006) use climate-war-ming scenarios to estimate up to 43% loss of specieswithin biodiversity hotspots. This prediction is based ona climate-envelope approach that assumes the distribu-tion, and hence extinction, probability of every speciesis predicted by climate alone. We agree that global cli-mate change will have substantial effects on biodiversityand will cause extinctions (Crowley & North 1990; Hoff-man et al. 2003). Nevertheless, the climate-envelope ap-proach presents a distorted estimate of extinction prob-abilities. Most notably, the approach does not considerevolution and therefore implicitly assumes that speciescannot evolve in response to changing climate.Current empirical evidence suggests that evolution isresponsive to climate variation and occurs at rates thatmake it relevant for consideration of current and pro-jected responses to climate change. For a wide varietyof taxa, thermal performance varies within species’ geo-graphic ranges, suggesting both genetic variation in criti-cal traits and localized evolution in response to climatevariation (Conover & Schultz 1995; Gilchrist et al. 2004).Many examples of contemporary evolution in responseto climate change exist. In less than 40 years, populationsof the frog

Perceived discrimination as worldview threat or worldview confirmation: implications for self-esteem.

Abstract: In 3 studies, the authors tested the hypothesis that discrimination targets' worldview moderates the impact of perceived discrimination on self-esteem among devalued groups. In Study 1, perceiving discrimination against the ingroup was negatively associated with self-esteem among Latino Americans who endorsed a meritocracy worldview (e.g., believed that individuals of any group can get ahead in America and that success stems from hard work) but was positively associated with self-esteem among those who rejected this worldview. Study 2 showed that exposure to discrimination against their ingroup (vs. a non-self-relevant group) led to lower self-esteem, greater feelings of personal vulnerability, and ingroup blame among Latino Americans who endorsed a meritocracy worldview but to higher self-esteem and decreased ingroup blame among Latino Americans who rejected it. Study 3 showed that compared with women informed that prejudice against their ingroup is pervasive, women informed that prejudice against their ingroup is rare had higher self-esteem if they endorsed a meritocracy worldview but lower self-esteem if they rejected this worldview. Findings support the idea that perceiving discrimination against one's ingroup threatens the worldview of individuals who believe that status in society is earned but confirms the worldview of individuals who do not.

Assessment of skill and portability in regional marine biogeochemical models : Role of multiple planktonic groups

Abstract: [1] Application of biogeochemical models to the study of marine ecosystems is pervasive, yet objective quantification of these models’ performance is rare. Here, 12 lower trophic level models of varying complexity are objectively assessed in two distinct regions (equatorial Pacific and Arabian Sea). Each model was run within an identical onedimensional physical framework. A consistent variational adjoint implementation assimilating chlorophyll-a, nitrate, export, and primary productivity was applied and the same metrics were used to assess model skill. Experiments were performed in which data were assimilated from each site individually and from both sites simultaneously. A cross-validation experiment was also conducted whereby data were assimilated from one site and the resulting optimal parameters were used to generate a simulation for the second site. When a single pelagic regime is considered, the simplest models fit the data as well as those with multiple phytoplankton functional groups. However, those with multiple phytoplankton functional groups produced lower misfits when the models are required to simulate both regimes using identical parameter values. The cross-validation experiments revealed that as long as only a few key biogeochemical parameters were optimized, the models with greater phytoplankton complexity were generally more portable. Furthermore, models with multiple zooplankton compartments did not necessarily outperform models with single zooplankton compartments, even when zooplankton biomass data are assimilated. Finally, even when different models produced similar least squares model-data misfits, they often did so via very different element flow pathways, highlighting the need for more comprehensive data sets that uniquely constrain these pathways.

The Kelp Highway Hypothesis: Marine Ecology, the Coastal Migration Theory, and the Peopling of the Americas

Abstract: In this article, a collaborative effort between archaeologists and marine ecologists, we discuss the role kelp forest ecosystems may have played in facilitating the movement of maritime peoples from Asia to the Americas near the end of the Pleistocene. Growing in cool nearshore waters along rocky coastlines, kelp forests offer some of the most productive habitats on earth, with high primary productivity, magnified secondary productivity, and three-dimensional habitat supporting a diverse array of marine organisms. Today, extensive kelp forests are found around the North Pacific from Japan to Baja California. After a break in the tropics—where nearshore mangrove forests and coral reefs are highly productive—kelp forests are also found along the Andean Coast of South America. These Pacific Rim kelp forests support or shelter a wealth of shellfish, fish, marine mammals, seabirds, and seaweeds, resources heavily used historically by coastal peoples. By about 16,000 years ago, the North Pacific Coast ...

Geodynamics of the southeastern Tibetan Plateau from seismic anisotropy and geodesy

Abstract: Ongoing plate convergence between India and Eurasia provides a natural laboratory for studying the dynamics of continental collision, a fi rst-order process in the evolution of continents, regional climate, and natural hazards. In southeastern Tibet, the fast directions of seismic anisotropy determined using shear-wave splitting analysis correlate with the surfi cial geology including major sutures and shear zones and with the surface strain derived from the global positioning system velocity fi eld. These observations are consistent with a clockwise rotation of material around the eastern Himalayan syntaxis and suggest coherent distributed lithospheric deformation beneath much of southeastern Tibet. At the southeastern edge of the Tibetan Plateau we observe a sharp transition in mantle anisotropy with a change in fast directions to a consistent E-W direction and a clockwise rotation of the surface velocity, surface strain fi eld, and fault network toward Burma. Around the eastern Himalayan syntaxis, the coincidence between structural crustal features, surface strain, and mantle anisotropy suggests that the deformation in the lithosphere is mechanically coupled across the crust-mantle interface and that the lower crust is suffi ciently strong to transmit stress. At the southeastern margin of the plateau in Yunnan province, a change in orientation between mantle anisotropy and surface strain suggests a change in the relationship between crustal and mantle deformation. Lateral variations in boundary conditions and rheological properties of the lithosphere play an important role in the geodynamic evolution of the Himalayan orogen and Tibetan Plateau and require the development of three-dimensional models that incorporate lateral heterogeneity.

Influence of Gender on Parental Socialization of Children's Sadness Regulation

Abstract: Mothers' (N = 60) and fathers' (N = 53) perceptions of and desire for change in their 6- to 11-year-old daughters' (N = 59) and sons' (N = 54) sadness regulation behaviors (i.e., inhibition, dysregulation, coping) were examined in addition to parental responses to children's hypothetical sadness displays. Results of multivariate analyses of variance and regression analyses suggest that parental perceptions of and desired change in children's sadness behavior differ as a function of parent gender, child gender and child age (younger (grades 1, 2), older (grades 4, 5)), and predict the likelihood of contingent responses to children's sadness behavior. Overall, fathers reported being likely to respond to sadness with minimization whereas mothers reported being likely to respond with expressive encouragement and problem-focused strategies. These parent-reported socialization response tendencies, however, were more fully explained by the interaction between perceptions of children's sadness regulation behaviors and satisfaction with these behaviors. These findings highlight the need to include parent gender and parental cognitions as important variables in emotion socialization research.

Alkalilimnicola ehrlichii sp. nov., a novel, arsenite-oxidizing haloalkaliphilic gammaproteobacterium capable of chemoautotrophic or heterotrophic growth with nitrate or oxygen as the electron acceptor.

Abstract: A facultative chemoautotrophic bacterium, strain MLHE-1(T), was isolated from Mono Lake, an alkaline hypersaline soda lake in California, USA. Cells of strain MLHE-1(T) were Gram-negative, short motile rods that grew with inorganic electron donors (arsenite, hydrogen, sulfide or thiosulfate) coupled with the reduction of nitrate to nitrite. No aerobic growth was attained with arsenite or sulfide, but hydrogen sustained both aerobic and anaerobic growth. No growth occurred when nitrite or nitrous oxide was substituted for nitrate. Heterotrophic growth was observed under aerobic and anaerobic (nitrate) conditions. Cells of strain MLHE-1(T) could oxidize but not grow on CO, while CH(4) neither supported growth nor was it oxidized. When grown chemoautotrophically, strain MLHE-1(T) assimilated inorganic carbon via the Calvin-Benson-Bassham reductive pentose phosphate pathway, with the activity of ribulose 1,5-bisphosphate carboxylase (RuBisCO) functioning optimally at 0.1 M NaCl and at pH 7.3. Strain MLHE-1(T) grew over broad ranges of pH (7.3-10.0; optimum, 9.3), salinity (15-190 g l(-1); optimum 30 g l(-1)) and temperature (13-40 degrees C; optimum, 30 degrees C). Phylogenetic analysis of 16S rRNA gene sequences placed strain MLHE-1(T) in the class Gammaproteobacteria (family Ectothiorhodospiraceae) and most closely related to Alkalispirillum mobile (98.5 %) and Alkalilimnicola halodurans (98.6 %), although none of these three haloalkaliphilic micro-organisms were capable of photoautotrophic growth and only strain MLHE-1(T) was able to oxidize As(III). On the basis of physiological characteristics and DNA-DNA hybridization data, it is suggested that strain MLHE-1(T) represents a novel species within the genus Alkalilimnicola for which the name Alkalilimnicola ehrlichii is proposed. The type strain is MLHE-1(T) (=DSM 17681(T)=ATCC BAA-1101(T)). Aspects of the annotated full genome of Alkalilimnicola ehrlichii are discussed in the light of its physiology.

Plasma Antioxidant Capacity Changes Following a Meal as a Measure of the Ability of a Food to Alter In Vivo Antioxidant Status

Abstract: Objective: Determine 1) if consumption of a meal of different fruits or berries increases plasma hydrophilic (H-) or lipophilic (L-) antioxidant capacity (AOC) measured as Oxygen Radical Absorbance Capacity (ORACFL); 2) if including macronutrients in the meal alters postprandial changes in AOC; and 3) if preliminary recommendations can be developed for antioxidant intake.Methods: Changes in plasma AOC following consumption of a single meal of berries/fruits (blueberry, dried plum, dried plum juice, grape, cherry, kiwifruit and strawberry) were studied in 5 clinical trials with 6–10 subjects per experiment. In two studies with blueberry or grape, additional macronutrients (carbohydrate, fat, protein) were included in the control and treatment meals. Blood samples collected before and after the meal were analyzed for AOC.Results: Consumption of dried plums or dried plum juice did not alter either the H- or L-AOC area under the curve (AUC). Consumption of blueberry in 2 studies and of mixed grape powder [12....

The calpains: modular designs and functional diversity

Abstract: The calpain family is named for the calcium dependence of the papain-like, thiol protease activity of the well-studied ubiquitous vertebrate enzymes calpain-1 (μ-calpain) and calpain-2 (m-calpain). Proteins showing sequence relatedness to the catalytic core domains of these enzymes are included in this ancient and diverse eukaryotic protein family. Calpains are examples of highly modular organization, with several varieties of amino-terminal or carboxy-terminal modules flanking a conserved core. Acquisition of the penta-EF-hand module involved in calcium binding (and the formation of heterodimers for some calpains) seems to be a relatively late event in calpain evolution. Several alternative mechanisms for binding calcium and associating with membranes/phospholipids are found throughout the family. The gene family is expanded in mammals, trypanosomes and ciliates, with up to 26 members in Tetrahymena, for example; in striking contrast to this, only a single calpain gene is present in many other protozoa and in plants. The many isoforms of calpain and their multiple splice variants complicate the discussion and analysis of the family, and challenge researchers to ascertain the relationships between calpain gene sequences, protein isoforms and their distinct or overlapping functions. In mammals and plants it is clear that a calpain plays an essential role in development. There is increasing evidence that ubiquitous calpains participate in a variety of signal transduction pathways and function in important cellular processes of life and death. In contrast to relatively promiscuous degradative proteases, calpains cleave only a restricted set of protein substrates and use complex substrate-recognition mechanisms, involving primary and secondary structural features of target proteins. The detailed physiological significance of both proteolytically active calpains and those lacking key catalytic residues requires further study.

Design principles for Brownian molecular machines: how to swim in molasses and walk in a hurricane.

Abstract: Protein molecular motors—perfected over the course of millions of years of evolution—play an essential role in moving and assembling biological structures. Recently chemists have been able to synthesize molecules that emulate in part the remarkable capabilities of these biomolecular motors (for extensive reviews see the recent papers: E. R. Kay, D. A. Leigh and F. Zerbetto, Angew. Chem., Int. Ed., 2006, 46, 72–191; W. R. Browne and B. L. Feringa, Nat. Nanotechnol., 2006, 1, 25–35; M. N. Chatterjee, E. R. Kay and D. A. Leigh, J. Am. Chem. Soc., 2006, 128, 4058–4073; G. S. Kottas, L. I. Clarke, D. Horinek and J. Michl, Chem. Rev., 2005, 105, 1281–1376; M. A. Garcia-Garibay, Proc. Natl. Acad. Sci., U. S. A., 2005, 102, 10771–10776)). Like their biological counterparts, many of these synthetic machines function in an environment where viscous forces dominate inertia—to move they must “swim in molasses”. Further, the thermal noise power exchanged reversibly between the motor and its environment is many orders of magnitude greater than the power provided by the chemical fuel to drive directed motion. One might think that moving in a specific direction would be as difficult as walking in a hurricane. Yet biomolecular motors (and increasingly, synthetic motors) move and accomplish their function with almost deterministic precision. In this Perspective we will investigate the physical principles that govern nanoscale systems at the single molecule level and how these principles can be useful in designing synthetic molecular machines.

Building Trust in Natural Resource Management Within Local Communities: A Case Study of the Midewin National Tallgrass Prairie

Abstract: Communities neighboring federally pro- tected natural areas regularly weigh the costs and benefits of the administering agency's programs and policies. While most agencies integrate public opinion into decision making, efforts to standardize and formalize public involvement have left many local communities feeling marginalized, spurring acrimony and opposition. A significant body of research has examined barriers to effective public participation as well as strategies for relationship building in planning processes; many of which point to trust as a key factor. Trust is especially tenuous in local communities. This paper explores perceptions of trust, expectations for management, as well as constraints to building trust. In-depth interviews were conducted with 21 commu- nity members and USDA Forest Service personnel at the Midewin National Tallgrass Prairie in northeastern Illinois. The interviews revealed that trust is perceived as important to effective management. Distinct expec- tations for management outcomes and processes emerged, including the values, knowledge, and capac- ity demonstrated in management decisions and actions and opportunities provided for communication, collab- oration, and cooperation within the agency-community relationship. The case study identified several con- straints to building trust, including competing values, knowledge gaps, limited community engagement, and staff turnover.

Climate change and moving species: furthering the debate on assisted colonization.

Abstract: With global climate change looming large in the public psyche, the recent paper by McLachlan et al. (2007) and its popular accompaniment (Fox 2007) are timely indeed. Of course some conservation biologists will not wish to think about the prospect of actively moving species that are threatened with extinction by climate change. For them this would be almost analogous to handing out placebos in the midst of an epidemic and worse yet, these placebos may have serious unintended consequences if translocated species become invasive. They will probably argue that we should focus almost exclusively on two central roles for conservation biology: (1) facilitating natural range shifts by redoubling efforts to maintain or restore large-scale connectivity (Hunter et al. 1988; Hannah et al. 2002) and (2) working with our fellow environmental professionals to avoid carbon-management solutions that will have unacceptable consequences for biodiversity (e.g., by directing biofuel production away from sites that would involve the conversion of native vegetation into fuel farms; Cook & Beyea 2000). These two roles will be very demanding, but I believe we should allocate a small portion of our attention to the issue of assisted colonization that McLachlan et al. (2007) have brought to the fore. McLachlan et al. propose framing the debate around two considerations—perception of risk and confidence in ecological understanding—that can be construed to generate an axis or continuum from scientists who would strongly support assisted colonization to those who would oppose it. I think it is useful to advance this exercise by considering three issues that can also be construed as continua: species that are more or less acceptable to translocate, sites that are more or less acceptable for receiving translocations, and projects that are more or less acceptable because of their socioeconomic ramifications and feasibility. I have used the term assisted colonization in contrast to assisted migration used by McLachlan et al.