Cycas micronesica was threatened by the 2003–07 invasions of Aulacaspis yasumatsui Takagi and two other specialist insect pests to the islands of Guam and Rota (Marler, 2012; Marler and Muniappan, 2006; Moore et al., 2005). This unique gymnosperm was a common member of commercial and home landscapes and was the most abundant tree species in Guam’s forests at the time (Donnegan et al., 2004). The invasions generated unexpected interactions among the nonnative herbivores (Marler, 2013b) and substantial responses by the host plant (Marler, 2013a; Marler and Dongol, 2016b; Marler et al., 2016b). The rapid epidemic tree mortality (Marler and Lawrence, 2012) propelled the species to designations of Endangered status under the International Union for Conservation of Nature (Marler et al., 2010) and Threatened status under the U.S. Endangered Species Act (ESA) (U.S. Fish & Wildlife Service, 2015).
Several conservation projects were initiated during the ensuing years, including establishment of an ex situ germplasm collection on the island of Tinian (Anonymous, 2014; Marler et al., 2016a). Seeds were collected throughout Guam habitats beginning 2006, and the subsequent Tinian nursery observations revealed that the Guam plants with the greatest infestation levels of A. yasumatsui directly on the collected seeds provisioned seeds with inferior germination and increased seedling mortality compared with seeds with minimal levels of infestation (unpublished data). This held true for subpopulations suffering from heavy A. yasumatsui infestations and subpopulations where the infestation level was moderate. For example, the two Guam subpopulations with the greatest level of direct seed infestations of A. yasumatsui exhibited germination of 7%. In contrast, the Guam subpopulation with the least level of seed infestation exhibited germination of 43%. These observations illuminated a need to more fully understand this conservation threat.
The healthy C. micronesica seed is a powerhouse of nonstructural carbohydrate resources (Marler and Dongol, 2016a), and a reduction of these seed resources during direct seed infestations of A. yasumatsui may occur. Visual observation of infested ovules and seeds (Fig. 1) illuminates the potential for depletion of resources. A greater understanding of the consequences to seed resources caused by direct infestations of this pest is clearly needed. Our objectives were to use observational and experimental data to determine the influence of seed infestations by A. yasumatsui on nonstructural carbohydrate relations of various C. micronesica seed tissues. We predicted free sugars and starch would decline following A. yasumatsui herbivory and the relative declines of carbohydrates in the exposed sarcotesta tissues of the integument would exceed those in the other seed tissues.
Anonymous2014Conserving our nation’s only native cycad species. Currents [Fall issue] p. 28–31. 17 May 2019. <https://navysustainability.dodlive.mil/files/2014/10/Fall14_Conserving_Cycad_Species.pdf>
DonneganJ.A.ButlerS.L.GrabowieckiW.HiseroteB.A.LimtiacoD.2004Guam’s forest resources 2002. Resource Bulletin PNW-RB-243. U.S. Department of Agriculture Forest Service Pacific Northwest Research Station Portland OR
MarlerT.E.2013aIncreased threat of island endemic tree’s extirpation via invasion-induced decline of intrinsic resistance to recurring tropical cyclonesCommun. Integr. Biol.6e22361doi: 10.4161/cib.22361
MarlerT.E.2013bTemporal variations in leaf miner, butterfly, and stem borer infestations of Cycas micronesica in relation to Aulacaspis yasumatsui incidenceHortScience4813341338
MarlerT.E.2018Stem carbohydrates and adventitious root formation of Cycas micronesica following Aulacaspis yasumatsui infestationHortScience5311251128
MarlerT.E.CascasanA.N.J.2018Carbohydrate depletion during lethal infestation of Aulacaspis yasumatsui on Cycas revolutaIntl. J. Plant Sci.179497504
MarlerT.E.DongolN.2016aSeed ontogeny and nonstructural carbohydrates of Cycas micronesica megagametophyte tissueHortScience5111441147
MarlerT.E.DongolN.2016bThree invasive insects alter Cycas micronesica leaf chemistry and predict changes in biogeochemical cyclingCommun. Integr. Biol.9e1208324doi: 10.1080/19420889.2016.1208324
MarlerT.E.DongolN.CruzG.N.2016aLeucaena leucocephala and adjacent native limestone forest habitats contrast in soil properties on Tinian IslandCommun. Integr. Biol.9e1212792doi: 10.1080/19420889.2016.1212792
MarlerT.HaynesJ.LindströmA.2010Cycas micronesica. The IUCN Red List of Threatened Species. Version 2014.3. 17 May 2019. <http://www.iucnredlist.org>
MarlerT.E.LawrenceJ.H.2012Demography of Cycas micronesica on Guam following introduction of the armoured scale Aulacaspis yasumatsuiJ. Trop. Ecol.28233242
MarlerT.E.LawrenceJ.H.CruzG.N.2016bTopographic relief, wind direction, and conservation management decisions influence Cycas micronesica K.D. Hill population damage during tropical cycloneJ. Geogr. Nat. Disast.6178doi: 10.4172/2167-0587.1000178
MarlerT.E.MuniappanR.2006Pests of Cycas micronesica leaf, stem, and male reproductive tissues with notes on current threat statusMicronesica3919
SchloterM.WinklerJ.B.AnejaM.KochN.FleischmannF.PritschK.HellerW.StichS.GramsT.E.GöttleinA.MatyssekR.MunchJ.C.2005Short term effects of ozone on the plant-rhizosphere-bulk soil system of young beech treesPlant Biol. (Stuttg)7728736
U.S. Fish & Wildlife Service2015Endangered and threatened wildlife and plants; endangered status for 16 species and threatened status for 7 species in MicronesiaFed. Regist.805942459497
XuF.KuoT.RosliY.LiuM.-S.WuL.ChenL.-F.O.FletcherJ.C.SungZ.R.PuL.2018Trithorax group proteins act together with a polycomb group protein to maintain chromatin integrity for epigenetic silencing during seed germination in ArabidopsisMol. Plant11659677
YoungF.J.1988Soil survey of Territory of Guam. U.S. Dept. of Agric. Soil Conservation Service