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1. Patterns of nectar production in Asclepias curassavica (Apocynaceae)

   Broyles, Steven B; Stoj, Kiley R (January 2019, Journal of pollination ecology)

   Milkweeds are important nectar resources for insects in the New World. In addition, nectar is the germination medium for milkweed pollen. This study is the first controlled, greenhouse examination of patterns of nectar production in a milkweed species. We measured nectar volume, concentration, and mg of sugar in the pantropical, weedy milkweed Asclepias curassavica. Our results show that A. curassavica secretes nectar primarily during daylight hours and it continues at a constant daily rate for four to five days. Freshly secreted nectar is lower in sugar concentration than older nectar. This provides an opportunity for milkweed pollen to germinate throughout the day, but pollen germination could be inhibited at times when the sugar concentration increases. Nectar production in A. curassavica is adapted to attract diurnal insect pollinators over several days and to allow pollen germination to occur quickly. Significant differences in nectar production exist among plants and inflorescences within plants. Nectar production increases in flowers when nectar is extracted using paper wicks that simulate removal by insects in nature. Removal-enhanced nectar production in milkweeds may allow plants to adjust resources to inflorescences receiving insect visitation. Significant inter-plant differences in nectar production and the unique milkweed flower provides a model system for examining the role of pollinator-mediated selection on nectar traits. 

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2. Cardenolides in Asclepias syriaca Seeds: Exploring the Legacy of Tadeus Reichstein

   https://doi.org/10.1021/acs.jnatprod.4c00960  

   Rubiano-Buitrago, Paola; White, Ronald A; Hastings, Amy P; Schroeder, Frank C; Agrawal, Anurag A; Duplais, Christophe (January 2025, Journal of Natural Products)
3. Evolution at the tips: Asclepias phylogenomics and new perspectives on leaf surfaces

   https://doi.org/10.1002/ajb2.1062  

   Fishbein, Mark; Straub, Shannon C.; Boutte, Julien; Hansen, Kimberly; Cronn, Richard C.; Liston, Aaron (March 2018, American Journal of Botany)
4. Role of plant relatedness in plant–soil feedback dynamics of sympatric Asclepias species

   https://doi.org/10.1002/ece3.9763  

   Duell, Eric B.; Bever, James D.; Wilson, Gail W. (January 2023, Ecology and Evolution)

   Abstract Plants affect associated biotic and abiotic edaphic factors, with reciprocal feedbacks from soil characteristics affecting plants. These two‐way interactions between plants and soils are collectively known as plant–soil feedbacks (PSFs). The role of phylogenetic relatedness and evolutionary histories have recently emerged as a potential driver of PSFs, although the strength and direction of feedbacks among sympatric congeners are not well‐understood. We examined plant–soil feedback responses ofAsclepias syriaca, a common clonal milkweed species, with several sympatric congeners across a gradient of increasing phylogenetic distances (A. tuberosa,A. viridis,A. sullivantii, andA. verticillata, respectively). Plant–soil feedbacks were measured through productivity and colonization by arbuscular mycorrhizal (AM) fungi.Asclepias syriacaproduced less biomass in soils conditioned by the most phylogenetically distant species (A. verticillata), relative to conspecific‐conditioned soils. Similarly, arbuscular mycorrhizal (AM) fungal colonization ofA. syriacaroots was reduced when grown in soils conditioned byA. verticillata, compared with colonization in plants grown in soil conditioned by any of the other threeAsclepiasspecies, indicating mycorrhizal associations are a potential mechanism of observed positive PSFs. This display of differences between the most phylogenetically distant, but not close or intermediate, paring(s) suggests a potential phylogenetic threshold, although other exogenous factors cannot be ruled out. Overall, these results highlight the potential role of phylogenetic distance in influencing positive PSFs through mutualists. The role of phylogenetic relatedness and evolutionary histories have recently emerged as a potential driver of plant–soil feedbacks (PSFs), although the strength and direction of feedbacks among sympatric congeners are not well‐understood. Congeneric, sympatric milkweeds typically generated positive PSFs in terms of productivity and AM fungal colonization, suggesting the low likelihood of coexistence among tested pairs, with a strength of feedback increasing as the phylogenetic distance increases. 

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5. Ecology of Asclepias brachystephana : a plant for roadside and right-of-way management

   https://doi.org/10.3368/npj.22.3.256  

   McCoshum, Shaun M; Agrawal, Anurag A (January 2021, Native Plants Journal)