Are Hylobates lar Extirpated from China?

The Nangunhe Nature Reserve in Southwest Yunnan (PRC) has long been presumed to be the last stronghold of lar (or white-handed) gibbons (Hylobates lar) in China and the likely last place of occurrence of Hylobates lar yunnanensis. We conducted a comprehensive survey to assess the status of lar gibbons at Nangunhe. We found no visual or auditory evidence of them still residing at the reserve and therefore tentatively conclude that lar gibbons have become extinct in China. It appears that large-scale destruction of primary forests in the 1960s and 1970s brought about an initial decline in their numbers, and subsequent uncontrolled hunting has resulted in their extirpation. The situation for the six Chinese ape taxa is nothing less than disastrous, with 1 taxon assumed to have become extinct during the last few years, 1 taxon not having been confirmed since the 1980s, and 2 species at the very brink of extinction with only tens of individuals remaining in China

Latitudinal patterns in stabilizing density dependence of forest communities

Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1, 2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4, 5, which increases community stabilization, species coexistence and the diversity of local tree species6, 7. Previous analyses supporting such a latitudinal gradient in CNDD8, 9 have suffered from methodological limitations related to the use of static data10–12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14, 15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests

Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+. Though broad scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8–50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass (AGB) at spatial grains ranging from 5 to 250m (0.025–6.25 ha), and we evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that the spatial sampling error in AGB is large for standard plot sizes, averaging 46.3% for 0.1 ha subplots and 16.6% for 1 ha subplots. Topographically heterogeneous sites showed positive spatial autocorrelation in AGB at scales of 100m and above; at smaller scales, most study sites showed negative or nonexistent spatial autocorrelation in AGB. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGB leads to a substantial “dilution” bias in calibration parameters, a bias that cannot be removed with current statistical methods. Overall, our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise

Mycorrhizal feedbacks influence global forest structure and diversity

One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure

Age related decline in female lar gibbon great call performance suggests that call features correlate with physical condition

Background: White-handed gibbons (Hylobates lar) are small Asian apes known for living in stable territories and producing loud, elaborate vocalizations (songs), often in well-coordinated male/female duets. The female great call, the most conspicuous phrase of the repertoire, has been hypothesized to function in intra-sexual territorial defense. We therefore predicted that characteristics of the great call would correlate with a caller’s physical condition, and thus might honestly reflect resource holding potential (RHP). Because measurement of RHP is virtually impossible for wild animals, we used age as a proxy, hypothesizing that great call climaxes are difficult to produce and maintain over time, and that older adults will therefore perform lower quality great calls than young adults. To test this we analyzed the great call climaxes of 15 wild lar gibbon females at Khao Yai National Park, Thailand and 2 captive females at Leo Conservation Center, Greenwich, CT. Results: Findings show that call climaxes correlate with female age, as young animals (n = 8, mean age: 12.9 years) produced climaxes with a higher frequency range (delta F0), maximum F0 frequency and duty cycle than old animals (n = 9, mean age: 29.6 years). A permuted discriminant function analysis also correctly classified calls by age group. During long song bouts the maximum F0 frequency of great call climaxes’ also decreased. Additional data support the hypothesis that short high notes, associated with rapid inhalation as an individual catches its breath, reflect increased caller effort. Older females produced more high notes than younger females, but the difference only approached statistical significance, suggesting that calling effort may be similar across different ages. Finally, for the first time in this species, we measured peak intensity of calls in captive females. They were capable of producing climaxes in excess of 100 dB at close range (2.7 m). Conclusions: Age and within-bout differences in the lar gibbon great call climax suggest that call features correlate with physical condition and thus the call may have evolved as an honest signal in the context of intra-sexual territorial defense and possibly also in male mate choice via sexual selection, although further testing of these hypotheses is necessary. Results: Findings show that call climaxes correlate with female age, as young animals (n = 8, mean age: 12.9 years) produced climaxes with a higher frequency range (delta F0), maximum F0 frequency and duty cycle than old animals (n = 9, mean age: 29.6 years). A permuted discriminant function analysis also correctly classified calls by age group. During long song bouts the maximum F0 frequency of great call climaxes’ also decreased. Additional data support the hypothesis that short high notes, associated with rapid inhalation as an individual catches its breath, reflect increased caller effort. Older females produced more high notes than younger females, but the difference only approached statistical significance, suggesting that calling effort may be similar across different ages. Finally, for the first time in this species, we measured peak intensity of calls in captive females. They were capable of producing climaxes in excess of 100 dB at close range (2.7 m). Conclusions: Age and within-bout differences in the lar gibbon great call climax suggest that call features correlate with physical condition and thus the call may have evolved as an honest signal in the context of intra-sexual territorial defense and possibly also in male mate choice via sexual selection, although further testing of these hypotheses is necessary

Response to Comment on “Plant diversity increases with the strength of negative density dependence at the global scale”

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings—(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance—persist even after controlling for other processes that might influence spatial relationships between adults and recruits

Circulating microRNAs in sera correlate with soluble biomarkers of immune activation but do not predict mortality in ART treated individuals with HIV-1 infection: A case control study

Introduction: The use of anti-retroviral therapy (ART) has dramatically reduced HIV-1 associated morbidity and mortality. However, HIV-1 infected individuals have increased rates of morbidity and mortality compared to the non-HIV-1 infected population and this appears to be related to end-organ diseases collectively referred to as Serious Non-AIDS Events (SNAEs). Circulating miRNAs are reported as promising biomarkers for a number of human disease conditions including those that constitute SNAEs. Our study sought to investigate the potential of selected miRNAs in predicting mortality in HIV-1 infected ART treated individuals. Materials and Methods: A set of miRNAs was chosen based on published associations with human disease conditions that constitute SNAEs. This case: control study compared 126 cases (individuals who died whilst on therapy), and 247 matched controls (individuals who remained alive). Cases and controls were ART treated participants of two pivotal HIV-1 trials. The relative abundance of each miRNA in serum was measured, by RTqPCR. Associations with mortality (all-cause, cardiovascular and malignancy) were assessed by logistic regression analysis. Correlations between miRNAs and CD4+ T cell count, hs-CRP, IL-6 and D-dimer were also assessed. Results: None of the selected miRNAs was associated with all-cause, cardiovascular or malignancy mortality. The levels of three miRNAs (miRs -21, -122 and -200a) correlated with IL-6 while miR-21 also correlated with D-dimer. Additionally, the abundance of miRs -31, -150 and -223, correlated with baseline CD4+ T cell count while the same three miRNAs plus miR- 145 correlated with nadir CD4+ T cell count. Discussion: No associations with mortality were found with any circulating miRNA studied. These results cast doubt onto the effectiveness of circulating miRNA as early predictors of mortality or the major underlying diseases that contribute to mortality in participants treated for HIV-1 infection

Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDDC (Reducing Emissions from Deforestation and Forest Degradation). Though broad-scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8-50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass density (AGBD in Mgha⁻¹) at spatial scales ranging from 5 to 250 m (0.025-6.25 ha), and to evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that local spatial variability in AGBD is large for standard plot sizes, averaging 46.3% for replicate 0.1 ha subplots within a single large plot, and 16.6% for 1 ha subplots. AGBD showed weak spatial autocorrelation at distances of 20-400 m, with autocorrelation higher in sites with higher topographic variability and statistically significant in half of the sites. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGBD leads to a substantial “dilution” bias in calibration parameters, a bias that cannot be removed with standard statistical methods. Our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise