Developmental Selection in the Common Monkeyflower (Mimulus guttatus)
Fundamental differences in the processes of plant reproduction and development compared to animals has implications of the processes of mutation accumulation and evolution. In animals a germline is set aside early in development so any genetic modifications that occur during growth are not heritable. In plants the same set of cells that are responsible for vegetative growth also produce flowers and gametes. Many thousands of cell division occur during vegetative growth. Since mutations occr with every cell division, plants have substantially greater potential for mutation accumulation than animals. In spite of this greater potential, mutation accumulation rates across generations are similar for plants and animals. Our goal is to resolve this paradox.
Selection During Reproduction - Plants have a unique life cycle that allows natural selection to affect the adult stage, as well as the earliest stages of reproduction—when pollen delivers genetic material and seeds begin to develop. This project explores how plants may improve the quality of their offspring by favoring certain genetic traits during these stages of reproduction. By influencing which traits are passed on to subsequent generations, these processes may help eliminate harmful mutations and promote characteristics that increase survival under challenging environmental conditions. We are using genomic approaches to nderstand how selection works at these critical early points in development, which will shed light on how plants adapt to changing environments and maintain the genetic diversity necessary for long-term evolutionary success.
Clonal Evolution During Vegetative Growth - We are using genomic approaches to evaluate the effects of cell lineage selection during stem growth on the process of clonal evolution and adaption in plants. This work is supplemented by analyses of the potential for gametophytic selection during pollen growth and selective ovule abortion after fertilization to filter deleterious mutations. This research has broader implications as clonal evolution occurs in a wide range of microbial species and is the fundamental cause of mammalian cancer.
Selection During Reproduction - Plants have a unique life cycle that allows natural selection to affect the adult stage, as well as the earliest stages of reproduction—when pollen delivers genetic material and seeds begin to develop. This project explores how plants may improve the quality of their offspring by favoring certain genetic traits during these stages of reproduction. By influencing which traits are passed on to subsequent generations, these processes may help eliminate harmful mutations and promote characteristics that increase survival under challenging environmental conditions. We are using genomic approaches to nderstand how selection works at these critical early points in development, which will shed light on how plants adapt to changing environments and maintain the genetic diversity necessary for long-term evolutionary success.
Clonal Evolution During Vegetative Growth - We are using genomic approaches to evaluate the effects of cell lineage selection during stem growth on the process of clonal evolution and adaption in plants. This work is supplemented by analyses of the potential for gametophytic selection during pollen growth and selective ovule abortion after fertilization to filter deleterious mutations. This research has broader implications as clonal evolution occurs in a wide range of microbial species and is the fundamental cause of mammalian cancer.
Novel selection strategies to bolster climate resilience in restoration planting stock
Methods to encourage the rapid adaptation of heat- and drought-resistant native plants have already been implemented in the Pacific Northwest, primarily through assisted migration (AM). AM is unfortunately fraught with risk due to the complexity of natural systems - it is not adequate to source simply from populations found in drier or warmer climates. There are 17 bioclimatic variables linked to plant fitness beyond mean annual temperature and mean annual precipitation; conditions like the range and regularity of climatic events can be just as critical for the survival of a population. Assisted Gene Flow (AGF) can eliminate the hazards associated with AM by admixing genetic material from populations with desired traits. Our work focuses on crossing cold-hardy local grasses (Elymus elymoides, Poa secunda and Pseudoroegneria spicata) from eastern Oregon with the same species from more arid habitat in Nevada, then evaluating fitness of said crosses through genomic and phenotypic analyses. Autogamy Selection (AS) scenarios, through which selfing plants amplify beneficial mutations during somatic cell division along the apical meristem of a single plant, are also being tested alongside and in combination with AGF treatments.
The Ten Thousand Oaks Project
The Ten Thousand Oaks Project is a collective effort led by Portland State University to assess the genetic and demographic health of the Oregon White Oak across its range (Quercus garryana var. garryana). We are integrating ecological, genetic, geographic, climate, and paleontological information using bioinformatics, phylogeography, landscape genetics, ecological niche modeling, and Geographic Information Systems (GIS) analyses. Our goals are: 1) To understand the origins of oak populations in the Pacific Northwest, 2) identify those that are most susceptible to decline due to climate change, and 3) locate source populations for genetic remediation of vulnerable populations. Accomplishing these goals will require extensive demographic and genetic sampling of Oregon oak populations throughout it’s range from southern British Columbia to coastal regions of Northern California. Management plans implemented from the knowledge gained will help ensure the long-term preservation of Oregon white oak populations across the Pacific Northwest.
Our approach recognizes the importance of understanding sustainability of oak stands through demographic analyses, and the importance of local adaptive genetic variation for long-term persistence. Rather than replacing local genotypes by assisted migration, we plan to combine local adaptive variation with genotypes adapted to more arid conditions through admixture (within-species hybridization). We plan to accomplish this by obtaining admixed acorns through controlled pollination of regional trees with pollen from populations occurring in more arid conditions. Hybrid and pure acorns from arid and local sources will be tested in trial plantings and monitored for several years to assess survival rates prior to engaging in more major remediation efforts.
Our approach recognizes the importance of understanding sustainability of oak stands through demographic analyses, and the importance of local adaptive genetic variation for long-term persistence. Rather than replacing local genotypes by assisted migration, we plan to combine local adaptive variation with genotypes adapted to more arid conditions through admixture (within-species hybridization). We plan to accomplish this by obtaining admixed acorns through controlled pollination of regional trees with pollen from populations occurring in more arid conditions. Hybrid and pure acorns from arid and local sources will be tested in trial plantings and monitored for several years to assess survival rates prior to engaging in more major remediation efforts.
Invasion biology of slender false brome (Brachypodium sylvaticum)
False brome was first introduced into Oregon in the early part of the last century to test its potential for rangeland improvement, but B. sylvaticum has become an aggressive invader during the last 15 years. Accessions apparently crossed so the invasive plants now spreading across Oregon forests are recombinant products of hybridization. Introductions in Corvallis and Eugene retain unique marker signatures, but similar sets of native accessions contributed to the hybrid genotypes that are now spreading from each introduction location (Rosenthal et al. 2008). The false brome invasion is in early stages of range expansion and transition from a benign introduced species to an aggressive invader. Near introduction sites in Corvallis, many hectares of forest understory are dominated by monocultures of false brome that exclude native species and prevent the regeneration of canopy trees. Towards the leading edge of the expanding range in Oregon, populations are sparse and plant densities are low, with some notable exceptions.
A summary of our work is available here: Cruzan, M.B. 2019. How to Make a Weed–The Saga of the Slender False Brome Invasion in the North American West and Lessons for the Future. BioSceince 69:496-507. (https://doi.org/10.1093/biosci/biz051)
A summary of our work is available here: Cruzan, M.B. 2019. How to Make a Weed–The Saga of the Slender False Brome Invasion in the North American West and Lessons for the Future. BioSceince 69:496-507. (https://doi.org/10.1093/biosci/biz051)
