Evaluating the factors that drive patterns of population differentiation in plants is critical for understanding several biological processes such as local adaptation and incipient speciation. Previous studies have given conflicting results regarding the significance of pollination mode, seed dispersal mode, mating system, growth form and latitudinal region in shaping patterns of genetic structure, as estimated by FST values, and no study to date has tested their relative importance together across a broad scale. Here, we assembled a 337‐species data set for seed plants from publications with data on FST from nuclear markers and species traits, including variables pertaining to the sampling scheme of each study. We used species traits, while accounting for sampling variables, to perform phylogenetic multiple regressions. Results demonstrated that FST values were higher for tropical, mixed‐mating, non‐woody species pollinated by small insects, indicating greater population differentiation, and lower for temperate, outcrossing trees pollinated by wind. Among the factors we tested, latitudinal region explained the largest portion of variance, followed by pollination mode, mating system and growth form, while seed dispersal mode did not significantly relate to FST. Our analyses provide the most robust and comprehensive evaluation to date of the main ecological factors predicted to drive population differentiation in seed plants, with important implications for understanding the basis of their genetic divergence. Our study supports previous findings showing greater population differentiation in tropical regions and is the first that we are aware of to robustly demonstrate greater population differentiation in species pollinated by small insects.

The circadian clock is a transcriptional/translational feedback loop that drives the rhythmic expression of downstream mRNAs. Termed “clock-controlled genes,” these molecular outputs of the circadian clock orchestrate cellular, metabolic, and behavioral rhythms. As part of our on-going work to characterize key upstream regulators of circadian mRNA expression, we have identified a novel clock-controlled gene in Drosophila melanogaster, Achilles (Achl), which is rhythmic at the mRNA level in the brain and which represses expression of anti-microbial peptides in the immune system. Achilles knock-down in neurons dramatically elevates expression of crucial immune response genes, including IM1 (Immune induced molecule 1), Mtk (Metchnikowin), and Drs (Drosomysin). As a result, flies with knocked-down Achilles expression are resistant to bacterial challenges. Meanwhile, no significant change in core clock gene expression and locomotor activity is observed, suggesting that Achilles influences rhythmic mRNA outputs rather than directly regulating the core timekeeping mechanism. Notably, Achilles knock-down in the absence of immune challenge significantly diminishes the fly’s overall lifespan, indicating a behavioral or metabolic cost of constitutively activating this pathway. Together, our data demonstrate that (1) Achilles is a novel clock-controlled gene that (2) regulates the immune system, and (3) participates in signaling from neurons to immunological tissues.

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Animal pollinators directly affect plant gene flow by transferring pollen grains between individuals. Pollinators with restricted mobility are predicted to limit gene flow within and among populations, whereas pollinators that fly longer distances are likely to promote genetic cohesion. These predictions, however, remain poorly tested. We examined population genetic structure and fine‐scale spatial genetic structure (FSGS) in six perennial understory angiosperms in Andean cloud forests of northwestern Ecuador. Species belong to three families (Gesneriaceae, Melastomataceae, and Rubiaceae), and within each family we paired one insect‐pollinated with one hummingbird‐pollinated species, predicting that insect‐pollinated species have greater population differentiation (as quantified with the FST statistic) and stronger FSGS (as quantified with the SP statistic) than hummingbird‐pollinated species. We confirmed putative pollinators through a literature review and fieldwork, and inferred population genetic parameters with a genome‐wide genotyping approach. In two of the three species pairs, insect‐pollinated species had much greater (>2‐fold) population‐level genetic differentiation and correspondingly steeper declines in fine‐scale genetic relatedness. In the Gesneriaceae pair, however, FST and SP values were similar between species and to those of the other hummingbird‐pollinated plants. In this pair, the insect pollinators are euglossine bees (as opposed to small bees and flies in the other pairs), which are thought to forage over large areas, and therefore may provide similar levels of gene flow as hummingbirds. Overall, our results shed light on how different animal pollination modes influence the spatial scale of plant gene flow, suggesting that small insects strongly decrease genetic cohesion.

Arabidopsis thaliana has a wide elevational range and much of its diversity may be associated with local adaptation to elevation. We took a multi-regional view of the genomics and physiology of elevational adaptation in Arabidopsis, with >200 ecotypes, including 17 newly collected from Africa. We measured plant responses to potential high elevation stressors: low pCO2, high light, and night freezing and conducted genome-wide association studies (GWAS). We found evidence of an adaptive cline in the western Mediterranean with low δ13C/early flowering at low elevations to high δ13C/late flowering at high elevations. By contrast, central Asian high elevation ecotypes flowered earlier. Antioxidants and pigmentation under high light and freezing showed regional differentiation but not elevational clines and may be associated with maladaptive plasticity. We found natural variation in non-photochemical quenching (NPQ) kinetics in response to chilling and fluctuating light, though with an unclear role in local adaptation. There were several candidate genetic loci mapped, including the ascorbate transporter PHT4;4 (associated with antioxidants) that influences the xanthophyll cycle, and may be involved in local adaptation to Morocco. Our study shows how the ecological strategies and genetic loci causing local adaptation to elevation change across regions and contribute to diversity in Arabidopsis.