Resume
Cang Hui (born June 10, 1977; family name: Hui; name in Chinese: 惠苍) is a mathematical ecologist. He got his BSc (1998) at the Department of Applied Mathematics, Xi'an Jiaotong University, his MSc (2001) in Optimalzation and Biological Mathematics at the Department of Mathematics, Lanzhou University, and his PhD (2004) in Mathematical Ecology at the State Key Laboratory of Arid Agroecology, Department of Ecology, Lanzhou University. He is currently doing his postdoctoral research with the Spatial, Physiological and Conservation Ecology (SPACE) group and the DST-NRF Centre of Excellence for Invasion Biology, at the Department of Conservation Ecology and Entomology, Stellenbosch University. He has published around 40 papers and book chapters in field of ecological modelling and macroecological patterns in ecological community and ecosystems.
Research Interests
His investigations rely heavily on the tools of mathematical analysis, ecological modelling, and biological simulations to support him in his exploration of key theoretical questions in ecology.
Key period: (1996-2001) Initial Explorations
This was the starting point for him to link his mathematical knowledge with ecological science. Using the phase-plane analysis in ordinary differential equations, He analyzed the effect of time-varied parameters on the threshold of epidemic break-out in the susceptible-infectious-resistance (SIR) model. This work further lead to the combining of epidemiological models with economic analysis (book chapter in SARS and China Society) and the spatial dynamics analysis of the epidemic influence in a predator-prey system. He explored models on bio-economic systems, concerning wetland management, renewable resource harvests and restoration plans for oasis agriculture in semi-desert zones. These models included a wide range of mathematical methods, i.e. input-output analysis, optimal control, niche theory, ecological risk and footprint analysis.
Key period: (1999-2005) Spatial Ecology, using metapopulations as a framework
He started to pursue his major interests in spatial ecology using metapopulations as a framework. Using the phase-plane analysis and the bifurcation diagram of ordinary differential equations, He analyzed the characteristics of the equilibriums from a variety of models and then performed their spatiotemporal dynamics by the spatial simulations, e.g. cellular automata (the lattice model) and the incidence function model. Through this process he accumulated much programming experience and confidence. His MSc thesis presented a spatially explicit model dealing with the spatial carrying capacity in a realistic landscape, using the matrix method and spatial modelling. Once again using metapopulations as a framework, he further explored the influence of the density dependent mechanisms (Allee effect, rescue effect and overcrowding effect) and habitat destruction (patch loss, isolation and habitat deterioration) on patterns of the spatial dynamics in his PhD work. The self-organized spatial patterns caused by interspecific interactions (such as competition and predation) have also been explored. Using pair approximation, a method from theoretical physics, I studied the multi-equilibriums of metapopulation dynamics spatially and temporally caused by the Allee effect. Niche construction (also ecosystem engineering and local facilitation) and the evolution of cooperation (evolutionary stable strategy in altruism), as well as allopatric speciation and community structures have also been explored using the spatial modelling of metapopulations. These results showed the importance of spatial structure in shaping the ecological and evolutionary consequences.
Key period: (2004-2007) Scaling and sampling in species distributions
Using Bayes’ rule in probability, Hui et al. (2006) developed the formula governing the scaling pattern of occupancy, which equals the mapping unit variable problem (MUVP) in landscape ecology. This scaling pattern of occupancy is analogous to Kunin’s area-of-occupancy, which remains a major interest of him. The scaling pattern of occupancy is correlated with, but not identical to the occupancy-abundance relationships. Moreover, Hui and McGoech (2007a) explored the traditional occupancy-abundance relationships and revealed its “droopy tail” characteristics, a percolation process with scaling-up. As for a community, the proportion of common and rare species is prevalent leading to the bimodality in the occupancy frequency distribution. This distribution, reviewed in McGeoch and Gaston (2002), lacked the support of a theoretical model. Using a self-similarity bisection scheme, Hui and McGeoch (2007b) built a probability transition model to explain this prevalence of bimodality and the effect of scaling (sample grain) on this frequency distribution. Hui and McGeoch (2007c) have further relaxed the assumption of self-similarity in species distributions, which leads to more biologically realistic shapes for this distribution. The analysis of species distributions evokes an important concept, i.e. aggregation (which has synonyms with different shades of meaning: clustering, clumped, spatial autocorrelation, over-dispersed).
Future
The analysis of community pattern formation (especially for the patterns related to species abundance and distribution) will remain a major research focus for him in the future. Issues on the beta-diversity and the nestedness in communities have gradually come up. These issues, together with occupancy frequency distributions, occupancy-abundance relationships and scaling patterns of occupancy, will together bring a clearer understanding of the assemblage rules of species in a community. For example: Hubbell’s neutral model has proposed a general understanding of community patterns generated by basic ecological interactions without distinguishing the species characteristics. Hui and his colleagues’ work are to try to demonstrate the effect of statistical essence in ecological patterns. He believe that basic interactions, statistical and sampling effects can together largely account for the community patterns observed in nature. Formulizing these entangled issues will be interesting and important. It will also be useful for understanding the community structure from an evolutionary perspective. Hui and McGeoch's (2006) work on allopatric speciation provides a good explanation for distributions of body size, dietary variety and range size (tested by empirical data), which could serve as a starting point.
Moreover, the applications of the occupancy-abundance relationship and scaling patterns of occupancy have significant potential value in conservation and species management, as it can be used to predict species abundance from measures of their occupancy or occurrence. The relationships between trends in abundance, occupancy and aggregation are also an interesting and valuable line of research. For example, how do the changes in species range (described in atlases as different time periods or different regions) affect the change of abundance for focal species, especially for those that are endangered or invasive. Statistical analysis of spatial patterns will be another focus of future research, which is highly correlated with species abundance and distributions at different scales. There are dozens of analysis methods and indices out there essentially dealing with the non-randomness of species distributions. Unifying those interconnected methods and understanding each one’s emphasis will be useful in experimental comparison and bring a clear understanding of species spatiotemporal dynamics.
Besides these main pursuits, the evolution of social hierarchy; the emergence of social animal and fish school behavior; as well as other such phenomena which involve self-organization and pattern formation in nature, are also of great interest to him. Using a problem-solving, scenario thinking strategy of interdisciplinary research on complex questions (e.g. adaptive complex system) and social-science interface (e.g. environmental changes and sustainability) is also one of his new interests.
Selected Publication
Hui, C. & McGeoch, M.A. 2007a. Capturing the ‘droopy tail’ in the occupancy-abundance relationship. Écoscience, 14: 103-108. [Link]
Hui, C. & McGeoch, M.A. 2007b. A self-similarity model for occupancy frequency distribution. Theoretical Population Biology, 71: 61-70. [Link]
Hui, C. & McGeoch, M.A. 2007c. Modeling species distributions by breaking the assumption of self-similarity. Oikos, in press. [Link]
Hui, C. & McGeoch, M.A. 2007d. Spatial patterns of prisoner’s dilemma game in metapopulations. Bulletin of Mathematical Biology, 69: 659-676. [Link]
Hui, C. & McGeoch, M.A. 2006. Evolution of body size, range size and food composition in a predator-prey metapopulation. Ecological Complexity, 3: 148-159. [Link]
Hui, C., McGeoch, M.A., & Warren, M. 2006. A spatially explicit approach to estimating species occupancy and spatial correlation. Journal of Animal Ecology, 75: 140-147. [Link]
Hui, C., Zhang, F., Han, X., & Li, Z. 2005. Cooperation evolution and self-regulation dynamics in metapopulation: stage-equilibrium hypothesis. Ecological Modelling, 184: 397-412. [Link]
Hui, C. & Yue, D. 2005. Niche construction and polymorphism maintenance in metapopulations. Ecological Research, 20: 115-119. [Link]
Hui, C., Li, Z., & Yue, D. 2004. Metapopulation dynamics and distribution, and environmental heterogeneity induced by niche construction. Ecological Modelling, 177: 107-118. [Link]
Hui, C. & Li, Z. 2004. Distribution patterns of metapopulation determined by Allee effects. Population Ecology, 46: 55-63. [Link]
Hui, C. & Li, Z. 2003. Dynamical complexity and metapopulation persistence. Ecological Modelling, 164: 201-209. [Link]
Invited Speeches on Sustainability and Environmental Changes
Hui C. 2007. Climate change, environmental sustainability and the future. The Prince of Wales Seminar Series, Cambridge University Programme for Industry, Stanford Valley, South Africa.
Hui C. 2007. Climate change: threats and opportunity to finical services industry. Nedbank Seminar, Johannesburg, South Africa.
Hui C. 2007. A dilemma between social development and environmental sustainability. Leaders Training Seminar, Mandela-Rhodes Foundation, Robin Island, Cape Town, South Africa.
Hui C. 2007. Sustainability: A story of life and death. The Prince of Wales Seminar Series, Cambridge University Programme for Industry, Stanford Valley, South Africa.
Hui C. 2005. China: environment, culture and business opportunities. KWV International Consulting Workshop, Franshoeck, South Africa.
Hui C. 2005. Framework of ecology and its applications. Rainbow Forum, Stellenbosch, South Africa.