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Marler TE, Lindström AJ, Marler PN. Diversity in Cycas (Cycadales: Cycadaceae) Species Offered as Larval Food Influences Fecundity of Chilades pandava (Lepidoptera: Lycaenidae) Adults. INTERNATIONAL JOURNAL OF INSECT SCIENCE 2017; 9:1179543317745863. [PMID: 29238238 PMCID: PMC5721961 DOI: 10.1177/1179543317745863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/30/2017] [Indexed: 06/07/2023]
Abstract
Chilades pandava (Lepidoptera: Lycaenidae) larval food quality was studied to determine its influence on adult life history traits. A wild population from Cycas nongnoochiae (Cycadales: Cycadaceae) endemic habitat behaved similarly to the population collected from a garden setting. Cycas micronesica, Cycas revoluta, and Cycas seemannii leaves were used as high-quality food, whereas C nongnoochiae, Cycas taitungensis, and Cycas condaoensis leaves were used as low-quality food. The daily oviposition rate was not influenced by food quality, but longevity and lifetime fecundity of females were increased by high-quality larval food. These results indicate that in situ Cycas species impose a physiological constraint on the genetic capacity to produce offspring by C pandava. The removal of that constraint by high-quality novel Cycas species may be one reason this butterfly can increase in population rapidly after an invasion event and express greater herbivory of Cycas species within invaded regions.
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Marler TE. Increasing relevance of sunfleck research. PLANT SIGNALING & BEHAVIOR 2017; 12:e1334030. [PMID: 28569588 PMCID: PMC5566253 DOI: 10.1080/15592324.2017.1334030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 05/19/2017] [Accepted: 05/19/2017] [Indexed: 06/07/2023]
Abstract
Contemporary reviews of leaf responses to sunflecks indicate gymnosperms exhibit slower photosynthetic inductions times than angiosperms, but the gymnosperms were represented exclusively by conifers. I recently reported that the gymnosperm Cycas micronesica exhibited photosynthetic induction times in conformity with some of the most rapid angiosperms and opined that representatives from non-conifer gymnosperms must be added to the published conifer database before gymnosperm-wide conclusions can be formulated. Guiding principles for this urgently needed research will maximize relevance and improve accuracy of conclusions.
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Marler TE. Diel root extension patterns of three Serianthes species are modulated by plant size. PLANT SIGNALING & BEHAVIOR 2017; 12:e1327496. [PMID: 28532228 PMCID: PMC5566354 DOI: 10.1080/15592324.2017.1327496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 04/29/2017] [Accepted: 05/01/2017] [Indexed: 06/07/2023]
Abstract
Diel root extension was observed for Serianthes grandiflora, Serianthes kanehirae, and Serianthes nelsonii plants ranging in size from seedlings to 2-m tall saplings. The percentage of daily root extension that occurred at night declined from 65% for seedlings to 51% for 200-cm tall plants for S. grandiflora, from 58% for seedlings to 54% for 200-cm tall plants for S. kanehirae, and from 72% for seedlings to 55% for 200-cm tall plants for S. nelsonii. These results indicate the timing of root extension rates throughout a diel cycle may be included in the list of phenology and physiology traits that change as plants increase in size.
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Marler TE, Dongol N. Three invasive insects alter Cycas micronesica leaf chemistry and predict changes in biogeochemical cycling. Commun Integr Biol 2016; 9:e1208324. [PMID: 27829976 PMCID: PMC5100656 DOI: 10.1080/19420889.2016.1208324] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 06/23/2016] [Accepted: 06/24/2016] [Indexed: 11/05/2022] Open
Abstract
Leaf litter chemical traits were measured for Cycas micronesica plants in Guam following leaf herbivory by the scale Aulacaspis yasumatsui, the butterfly Chilades pandava caterpillar, or the leaf miner Erechthias sp. to determine the influence of the non-native pests on litter quality. Scale herbivory increased litter phenols above those of undamaged leaves but did not influence lignin or cellulose concentrations. Butterfly caterpillar herbivory increased litter phenols above and decreased litter lignin below those of undamaged leaves, but did not influence cellulose concentrations. Leaf miner herbivory increased litter lignin concentrations above those of undamaged leaves, but did not influence phenols or cellulose concentrations. Herbivory influenced 8 of 12 essential elements that were quantified. Herbivory by all 3 insects increased nitrogen and potassium litter concentrations and decreased calcium and iron litter concentrations when compared with undamaged litter. The responses were idiosyncratic among herbivores for the remaining essential elements. Stoichiometry among the chemical constituents indicated that herbivory increased litter quality and predicted more rapid biogeochemical cycling in Guam's ecosystems as a result of these 3 non-native insect invasions.
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Marler TE, Dongol N, Cruz GN. Leucaena leucocephala and adjacent native limestone forest habitats contrast in soil properties on Tinian Island. Commun Integr Biol 2016; 9:e1212792. [PMID: 27829978 PMCID: PMC5100652 DOI: 10.1080/19420889.2016.1212792] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 07/06/2016] [Accepted: 07/08/2016] [Indexed: 11/22/2022] Open
Abstract
An ex situ germplasm collection of the endangered Cycas micronesica was established in a transition zone between biodiverse native forest and mature stands of the invasive species Leucaena leucocephala. Soil chemical properties were determined for the 2 tree cover types to inform management decisions. Total carbon, total nitrogen, calcium, and net ammonification were greater in native forest cover than in L. leucocephala patches. Net nitrification and net mineralization were greater under L. leucocephala cover. Trace metals also differed between the 2 forest cover types, with chromium, cobalt, and nickel accumulating to greater concentration under L. leucocephala cover and zinc accumulating to greater concentration under native forest cover. The results indicated that L. leucocephala cover generated substantial changes in soil chemical properties when compared with native forest tree cover, illuminating one means by which understory vegetation may be affected by changes in invasive tree cover.
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Marler TE, Lindström AJ, Marler PN. Chilades pandava mothers discriminate among Cycas species during oviposition choice tests, but only in an endemic naïve population. PLANT SIGNALING & BEHAVIOR 2016; 11:e1208879. [PMID: 27391307 PMCID: PMC5022404 DOI: 10.1080/15592324.2016.1208879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/28/2016] [Accepted: 06/29/2016] [Indexed: 06/06/2023]
Abstract
Host and non-host plant species communicate with insect herbivores to influence oviposition decisions. We studied if Chilades pandava female adults expressed oviposition preferences among host Cycas species in 2 choice tests, counting 39,420 eggs among assays from 4 butterfly populations. A naïve butterfly population from Cycas nongnoochiae habitat oviposited 2.2-fold more eggs on leaves of Cycas species that are susceptible to butterfly herbivory than on leaves of its native host Cycas nongnoochiae. In contrast, Chilades pandava populations experienced with novel Cycas species in Thailand, Philippines, and Guam exhibited no preference in choice tests between leaves of susceptible versus leaves of minimally damaged Cycas species. The results indicated that oviposition deterrents and/or stimulants partly mediate the sustainable relationship between an endemic Cycas species and the naïve Chilades pandava population from its habitat. Alternatively, differences in infochemicals among Cycas species do not enable discrimination in oviposition choices for Chilades pandava populations that have experienced Cycas species exhibiting no evolutionary history with Chilades pandava.
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Cascasan AN, Marler TE. Publishing trends for the Cycadales, the most threatened plant group. JOURNAL OF THREATENED TAXA 2016. [DOI: 10.11609/jott.2369.8.3.8575-8582] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Trends in published cycad research within various fields of study were determined using proceedings from international conferences on cycad biology and Google Scholar to access the primary literature. Both search methods indicated that phylogeny, systematics and ecology are strongly represented in recent cycad literature, while there is a need for more research in horticulture and pathology, reviews and clarification of correspondence between current and discontinued species designations.
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Marler TE, Cascasan AN. Number of emerged seedlings and seedling longevity of the non-recruiting, Critically Endangered Håyun lågu Tree Serianthes nelsonii Merr. (Fabales: Leguminosae) are influenced by month of emergence. JOURNAL OF THREATENED TAXA 2015. [DOI: 10.11609/jott.2100.7.15.8221-8225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
<p>Emergence and longevity of seedlings beneath Guam’s only known Håyun lågu Tree <em>Serianthes nelsonii</em> were studied to determine the fate of every observed seedling during 2013. Newly emerged seedlings were marked with wire stakes every 15 days, then the stakes were collected at each seedling upon death. Longevity of each seedling was calculated from the marked ending and emergence dates. The least number of newly emerged seedlings was recorded at the end of the dry season, and the greatest number of newly emerged seedlings was recorded in the beginning of the rainy season. More than half of the year’s 374 seedlings died in less than 30 days. Seedling longevity ranged from a mean of 31 days for seedlings that emerged in May to 78 days for seedlings that emerged in June. Our results reveal that the baseline level of recruitment potential of the lone survivor of this species on Guam is substantial, and underscore the need for further research to determine the factors associated with the acutely limited seedling lifespan.</p><div> </div>
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Marler TE. Promoting the confluence of tropical cyclone research. Commun Integr Biol 2015; 8:e1017165. [PMID: 26480001 PMCID: PMC4594373 DOI: 10.1080/19420889.2015.1017165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 01/05/2015] [Accepted: 01/13/2015] [Indexed: 11/22/2022] Open
Abstract
Contributions of biologists to tropical cyclone research may improve by integrating concepts from other disciplines. Employing accumulated cyclone energy into protocols may foster greater integration of ecology and meteorology research. Considering experienced ecosystems as antifragile instead of just resilient may improve cross-referencing among ecological and social scientists. Quantifying ecosystem capital as distinct from ecosystem services may improve integration of tropical cyclone ecology research into the expansive global climate change research community.
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Marler TE, Lindström AJ. Carbohydrates, pollinators, and cycads. Commun Integr Biol 2015; 8:e1017162. [PMID: 26479502 PMCID: PMC4594462 DOI: 10.1080/19420889.2015.1017162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 12/10/2014] [Indexed: 10/29/2022] Open
Abstract
Cycad biology, ecology, and horticulture decisions are not supported by adequate research, and experiments in cycad physiology in particular have been deficient. Our recent report on free sugar content in a range of cycad taxa and tissues sets the stage for developing continued carbohydrate research. Growth and development of cycad pollen, mediation of the herbivory traits of specialist pollinators, and support of expensive strobilus behavioral traits are areas of cycad pollination biology that would benefit from a greater understanding of the role of carbohydrate relations.
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Marler TE, Lindström AJ. The value of research to selling the conservation of threatened species: the case of Cycas micronesica (Cycadopsida: Cycadales: Cycadaceae). JOURNAL OF THREATENED TAXA 2014. [DOI: 10.11609/jott.o4098.6523-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Marler TE, Lindström AJ. Free sugar profile in cycads. FRONTIERS IN PLANT SCIENCE 2014; 5:526. [PMID: 25339967 PMCID: PMC4188140 DOI: 10.3389/fpls.2014.00526] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 09/17/2014] [Indexed: 05/08/2023]
Abstract
The sugars fructose, glucose, maltose, and sucrose were quantified in seven tissues of Zamia muricata Willd. to determine their distribution throughout various organs of a model cycad species, and in lateral structural roots of 18 cycad species to determine the variation in sugar concentration and composition among species representing every cycad genus. Taproot and lateral structural roots contained more sugars than leaf, stem, female strobilus, or coralloid roots. For example, taproot sugar concentration was 6.4-fold greater than stem sugar concentration. The dominant root sugars were glucose and fructose, and the only detected stem sugar was sucrose. Sucrose also dominated the sugar profile for leaflet and coralloid root tissue, and fructose was the dominant sugar in female strobilus tissue. Maltose was a minor constituent of taproot, leaflet, and female strobilus tissue, but absent in other tissues. The concentration of total free sugars and each of the four sugars did not differ among genera or families. Stoichiometric relationships among the sugars, such as the quotient hexoses/disaccharides, differed among organs and families. Although anecdotal reports on cycad starch have been abundant due to its historical use as human food and the voluminous medical research invested into cycad neurotoxins, this is the first report on the sugar component of the non-structural carbohydrate profile of cycads. Fructose, glucose, and sucrose are abundant in cycad tissues, with their relative abundance highly contrasting among organs. Their importance as forms of carbon storage, messengers of information, or regulators of cycad metabolism have not been determined to date.
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Marler TE, Ferreras U. Differential leaflet mortality may influence biogeochemical cycling following tropical cyclones. Commun Integr Biol 2014; 7:e27924. [PMID: 25083171 PMCID: PMC4094194 DOI: 10.4161/cib.27924] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 01/21/2014] [Indexed: 11/19/2022] Open
Abstract
Intensity of tropical cyclones is expected to increase in the coming century, and an improved understanding of their influence on biogeochemical cycles would benefit ecologists and conservationists. We studied the November 2013 Typhoon Haiyan damage to observe that numerous examples of partial leaf necrosis on intact leaves of trees in the Cycadaceae and Arecaceae families resulted, leaving behind a copious amount of arboreal dead leaf material attached to live leaves. The decay process of this form of arboreal litter has not been previously studied. When compared with decay of ground litter or detached litter suspended in the canopy, we predict the decay process of this form of arboreal litter will include increased photooxidation, leaching, and comminution by detritivorous insects and mites; but decreased catabolism of organic molecules by saprophytic organisms.
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Watson G, Marler TE. Does cycad aulacaspis scale (Aulacaspis yasumatsui, Hemiptera: Diaspididae) play a direct role in causing soil phytotoxicity? Commun Integr Biol 2014; 7:e27881. [PMID: 25083170 PMCID: PMC4094193 DOI: 10.4161/cib.27881] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 01/16/2014] [Indexed: 12/05/2022] Open
Abstract
Cycad aulacaspis scale (CAS, Aulacaspis yasumatsui, Hemiptera: Diaspididae) was accidentally introduced to Guam in 2003, and has caused acute mortality of the dominant, endemic forest tree Cycas micronesica. A phytotoxic legacy in the soils beneath cycad trees killed by CAS over a period of about three years has been demonstrated. The origin of the toxicity may be large quantities of CAS-encrusted cycad leaf litter. We explore the possibility that a major contribution to this toxic legacy may come from the scale insects, not just from the plant material.
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Gorelick R, Marler TE. Kin recognition by roots occurs in cycads and probably in conifers. Commun Integr Biol 2014; 7:e28009. [PMID: 24778761 PMCID: PMC3995734 DOI: 10.4161/cib.28009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 01/26/2014] [Accepted: 01/27/2014] [Indexed: 01/09/2023] Open
Abstract
Kin recognition by the roots of Cycas edentata was recently demonstrated. Our extensive literature search revealed this to be the first report of kin recognition in any spermatophyte other than angiosperms. Based on this new validation that the phenomenon occurs among phylogenetically diverse taxa, we conclude that kin recognition by roots may be an ancient phenomenon.
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Marler TE. The intersection of a military culture and indigenous peoples in conservation issues. Commun Integr Biol 2013; 6:e26665. [PMID: 24567778 PMCID: PMC3925457 DOI: 10.4161/cib.26665] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 10/01/2013] [Indexed: 11/19/2022] Open
Abstract
Military operations impose various positive and negative consequences on the environment. Three case studies are presented illuminating how local indigenous peoples as stakeholders may be vulnerable to being disenfranchised from important discussions concerning military activities. The study of ecological issues associated with sustaining a military footprint may be particularly useful for informing the global debate that pits strict conservation against human well-being.
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Roemer RB, Terry LI, Marler TE. Cone thermogenesis and its limits in the tropical Cycas micronesica (Cycadaceae): association with cone growth, dehiscence, and post-dehiscence phases. AMERICAN JOURNAL OF BOTANY 2013; 100:1981-1990. [PMID: 24081147 DOI: 10.3732/ajb.1300047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
PREMISE OF THE STUDY Thermogenesis is a prominent pollination-related feature of cycad cones and is generally assumed to play a role in pollination. Although typically studied just before, during, and immediately after the cones' pollination phase, thermogenesis may be present in other cone developmental phases. • METHODS We assayed thermogenesis in Cycas micronesica, Guam's endangered cycad, over successive cone developmental phases by measuring temperatures in shaded and unshaded in situ cones for up to 7 wk. We also studied the effect of ambient conditions on cone thermogenesis in laboratory experiments and estimated the cones' metabolic heating rates. • KEY RESULTS Pollen cones exhibit a continuous, but small, metabolically generated thermogenesis for multiple weeks, including a single thermogenic peak temperature greater than peak ambient each day. The magnitudes of those daily peak temperature elevations above ambient reach maxima twice during cone development: a few days before dehiscence and approximately 1 wk post-dehiscence. Excised cones in dark, fixed temperature environments generated multiple thermogenic events (∼24 h period) over ∼10 d. Cones appear to initiate a protective temperature regulatory response at temperatures ≥∼38°C. • CONCLUSIONS Cycas micronesica pollen cones exhibit several thermogenic attributes not reported in other cycads, including continuous thermogenesis for many weeks. These cones grow in a hot tropical environment that likely confines their metabolically generated temperature increases to a small thermogenic window beyond which they encounter heat stress. These findings suggest the presence of thermogenic functions not strictly related to pollination and a potential vulnerability to warming climates.
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Shaw CA, Marler TE. Aluminum and the human diet revisited. Commun Integr Biol 2013; 6:e26369. [PMID: 24505503 PMCID: PMC3914913 DOI: 10.4161/cib.26369] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 09/03/2013] [Indexed: 11/19/2022] Open
Abstract
Concerns about aluminum (Al) exposure in the human diet have persisted for one century. We suggest that continued research would benefit from better reporting of environmental factors that are known to influence Al accumulation in plant organs that are consumed, focusing on subsets of the general public that exhibit the highest risk for neuropathological responses, increased evaluation of commercial processing procedures that may concentrate Al or other toxic substances, and designing studies with low dose, chronic exposure rather than further study of acute, brief exposure.
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Marler TE, Del Moral R. Primary succession in Mount Pinatubo: Habitat availability and ordination analysis. Commun Integr Biol 2013; 6:e25924. [PMID: 24505499 PMCID: PMC3913662 DOI: 10.4161/cib.25924] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 07/27/2013] [Indexed: 11/19/2022] Open
Abstract
Vegetation structure on the east flank of Mount Pinatubo was investigated to determine the inventory of species at 15 y post-eruption, then to ascertain environmental variables that have influenced the early patterns of primary succession. Unconstrained and constrained ordination methods were used to determine the influence of spatial, elevation, and substrate patterns on vegetation. Vegetation was assigned to one of 3 habitat types. Scours were eroded flat surfaces, terraces were perched flat surfaces, and talus piles were created along the canyon edges as mass waste events. The influence of habitat type on vegetation was multifaceted because they represent different conditions and different histories. The talus piles have preferential access to colonists from the vegetation on the canyon walls above and a more benign microclimate than the exposed terrace and scour sites. Scoured sites on the valley floor exhibited the least vegetation cover, as these substrates had the least mature surfaces and the most restricted capacity for root exploration. Perched terraces exhibited greater plant dominance than did the other habitats in the early stages of succession because of the ubiquitous appearance of Parasponia rugosa as initial colonists on these relatively flat surfaces. Polynomial canonical correspondence analysis was more closely aligned with the pattern of vegetation than linear canonical correspondence analysis, and therefore more closely approximated accurate descriptions of correlations among site ordination positions and measured variables. These results confirm that a variety of statistical approaches can clarify applications for restoration ecology following landslide and volcanic disturbances or agriculture and forestry anthropogenic disturbances in the lowland tropics.
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Marler TE. Vertical stratification in arthropod spatial distribution research. Commun Integr Biol 2013; 6:e25749. [PMID: 24567772 PMCID: PMC3926874 DOI: 10.4161/cib.25749] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 07/14/2013] [Indexed: 11/19/2022] Open
Abstract
Spatial heterogeneity within individual host trees is often overlooked in surveys of phytophagous arthropod abundance and distribution. The armored scale Aulacaspis yasumatsui is controlled by the predator Rhyzobius lophanthae to a greater degree on leaves at 75-cm height than on leaves at ground level within its host tree Cycas micronesica. The direct influence of elevation on the predator indirectly generates vertical heterogeneity of the scale insect. Arthropod sampling schemes that fail to include all strata within the vertical profile of the host tree species may generate misleading outcomes. Results indicate that sub-meter increments can reveal significant differences in vertical distribution of phytophagous insects, and that inclusion of observations on other organisms that interact with the target arthropod may illuminate determinants of vertical heterogeneity.
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Marler TE, Lawrence JH. Canopy and knowledge gaps when invasive alien insects remove foundation species. Commun Integr Biol 2013; 6:e22331. [PMID: 23847712 PMCID: PMC3689568 DOI: 10.4161/cib.22331] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 09/22/2012] [Indexed: 12/15/2022] Open
Abstract
The armored scale Aulacaspis yasumatsui invaded the northern range of the cycad Cycas micronesica in 2003, and epidemic tree mortality ensued due to a lack of natural enemies of the insect. We quantified cycad demographic responses to the invasion, but the ecological responses to the selective removal of this foundation species have not been addressed. We use this case to highlight information gaps in our understanding of how alien invasive phytophagous insects force cascading adverse ecosystem changes. The mechanistic role of unique canopy gaps, oceanic island examples and threatened foundation species with distinctive traits are three issues that deserve research efforts in a quest to understand this facet of ecosystem change occurring across multiple settings globally.
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Marler TE. Increased threat of island endemic tree's extirpation via invasion-induced decline of intrinsic resistance to recurring tropical cyclones. Commun Integr Biol 2013; 6:e22361. [PMID: 23802037 PMCID: PMC3689569 DOI: 10.4161/cib.22361] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 09/22/2012] [Accepted: 09/25/2012] [Indexed: 12/03/2022] Open
Abstract
Cycas micronesica populations in Guam have been threatened by the invasion of the armored scale Aulacaspis yasumatsui. I integrate four factors that illuminate an acute need for intervention to reduce an unprecedented threat caused by the invasion. First, mechanical failure of healthy C. micronesica trees during catastrophic winds is rare because of the cycad tree’s unique pachycaulis stem design. Second, tree-winching and three-point bend stress tests revealed the natural resistance to damage from tropical cyclones has been compromised by the chronic feeding of this homopteran pest. Third, no typhoon event has occurred since the arthropod’s invasion and its spread in the year 2005 to actually test extent of mechanical failure for the unhealthy remaining trees. Fourth, historical records indicate the probability that Guam will experience typhoon force winds is 0.51 in three years and 0.91 in 10 y. These four factors integrate to predict the next typhoon may eliminate the surviving C. micronesica trees and stewardship of this declining population requires intervention to counter this prediction.
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Marler TE. Boomeranging in structural defense: phytophagous insect uses cycad trichomes to defend against entomophagy. PLANT SIGNALING & BEHAVIOR 2012; 7:1484-7. [PMID: 22990448 PMCID: PMC3548874 DOI: 10.4161/psb.22013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Plant defensive behaviors that resist arthropod herbivory include trichome-mediated defenses, and variation in plant trichome morphology and abundance provides examples of the mechanistic complexities of insect-plant interactions. Trichomes were removed from Cycas revoluta cataphylls on the island of Guam to reveal Aulacaspis yasumatsui scale infestation, and predation of the newly exposed insects by pre-existing Rhyzobius lophanthae beetles commenced within one day. The quotient of predated/total scale insects was 0.5 by day 4 and stabilized at that found on adjacent glabrous leaves in about one week. The trichome phenotype covering the C. revoluta cataphyll complex offers the invasive A. yasumatsui armored scale effectual enemy-free space in this system. This pest and predator share no known evolutionary history with C. revoluta, therefore, the adaptive significance of this plant behavior in natural habitat is not yet known.
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Marler TE, Lindström A, Terry LI. Information-based or resource-based systems may mediate Cycas-herbivore interactions. PLANT SIGNALING & BEHAVIOR 2012; 7:760-762. [PMID: 22751309 PMCID: PMC3583958 DOI: 10.4161/psb.20470] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Invasive arthropod herbivores comprise one of the greatest threats to cycad conservation both in situ and ex situ. We discuss two mechanisms, not necessarily mutually exclusive, that may underlie the disparity in Chilades pandava damage among Cycas species. In an information-based system, plant infochemicals may differentially influence oviposition behavior of Ch. pandava adults or host finding behavior of this butterfly's natural enemies. Alternatively, heterogeneity in damage may be mediated by a resource-based system whereby plant substrate is more palatable to larvae for susceptible species or more defended by less damaged species.
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