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1. Putting a New Spin on the Flight of Jabillo Seeds

   https://doi.org/10.1093/icb/icaa117  

   Ribera, Jesse; Desai, Aman; Whitaker, Dwight L (August 2020, Integrative and Comparative Biology)

   null (Ed.)

   Synopsis Our article describes the explosive seed dispersal of the Hura crepitans fruit. Through high-speed video analysis of an exploding fruit, we observe that the seeds fly with backspin as opposed to topspin, which was previously assumed. Backspin orients seeds to minimize drag during flight and consequently increases dispersal distance. The seeds’ dispersal distance is estimated by using results from the seeds of Ruellia ciliatiflora, which are similarly shaped but ∼10 times smaller than those of H. crepitans. We note that the effects of lowering drag on the dispersal distance are more pronounced at higher speeds. We also see that the effect of launch height on the dispersal distance of the seeds becomes less consequential at higher launch speeds. We conclude that the increased dispersal distance due to flying with backspin should improve fitness in colonizing new habitats or escaping disease or predation and that comparisons of the seed dispersal mechanisms across species within the Euphorbiaceae and Acanthaceae might help reveal the adaptive significance of this behavior. 

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2. Past energy allocation overwhelms current energy stresses in determining energy allocation trade‐offs

   https://doi.org/10.1002/ece3.10402  

   Griffen, Blaine D.; Bolander, Mikayla; Blakeslee, April; Crane, Laura C.; Repetto, Michele F.; Tepolt, Carolyn K.; Toscano, Benjamin J. (August 2023, Ecology and Evolution)

   Abstract Regeneration of lost appendages is a gradual process in many species, spreading energetic costs of regeneration through time. Energy allocated to the regeneration of lost appendages cannot be used for other purposes and, therefore, commonly elicits energetic trade‐offs in biological processes. We used limb loss in the Asian shore crabHemigrapsus sanguineusto compare the strength of energetic trade‐offs resulting from historic limb losses that have been partially regenerated versus current injuries that have not yet been repaired. Consistent with previous studies, we show that limb loss and regeneration results in trade‐offs that reduce reproduction, energy storage, and growth. As may be expected, we show that trade‐offs in these metrics from historic limb losses far outweigh trade‐offs from current limb losses, and correlate directly with the degree of historic limb loss that has been regenerated. As regenerating limbs get closer to their normal size, these historical injuries get harder to detect, despite the continued allocation of additional resources to limb development. Our results demonstrate the importance of and a method for identifying historic appendage losses and of quantifying the amount of regeneration that has already occurred, as opposed to assessing only current injury, to accurately assess the strength of energetic trade‐offs in animals recovering from nonlethal injury. 

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3. Common milkweed seeds exhibit latitudinal clines more consistent with adaptation to growing season length than temperature

   https://doi.org/10.1111/rec.13878  

   Mohl, Emily K.; McCall, Andrew C.; Wood, Madelyn; Sherman, Lauren; Reid, Mari V.; Saunders, Patricia A.; Scanga, Sara E.; Danielson, Clara; Fisher‐Reid, M. Caitlin; Marella, Heather; et al (February 2023, Restoration Ecology)

   Overwintering monarch (Danaus plexippus) populations have declined since the 1990s. In response, restoration of milkweeds, including Asclepias syriaca (common milkweed), an important host plant in their breeding grounds, has become increasingly common. However, latitudinal variation in milkweed populations suggests the possibility of regional adaptation and the potential for seed provenance to affect restoration success. Using seeds from 20 populations throughout the range of A. syriaca, we tested whether seed mass, germination success, and germination time in the greenhouse demonstrate geographic clines consistent with available evidence for this species from other studies. In addition, we tested for patterns in germination traits consistent with adaptation to spring thermal conditions by planting seeds from 10 populations in growth chambers simulating Minnesota and Kentucky spring temperatures. Even after accounting for seed mass, seeds from higher latitudes germinated faster on average under all conditions. Elevated temperatures accelerated germination time and leaf development time; however, we did not detect geographic patterns in leaf development time, indicating that the processes underlying the latitudinal cline in germination time may be unique to the germination stage. In the thermal adaptation study, high-latitude populations produced larger seeds and seeds that germinated at a higher rate; however, neither latitudinal trend was observed in the geographic clines study, even though individual seed mass predicted germination success. High-latitude populations express more favorable germination traits in every setting measured, perhaps due to reduced dormancy. Consequently, we conclude that latitudinal clines are more consistent with adaptation to growing season length than to spring temperatures. 

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4. Emerging investigator series: molecular mechanisms of plant salinity stress tolerance improvement by seed priming with cerium oxide nanoparticles

   https://doi.org/10.1039/D0EN00387E  

   An, Jing; Hu, Peiguang; Li, Fangjun; Wu, Honghong; Shen, Yu; White, Jason C.; Tian, Xiaoli; Li, Zhaohu; Giraldo, Juan Pablo (January 2020, Environmental Science: Nano)

   Engineered nanomaterials interfaced with plant seeds can improve stress tolerance during the vulnerable seedling stage. Herein, we investigated how priming seeds with antioxidant poly(acrylic acid)-coated cerium oxide nanoparticles (PNC) impacts cotton ( Gossypium hirsutum L.) seedling morphological, physiological, biochemical, and transcriptomic traits under salinity stress. Seeds primed with 500 mg L −1 PNC in water (24 h) and germinated under salinity stress (200 mM NaCl) retained nanoparticles in the seed coat inner tegmen, cotyledon, and root apical meristem. Seed priming with PNC significantly ( P < 0.05) increased seedling root length (56%), fresh weight (41%), and dry weight (38%), modified root anatomical structure, and increased root vitality (114%) under salt stress compared with controls (water). PNC seed priming led to a decrease in reactive oxygen species (ROS) accumulation in seedling roots (46%) and alleviated root morphological and physiological changes induced by salinity stress. Roots from exposed seeds exhibited similar Na content, significantly decreased K (6%), greater Ca (22%) and Mg content (60%) compared to controls. A total of 4779 root transcripts were differentially expressed by PNC seed priming alone relative to controls with no nanoparticles under non-saline conditions. Under salinity stress, differentially expressed genes (DEGs) in PNC seed priming treatments relative to non-nanoparticle controls were associated with ROS pathways (13) and ion homeostasis (10), indicating that ROS and conserved Ca 2+ plant signaling pathways likely play pivotal roles in PNC-induced improvement of salinity tolerance. These results provide potential unifying molecular mechanisms of nanoparticle-seed priming enhancement of plant salinity tolerance. 

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5. Fruit secondary metabolites alter the quantity and quality of a seed dispersal mutualism

   https://doi.org/10.1002/ecy.4032  

   Nelson, Annika S.; Gelambi, Mariana; Morales‐M., Estefania; Whitehead, Susan R. (March 2023, Ecology)

   Abstract Plant secondary metabolites are key mechanistic drivers of species interactions. These metabolites have primarily been studied for their role in defense, but they can also have important consequences for mutualisms, including seed dispersal. Although the primary function of fleshy fruits is to attract seed‐dispersing animals, fruits often contain complex mixtures of toxic or deterrent secondary metabolites that can reduce the quantity or quality of seed dispersal mutualisms. Furthermore, because seeds are often dispersed across multiple stages by several dispersers, the net consequences of fruit secondary metabolites for the effectiveness of seed dispersal and ultimately plant fitness are poorly understood. Here, we tested the effects of amides, nitrogen‐based defensive compounds common in fruits of the neotropical plant genusPiper(Piperaceae), on seed dispersal effectiveness (SDE) by ants, which are common secondary seed dispersers. We experimentally added amide extracts toPiperfruits both in the field and lab, finding that amides reduced the quantity of secondary seed dispersal by reducing ant recruitment (87%) and fruit removal rates (58% and 66% in the field and lab, respectively). Moreover, amides not only reduced dispersal quantity but also altered seed dispersal quality by shifting the community composition of recruiting ants (notably by reducing the recruitment of the most effective disperser by 90% but having no detectable effect on the recruitment of a cheater species that removes fruit pulp without dispersing seeds). Although amides did not affect the distance ants initially carried seeds, they altered the quality of seed dispersal by reducing the likelihood of ants cleaning seeds (67%) and increasing their likelihood of ants redispersing seeds outside of the nest (200%). Overall, these results demonstrate that secondary metabolites can alter the effectiveness of plant mutualisms, by both reducing mutualism quantity and altering mutualism quality through multiple mechanisms. These findings present a critical step in understanding the factors mediating the outcomes of seed dispersal and, more broadly, demonstrate the importance of considering how defensive secondary metabolites influence the outcomes of mutualisms surrounding plants. 

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