The periodic flood pulse of the Amazon River has been the main controlling factor in the local ecosystems for at least two million years. Numerous adaptations, in some cases along with speciation, have evolved in local terrestrial invertebrates. The small millipede Poratia obliterata (Kraus, 1960), which probably originates from the Andes, is currently known from a remarkably broad range of Central Amazonian biotopes, i.e. various seasonal inundation forests, upland forest and plantations. Like most native millipedes, P. obliterata appears to escape flooding by tree ascents. Such developed survival strategies adaptive to annual inundation can either reflect ecological plasticity or implicate ecological speciation, .i.e. `biotope-specific races' or ecotypes. To assess the causal mode of adaptation, ecological studies with genetic analyses are combined in this work.
Editorial -- 5 1 Introduction -- 13 1.1 Study Area -- 13 1.1.1 Geology of the Amazon Basin -- 13 1.1.2 Climate -- 15 1.1.3 Water Level Regime -- 16 1.1.4 Seasonal Inundation Forests -- 16 1.2 The Millipede Poratia obliterata -- 17 1.2.1 Classification and Biology -- 17 1.2.1.1 Systematics -- 17 1.2.1.2 Basic Anatomy -- 18 1.2.1.3 Characterisation -- 19 1.2.1.4 Development -- 20 1.2.1.5 Ecology -- 21 1.2.1.6 Dispersal Ability -- 23 1.2.2 Origin and Range of P. obliterata Populations -- 23 1.2.3 Biotope-Related Adaptation and Speciation? -- 24 1.3 Survival Strategies in Central Amazonian Floodplains -- 26 1.4 Molecular Markers in Population Genetics -- 29 1.4.1 Definition of Molecular Markers -- 29 1.4.2 Subject of Population Genetics -- 29 1.4.3 Application of Molecular Markers -- 29 1.4.3.1 Classification and Speciation -- 29 1.4.3.2 Adaptive Divergence among Populations -- 31 1.4.4 Technique -- 31 1.4.5 Appraisal: Choice of an Appropriate Marker -- 32 2 Thesis Outline -- 33 2.1 Part I: Ecological Traits -- 33 2.2 Part II: Genetic Variation -- 33 3 Ecological Traits -- 35 3.1 Material and Methods -- 35 3.1.1 Study Sites -- 35 3.1.1.1 Varzea -- 35 3.1.1.2 Igapo -- 38 3.1.1.3 Varzea & Igapo -- 41 3.1.1.4 Terra firme -- 44 3.1.1.4.1 Banana Plantation at CPPA/Embrapa -- 44 3.1.1.4.2 Upland Forest Reserve 'Reserva A. Ducke' -- 45 3.1.2 Monitoring and Sampling of P. obliterata in the Field -- 46 3.1.2.1 Inundation Forests -- 46 3.1.2.2 Banana Plantation -- 47 3.1.3 Estimation of Flood Periods for Individual Sample Trees -- 47 3.1.4 Determination of Humidity in Microhabitats -- 47 3.1.5 Identification of Collected Millipedes -- 48 3.1.6 Laboratory Experiments -- 49 3.1.6.1 Flooding Experiment -- 49 3.1.6.2 Reproduction Experiment -- 49 3.1.7 Data Analysis and Statistics -- 52 3.2 Results -- 54 3.2.1 Abiotic Factors -- 54 3.2.1.1 Precipitation -- 54 3.2.1.2 Water Level -- 55 3.2.1.3 Minimum Flood Period at Study Sites -- 56 3.2.1.4 Humidity in the Microhabitat -- 58 3.2.2 Morphology -- 59 3.2.2.1 Poratia obliterata -- 59 3.2.2.2 Other Millipede Species -- 59 3.2.3 Ethology -- 60 3.2.3.1 Inundation Forests -- 60 3.2.3.1.1 Seasonal Vertical Migration -- 60 3.2.3.1.2 Preferred Microhabitats and Gregarious Behaviour -- 61 3.2.3.2 Banana Plantation -- 79 3.2.4 Phenology -- 79 3.2.4.1 Life Cycle (Progress of Stages, Sex Ratio) -- 79 3.2.4.1.1 Inundation Forests -- 79 3.2.4.1.2 Banana Plantation -- 84 3.2.4.2 Reproduction (Mating, Eggs) -- 84 3.2.4.2.1 Inundation Forests -- 84 3.2.4.2.2 Banana Plantation -- 86 3.2.5 Laboratory Experiments -- 87 3.2.5.1 Flooding Experiment -- 87 3.2.5.2 Reproduction Experiment -- 89 3.3 Discussion -- 97 3.3.1 Abundance in Different Biotopes -- 97 3.3.2 Life History Traits -- 100 3.3.2.1 Seasonal Vertical Migration -- 100 3.3.2.2 Microhabitat Selection and Social Behaviour -- 104 3.3.2.2.1 Choice of Adequate Microhabitats -- 104 3.3.2.2.2 Gregarious Behaviour -- 107 3.3.2.2.3 Species Interactions -- 110 3.3.2.3 Life Cycle and Postembryonic Development -- 113 3.3.2.3.1 Life Cycle in the Field -- 113 3.3.2.3.2 Evolution of the Univoltine Life Cycle -- 117 3.3.2.3.3 Regulation by Maternal Effects -- 118 3.3.2.3.4 External Cues for Reproduction and Development -- 121 3.3.3 Synopsis -- 125 4 Genetic Variation -- 127 4.1 Material and Methods -- 127 4.1.1 Sample Collection -- 127 4.1.2 Agarose Gel Isoelectric Focussing (AGIF) -- 128 4.1.2.1 Sample Preparation -- 128 4.1.2.2 Preparation of the Agarose Gel -- 131 4.1.2.3 Isoelectric Focussing -- 132 4.1.2.4 Staining Procedure -- 132 4.1.2.5 Interpretation of Zymograms -- 133 4.1.3 Data Analysis and Statistics -- 133 4.2 Results -- 134 4.2.1 Zymograms -- 134 4.2.2 Allelic Variation within and among Biotope Types -- 135 4.2.3 Heterozygosis and Hardy-Weinberg Distribution -- 138 4.2.4 Effective Number of Alleles per Locus -- 138 4.2.5 Genotypic Linkage Equilibrium between Loci -- 139 4.2.6 Genetic Differentiation among Populations -- 139 4.2.6.1 Within-Subpopulation Variance of Genetic Diversity -- 139 4.2.6.2 Genetic Variability between Subpopulations -- 143 4.2.6.3 Genotypic Distinction of Biotope Types -- 150 4.2.7 Population Genetic Structure -- 151 4.2.8 Isolation by Distance and Effective Number of Migrants -- 153 4.2.9 Cluster Analysis of Genetic Similarity -- 155 4.3 Discussion -- 158 4.3.1 Population Dynamics and Adaptation in P. obliterata -- 158 4.3.1.1 Concept of Dispersal -- 158 4.3.1.2 Adaptation Hypothesis -- 159 4.3.1.3 Population Genetic Implications from Allozyme Data -- 159 4.3.1.3.1 Random Mating and Outcrossing -- 159 4.3.1.3.2 Gene Flow and Population Subdivision -- 161 4.3.1.3.3 Unidirectional Dispersal and Biotope-Related Differentiation -- 163 4.3.1.4 Local Adaptation versus Phenotypic Plasticity -- 165 4.3.2 Allozyme Variability within Populations of P. obliterata -- 168 4.3.3 Synopsis -- 169 5 Conclusions -- 171 6 Acknowledgements -- 173 7 References -- 175