Island Invasion by a Threatened Tree Species: Evidence for Natural Enemy Release of Mahogany (Swietenia macrophylla) on Dominica, Lesser Antilles

Despite its appeal to explain plant invasions, the enemy release hypothesis (ERH) remains largely unexplored for tropical forest trees. Even scarcer are ERH studies conducted on the same host species at both the community and biogeographical scale, irrespective of the system or plant life form. In Cabrits National Park, Dominica, we observed patterns consistent with enemy release of two introduced, congeneric mahogany species, Swietenia macrophylla and S. mahagoni, planted almost 50 years ago. Swietenia populations at Cabrits have reproduced, with S. macrophylla juveniles established in and out of plantation areas at densities much higher than observed in its native range. Swietenia macrophylla juveniles also experienced significantly lower leaf-level herbivory (∼3.0%) than nine co-occurring species native to Dominica (8.4–21.8%), and far lower than conspecific herbivory observed in its native range (11%–43%, on average). These complimentary findings at multiple scales support ERH, and confirm that Swietenia has naturalized at Cabrits. However, Swietenia abundance was positively correlated with native plant diversity at the seedling stage, and only marginally negatively correlated with native plant abundance for stems ≥1-cm dbh. Taken together, these descriptive patterns point to relaxed enemy pressure from specialized enemies, specifically the defoliator Steniscadia poliophaea and the shoot-borer Hypsipyla grandella, as a leading explanation for the enhanced recruitment of Swietenia trees documented at Cabrits

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

The Impact of Polypore Fungi on Growth and Physiology of Yellow Birch and Molecular Detection of Fungal Pathogens in Live Trees

Pathogenic fungi, such as polypore fungi that infect live sapwood, decrease quality and value of wood; however their effects on canopy physiology and growth have been little examined. This study examines how Fomes fomentarius, a species of polypore fungus affects canopy physiology in Betula alleghaniensis. A mobile canopy lift enabled the collection of leaf physiology, morphology and chemistry data from canopies of infected, damaged, and control trees. A molecular protocol developed to detect and identify polypore fungi in live trees confirmed that F. fomentarius was the major species present in infected trees. Infected trees exhibited reductions in physiological performance and growth, along with higher leaf carbon and chlorosis. While some characteristics of fungal infection were consistent with a mechanism involving partial xylem occlusion, patterns did not resemble those of a simple drought response. Likely, other factors such as fungal toxins or host defense mechanisms also contribute to these patterns.MAS

Data from: Tropical trees in a wind-exposed island ecosystem: height-diameter allometry and size at onset of maturity

1. Tropical tree species adapted to high wind environments might be expected to differ systematically in terms of stem allometry and life-history patterns, as compared with species found in less windy forests. We quantified height-diameter (H-D) allometries and relative size at onset of maturity (RSOM) for rainforest tree and tree fern species native to Dominica, West Indies, an island that experiences some of the highest average wind speeds pantropically. 2. H-D allometries for 17 Dominican angiosperm tree species were strongly concave on a log-log scale with asymptotic heights ranging from 9-32 m among species, averaging 25 m for canopy trees. H-D allometries for species-pooled data deviated strongly from recorded patterns for other tropical forest trees: asymptotic heights for trees in Dominica were 30-116% lower than those recorded for continental rainforest trees in Australia, South America, Africa, and Southeast Asia. In a subset of canopy trees sampled in steep, sheltered valleys, heights were 12-26% larger at a given diameter, and approached those observed in other tropical regions, suggesting large phenotypic responses of H-D allometries to wind conditions. 3. RSOM (quantified as the ratio of height at onset of reproduction to asymptotic maximum height) for Dominican angiosperm species was highly variable, ranging from 0.23-0.89 (mean 0.54), similar to patterns observed in Malaysia and Panama; very low RSOM values were estimated for two tree fern species. Pooling data from Dominica with published values from other tropical forests, we observed a significant negative correlation between RSOM and wood density. 4. Synthesis: Our data suggest that wind regimes are a critical determinant of height-diameter (H-D) allometries of tropical trees at both the local and global scale. Although we found no evidence for a systematic differences in reproductive onset related to wind regime, RSOM was negatively correlated with species’ wood density, suggesting that more shade-tolerant tree species show a longer period of gradually increasing reproductive allocation through ontogeny

Thomas_etal_2014_Dryad2

Data on tree allometry in exposed vs. shelter sites collected in the field at various sites in Dominica, Lesser Antilles in 2008-2010. Abbreviated headlines are as follows: "expos" = classification of site exposure: "exp" = exposed, "sh" = sheltered; "sp" = species code; "diam_cm" = stem diameter in cm at 1.3 m height, "incallom" = excluded/included in allometric analyses based on assessment of crown and stem damage, scored as (0/1)

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4 m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5 m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 yr, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit