Jeremie B. Fant

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.

Chloroplast evidence for the multiple origins of the hybrid Potamogeton × sudermanicus Hagstr.

A previous study of the sole British population of Potamogeton×sudermanicusHagstr. supported the putative origin of this taxon as a result of hybridization between Potamogeton acutifoliusLink and Potamogeton berchtoldiiFieber. In this study, the TrnL (UAA) chloroplast region was used to identify the maternal parent of this hybrid. It was found that the two multi-enzyme phenotypes identified in previous studies had different chloroplast sequences. These sequences were shown to correspond to those of the two parental species. This is further evidence that this population is the result of at least two hybridization events and that the plants attributed to this hybrid are not an aneuploid of either of the parental species.

Isozyme evidence of the parental origin and possible fertility of the hybrid Potamogeton×fluitans Roth

Abstract. The hybrid Potamogeton×fluitans Roth is thought to have resulted from hybridization between P. lucens L. and P. natans L. This hybrid has only been recorded at a few locations in the British Isles. At most of these sites the number of individuals found have been quite low. The one exception to this being a population in the Moors River, Dorset and South Hampshire, England, where a substantially larger population exists. Using seven different enzyme systems, this study provided support for the putative parental origin of this hybrid. In addition, the population in the Moors River was shown to contain numerous multi-locus phenotypes suggesting that these individuals may be partially fertile and may backcross to one of its parental species, or alternatively undergo selfing or crossing to produce an F2 generation.

Influences of landscape and pollinators on population genetic structure: Examples from three Penstemon (Plantaginaceae) species in the Great Basin

PREMISE OF THE STUDY Despite rapid growth in the field of landscape genetics, our understanding of how landscape features interact with life history traits to influence population genetic structure in plant species remains limited. Here, we identify population genetic divergence in three species of Penstemon (Plantaginaceae) similarly distributed throughout the Great Basin region of the western United States but with different pollination syndromes (bee and hummingbird). The Great Basins mountainous landscape provides an ideal setting to compare the interaction of landscape and dispersal ability in isolating populations of different species. METHODS We used eight highly polymorphic microsatellite loci to identify neutral population genetic structure between populations within and among mountain ranges for eight populations of P. deustus, 10 populations of P. pachyphyllus, and 10 populations of P. rostriflorus. We applied traditional population genetics approaches as well as spatial and landscape genetics approaches to infer genetic structure and discontinuities among populations. KEY RESULTS All three species had significant genetic structure and exhibited isolation by distance, ranging from high structure and low inferred gene flow in the bee-pollinated species P. deustus (F(ST) = 0.1330, R(ST) = 0.4076, seven genetic clusters identified) and P. pachyphyllus (F(ST) = 0.1896, R(ST) = 0.2531, four genetic clusters identified) to much lower structure and higher inferred gene flow in the hummingbird-pollinated P. rostriflorus (F(ST) = 0.0638, R(ST) = 0.1116, three genetic clusters identified). CONCLUSIONS These three Penstemon species have significant yet strikingly different patterns of population genetic structure, findings consistent with different interactions between landscape features and the dispersal capabilities of their pollinators.

Isozyme evidence for the origin of Potamogeton × sudermanicus as a hybrid between P. acutifolius and P. berchtoldii

Abstract Potamogeton × sudermanicus Hagstr. has been interpreted morphologically as a hybrid between P. acutifolius Link and P. berchtoldii Fieber. Both parents belong to section Graminifolii where hybrids appear to be less frequent than in other sections. This reputed hybrid has been recorded at only a few sites in Europe and at a single locality in Britain. Using seven different isozyme systems it was shown that all the bands present within the British population of the hybrid were found in P. acutifolius or P. berchtoldii , supporting the putative origin of this taxon. In addition, the identification of two multi-enzyme phenotypes implies that this hybrid has arisen at least twice at this site.

Ecology of native vs. introduced Phragmites australis (common reed) in Chicago-area wetlands.

Rapid spread of Phragmites australis (common reed) in North American wetlands is widely attributed to cryptic invasion by an introduced lineage. However, in the Midwestern U.S., the native subspecies (subsp. americanus) may also exhibit rapid expansion. Where both lineages occur, wetland managers are sometimes unsure whether they should limit management activities to the introduced lineage or control both. We conducted field studies to contrast the ecology of native and introduced Phragmites by pairing patches of each with native reference vegetation. We measured each lineage’s association with environmental conditions, their growth metrics (stem heights, stem densities, and plant cover), and their invasiveness as indicated by the diversity and composition of associated plant communities. Introduced Phragmites exhibited more robust growth than the native, and its growth was more positively correlated with increases in soil nutrient availability and salinity. Areas with introduced Phragmites had lower plant diversity and altered species composition relative to reference vegetation. We did not observe similar evidence of invasiveness in native Phragmites. We encourage wetland managers to differentiate populations by lineage and, unless there is compelling evidence to do otherwise, restrict control efforts to the introduced lineage.

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.

Local Topography Shapes Fine-Scale Spatial Genetic Structure in the Arkansas Valley Evening Primrose, Oenothera harringtonii (Onagraceae)

Identifying factors that shape the spatial distribution of genetic variation is crucial to understanding many population- and landscape-level processes. In this study, we explore fine-scale spatial genetic structure in Oenothera harringtonii (Onagraceae), an insect-pollinated, gravity-dispersed herb endemic to the grasslands of south-central and southeastern Colorado, USA. We genotyped 315 individuals with 11 microsatellite markers and utilized a combination of spatial autocorrelation analyses and landscape genetic models to relate life history traits and landscape features to dispersal processes. Spatial genetic structure was consistent with theoretical expectations of isolation by distance, but this pattern was weak (Sp = 0.00374). Anisotropic analyses indicated that spatial genetic structure was markedly directional, in this case consistent with increased dispersal along prominent slopes. Landscape genetic models subsequently confirmed that spatial genetic variation was significantly influenced by local topographic heterogeneity, specifically that geographic distance, elevation and aspect were important predictors of spatial genetic structure. Among these variables, geographic distance was ~68% more important than elevation in describing spatial genetic variation, and elevation was ~42% more important than aspect after removing the effect of geographic distance. From these results, we infer a mechanism of hydrochorous seed dispersal along major drainages aided by seasonal monsoon rains. Our findings suggest that landscape features may shape microevolutionary processes at much finer spatial scales than typically considered, and stress the importance of considering how particular dispersal vectors are influenced by their environmental context.

Hybridization between the threatened plant, Lespedeza leptostachya Englem. and its co-occurring congener Lespedeza capitata Michx.: morphological and molecular evidence

Natural hybridization is common in the genus Lespedeza. No hybrids between Lespedeza leptostachya Englem. and Lespedeza capitata Michx. are formally recognized in any of the current floras, however observations in the field suggest that hybridization might occur in many of their shared habitats. Putative hybrids were compared to L. leptostachya and L. capitata using morphological measurements and screened for the presence of species-specific trnL-F gene region (cpDNA) and the ITS gene region (nrDNA). A discriminate analysis of 10 morphological measurements identified the hybrids as intermediate to both parents with two PCA axes explaining 99% of the variation between taxa. The presence of hybrids was confirmed by genetic markers with individuals morphologically identified as hybrids having cpDNA trnL-F genotypes identical to L. leptostachya and the ITS (nrDNA) phenotypes in most cases contain the ITS genotype of both parents, however, some putative hybrid individuals contained the ITS genotype of only one parents. Those individuals with L. leptostachya ITS and trnL-F could be a case of misclassification, but the presence of both L. capitata ITS genotypes and L. leptostachyatrnL-F genotypes suggest segregation has occurred, which may result from either selfing or backcrossing.

Assessing Potential Seed Transfer Zones for Five Forb Species from the Great Basin Floristic Region, USA

ABSTRACT: For plant species important in ecological restoration, seed transfer zones have been developed to maximize the probability that sown seed will germinate, establish, persist, and reproduce without negatively impacting the genetic composition of remnant plant populations. However, empirically based seed transfer zones have not been developed for most species. In their absence, maps based on ecological or climatic variables have been suggested as proxies. In the United States, these maps typically include the Environmental Protection Agencys Levels III and IV Ecoregion maps and the US Forest Services Provisional Seed Zones. Maps of different spatial scales represent a compromise between economic and ecological considerations; those that delineate larger seed transfer zones are less costly to implement but impose more risk of poor adaptation to local conditions. To test the relative suitability of each map in delineating seed transfer zones, we conducted common garden experiments using five forb species found throughout the Great Basin and measured variation in traits thought to influence plant performance. We distinguished between environmentally and genetically controlled variation in measured traits and assessed how well this variation was explained by different candidate seed transfer zones. We found significant, population-level variation in all species for most measured traits. All tested seed transfer zones significantly explained some of this variation, but the proportion explained generally decreased with increasing zone size. Results suggest the intersection of Provisional Seed Zones and Level III Ecoregions was the best proxy for formal seed transfer zones developed based on common garden studies. This spatial scale captured 80% of the variation among source populations on average, and represents a viable compromise between ecological and economic considerations.