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

Abstract

<jats:p>Large stem cuttings were removed from <jats:italic>Cycas micronesica</jats:italic> 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 <jats:italic>Aulacaspsis yasumatsui</jats:italic> Takagi infestations and unhealthy source trees had suffered from chronic <jats:italic>A. yasumatsui</jats:italic> 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 <jats:italic>A. yasumatsui</jats:italic> herbivory of <jats:italic>C. micronesica</jats:italic> trees reduces stem carbohydrates and decreases asexual propagation success. The results indicate that the use of large cuttings from unhealthy <jats:italic>C. micronesica</jats:italic> trees to rescue tree populations from construction sites is not a wise conservation decision in habitats where <jats:italic>A. yasumatsui</jats:italic> herbivory has been uncontrolled. Protocols for future rescue operations designed to transplant <jats:italic>C. micronesica</jats:italic> trees from construction sites may be improved by this new knowledge.</jats:p>

Source and Sink Relations Mediate Depletion of Intrinsic Cycad Seed Carbohydrates by Aulacaspis yasumatsui Infestation

“…The documented declines in carbohydrates following infestations of A. yasumatsui on Cycas L. plants are not restricted to seeds. A reduction in stem carbohydrates after chronic A. yasumatsui herbivory was correlated with capacity to develop adventitious roots (Marler, 2018). A reduction in whole-plant carbohydrates during lethal A. yasumatsui infestations preceded plant mortality (Marler and Cascasan, 2018).…”

“…Whole-tree protection. Several plots throughout Guam were established in 2007 for protection from A. yasumatsui threat by using root drenches of imidacloprid every 3 to 4 months (Marler, 2018). A site on the east coast of Guam containing the same soil series described in the preceding text was used to determine seed carbohydrate status with and without plant protection.…”

Cycas micronesica Stem Carbohydrates Decline Following Leaf and Male Cone Growth Events

“…The plot was positioned at 20-60 m above sea level, aspect was 120-150 • , and mature plant density was 1050 stems per ha. More details for the site are contained elsewhere [7,15,16]. The edaphic substrates at this site were coralline soils formed in slope alluvium, loess, and residuum overlying limestone (clayey-skeletal, gibbsitic, nonacid, isohyperthermic Lithic Ustorthents) [17].…”

“…Carbohydrate resources using contemporary analytical approaches have been quantified for Cycas micronesica K.D. Hill [6,7], Cycas revoluta Thunb. [8], and Zamia muricata Willd.…”

Tree conservation can be constrained by agents from conservation permitting and funding agencies

“…Indeed, ecosystem changes can be misunderstood in insular settings if consistent monitoring is not used [50]. This wise approach of a funding agency enabled the accumulation of the only existing long-term C. micronesica survival data set throughout three islands and has resulted in numerous peer-reviewed articles that are available to inform future C. micronesica conservation decisions [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68].…”