Kayri Havens

Assisted migration: part of an integrated conservation strategy

As part of a group of conservation biologists working to develop a framework for the appropriate use of assisted migration, we read with great interest the recent Opinion article in TREE by Ricciardi and Simberloff [1]. Although we agree with several of their points, we believe that assisted migration could become an important part of integrated conservation strategies. Ricciardi and Simberloff focus on extreme examples of species translocations, including the ‘re-wilding’ of North America with African mammals and other examples of intercontinental and long distance transport of species.

Ex Situ Plant Conservation and Beyond

Abstract In recent years, the mission of many botanic gardens and arboreta has expanded from a traditional focus on developing a horticultural collection to one that includes taking a proactive role in plant conservation. To use their limited resources more effectively, many gardens are seeking ways to quantify their contributions to conservation efforts, both as a self-assessment tool to improve their effectiveness and as a way to give an explicit accounting of activities to donors and funding agencies. We suggest many ways gardens can measure the success of their conservation programs, and present results from a survey conducted to assess current conservation activities at botanic gardens.

Seed Sourcing for Restoration in an Era of Climate Change

ABSTRACT: Proper sourcing of seed for ecological restoration has never been straightforward, and it is becoming even more challenging and complex as the climate changes. For decades, restoration practitioners have subscribed to the “local is best” tenet, even if the definition of “local” was often widely divergent between projects. However, given our increasing ability to characterize habitats, and rapid climate change, we can no longer assume that locally sourced seeds are always the best or even an appropriate option. We discuss how plants are responding to changing climates through plasticity, adaptation, and migration, and how this may influence seed sourcing decisions. We recommend focusing on developing adequate supplies of “workhorse” species, undertaking more focused collections in both “bad” years and “bad” sites to maximize the potential to be able to adapt to extreme conditions as well as overall genetic diversity, and increasing seed storage capacity to ensure we have seed available as we continue to conduct research to determine how best to deploy it in a changing climate.

Arabidopsis thaliana: A New Test Species for Phytotoxic Bioassays

Lettuce seeds (Lactuca sativa L.) and other crop species are often used in phytotoxic bioassays that are designed to detect allelochemicals. The seeds of these species are considered ideal because they are readily available, germinate rapidly and uniformly, and are routinely used in laboratories around the world. Despite their common use, however, the seeds of these species are often not as sensitive or responsive to some phytotoxic chemicals as are the seeds of other species. While searching for a more sensitive test species for phytotoxic bioassays, the Columbia ecotype of Arabidopsis thaliana exhibited greater sensitivity to seven potent allelochemicals than did lettuce seeds, which, in some cases, did not respond at all to those substances. Sensitivity satisfies one of the criteria for selecting a test species for bioassays. We now report on the results of our study and offer additional reasons for using A. thaliana seeds.

Implementing Invasive Screening Procedures: The Chicago Botanic Garden Model1

Abstract Because of the severe environmental and economic costs of invasive plants, organizations and individuals importing plants into new regions should evaluate plant introductions for their potential to escape cultivation and invade natural areas. Current weed risk assessment (WRA) models used in the United States are not precise enough to provide a definitive answer for woody taxa and have not yet been developed specifically for annuals and herbaceous perennials. We tested several WRA models to determine their effectiveness for the Chicago region and selected one for use in the invasive screening protocol at Chicago Botanic Garden that includes the use of regional invasive plant lists, commercial availability, WRA, and on-site evaluation of plants. By using this integrated approach, we have implemented a screening protocol that has increased our confidence in predicting invasiveness, is time and space efficient, and is user-friendly. Additional index words: Alien plants, botanic garden, Chicago, evaluation, horticulture, invasive plants, weed risk assessment. Abbreviations: CBG, Chicago Botanic Garden; NISC, National Invasive Species Council; WRA, weed risk assessment.

SAMPLING FOR EFFECTIVE EX SITU PLANT CONSERVATION

Sampling a whole flora or any significant subset for ex situ conservation purposes is a complex, long-term proposition. Thus, it is important to consider what constitutes an adequate sample not only for all taxa as a whole but also for each taxon individually as well as how to strategically schedule collection over time. There are five basic sampling questions: from which species to collect, from how many and which populations, from how many and which individuals, how many and what kind of propagules to collect, and, finally, at what point is the desired sample size too great for a population to bear in one year? There is no single correct sampling strategy or protocol. Each situation must be evaluated in the context of the particular purposes, goals, and uses for which the collection is being made as well as the nature of the sampling universe, the manner in which the samples will be stored and maintained, the period of time they will be stored, and whether the wild-collected samples are to be used directly or whether their numbers will be increased by agricultural growouts. Purposes include providing a long-term “insurance policy” against extinction in the wild and, in the near to medium term, supplying native plant material for small- to large-scale restoration purposes. The term “sampling universe” refers to the target taxa of interest: it could be the entire seed plant flora of Taiwan or particular subsets, such as endemics, higher-elevation plants, ecologically important taxa, rare plants, and so on. Plants with orthodox seeds are much easier to work with and are more economically stored as dried, frozen seeds in a seed bank than either plants with recalcitrant seeds or taxa maintained as growing plants.

Will the Use of Less Fecund Cultivars Reduce the Invasiveness of Perennial Plants

Many invasive species were originally introduced for horticultural purposes, and several continue to be profitable for the green (nursery, horticulture, and landscape) industry. Recently, some plant suppliers have marketed less fecund cultivars of several invasive species, including glossy buckthorn (Frangula alnus), burning bush (Euonymus alatus), and Japanese barberry (Berberis thunbergii), as “safe” alternatives to invasive relatives. We use published matrix population models to simulate the effect of reducing fecundity on the population growth rates of invasive species. We show that large changes in fecundity result in relatively small changes to the population growth rates of long-lived species, which suggests that less fecund cultivars may still provide an invasive threat. Furthermore, many cultivars are clonal selections, and if crossed with other cultivars or selfed, they produce offspring with traits and fecundities that do not resemble the parent plant. On the basis of these two lines of evidence, we suggest that only female sterile cultivars that cannot reproduce asexually should be considered “safe” and noninvasive. Marketing less fecund cultivars as “safe” is premature at this time, and further research is necessary to determine the potential invasiveness of different cultivars.

Ex Situ Germination Responses of Midwestern USA Prairie Species to Plant-derived Smoke

ABSTRACT Tallgrass prairie species often require a period of cold stratification to break seed dormancy, but not all species germinate when this occurs. Fire, which has historically played an important role in defining the prairie landscape, may also play some role in breaking dormancy by producing a variety of biologically active smoke substances. The role of smoke as a germination cue was investigated in this study, during which the ex situ germination of 37 prairie species was measured in response to aerosol smoke treatment. Overall, one third of the species responded positively, while others were either inhibited or exhibited no response at all. Smoke may therefore play a more significant role in maintaining the composition and structure of tallgrass prairie communities than was previously realized.

Getting Plant Conservation Right (or Not): The Case of the United States

Effective plant conservation includes addressing basic needs such as information about species distribution and rarity; research, management, education, and training capacity to mitigate threats facing threatened species; policy and funding to support continued capacity and conservation; and, ultimately, a public that understands and supports the importance of plants and the need for their conservation. Coordination of plant conservation efforts is also needed to ensure that resources and expertise are used in a strategic, efficient, and effective manner. We argue that no country is currently getting plant conservation right; plants are becoming increasingly rare around the world. Plants are often not fully protected by policy, their conservation is underfunded, and their importance is underappreciated. However, some countries have progressed further than others. Here we outline areas where the United States is strong and highlight components that need work to meet the country’s plant conservation needs.

The influence of contemporary and historic landscape features on the genetic structure of the sand dune endemic, Cirsium pitcheri (Asteraceae)

Narrow endemics are at risk from climate change because of their restricted habitat preferences, lower colonization ability and dispersal distances. Landscape genetics combines new tools and analyses that allow us to test how both past and present landscape features have facilitated or hindered previous range expansion and local migration patterns, and thereby identifying potential limitations to future range shifts. We have compared current and historic habitat corridors in Cirsium pitcheri, an endemic of the linear dune ecosystem of the Great Lakes, to determine the relative contributions of contemporary migration and post-glacial range expansion on genetic structure. We used seven microsatellite loci to characterize the genetic structure for 24 populations of Cirsium pitcheri, spanning the center to periphery of the range. We tested genetic distance against different measures of geographic distance and landscape permeability, based on contemporary and historic landscape features. We found moderate genetic structure (Fst=0.14), and a north–south pattern to the distribution of genetic diversity and inbreeding, with northern populations having the highest diversity and lowest levels of inbreeding. High allelic diversity, small average pairwise distances and mixed genetic clusters identified in Structure suggest that populations in the center of the range represent the point of entry to the Lake Michigan and a refugium of diversity for this species. A strong association between genetic distances and lake-level changes suggests that historic lake fluctuations best explain the broad geographic patterns, and sandy habitat best explains local patterns of movement.