Browsing by Author "Pizza, Riley"

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    Dataset supporting Domestication during restoration: Unintentional selection during eight generations of wild seed propagation reduces herkogamy, dichogamy, and heterozygosity in Clarkia pulchella
    (2024-08-29) Etterson, Julie; Fliehr, Paige; Pizza, Riley; Gross, Briana; jetterso@d.umn.edu; Etterson, Julie; Etterson & Gross labs, University of Minnesota Duluth
    Seed production on native seed farms has increased to meet the rising demand for plant material for restoration. However, few studies have tested whether cultivation of wild populations imposes selection and elicits evolutionary change that aligns with process of crop domestication, and those that have report mixed results. Here we show that eight generations of propagation resulted in floral and genomic change in Clarkia pulchella Pursh (Onagraceae) compared to the wild source populations. Both herkogamy and dichogamy i.e., the physical and temporal separation of male and female flower parts, respectively) were significantly decreased between cultivated and wild populations. To determine if these changes resulted in the loss of heterozygosity and overall levels of genetic diversity, we examined >6,500 SNPs derived from RAD-seq data from 46 wild and 47 farmed samples. We show that mean and median heterozygosity of the farmed samples was 81.7% and 61.9% less than that of the wild samples, respectively. This was strongly driven by a loss of alleles, resulting in more than double the number of SNPs with a heterozygosity of zero. This reduction in genetic diversity was significant whether the farmed samples were compared to the pooled wild samples or to a single population. This suggests cultivation of wild populations may be having similar effects to the early stages of crop domestication. We discuss these results in the context of native seed farming and measures that can retain the genetic integrity of wild population during the process of seed increase for restoration. (Genomic data stored in GenBank)
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    The Effects Of Cultivation On Seed For Restoration
    (2020-05) Pizza, Riley
    Native seed for restoration is in high demand, but due to widespread habitat degradation it is unlikely that we will be able to sustainably harvest enough seed from wild populations to meet this need. In recent decades, propagation farming of native species for seed increase has emerged to address this resource gap. ¬However, few studies have tested whether this process also causes genetic degradation and loss of plant fitness which may ultimately undermine restoration success, especially under stressful conditions. To test this, we grew the eighth generation of farm-propagated Clarkia pulchella Pursh (Onagraceae) alongside seeds from the wild source populations that established the farm fields under two watering treatments. Overall, farmed seeds were 4.1% larger and had 4% greater germination compared to wild-collected seed. Additionally, farmed plants were 22% taller at flowering and had 20% larger stigmas after accounting for differences in initial seed size. Despite plants from both seed sources decreasing growth under the low-water treatment, farmed plants had 37% lower survival to the end of the experiment. Moreover, farmed plants under the high-water treatment had 80% lower fitness than wild plants due to the 1.3% greater weekly mortality and a 3-fold reduction in flowering likelihood. Together, these data suggest that bottlenecks during initial sampling and/or unintentional selection during propagation severely reduced fitness, potentially due to increased levels of inbreeding depression. To avoid degradation of seed quality during commercial propagation of native species, attention should focus on bolstering the genetic diversity of the sampled population by obtaining seed from many maternal plants from multiple large wild populations, and limiting the number of sequential generations of cultivation prior to genetic augmentation, as is supported in some seed certification programs.
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    How to talk about climate change: A discussion for students
    (2019) Gomez, Maria; Pizza, Riley; Spear, Marissa; Robinson, Eva; Bucar, Leslie; Gebhard, Steve