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The Ramsey lab combines molecular analyses, garden studies, and field experiments to address questions about ecological adaptation and speciation in flowering plants.  We are particularly interested in polyploidy -- whole genome duplication -- and its broader implications for plant ecology and systematics.  As is traditional in our area of research, we work on non-model plant species selected on the basis of natural history, taxonomic interest, and amenability to experimental manipulation.  Our work has recently been supported by a South Dakota Biomedical Research Infrastructure Network Faculty Fellowship (NIH IMBRE; 2016-2019), the National Science Foundation (CAREER award; 2010-2016), South Dakota BOR Competitive Research Grants (2015-2016 and 2018-2019), and Prairie Biotic Inc. small grants (2018-2020).

In addition to its basic research, the Ramsey lab leverages skills in field sampling and plant identification to conduct conservation-focused activities.  These efforts have recently focused on questions about forest stand structure and tree recruitment in remnant old-growth of western New York, as well as taxonomic diversity, spatial clustering and health assessment of wild and cultivated trees on the Black Hills State campus (Tree ATLAS project, which can be read about here).

WILD YARROW.  Achillea borealis (Asteraceae) is a complex of ecological races occurring in diverse climatic and edaphic conditions throughout North America.  The species is notorious for its taxonomic complexity, incidence of polyploidy, and high degree of local adaptation.  Our studies have three foci.  (1) Characterization of population genetic structure and historical relationships in the circumpolar Achillea millefolium aggregate, using DNA sequence data (cpDNA, nrDNA, low copy nuclear genes) and molecular markers (AFLPs, microsatellites). (2) Evaluation of autopolyploidy as mechanism of adaptive divergence and incipient speciation, based on experimental comparisons of naturally-occurring polyploids (“established” polyploid populations) vs. neopolyploids (spontaneous polyploid mutants screened from progenitor populations).  (3) Analysis of the phenotypic and genetic basis of ecological adaptation within established polyploid lineages, inferred from physiological measurements, classical genetic methods (segregation of traits in experimental hybrid pedigrees), and candidate genes approaches.

ENGLISH IVY.  Ivy (Hedera spp, Araliaceae) is a polyploid complex of woody vines native to Eurasia but cultivated worldwide for its attractive foliage, hardiness, and ease of propagation.  Ivy is a serious pest in forests along the Atlantic Seaboard and Pacific Coast of North America.  Despite its horticultural value and ecological impacts, the systematics and invasion biology of ivies are poorly understood.  Our work involves four components.  (1) Resolution of Hedera phylogeny based on DNA sequences (cpDNA, rDNA, low copy nuclear genes) and molecular markers (microsatellites).  (2) Analysis of the taxonomic composition and genetic structure of invasive populations.  (3) Evaluation of the relationship between polyploidy and invasiveness, inferred from field surveys and common garden experiments with sister species H. helix (diploid) and H. hibernica (tetraploid). (4) Characterization of fruit dispersal and recruitment in naturalized populations, and use of sterile triploids (F1 H. helix x H. hibernica) to reduce invasion.

CREOSOTE BUSH.  Larrea tridentata (Zygophyllaceae) is a dominant shrub across the Mojave, Sonoran and Chihuahuan deserts of the southwestern U.S. and northern Mexico.  This taxonomic species is comprised of diploid, tetraploid, and hexaploid populations that replace each other along a longitudinal gradient.  We have worked on three projects in this system.  (1) Characterization of phylogeography and cytogeography of L. tridentata in comparison to its South American relatives, based on DNA sequence data (cpDNA, nrDNA), molecular markers (AFLPs), and flow cytometry.  (2)  Measurement of pre-zygotic barriers (habitat isolation, phenological isolation) and post-zygotic barriers (triploid block, sterility) isolating diploid and autopolyploid races of L. tridentata, as inferred from field observations and experiments.  (3) Analysis of gene flow and morphological boundaries of creosote cytotype populations, and hence their status as biological and taxonomic species.  You can learn more about creosote bush research from Rob Laport at Rhodes College.

Tetraploid wild yarrow of the Black Hills and Great Plains, as studied on an elevational transect in western South Dakota. (A) Vegetation ordination based on presence-absence of plant species in 16 study sites. Cluster analysis indicates divergence of low vs. high elevation sites occupied by vars. lanulosa (maroon) vs. pacifica (blue) and alpicola (lavender).  (B) Icons showing mean stem/leaf size and flower number for yarrows measured in natural  populations.  Large yarrows occur only on mesic, mid-elevation montane grasslands and deciduous forests; small yarrows occur at xeric sites at both low and high elevations (shortgrass prairies, mountain summits).  Across the transect, mean leaf and stem sizes vary ~10- and 3-fold, respectively, while flower head number varies ~6-fold.  Experiments indicate a strong genetic component for these phenotypic differences, based on correlations  of size and phenology traits measured on populations in the field vs. common garden.

Species, cytotype, and genotype composition of invasive ivy populations in the USA.  (A) Leaf morphology of wild Hedera species, as grown in a common garden. Taxonomic identification in naturalized populations is complicated by the many species in the genus, phenotypic plasticity, and occurrence of both ornamental and wild-type individuals.  (B) Partial haplotype table based on cpDNA (five noncoding regions).  The vast majority of North American invasives have haplotypes identical to European taxa (diploid H. helix and its sister species, autotetraploid H. hibernica) and distinct from Mediterranean and Asian species. In garden experiments, 2x H. helix and 4x H. hibernica differ in leaf/stem size, anatomy, and transpiration; the two species may be predisposed to invade different climate zones.  (C) Microsatellite alleles recovered in samples from one small area of dense growth in forest near Seattle.  Ivy patches are frequently comprised of multiple genotypes, highlighting the role of avian frugivory and sexual recruitment for invasion dynamics of this long-lived clonal plant.

Phylogeography and incipient speciation in North American creosote bush.  (A) Spatial distribution of diploid, tetraploid and hexaploid populations (icons) in relation to traditionally-defined floristic boundaries in North American warm deserts (colored backgrounds).  Cytotype distributions correspond roughly to the Chihuahuan (2x), Sonoran (4x) and Mojave (6x) deserts, with cytotype co-occurrence in some areas.  (B) Creosote bush phylogeny inferred from nrDNA and cpDNA.  The North American creosote bush is monophyletic, closely-related to South American L. divaricata, and underwent rapid demographic expansion following its long-distance, intercontinental dispersal  (C) Flowering phenology (number of open flowers) through the growing season in a contact zone (4x-6x, in California).  Habitat and phenological isolation supplement postzygotic barriers between ploidy levels, so there is limited opportunity for intercytotype gene flow.

FOREST ECOLOGY & CONSERVATION.  In addition to its evolution-focused work, the Ramsey lab conducts conservation-focused research in New York’s lakeplain forests.  These efforts have four major foci.  (1) Identification of old-growth stands using GIS, historical aerial photography, and tree coring.  (2) Analysis of canopy tree structure and coarse woody debris loads in old-growth vs. second-growth stands.  (3) Characterization of understory plant communities and their association with physiographic and soil features.  (4)  Evaluation of exotic plant invasion and its association with land-use history.  To complement these research projects, the Ramsey lab sponsored community outreach efforts focused on Rochester-area old-growth.  To learn more, please visit our Rochester Forests and South Campus webpages.

Additional information about Ramsey lab research may be found on the Publications and Photos & News pages, as well as websites run by Rob Laport and Adam Green.

(A) Old-growth forest stand in Durand-Eastman Co. Park, north of Rochester.  Located on a steeply sloping hill, this 3.5 hectare site was never deforested or converted to agricultural production, unlike most other parts of the park.  (B) Total canopy tree basal area, and contributions of so-called sapling, pole, mature, and large size classes, at eight old-growth sites across Monroe Co.  Most stands we surveyed have structural indices that meet or exceed thresholds for old-growth designation developed in more remote areas of eastern forest.  Taxonomic and structural composition of the stands, however, varies from site-to-site.  (C) Relationship of stand size and species diversity in remnant old-growth.  While there is a clear statistical association, small stands harbor substantial vascular plant diversity.

Hybridization of prairie and wavy leaf thistles (Cirsium canescens, C. undulatum) in Thunder Basin, Wyoming.  (A) Flower heads that illustrate variation in pigmentation traits across a natural hybrid zone; parental types are shown in the lower left (canescens) and upper right (undulatum).  (B) Correlation in pigmentation (0-3 intensity scale) for different flower parts (petals, anther, style, stigma, joint) in ~300 randomly-selected plants.  There is general correspondence in pigmentation of flower parts in a plant, however, introgression is evidenced by some individuals (white stigmas in otherwise dark purple flower heads, etc.).  (C) Statistical analyses of flower and leaf traits in the aforementioned 300 individuals.  Plants are separated into two morphometric clusters by multivariate approaches, despite substantial trait value overlap evident in univariate histograms.

NATIVE THISTLES. True thistles (Circium spp., Asteraceae) of the Great Plains and Rocky Mountains are taxonomically complex, ecologically diverse, and -- perhaps due to their numerous and very sharp protrusions! -- poorly studied.  The Ramsey lab recently began work on hybridization in thistles, which co-occur and interbreed in multiple pairwise combinations across the Missouri River Plateau.  Our efforts, still in early stages, focus on geographic locations of hybrid zones, morphological and ecological characterization of parental and mixed populations,  and pollination biology.