Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

     

Collateral damage: impacts of ethno-civil strife on biodiversity and natural resource use near Indian nature reserves

Civil conflicts often affect the control of natural resources, altering their access and use. Using a combination of questionnaires, remote sensing, and a review of articles in the popular print media, we investigated the impact of a protracted armed conflict on forest loss, livelihoods, and forest use near two globally important tiger reserves in northeastern India. Over a 23 year period, we found evidence of large-scale forest loss in the vicinity of Nameri and Pakke Tiger Reserves. Nearly all (99 %) interviewees opined that the ethno-civil strife was to blame for declining forest cover. Most interviewees identified 1990 as the year of onset of strife-mediated deforestation. This is partially supported by a review of print-media articles that reported conflict, violence, displacement, and the onset of large-scale migration in the previous year. According to respondents, ethno-civil strife has radically altered access to, and use of forests, by resident communities (causing economic hardship, increased costs, and reduced availability of essential timber products), and has also accelerated forest loss and increased poaching. We conclude that forests and wildlife in these protected areas are at immediate risk from ethno-civil strife. Urgent interventions are needed to reduce the environmental and societal impacts of civil strife in this biologically crucial region of India.     

Genetic Admixture in the Culturally Unique Peranakan Chinese Population in Southeast Asia

The Peranakan Chinese are culturally unique descendants of immigrants from China who settled in the Malay Archipelago ∼300–500 years ago. Today, among large communities in Southeast Asia, the Peranakans have preserved Chinese traditions with strong influence from the local indigenous Malays. Yet, whether or to what extent genetic admixture co-occurred with the cultural mixture has been a topic of ongoing debate. We performed whole-genome sequencing (WGS) on 177 Singapore (SG) Peranakans and analyzed the data jointly with WGS data of Asian and European populations. We estimated that Peranakan Chinese inherited ∼5.62% (95% confidence interval [CI]: 4.76–6.49%) Malay ancestry, much higher than that in SG Chinese (1.08%, 0.65–1.51%), southern Chinese (0.86%, 0.50–1.23%), and northern Chinese (0.25%, 0.18–0.32%). A sex-biased admixture history, in which the Malay ancestry was contributed primarily by females, was supported by X chromosomal variants, and mitochondrial (MT) and Y haplogroups. Finally, we identified an ancient admixture event shared by Peranakan Chinese and SG Chinese ∼1,612 (95% CI: 1,345–1,923) years ago, coinciding with the settlement history of Han Chinese in southern China, apart from the recent admixture event with Malays unique to Peranakan Chinese ∼190 (159–213) years ago. These findings greatly advance our understanding of the dispersal history of Chinese and their interaction with indigenous populations in Southeast Asia.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

The Influence of Hunting on Antipredator Behavior in Central African Monkeys and Duikers

Many animals can adjust their behavioral strategies to reduce predation risk. We investigated whether rain forest monkeys and duikers alter their antipredatory behavior in response to hunting by humans in southwestern Gabon. We compared monkey and duiker responses to human observers in an area where hunting is prohibited, to those in a nearby area where hunting pressure is moderate but spatially variable. The results of our study indicate that monkeys become more secretive when hunted, commencing alarm calls only when at a certain distance (typically > 50 m) from humans. We found no difference in monkey group size between hunted and no-hunting areas. In no-hunting areas, duikers often freeze in response to approaching observers, but in hunted areas they abandon this strategy and rapidly flee from humans. Duikers also whistle more often in areas where they are hunted frequently. Our findings have at least two important implications. First, behavioral observations of monkeys and duikers may be useful in gauging local hunting intensity in African rain forests. Second, duiker densities are likely to be overestimated in hunted areas, where they more readily flee and whistle, and underestimated in no-hunting areas, where they rely on freezing behavior to avoid detection. Because behavioral adaptations to hunting vary both among species and localities, these differences should be considered when attempting to derive population-density estimates for forest wildlife.