Thomas E. Marler

When North and South don’t mix: genetic connectivity of a recently endangered oceanic cycad, Cycas micronesica, in Guam using EST‐microsatellites

Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST‐microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self‐recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam’s genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed‐bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST‐locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species’ vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general.

Root development of ‘Red Lady’ papaya plants grown on a hillside

Abstract‘Red Lady’ papaya (Carica papaya L.) seedlings were grown for 7 weeks in one experiment and 17 weeks in a second experiment on a 60% to 70% sloped hillside. Depth and lateral root developmental characteristics were determined to establish a more informed basis for developing management procedures during hillside production of papaya. A trench was dug perpendicular to the contour line, and positioned 10 cm from the stem base of each plant. A 1 cm layer of soil was removed from the profile wall, and the roots on the trench profile were mapped. Thereafter, the intact half of each root system was excavated to determine the dry mass and length distribution. Roots were separated into the taproot system, and the lateral roots of the uphill and downhill sides. The downhill portion of lateral roots accounted for 56% of total length and 64% of total mass after 7 weeks, and 71% of total length and 69% of total mass after 17 weeks. Some lateral roots on the uphill side of the plants developed with a negative gravitropic orientation to maintain a portion of the root system, close to the surface of the slope. After 17 weeks, 34% of the roots on the uphill side of the trench profile walls were located above a horizontal plane positioned at the stem base. Root growth of ‘Red Lady’ papaya plants growing on hillsides was maintained in all directions, including up the slope. The results signify that there may be no need to modify fertilizer placement practices for hillside production of papaya. However, the higher concentration of roots on the downhill side of these plants indicates a need for placement of soil moisture sensors for irrigation scheduling in uphill and downhill sites.

Demography of Cycas micronesica on Guam following introduction of the armoured scale Aulacaspis yasumatsui

Following the 2003 invasion of the armoured scale Aulacaspis yasumatsui to Guam, changes to population traits of the dominant Cycas micronesica were determined. Belt transects with a width of 4 m and an average length of 120mwereestablishedinOctober2004todocumentplantmortalityuntilJanuary2011.Stemheight,basaldiameter and leaf number were also measured for each plant and used to determine density, demography and allometric relationships. Allometric traits and a left-skewed demographic structure of the pre-invasion C. micronesica habitat documented a thriving population with high recruitment potential. Aulacaspis yasumatsui dispersed into the study site 4 mo after the initial census. All seedlings were killed within 9 mo and all juvenile plants were killed within 40 ± 10mo.Mortalityreached92%by6yafterchronicscaleinfestations.Allometryanddemographyofthe2011survivors described a collapsing C. micronesica population of stressed and reproductively challenged trees with no recruitment. This classic example of the enemy release hypothesis has resulted in a homogeneous decline in plant density from 2007-2011. The trend predicts extirpation of C. micronesica from west Guam habitats by 2019.

Cycas micronesica (Cycadales) plants devoid of endophytic cyanobacteria increase in β-methylamino-l-alanine

Cycads are among the most ancient of extant Spermatophytes, and are known for their pharmacologically active compounds. beta-methylamino-l-alanine (BMAA) is one metabolite that been implicated as causal of human neurodegenerative diseases in Guam. We grew Cycas micronesica seedlings without endophytic cyanobacteria symbiosis, and quantified initial and ending BMAA in various plant tissues. BMAA increased 79% during nine months of seedling growth, and root tissue contained 75% of the ultimate BMAA pool. Endophytic cyanobacteria symbionts were not the source of BMAA increase in these seedlings, which contradicts previously reported claims that biosynthesis of this toxin by cyanobacteria initiates its accumulation in the Guam environment. The preferential loading of root tissue with BMAA does not support earlier reports that this toxin serves a defensive role against herbivory of leaf or seed tissues. The long history of conflicting results in Guams cycad toxin research continues, and recent developments underscore the sense of urgency in continued research as this endangered cycad population approaches extirpation from the island.

Cycad mutualist offers more than pollen transport

Specialist insects share obligate mutualisms with some contemporary cycad species whereby the insects pollination services are rewarded with a nursery in which the insects larvae consume the postdispersal male cone. I prevented visits of the pollinator moth Anatrachyntis sp. to male Cycas micronesica (Cycadaceae) cones to show that consumption of the cone tissue by the mutualist hastened initiation of the plants subsequent reproductive event. This is the first documented case where removal of a postdispersal cycad pollination organ speeds up subsequent reproductive events, and the current paradigm that the offering of cone tissue as a nursery is a sacrifice by the plant in return for the pollination services is therefore inaccurate. In C. micronesica, the herbivory stage of pollination mutualism confers a cryptic benefit of cone tissue disposal, which translates into an increase in ultimate lifetime reproductive effort. The plant population relies on the pollinator for moving gametes, as well as for increasing the number of male coning events. The dual benefits afforded to the plant by associating with this pollinator shows that mutualism can operate simultaneously on very different traits.

Steryl glucoside concentration declines with Cycas micronesica seed age

Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Guam neurological disease cluster, amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC). Some of these neurotoxins remain in the washed cycad seed flour that was historically an important part of the Chamorro diet. Of these, variant steryl glucosides have been identified by us as a possible etiological factor in the disease. In vitro and in vivo animal studies have strongly supported a role for these molecules in some forms of neurodegeneration. As part of a series of studies, we have now determined the concentrations of several steryl glucosides and their sterol precursors as affected by the age of C. micronesica seeds. The concentration of these molecules declined with seed age from 2.0 to 30.5 months. Following log-transformation of both axes, the decline was linear. Similarly, concentration of all but one of the molecules declined with age when samples were restricted to gametophyte tissue. Factors suspected of influencing phenotypic plasticity must be addressed when interpreting plant physiology data. Our results confirm for the first time that tissue age must be documented and reported in cycad seed biochemistry studies to remove ambiguities from results. Past studies in this important area of research have failed to account for the potential impact of seed age, rendering previous outcomes and interpretations of cycad neurotoxins in their impact on ALS-PDC ambiguous.

Pacific island tropical cyclones are more frequent and globally relevant, yet less studied

Typhoon Haiyan devastated the Philippines in 2013 and illuminates the fact that the majority of tropical cyclone (TC) research has focused on the Atlantic Basin, continental socio-ecological systems, affluent regions where the resilience attributes of the human element differ from that of the of majority the world’s population, and organized countries where research and relief capacities are among the best worldwide. I contend that this collective international bias minimizes the usefulness of global TC research in light of global change forecasts, which predict increased frequency of intense TCs. Moreover, paleoecological studies indicate ecosystem resilience following a TC is greatly increased within habitats that experienced a prior history of frequent TCs. When these retrospective and future visions are connected, science-based analysis of the influences of climate change on TC disturbance argues for an increase in contemporary research on TCs of developing island nations in the western Pacific where TCs are already relatively frequent. Otherwise the current research trajectory may further widen the disconnect between best available science and future management decisions.

Primary Succession along an Elevation Gradient 15 Years after the Eruption of Mount Pinatubo, Luzon, Philippines

Abstract: We determined vegetation structure and environmental variables in the Pasig-Potrero and Sacobia River systems on the east flank of Mount Pina-tubo, Luzon, Philippines, to define growth form and taxonomic groups that have influenced primary succession during the 15 yr since the eruption. We selected eight sites within an east-west range of 11.5 km, a north-south range of 7 km, and an elevation gradient of ca. 500 m. The 58 plant taxa we encountered among 63 sampled plots belonged to 21 families. Cover was dominated by Parasponia rugosa (tree) and Saccharum spontaneum (large grass). Cover of these two species was inversely related at the plot level. Exotic species represented nearly 60% of this flora but only 32% of the vegetation cover. Family richness was high for Asteraceae, Fabaceae, and Poaceae. Elevation, distance to the caldera, and distance to human settlement exhibited the most control over the vegetation. The influence of elevation on cover, species composition, and structure differed in these adjacent canyons. Plot species richness, cover, and diversity indices were greatest at the highest elevation of the Pasig-Potrero River. On a small scale, current dominant species may control progression of species assemblages as mediated by geophysical, chemical, facilitative, and competitive changes. Our findings indicate that ongoing anthropogenic disturbances and the prevalence of exotic species may prevent the vegetation from returning to its preeruption state. The invasive Pennisetum setaceum and Chromolaena odorata were widespread in this landscape, and their negative influence on vegetation recovery is probable. Ours is the first detailed survey of vegetation on newly created volcanic surfaces in the region and provides a baseline for understanding the landscape-level processes determining continuing succession.

SEX AND POPULATION DIFFERENCES IN THE ALLOMETRY OF AN ENDANGERED CYCAD SPECIES, CYCAS MICRONESICA (CYCADALES)

Four natural populations of Cycas micronesica K. D. Hill growing under differing ecological conditions were surveyed over a 4‐yr period to assess the response of juveniles before and after the introduction of the cycad aulacaspis scale insect (Aulacaspis yasumatsui Takagi) and to test the hypothesis that monopodial ovulate plants are taller than pollen‐producing plants with equivalent diameter (D). Height (H), D, and leaf and stem tip numbers were recorded for 297 ovulate and 186 pollen‐producing (“male” and “female,” respectively) plants and a total of 493 juveniles ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape