The Himalayan Soap Pod Tree (Gymnocladus assamicus): An Ecologically and Economically Important Tree on the Brink of Extinction

Gymnocladus assamicus is an archaic tree endemic to the Eastern Himalayan region of Northeast India. Locally known as “Menangmanba-shi” by the Monpa tribe of Arunachal Pradesh (India), mature G. assamicus pods contain high saponin and are used traditionally for cleansing purposes and rituals. Major intrinsic and extrinsic factors that might be responsible for population decline are described. More importantly, the book highlights a very rare mating system known as “androdioecy” in which male and hermaphrodite individuals co-exist in the natural population. Overall, the book highlights the story of a critically endangered tree species with a unique biological and socio-cultural importance and will serve as a case study and reference for other similar species both locally and globally. Cover Himalayan Soap Pod Tree (Gymnocladus assamicus): An Ecologically and Economically Important Tree on the Brink of Extinction Copyright Contents Acknowledgements General Introduction 1 Biology, Distribution and Population Status of Gymnocladus assamicus 1.1 Introduction 1.2 Taxonomy of G. assamicus 1.2.1 Taxonomic description 1.2.2 Floral sexuality 1.2.3 Hermaphrodite flower 1.2.4 Male flower 1.2.5 Fruit 1.3 Ethnobotanical Uses of Fruits 1.4 Distribution 1.5 Population Status of Soap Pod Tree and its Associated Vegetation 1.6 Microclimatic Conditions 1.7 References 2 Phylogeny and Phylogeography of the Genus Gymnocladus and its Close Relatives 2.1 Introduction 2.2 Legume Diversity in the Eastern Himalayan Region 2.3 Gymnocladus and its Affinity 2.4 Geographic Distribution of Gymnocladus and Gleditsia Species 2.5 Phylogenetic Relationship 2.5.1 The unique Umtiza clade 2.6 Placement of Gymnocladus and Gleditsia in the Phylogenetic Tree 2.7 Complex Evolutionary History of Gymnocladus and Gleditsia 2.8 References 3 Reproductive Ecology of Gymnocladus assamicus 3.1 Introduction 3.2 Breeding Systems in Plants 3.3 Breeding Systems in Gymnocladus assamicus 3.4 Materials and Methods 3.4.1 Study trees 3.4.2 Reproductive phenology and floral biology 3.4.3 Flower visitors 3.4.4 Pollen viability and stigma receptivity test 3.4.5 Pollen morphology 3.4.6 Breeding systems 3.5 Results 3.5.1 Phenology 3.5.2 Floral sexuality 3.5.3 Pollen fertility 3.5.4 Nectar production 3.5.5 Scanning election microscopy of pollen 3.5.6 Breeding system 3.5.7 Pollinator spectra 3.5.8 Equilibrium male frequency in the population 3.6 Discussion 3.7 Evolution of G. assamicus Breeding System 3.8 References 4 Seed Biology and Modes of Regeneration 4.1 Introduction 4.2 Materials and Methods 4.2.1 Pod collection and measurement of pod traits 4.2.2 Seed dimensions and weight 4.2.3 Seed morphology and anatomy 4.2.4 Seed viability, germination and moisture content 4.2.5 Seed dormancy and different treatments to break dormancy 4.2.6 Seed germination at different soil depths 4.2.7 Seed dispersal and predation in the field 4.2.8 Vegetative mode of regeneration 4.3 Results and Discussion 4.3.1 Pod and seed characteristics 4.3.2 Seed morphometry and related properties 4.3.3 Seed viability, germination and moisture content 4.3.4 Different treatments to break dormancy 4.3.5 Seed germination at different soil depths 4.3.6 Dispersal 4.3.7 Seed loss, predation and damage 4.3.8 Vegetative mode of regeneration 4.4 References 5 Seedling Dynamics and Ecology of Gymnocladus assamicus 5.1 Introduction 5.2 Materials and Methods 5.2.1 In situ experiments 5.2.2 Ex situ experiments in the nursery 5.2.3 Performance of reintroduced seedlings in natural habitats 5.3 Results and Discussion 5.3.1 Seedling functional morphology 5.3.2 Survival and growth of seedlings under in situ conditions 5.3.3 Growth and survival of seedlings under ex situ conditions 5.3.4 Survival and growth of transplanted seedlings 5.4 Implications for Silvicultural and Conservation Practices 5.5 References 6 Conservation and Management of Plant Biodiversity in the Eastern Himalayan Region with Emphasis on Soap Pod Tree ( Gymnocladus assamicus) 6.1 Introduction 6.2 Biodiversity in India 6.3 Biodiversity in Northeast India 6.4 State-wise Biodiversity Status in Northeast India 6.4.1 Arunachal Pradesh 6.4.2 Assam 6.4.3 Manipur 6.4.4 Meghalaya 6.4.5 Mizoram 6.4.6 Nagaland 6.4.7 Sikkim 6.4.8 Tripura 6.5 Future Conservation Initiatives in Northeast India 6.6 Effective Conservation Strategies for G. assamicus 6.6.1 Conservation through cultivation 6.6.2 Silvicultural approaches and protected area management 6.6.3 Community-based conservation initiatives 6.6.4 In vitro method of conservation 6.7 Future Studies 6.8 References Index Back Cover Extinction of species has alarmingly increased in recent decades due to anthropogenic activities, natural calamities and climate change. The life history, ecology and evolution of such species have often not been well studied. Gymnocladus assamicus is an archaic tree endemic to the Eastern Himalayan region of Northeast India. Locally known as 'Menangmanba-shi' by the Monpa tribe of Arunachal Pradesh (India), mature G. assamicus pods contain high saponin and are used traditionally for cleansing purposes and rituals. We rediscovered the species after more than 70 years from high altitude areas in the Himalayas through extensive field explorations and employing an ecological niche modeling approach. Our study revealed a very few actively reproducing mature G. assamicus trees surviving in unique microclimatic conditions. The species is classified as 'critically endangered' (IUCN red list). The book contains detailed information about G. assamicus and discusses its current distribution, population status, ethnobotanical uses and other ecological parameters. Major intrinsic and extrinsic factors that might be responsible for population decline are described. More importantly, we reported a very rare mating system known as 'androdioecy' in which male and hermaphrodite individuals co-exist in the natural population. Overall, the book highlights the story of a critically endangered tree species with a unique biological and socio-cultural importance and will serve as a case study and referencefor other similar species both locally and globally This book tells the story of a critically endangered tree species with a unique biological and socio-cultural importance. This is a unique case study showing an example of plant species conservation in action under difficult circumstances.