Tropical phenology in a time of change

Phenology is increasingly recognised as an important indicator to measure the impacts of global environmental change. Changes to the phenology of tropical ecosystems are likely to have wide-reaching impacts on species, human society and even feedback onto climate. However, tropical phenology data are often unavailable and analyses have been constrained by dependence on geographically limited, noncircular indicators and lack of power in statistical analyses. This thesis addresses these challenges by making available and analysing for the first time a 32-year long record of monthly focal-crown observations (>1000 individuals of >80 species) from western equatorial Africa (Lopé National Park, Gabon). In Chapter 2, I developed a novel application of Fourier analysis to objectively and quantitatively describe flowering phenology at Lopé (856 trees of 70 species). I tested the power of this approach under different scenarios of data noise (regularity of the cycle and detectability of phenological events) and data length using both simulations and field data. Most individual trees monitored at Lopé flower at regular intervals (59%) and most species have dominant annual flowering modes (88%). I showed that at least six years of data are necessary to confidently detect flowering cycles using this method. In Chapter 3, I considered how both existing, and emerging, tropical phenology monitoring programs could be made most effective for change analyses by investigating major sources of noise in data collection. Using Fourier analyses of focal crown observations from Lopé (827 trees of 61 species) I showed that regular annual cycles are more common among reproductive than vegetative phenophases. Using expert knowledge and Generalized Linear Mixed Modelling I showed that experienced field observers can provide important information on major sources of noise in data collection and that observation length, phenophase visibility and phenophase duration are all important positive predictors of cycle detectability. In Chapter 4, I assessed how local weather has changed in western equatorial Africa using Wavelet analysis and Generalised Linear Mixed Models of the long-term weather record from Lopé (34 years of rainfall and temperature observations). Lopé is characterised by a cool, cloudy, long dry season that contrasts with two bright rainy seasons. Lopé has warmed at a rate of 0.23°C per decade (minimum daily temperature) and dried at a rate of -52mm per decade (total annual precipitation) since 1984. Interannual variation in rainfall and temperature is significantly influenced by global weather patterns such as the El Niño Southern Oscillation and the Atlantic Cold Tongue. Given this context of change, in Chapter 5 I selected focal-crown observations from a representative subset of canopy tree species at Lopé (108 trees of 8 species representative of 63% of total canopy volume) to assess seasonal and interannual variation in leaf phenology. I found that the tree community is evergreen with dominant species exchanging leaves incrementally and that new leaf development is suppressed during the long dry season. Using Generalised Linear Mixed Models I demonstrated that moisture, light and leaf herbivory are all important positive predictors of new leaf production at seasonal scales. The community-wide probability of leaf flush at Lopé has declined since 1986 and is most strongly predicted by the rise in atmospheric CO2. Finally, in Chapter 6 I applied the knowledge accumulated in the previous chapters to assess the impacts of fluctuating resource availability on commercialisation of Moabi Oil, a traditional non-timber forest product in west central Africa. I combined over 15 years’ scientific monitoring of the phenology of Baillonella toxisperma at Lopé National Park with interviews of indigenous knowledge of Moabi oil producers in rural Gabon, to describe the factors that influence Moabi harvest success and explore its impacts on the rest of the Moabi oil value chain. Because of the temporal and regional variability of wild Moabi fruit availability I recommended a multi-species approach to NTFP commercialisation in the Gabonese NP buffer zones. In summary, I have shown that regularly cycling phenology is common in tropical tree communities although a wide range of strategies is evident. The evidence from Lopé supports the idea that western equatorial Africa experiences a strongly seasonal environment with a uniquely light deficient long dry season and that this seasonality in environmental conditions directly impacts the phenology of the plant community. The potential stresses on the plant community associated with the long-term warming and drying trends at Lopé appear to be compensated by CO2 fertilisation and the characteristic light deficiency of the region which improve water use efficiency. This thesis answers numerous calls for more quantitative assessment of tropical phenology data by making available evidence from a previously unpublished longterm dataset. This thesis also serves to link the cycles of tropical forest productivity and reproduction to global socio-ecological issues such as forest regeneration, climate mediation and resource availability for threatened animal species and human forest users

Rare ground data confirm significant warming and drying in western equatorial Africa

Background The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However, they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2,000 mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of persistent cloudiness and inability to ground-truth estimates. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests under future climate scenarios. Methods We have the rare opportunity to analyse a 34 year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in Gabon, western equatorial Africa. We used (generalized) linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns. Results Lopé’s weather is characterised by a cool, light-deficient, long dry season. Long-term climatic means have changed significantly over the last 34 years, with warming occurring at a rate of +0.25 °C per decade (minimum daily temperature) and drying at a rate of −75 mm per decade (total annual rainfall). Inter-annual climatic variability at Lopé is highly influenced by global weather patterns. Sea surface temperatures of the Pacific and Atlantic oceans have strong coherence with Lopé temperature and rainfall on multi-annual scales. Conclusions The Lopé long-term weather record has not previously been made public and is of high value in such a data poor region. Our results support regional analyses of climatic seasonality, long-term warming and the influences of the oceans on temperature and rainfall variability. However, warming has occurred more rapidly than the regional products suggest and while there remains much uncertainty in the wider region, rainfall has declined over the last three decades at Lopé. The association between rainfall and the Atlantic cold tongue at Lopé lends some support for the ‘dry’ models of climate change for the region. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of dry season clouds to ocean temperatures and the viability of humid evergreen forests in this dry region should the clouds disappear

A chemo- and regioselective tandem [3+2]heteroannulation strategy for carbazole synthesis : combining two mechanistically distinct bond-forming processes

A modular approach to prepare tri- and tetracyclic carbazoles by a sequential [3 + 2]heteroannulation is described. First, optimization of Pd-catalyzed Buchwald-Hartwig amination followed by C/N-arylation in a one-pot process is established. Second, mechanistic analyses identified the origins of chemo- and regioselective sequential control of both bond-forming steps. Finally, the substrate scope is demonstrated by the preparation of a range of tri- and tetracyclic carbazoles, including expedient access to several natural products and anti-cancer agents

Annual cycles are the most common reproductive strategy in African tropical tree communities

Abstract We present the first cross‐continental comparison of the flowering and fruiting phenology of tropical forests across Africa. Flowering events of 5446 trees from 196 species across 12 sites and fruiting events of 4595 trees from 191 species across 11 sites were monitored over periods of 6 to 29 years and analyzed to describe phenology at the continental level. To study phenology, we used Fourier analysis to identify the dominant cycles of flowering and fruiting for each individual tree and we identified the time of year African trees bloom and bear fruit and their relationship to local seasonality. Reproductive strategies were diverse, and no single regular cycle was found in >50% of individuals across all 12 sites. Additionally, we found annual flowering and fruiting cycles to be the most common. Sub‐annual cycles were the next most common for flowering, whereas supra‐annual patterns were the next most common for fruiting. We also identify variation in different subsets of species, with species exhibiting mainly annual cycles most common in West and West Central African tropical forests, while more species at sites in East Central and East African forests showed cycles ranging from sub‐annual to supra‐annual. Despite many trees showing strong seasonality, at most sites some flowering and fruiting occurred all year round. Environmental factors with annual cycles are likely to be important drivers of seasonal periodicity in trees across Africa, but proximate triggers are unlikely to be constant across the continent.Additional co-authors: Roman M. Wittig, Thomas Breuer, Mireille Breuer‐Ndoundou Hockemba, Crickette M. Sanz, David B. Morgan, Anne E. Pusey, Badru Mugerwa, Baraka Gilagiza, Caroline Tutin, Corneille E. N. Ewango, Douglas Sheil, Edmond Dimoto, Fidèle Baya, Flort Bujo, Fredrick Ssali, Jean‐Thoussaint Dikangadissi, Kim Valenta, Michel Masozera, Michael L. Wilson, Robert Bitariho, Sydney T. Ndolo Ebika, Sylvie Gourlet‐Fleury, Felix Mulindahabi, Colin M. Beal

The Relationship Between Ward Social Climate, Ward Sense of Community, and Incidents of Disruptive Behavior: A Study of a High Secure Psychiatric Sample

Assaults and seclusions within the UK impede patient recovery, and carry a combined UK cost of £126 million a year. Research has identified low ward social climate as a factor that contributes to such institutionalised disruptive behaviour. A related concept, sense of community, has been associated with disruptive behaviour in non-clinical communities, but has not been studied in forensic or psychiatric settings – and thus its contribution to disruptive behaviour in secure psychiatric care is unknown. The current study investigates the relationship between self-reported sense of community and social climate scores with incidents of disruptive behaviour (i.e. assaults and seclusions) within a UK high secure psychiatric hospital. Findings reveal that both social climate and sense of community predict incidents of disruptive behaviour, with hierarchical modelling suggesting that sense of community is the better predictor of disruptive behaviour. This study argues that sense of community should be monitored in high secure hospitals

PhotoAffinity bits : a photoaffinity-based fragment screening platform for efficient identification of protein ligands

Advances in genomic analyses enable the identification of new proteins that are associated with disease. To validate these targets, tool molecules are required to demonstrate that a ligand can have a disease-modifying effect. Currently, as tools are reported for only a fraction of the proteome, platforms for ligand discovery are essential to leverage insights from genomic analyses. Fragment screening offers an efficient approach to explore chemical space, however, it remains challenging to develop techniques that are both sufficiently high-throughput and sensitive. We present a fragment screening platform, termed PhABits (PhotoAffinity Bits), which utilises a library of photoreactive fragments to covalently capture fragment-protein interactions. Hits can be profiled to determine potency and site of crosslinking, and subsequently developed as reporters in a competitive displacement assay to identify novel hit matter. We envision that the PhABits will be widely applicable to novel protein targets, identifying starting points in the development of therapeutic

Reactive fragments targeting carboxylate residues employing direct to biology, high-throughput chemistry

The screening of covalent or ‘reactive’ fragment libraries against proteins is becoming an integral approach in hit identification, enabling the development of targeted covalent inhibitors and tools. To date, reactive fragment screening has been limited to targeting cysteine residues, thus restricting applicability across the proteome. Carboxylate residues present a unique opportunity to expand the accessible residues due to high proteome occurrence (∼12%). Herein, we present the development of a carboxylate-targeting reactive fragment screening platform utilising 2-aryl-5-carboxytetrazole (ACT) as the photoreactive functionality. The utility of ACT photoreactive fragments (ACT-PhABits) was evaluated by screening a 546-membered library with a small panel of purified proteins. Hits identified for BCL6 and KRASG12D were characterised by LC-MS/MS studies, revealing the selectivity of the ACT group. Finally, a photosensitised approach to ACT activation was developed, obviating the need for high energy UV-B light

The Native Copper- and Zinc- Binding Protein Metallothionein Blocks Copper-Mediated Aβ Aggregation and Toxicity in Rat Cortical Neurons

Background: A major pathological hallmark of AD is the deposition of insoluble extracellular b-amyloid (Ab) plaques. There are compelling data suggesting that Ab aggregation is catalysed by reaction with the metals zinc and copper. Methodology/Principal Findings: We now report that the major human-expressed metallothionein (MT) subtype, MT-2A, is capable of preventing the in vitro copper-mediated aggregation of Ab1–40 and Ab1–42. This action of MT-2A appears to involve a metal-swap between Zn 7MT-2A and Cu(II)-Ab, since neither Cu 10MT-2A or carboxymethylated MT-2A blocked Cu(II)-Ab aggregation. Furthermore, Zn7MT-2A blocked Cu(II)-Ab induced changes in ionic homeostasis and subsequent neurotoxicity of cultured cortical neurons. Conclusions/Significance: These results indicate that MTs of the type represented by MT-2A are capable of protecting against Ab aggregation and toxicity. Given the recent interest in metal-chelation therapies for AD that remove metal from Ab leaving a metal-free Ab that can readily bind metals again, we believe that MT-2A might represent a different therapeuti

Complement C3 and C3aR mediate different aspects of emotional behaviours; relevance to risk for psychiatric disorder

Complement is a key component of the immune system with roles in inflammation and host-defence. Here we reveal novel functions of complement pathways impacting on emotional reactivity of potential relevance to the emerging links between complement and risk for psychiatric disorder. We used mouse models to assess the effects of manipulating components of the complement system on emotionality. Mice lacking the complement C3a Receptor (C3aR−/−) demonstrated a selective increase in unconditioned (innate) anxiety whilst mice deficient in the central complement component C3 (C3−/−) showed a selective increase in conditioned (learned) fear. The dissociable behavioural phenotypes were linked to different signalling mechanisms. Effects on innate anxiety were independent of C3a, the canonical ligand for C3aR, consistent with the existence of an alternative ligand mediating innate anxiety, whereas effects on learned fear were due to loss of iC3b/CR3 signalling. Our findings show that specific elements of the complement system and associated signalling pathways contribute differentially to heightened states of anxiety and fear commonly seen in psychopathology