Every Friday during the academic years, plant aficionados from EEB gathering for informal discussion on diverse aspects of plant biology. We meet at 12.15 PM and for ± one hour. This fall 2020 semester the gathering will be virtual. We are inviting speakers from across the continent to share a 15 minutes talk (such as from the 2020 meeting of the Botanical Society of America) and participate in a Q&A session.
If you would like to be on the mailing list e-mail Bernard Goffinet
Brian Enquist (University of Arizona): The commonness of rarity: Global and future distribution of rarity across land plants. See publication. Abstract: Background/Question/Methods A key feature of life’s diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Rare species are orders of magnitude more likely to go extinct, making it puzzling how so many rare species can be maintained. Understanding rarity and the maintenance of rare species is also central to conservation biology and to understanding current and future changes in biodiversity due to global change. Despite this importance, we know unexpectedly little about the causes of commonness and rarity and their maintenance at a global scale Here, we use a global botanical database of unprecedented coverage to (i) assess global patterns of plant rarity, (ii) test several proposed hypotheses underlying the generation and persistence of rare species, (iii) identify regions that harbor hotspots of rare species and explore the drivers of these spatial patterns, and (iv) assess how current patterns of human impact and future climate change scenarios may affect plant diversity via impacts on rare species. For all known land plants (Embryophyta), we have compiled a global database of standardized botanical observation records—the integrated Botanical Information and Ecology Network (BIEN); http://bien.nceas.ucsb.edu/bien/. Together, these data constitute more than 200 million observations of plant species occurrences. Results/Conclusions: A large fraction, ~36.5% of Earth’s ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results have important implications for conservation in the face of climate change and other human impacts. If ~36% of species are rare and threatened, then ~158,000 plant species are at risk of extinction. In addition, our analyses show that rapid rates of current human impact and projected future climate change appear to disproportionately affect regions that harbor most of these rare species, whereas the rare species likely have been in relatively more stable climates through their evolutionary history. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth’s plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.
Uzay Sezen (Smithsonian Environmental Research Center): Comparative transcriptomics of tropical woody plants reveals convergent expression among lianas.
Ya Min (Harvard): “I do not need a superman when I have a superwoman”. Abstract: The initial phase of making a flower from the floral meristem (FM) is an art of coordination between different developmental processes. This includes the proper initiation and patterning of the organ primordia, maintaining the size of the FM during organ initiation, termination of the FM activity to ensure the correct number of organ production, and the overlay of the floral organ identity programs onto the primordia so that the boundaries of gene expression domains synchronize precisely with the physical boundaries between the primordia. For a long time, the initiation of primordia and the establishment of organ identity have been studied separately, and only a few genes are thought to bridge these two processes, including the C2H2 transcription factor SUPERMAN (SUP). In Arabidopsis thaliana, SUP defines the boundary of the B-class gene expression domain and regulates the physical boundary and FM termination through auxin biosynthesis. In this study, we investigated the function of the SUP ortholog in Aquilegia coerulea (AqSUP). AqSUP is expressed in a very restricted window during early floral development, in a ring of cells that will become the boundary between the staminode and carpel primordia. AqSUP also appears to define the boundary of the expression domains of B-class genes, likely both AqAP3-1 and AqAP3-2. Silencing of AqSUP expression, however, appears to result in the retraction of B-class gene expressions, which resulted in more carpels in the flower, rather than what was observed in A. thaliana that the B-class gene expression domain invaded into the center of the flower, leading to the production of more stamens. Further investigation into the sequence divergence in the coding and regulatory regions of the genes may cast light on the functional conservation and divergence of SUP in A. thaliana and A. coerulea.
|Oct. 2||Niki Patel (EEB, UCONN): Patterns and taxonomic consequences of autopolyploidy in mosses.|
Cynthia Jones (EEB, UCONN): The shapes of Botany. Abstract: I will use multiple meanings of “shape” to discuss “seeing” plants and why seeing diverse plant shapes is important from the perspective of individuals, educators, and institutions. I will speak briefly about my thoughts on why the world needs botany as a discipline more than ever, and I will argue that the pandemic of 2020 presents us, as botanists, an extraordinary opportunity to showcase our work and to shape the future of how plants are viewed in STEAM education. I will also offer ideas for possible next steps that we as individuals, scientists and educators can take with respect to communicating the importance of plants to non-botanical administrators and to the public.
|Oct. 16||Henry Frye (EEB, UCONN): Spectral diversity and plant biodiversity prediction in South Africa’s Greater Cape Floristic Region. Abstract: As plant biodiversity loss progresses, there is an urgent need to monitor the spatial distribution of multiple axes of biodiversity. Remote sensing is a critical tool in this endeavor. One of the major approaches in detecting biodiversity is based on the hypothesis that the spectral variation of plant communities is a proxy, or surrogate, of multiple dimensions of biodiversity. We investigated the generality of “surrogacy” by measuring spectral, species, functional, and phylogenetic diversity for 1,267 plots across the Greater Cape Floristic Region; a hyper-diverse region composed of several biomes and two adjacent biodiversity hotspots. Spectral diversity was calculated based on a community-weighted approach where leaf reflectance spectra were weighted by the percent cover of species present at a site. We found that spectral diversity was a robust predictor of all three biodiversity dimensions serving as a proof-of-concept that spectral diversity can be a suitable proxy of biodiversity across a hyper-diverse biogeographic region. While our results support the broader generality of the surrogacy relationships, they also varied based on dominant biome and subregions within the GCFR suggesting that underlying community differences can affect these relationships. We propose a way to view surrogacy relationships from an ecological perspective in order to provide a framework for studying the spectral properties of communities in the future.|
Sarah B. Carey or here (University of Florida): Cryptic evolutionary strata in an ancient UV sex chromosome system. Abstract: Sex chromosomes occur in diverse organisms and are complex, dynamic regions of the genome. A defining characteristic of sex chromosomes is suppressed recombination, which is widely believed to cause degeneration, including an accumulation of deleterious mutations and potentially gene loss. Degeneration in turn may drive the compensatory gain of new genes through translocations or the expansion of heterochromatin. In a few well-studied cases, multiple such events form blocks of genes that became sex-linked at the same time, called evolutionary strata. However, other processes involving sexual antagonistic selection also may drive these fusions. Distinguishing between these alternatives is difficult in most old sex chromosome systems, because the homologous genes necessary for evolutionary analysis are degenerate or absent. Here we sequenced and assembled chromosome-scale genomes for a male and female of the moss Ceratodon purpureus and use these data to examine sex chromosome evolution in mosses. The C. purpureus UV sex chromosomes comprise ~30% of the ~360 Megabase (Mb) genome and harbor ~12% of the gene content. We used synteny-based analyses to identify collinear chromosomes within C. purpureus (i.e., resulting from duplications) and between the hermaphroditic species Physcomitrium patens, which diverged over 200 million years ago. We show the moss genome is comprised of seven remarkably stable ancestral chromosomal elements. One stark exception are the C. purpureus sex chromosomes, which lack any synteny. Instead, we used a phylogenomic approach to reconstruct the history of the modern C. purpureus sex chromosomes. We find the moss sex chromosomes evolved at least 300 million years ago and have expanded from two distinct chromosomal fusions. We found the absence of evolutionary strata from these events is caused by rapid rearrangements within the non-recombining portions of the UV sex chromosomes. Contrary to other ancient sex chromosomes, we found only limited evidence of degeneration of C. purpureus UV sex chromosomes, but rather independent, parallel recruitment of genes in the liverwort Marchantia polymorpha suggests sexual antagonism is likely to have driven these translocations. Together these results highlight the role of the sex chromosomes in driving karyotypic change, and point to a major role for genomic conflict in this change.
|Oct. 30||Dr. Sohyun Park (Plant Science & Landscape Architecture, UCONN): Plants in Landscape Architecture.|
|Nov. 6||Emily Sessa (Department of Biology, University of Florida): Patterns and People in African Plant Systematics. Abstract: The continent of Africa is home to 55 countries, perhaps as many as 3000 languages, and nearly 50,000 plant species. The ecoregions of the continent range from deserts, mountains, and extensive bushlands and savanna, to tropical rainforests and wetlands, and include the world’s largest inland delta (the Okavango) as well as one of the planet’s richest botanical biodiversity hotspots, the Cape Floristic Region. This talk will explore the continent’s botanical diversity, including the Cape Floristic Region, Eastern Arc Mountains, Cameroon Volcanic Line, and Ethiopian “church forests”, and will describe several of the unique patterns that characterize botanical diversity in Africa, including the “odd man out” pattern and continental-scale disjunctions both within Africa, such as the “Rand flora” pattern of arid plant disjunctions, and between Africa and other continents, primarily South America. I will also discuss my own research on the evolution of the African fern flora, as well as other current studies on topics of interest in African plant systematics, highlighting work that is being led by scientists based on the continent.|
|Nov. 13||Nicolas Magain (University of Liège, Belgium)|