The Biology of the Cycads

Norstog, Knut; Nicholls, T. J.

doi:10.7591/9781501737329

Cited by 106 publications

(152 citation statements)

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“…Cycad plants associate with nitrogen-fixing cyanobacteria in specialized roots [5]. The increases in soil nitrogen in close proximity to the C. micronesica and Z. integrifolia plants illuminated one of the manners by which cycad plants improve ecosystem health by contributing the nitrogen that is originally fixed in their roots to the surrounding edaphic substrates over time.…”

Section: The Two Speciesmentioning

confidence: 99%

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Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils

Marler

Calonje

2020

Horticulturae

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The influences of Cycas micronesica and Zamia integrifolia plants on soil chemistry were determined in Tinian and Florida in order to more fully understand how cycad plants affect the environments in which they grow. The introduction of C. micronesica plants into a karst habitat generated decreases in soil phosphorus after five years and increases in soil nitrogen after six years. The carbon:nitrogen:phosphorus stoichiometry beneath the cycad plants significantly diverged from those of the adjacent native forests with Pisonia grandis, Psychotria mariana, Aglaia mariannensis, Cynometra ramiflora, and Ficus sp. cover after five years. Mineralization traits were determined beneath nine-year-old C. micronesica plants and revealed the plants greatly increased net nitrification and decreased net ammonification when compared to the native forest soils with Bursera simaruba, Pinus elliottii, and Quercus virginiana cover. These flux changes increased the total available nitrogen and percent available nitrogen in the soils beneath the cycad plants. The substrates of two soil series exhibited increased carbon and nitrogen concentrations beneath Z. integrifolia plants when compared with soils away from the cycad plants. No other mineral or metal was influenced by proximity to the Z. integrifolia plants. These gymnosperms exhibit distinct interactions with their subtending soils, and some of these traits improve ecosystems by increasing recalcitrant carbon and nitrogen and increasing spatial heterogeneity of soil chemistry.

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Section: The Two Speciesmentioning

confidence: 99%

“…The arborescent C. micronesica is found in the United States (U.S.) territorial island of Guam and the U.S. Commonwealth island of Rota. Another U.S. cycad species is the diminutive Zamia integrifolia L.f. (Zamiaceae, Cycadales), which is the only cycad species that is native to the conterminous U.S. [4,5].…”

Section: Introductionmentioning

confidence: 99%

Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils

Marler

Calonje

2020

Horticulturae

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“…Asexual propagation of healthy Cycas plants is routinely accomplished by inducing root formation on small adventitious stem cuttings (Norstog and Nicholls, 1997). The relatively low success rate for large C. micronesica stem cuttings may have resulted from the unhealthy status of the stems due to chronic A. yasumatsui damage to the donor plants (Marler and Cruz, 2017).…”

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confidence: 99%

Stem Carbohydrates and Adventitious Root Formation of Cycas micronesica following Aulacaspis yasumatsui Infestation

Marler

2018

horts

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Large stem cuttings were removed from Cycas micronesica K.D. Hill trees and used for asexual propagation to more fully understand resource factors that influence adventitious root formation success. Healthy source trees had received insecticide protection from ubiquitous Aulacaspsis yasumatsui Takagi infestations and unhealthy source trees had suffered from chronic A. yasumatsui infestations. Nonstructural carbohydrates were quantified from stem tissues at the base of each 1-m cutting, and induction of adventitious roots was attempted using field soil as the medium. Carbohydrate concentrations were increased in healthy, protected tree cuttings above those in unhealthy, infested tree cuttings. The relative increase was greatest in the hexoses, intermediate in sucrose, and least in starch. The total nonstructural carbohydrate concentration in cuttings of infested trees was 54% of that of protected trees, and the sugar/starch quotient of infested trees exceeded that of protected trees. Asexual propagation success was 30% for the unhealthy tree cuttings and 100% for the healthy tree cuttings. These manipulative experiments confirm that chronic A. yasumatsui herbivory of C. micronesica trees reduces stem carbohydrates and decreases asexual propagation success. The results indicate that the use of large cuttings from unhealthy C. micronesica trees to rescue tree populations from construction sites is not a wise conservation decision in habitats where A. yasumatsui herbivory has been uncontrolled. Protocols for future rescue operations designed to transplant C. micronesica trees from construction sites may be improved by this new knowledge.

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“…The reward obtained by the pollinators from using male sexual structures, is countered by the cost of visiting deceitful, non-rewarding female sexual structures. The plant's gain in deceit is likely ovule escape from herbivory, but the cost may be pollen limitation (Norstog & Nicholls, 1997;Dufaÿ & Anstett, 2003). This mutual exploitation appears to be sufficiently stable for long-term population persistence, even when in various cycad species seed set values rarely go over 60% with many plants showing evidence of receiving few or no pollen at all (Newell, 1983;Tang, 1987a;Kono & Tobe, 2007;Lazcano Lara, 2015;Proches and Johnson, 2009;Suinyuy, Donaldson, & Johnson, 2009;Terry, 2001;Wilson, 2002).…”

Section: Reproductive Successmentioning

confidence: 99%

“…Cycads are considered "living fossils", and indeed the major lineages are old (Chamberlain, 1919(Chamberlain, , 1935Norstog & Nicholls, 1997). Extant species, though, are not relicts, having diverged within the last my (Condamine et al, 2015) suggesting that the lineage has had some degree of evolutionary flexibility in relatively recent times.…”

Section: Conservation Applicationsmentioning

confidence: 99%

Peer Review #1 of "Best in the company of nearby males: female success in the threatened cycad, Zamia portoricensis (v0.1)"

2018

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Variation in plant reproductive success is affected by ecological conditions including the proximity of potential mates. We address the hypothesis that spatial distribution of sexes affects female reproductive success (RS) in the dioecious cycad, Zamia portoricensis. Are the frequencies of males, operational sex ratios, and distances to the nearest mate associated with RS in females? We studied the spatial distribution of sexes in two populations in Puerto Rico and compared RS of target females with the number of males and operational sex ratios. Population structure suggests regular successful recruitment. Adults, males, and females were randomly distributed with respect to one another. Reproductive success of females was highly variable, but was higher in neighborhoods with more males than females and generally decreased with increasing distance to the nearest male, becoming statistically significant beyond 190 cm. This possible mate-finding Allee effect indicates that pollinator movement among plants may be limited for this mutually dependent plant-pollinator interaction. Yet being close to male plants is a matter of chance, perhaps a factor generating the high intra-population genetic diversity in Z. portoricensis.

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The Biology of the Cycads

Cited by 106 publications

References 0 publications

Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils

Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils

Stem Carbohydrates and Adventitious Root Formation of Cycas micronesica following Aulacaspis yasumatsui Infestation

Peer Review #1 of "Best in the company of nearby males: female success in the threatened cycad, Zamia portoricensis (v0.1)"

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