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Ecological succession Henry A. Gleason 1882-1975 Frederic E. Clements 1874- 1945 Patterns in time Plant succession is the directional development of the vegetation of a given homogeneous area over a period of time towards a single climax structure (Clements 1916) Plant succession is the historically influenced random process leading to different stable states despite identical environmental conditions (Gleason 1927)

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The Human impact on the biosphere

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Primary Successional stages Bare soil of rocks Soils crusts, Cyanobacteria, Lichen, Mosses Annual and biannual plants Shrubs, trees Pioneer species Climax community Succession is not a deterministic process. The successional sequence might end in different final stable states In many temperature successioal series forests form the climax community

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Succesion of freshwater bodies

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Soil crusts Soil mosses and lichen Crusts are well adapted to severe growing conditions, drought and water loss. Cyanobacteria Crusts generally cover all soil spaces not occupied by vascular plants, and may be 70% or more of the living cover Soil crusts stabilize soils and increase water retention. Cyanobacteria, mosses, lichen

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Secondary succession Secondary succession is the change in faunal or floral composition after severe disturbance Major disturbances are Fire Storm Flooding Lava flows Secondary succession starts mainly from seed banks. Colonization is often of minor importance. Seeds remain healthy for some months to more than 1000 years. In cyclic succession (frequent fires) seed banks allow for fast recover.

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Generation time Reproductive effort Flight ability Morphological diversity Niche breadth Diversity Plants, herbivorous insects Plants, aphids Plants, birds, some insects Herbivorous insects Bees, wasps Plants, insects Adaptive strategies Young fieldMidfield Woodlands Successional stage Modified from Brown, Southwood 1987 Different successional stages filter for different life history strategies (habitat filtering)

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The r K A triangle Habitat templates (Southwood and Greenslade)

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Time Abundance Annuals and biannuals Shrubs Trees Time Species richness Annuals and biannuals Shrubs Trees Time Biomass Community patterns during succession Species richness, total abundance, and total biomass generally peak at intermediate stages of succession.

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Brown, Southwood 1987 Succession of beta diversity

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Intermediate disturbance Number of niches Extinction Immigration Competitiion New Zealand stream invertebrates (Townsend 1997)

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Species P. melana rius P. ob- longo- punc- tatus P. niger O. ob- scurus H. 4- punc- tatus C. granu- latus D0D1D2EV1 Pterostichus melanarius 0.0490.3360.2800.3150.1660.09812.004.634.980.940 Pterostichus oblongopunctatus 0.0930.0680.0520.0160.2680.2805.002.233.740.700 Pterostichus niger0.1050.1860.1580.0010.2070.0723.002.952.920.597 Oxypselaphus obscurus 0.2720.1070.1860.2610.0340.0874.005.534.120.751 Harpalus 4-punctatus0.2880.2770.0310.0910.2320.2381.005.775.051.000 Carabus granulatus0.1920.0260.2920.3160.0920.2261.004.895.190.908 Sum1.000 The Markov chain approach to succession Henry S. Horn 1941- Abundances Stable state (eigen)vector Column stochastic transition probability matrix

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Positive interactions Habitat amelioration Joint defences Increasing physical stress Increasing consumer pressure Frequency of positive interaction Frequency of competitive interactions Bertness, Leonhard, Ecology 78: 1976-1989 The stress gradient hypothesis predicts increased proportions of positive (mutualistic) interactions in plant communities at intermediate levels of stress and herbivore pressure.

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Linked patterns in time Population dynamics (1964 to 1983) of the red squirrel in 11 provinces of Finland (Ranta et al. 1997) Patrick A.P. Moran (1917-1988) The Moran effect Regional sychronization of local abundances due to correlated environmental effects

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3000000 2500000 0 500000 1000000 1500000 2000000 Acres Defoliated New Hampshire 0 500000 1000000 1500000 2000000 2500000 Acres Defoliated Massachusetts Year 2030405060708090 Defoliation by gypsy moths in New England states Lymantria dispar Data from Williams and Liebhold (1995) Gradation: The massive increase in density

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Taylors power law Assume an assemblage of species, which have different mean abundances and fluctuate at random but proportional to their abundance. The relationship between variance and mean follows a power function of the form Going Excel Taylors power law; proportional rescaling

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Ecological implications Temporal variability is a random walk in time Abundances are not regulated Extinctions are frequent Temporal species turnover is high Temporal variability is intermediate Abundances are or are not regulated Extinctions are less frequent Temporal species turnover is low Temporal variability is low Abundances are often regulated Extinctions are rare Temporal species turnover is very low

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Niche conservatism refers to the tendency of closely related species to have similar niche requirements. The requirements translate into similar ecological, morphological or behavioural traits mediated by genomic similarities. Evolutionary time scales SpidersBirds 100% 0% 50% Moisture tolerance Shading tolerance Moisture preference Shading preference Female body length Male body length European range size Habitat tolerance German range size Abundance Migratory behaviour Colours Dietary range Sex dimorphism Body size Entling et al. 2007, Gl. Ecol. Biogeogr. 16: 440-448 How much variance in important niche dimensions of European plants is explained by taxonomc relatedness? Prinzing et al. 2001. Proc. R. Soc. B 268: 1.

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Taxon species richness and local abundances The case of Hymenoptera 0 1 2 3 4 5 110100100010000 Number of species Mean density per species Continental taxon species richness of Hymenoptera is correlated to mean local abundances 0 0.2 0.4 0.6 0.8 1 110100100010000 Number of species Fraction of singletons 0 0.2 0.4 0.6 0.8 1 110100100010000 Number of species Fraction of abundant species Species rich hymenopteran taxa contain more locally rare and fewer locally abundant species

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Numbers of families and species scale allometrically to floral species richness y = 1.78x 0.77 R 2 = 0.94 0 10 20 30 40 50 60 020406080 Number of species in a flora Number of genera y = 1.9x 0.61 R 2 = 0.70 0 5 10 15 20 25 30 35 020406080 Number of species in a flora Number of families Species richer sites contain relatively less higher taxa. Species richer sites have higher species per genus (S/G) ratios Species richer sites contain higher proportions of ecologically similar species (environmental filtering) Enquist et al. 2002. Nature 419: 610-613 Darwins competition hypothesis: Closely related species should be ecologically more similar and under higher selection pressure than more distantly related species

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Zaplata et al. 2013 Local colonizers Regional pool of species Environmental filters Random colonization Regional pool of potential colonizers Regional pool of species No phylogenetic structure Phylogenetic clumping Early succession Facilitation Phylogenetic segregation Local community structure Competition No phylogenetic structure Phylogenetic clumping Later succession Positive interactions Phylogenetic segregation Neutral interactions