A network theoretic study of potential invasion and spread of Lantana camara in a part of Rajaji Tiger Reserve, India

摘要

Ecosystems are constantly under threat by invasive species which alter existing ecological networks as they spread. We use Geographic Information System methods coupled with complex network analysis to model the movement and spread of Lantana camara in Rajaji Tiger Reserve, India, as understanding spatial aspects of the spread mechanism are essential for better resource management in the region. Lantana mapping was carried out by field observations along multiple transects and plots, and the data generated was used as input for maximum entropy modelling to identify land patches in the study area that are favourable for lantana growth. The patch information so obtained was integrated with a raster map generated by identifying different topographical features in the study area which are favourable for lantana growth. The integrated data was analysed with a complex network perspective, where relatively dense and large potential lantana distribution patches were considered as vertices, connected by relatively sparse and thin potential lantana continuities, identified as edges. The network centrality analysis reveal key patches in the study area that play specialized roles in the spread of lantana in a large region. Hubs in the lantana network are primarily identified as dry seasonal river beds. The lantana network is found to exhibit small-world architecture with a well formed community structure. We infer that the above properties of the lantana network are major contributors in regulating the movement and spread of the plant through the entire region of study.