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Baobab ( Adansonia digitata ) is a long-lived tree endemic to Africa with economic, ecological, and cultural importance, yet its genomic features are underexplored. Here, we report a chromosome-level reference genome anchored to 42 chromosomes for A. digitata , alongside draft assemblies for a sibling tree, two trees from distinct locations in Africa, and A. za from Madagascar. The baobab genome is uniquely rich in DNA transposons, which make up 33%, while LTR retrotransposons account for 10%. A. digitata experienced whole genome multiplication (WGM) around 30 million years ago (MYA), followed by a second WGM event 3–11 MYA, likely linked to autotetraploidy. Resequencing of 25 trees identify three subpopulations, with gene flow across West Africa distinct from East Africa. Gene enrichment and fixation index ( Fst ) analyses show baobab retained multiple circadian, flowering, and light-responsive genes, which likely support longevity through the UV RESISTANCE LOCUS 8 (UVR8) pathway. In sum, we provide genomic resources and insights for baobab breeding and conservation. Baobab is a long-lived tree that holds great economic, ecological, and cultural value. Here, the authors report haploid chromosome-level reference genome of Adansonia digitata and draft assemblies for a sibling tree, two trees from distinct locations in Africa, and a related species from Madagascar.

Reticulate evolution (RE), involving hybridization and related processes, generates network-like rather than strictly bifurcating relationships among lineages and can obscure phylogenetic relationships. Detecting ancient hybridization is particularly challenging, as genomic signals may erode over time. The Malvatheca clade (Malvaceae), marked by multiple paleopolyploidy events since it’s estimated origin 66 my, offers a useful model for examining RE. Its three subfamilies—Bombacoideae (with high chromosome numbers, mostly trees), Malvoideae (lower chromosome numbers, mostly herbs), and the recently described Matisioideae—show unresolved relationships, with several taxa of uncertain placement. We conducted a phylogenomic analysis of 69 Malvatheca species via complete plastomes, 35S rDNA cistrons, nuclear low copy genes and comparative repeatome data. Most of the datasets consistently resolved four clades: (I) Bombacoideae, (II) Malvoideae, (III) Matisioideae, and (IV) a heterogeneous assemblage including representatives of Malvoideae, Matisioideae and several incertae sedis taxa. Chromosome numbers were negatively correlated with repeatome diversity: Bombacoideae presented higher counts but lower repeat diversity, possibly reflecting slower repeat evolution associated with woody growth forms. In contrast, clades III and IV showed marked heterogeneity in both chromosome number and repeat composition, which is consistent with a reticulate origin. Overall, our results show evidence of ancient hybridization and polyploidy in shaping Malvatheca evolution. These results highlight that reticulation and genome dynamics, rather than taxonomic boundaries alone, are central to understanding the diversification of Malvatheca.

Premise We present approaches used to generate long‐read Nanopore sequencing reads for the Liliales and demonstrate how modifications to standard protocols directly impact read length and total output. The goal is to help those interested in generating long‐read sequencing data determine which steps may be necessary for optimizing output and results. Methods Four species of Calochortus (Liliaceae) were sequenced. Modifications made to sodium dodecyl sulfate (SDS) extractions and cleanup protocols included grinding with a mortar and pestle, using cut or wide‐bore tips, chloroform cleaning, bead cleaning, eliminating short fragments, and using highly purified DNA. Results Steps taken to maximize read length can decrease overall output. Notably, the number of pores in a flow cell is correlated with the overall output, yet we did not see an association between the pore number and the read length or the number of reads produced. Discussion Many factors contribute to the overall success of a Nanopore sequencing run. We showed the direct impact that several modifications to the DNA extraction and cleaning steps have on the total sequencing output, read size, and number of reads generated. We show a tradeoff between read length and the number of reads and, to a lesser extent, the total sequencing output, all of which are important factors for successful de novo genome assembly.

Climate variability and resilience remain gaps in tree research, challenged by the interacting factors in climate change, long-term resilience and the influence of evolutionary legacy effects. In a multidisciplinary approach using 90-year (1930–2020) climate-growth data, we investigated the dynamics of climate variability on growth and resilience of the tropical African baobab (Adansonia digitata) at the range edge in climate-variable, southeast Africa. The main driver of climate variability, ENSO (El Niño-Southern Oscillation), triggered 83% of droughts exacerbated by positive Indian Ocean Dipole (pIOD) events. Growth over 90 years was positively correlated with maximum temperature and increased after the 1976–1977 Global Warming Shift. The influence of warming was compromised by climate variability and extreme events. Although growth is a measure of adaptive capacity, accelerated growth over the past 20 years contrasted with dehydration, canopy dieback and a novel Didymella pathogen. Resilience was contingent on high genetic diversity (polyploidy and heterozygosity) and Neotropical legacy effects of stem water storage and longevity trade-offs of low growth and recruitment, and also reproduction in the region. The evolution of resprouting in disturbed, fire-prone ecosystems and bark regeneration increased recovery from disturbance. As resource opportunists, baobabs adopted a fast-slow survival strategy. Rainfall and warming enhanced growth while low and variable rainfall favoured a conservative, low growth-higher survival strategy. Low rainfall, climate extremes and topography increased mortality risk. Mortality was higher at lower elevations on site and regionally. Low growth may conserve the baobab in climate warming but the southern hemisphere tropics is one of two identified global hotspots with amplified hot years. The heightened disturbance predicted from increased climate variability, hot droughts and landfalling tropical cyclones magnifies mortality risk for “Africa’s favourite tree.”

Botanical gardens are addressing urgent biodiversity issues through plant-based capacities including botanical research and data-sharing, conservation horticulture, ecological restoration, seed banking, and more. The Missouri Botanical Garden initiative BiodiverseCity St. Louis, led by the Garden’s sustainability division, adds broad community engagement to this mix. This work includes public and professional education, the demonstration and promotion of ecological landscaping and Green Infrastructure practices, citizen science programs, and coordinating communications for a regional network of partner organizations focused on biodiversity. Diverse activity engages businesses, local governments, elementary and secondary (K-12) schools, colleges, and community groups. Community biodiversity work at the Garden is informed by an institutional core of scientific rigor, provides opportunity for internal collaborations, and aligns with global strategies for plant conservation—to ground impactful local work. Missouri Botanical Garden’s experience offers a model for public gardens: leveraging modes of community engagement, in concert with diverse institutional strengths, to address biodiversity needs.

Baobabs (Adansonia) are a cohesive group of tropical trees with a disjunct distribution in Australia, Madagascar, and continental Africa, and diverse flowers associated with two pollination modes. We used custom-targeted sequence capture in conjunction with new and existing phylogenetic comparative methods to explore the evolution of floral traits and pollination systems while allowing for reticulate evolution. Our analyses suggest that relationships in Adansonia are confounded by reticulation, with network inference methods supporting at least one reticulation event. The best supported hypothesis involves introgression between Adansonia rubrostipa and core Longitubae, both of which are hawkmoth pollinated with yellow/red flowers, but there is also some support for introgression between the African lineage and Malagasy Brevitubae, which are both mammal-pollinated with white flowers. New comparative methods for phylogenetic networks were developed that allow maximum-likelihood inference of ancestral states and were applied to study the apparent homoplasy in floral biology and pollination mode seen in Adansonia. This analysis supports a role for introgressive hybridization in morphological evolution even in a clade with highly divergent and geographically widespread species. Our new comparative methods for discrete traits on species networks are implemented in the software PhyloNetworks.

We assessed the validity of a recently described baobab species Adansonia kilima that was suggested to be a diploid occurring in both eastern and southern Africa at high elevations within the range of the well-known tetraploid species A. digitata. We used a combination of phylogenetic analyses and statistical comparisons of various traits (e.g., flowers, stomata, pollen, chromosome counts) to test for the presence of two continental African baobab species. Ordination of the floral features of 133 herbarium specimens from across the natural range of A. digitata, including the putative type of A. kilima and other Tanzanian accessions as previously assigned A. kilima, revealed no distinct clusters of specimens. Likewise, stomatal size and density varied greatly across the specimens examined, with no clear bimodal pattern and no obvious association with altitude. The type specimen of A. kilima was found to have a chromosome number of 2n ≈ 166, showing it to be a tetraploid, like A. digitata. Phylogenetic analysis of the ITS region showed little resolution within the African baobab clade and a lack of distinction between the A. kilima type and A. digitata regional accessions. Among the 13 haplotypes detected, no distinct haplotype representing A. kilima was identified. Based on the data at hand we conclude that A. kilima is neither cytologically nor morphologically distinct and is here reduced to synonymy with A. digitata.

Baobabs have long fascinated botanists and travelers alike. Anyone who has had the pleasure of witnessing these majestic trees, their peculiar growth form, remarkable flowers, and colorful folklore is likely to want to know more about them. In my research I have sought to address some of the many scientific questions remaining unanswered to this day: What are the origins of this genus given their interesting geographic distribution? How and when did they come to occupy two separate continents, Africa and Australia? Why is it one species widespread across all of continental Africa yet 6 species are found endemic to Madagascar? What drivers have led to their remarkable diversity on Madagascar? What is the evolutionary history of their pollination systems and floral diversity? Do patterns of morphological variation in Africa correspond to cryptic species? My dissertation research addressed these questions via a diversity of approaches that today make up the field of plant systematics, including molecular phylogenetics, pollination biology, and chemical ecology. Briefly, my chapters addressed the following: 1) We conducted phylogenomic analyses of hundreds of nuclear loci, finding evidence that the three lineages (Africa, Australia, Madagascar) diverged from one another rapidly and that there was a second dispersal to Madagascar, which introduced some genes from the African species into the ancestor of two Malagasy species, and may have facilitated the parallel evolution of mammal pollination in Africa and Madagascar. 2) We sampled the six species of baobabs endemic to Madagascar across their ranges to assess the validity of traditional species designations. Our results show strong geographic signals within and between species, and we were able to identify several instances of introgression between morphological species. Our data suggests that northern populations of the most widespread Malagasy species A. za should probably be recognized as their own species (A. bozy), which corresponds to historical variety designations. 3) We compiled a comprehensive understanding of the pollination ecology of the African baobab, A. digitata. We confirmed that the African baobab is self-incompatible, mostly likely by late-acting self-incompatibility. At least in populations in South Africa, although this species has a classic bat-pollination syndrome, hawkmoths are serving as the primary pollinator. Assessing floral scent profiles we find evidence of geographic variation in floral scent between West, East, and Southern Africa. 4) We assessed the validity of the recently described diploid African species, A. kilima. Based on ordination of floral features, phylogenetics and chromosome counts, we conclude that A. kilima is not distinct from the tetraploid A. digitata.

PREMISE Measuring plant productivity is critical to understanding complex community interactions. Many traditional methods for estimating productivity, such as direct measurements of biomass and cover, are resource intensive, and remote sensing techniques are emerging as viable alternatives. METHODS We explore drone‐based remote sensing tools to estimate productivity in a tallgrass prairie restoration experiment and evaluate their ability to predict direct measures of productivity. We apply these various productivity measures to trace the evolution of plant productivity and the traits underlying it. RESULTS The correlation between remote sensing data and direct measurements of productivity varies depending on vegetation diversity, but the volume of vegetation estimated from drone‐based photogrammetry is among the best predictors of biomass and cover regardless of community composition. The commonly used normalized difference vegetation index (NDVI) is a less accurate predictor of biomass and cover than other equally accessible vegetation indices. We found that the traits most strongly correlated with productivity have lower phylogenetic signal, reflecting the fact that high productivity is convergent across the phylogeny of prairie species. This history of trait convergence connects phylogenetic diversity to plant community assembly and succession. DISCUSSION Our study demonstrates (1) the importance of considering phylogenetic diversity when setting management goals in a threatened North American grassland ecosystem and (2) the utility of remote sensing as a complement to ground measurements of grassland productivity for both applied and fundamental questions.