Ecological succession Patterns in time Ecological succession Frederic E. Clements 1874-1945 Henry A. Gleason 1882-1975 Plant succession is the historically influenced random process leading to different stable states despite identical environmental conditions (Gleason 1927) 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)

The Human impact on the biosphere

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

Succesion of freshwater bodies

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

Major disturbances are Fire Storm Flooding Lava flows 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.

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

Habitat templates (Southwood and Greenslade) The r – K – A triangle Habitat templates (Southwood and Greenslade) The habitat template of Southwood and Greenslade is a classical form to characterise species along a gradient of adaptational strategies but also to classify habitats. Modified from Brown and Southwood (1987) [Brown V. K., Southwood T. R. E. 1987 – Secondary succession: patterns and strategies (In: Colonization, Succession and Stability, Eds. A. J. Gray, M. J. Crawley, P. J. Edwards) – Blackwell, London, 315-337].

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

Succession of beta diversity Alpha Diversity of green plants peaks at intermediate successional stages. b diversity, the structural diversity on the other hand, rises. Macrofungi do not follow this pattern, there a diversity continuously rises during succession. Redrawn from Brown and Southwood (1987) [Brown V. K., Southwood T. R. E. 1987 – Secondary succession: patterns and strategies (In: Colonization, Succession and Stability, Eds. A. J. Gray, M. J. Crawley, P. J. Edwards) – Blackwell, London, 315-337]. Brown, Southwood 1987

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

P. ob-longo-punc-tatus The Markov chain approach to succession Henry S. Horn 1941- Species P. melanarius P. ob-longo-punc-tatus P. niger O. ob-scurus H. 4-punc-tatus C. granu-latus D0 D1 D2 EV1 Pterostichus melanarius 0.049 0.336 0.280 0.315 0.166 0.098 12.00 4.63 4.98 0.940 Pterostichus oblongopunctatus 0.093 0.068 0.052 0.016 0.268 5.00 2.23 3.74 0.700 Pterostichus niger 0.105 0.186 0.158 0.001 0.207 0.072 3.00 2.95 2.92 0.597 Oxypselaphus obscurus 0.272 0.107 0.261 0.034 0.087 4.00 5.53 4.12 0.751 Harpalus 4-punctatus 0.288 0.277 0.031 0.091 0.232 0.238 1.00 5.77 5.05 1.000 Carabus granulatus 0.192 0.026 0.292 0.316 0.092 0.226 4.89 5.19 0.908 Sum Abundances Column stochastic transition probability matrix 𝑁 𝑡+1 =𝑃 𝑁 𝑡 Stable state (eigen)vector

Positive interactions Bertness, Leonhard, Ecology 78: 1976-1989 Positive interactions Joint defences Habitat amelioration Frequency of competitive interactions Frequency of positive interaction Increasing physical stress Increasing consumer pressure The model of Bertless and Callaway (1994) predicts conditions under which positive interactions are expected to be important forces in community structure. Positive interactions are assumed to be important under harsh physical conditions or high consumer pressure. Redrawn from Bertness and Leonard (1997.[Bertness M. D., Callaway R. 1994 - Positive interactions in communities: a post cold war perspective - Trends Ecol. Evol. 9: 191-193.; Bertness M. D., Leonhard G. H. 1997 - The role of positive interactions in communities: lessons from intertidal habitats - 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.

Linked patterns in time Population dynamics (1964 to 1983) of the red squirrel in 11 provinces of Finland (Ranta et al. 1997) -3 -2 -1 1 2 3 1964 1968 1972 1976 1980 Oulu Vaasa Häme Turku-Pori Central Finland Uusimaa Lapland Kuopio North Karelia Mikkeli Kymi Patrick A.P. Moran (1917-1988) The Moran effect Regional sychronization of local abundances due to correlated environmental effects

Defoliation by gypsy moths in New England states 100000 200000 300000 400000 500000 600000 700000 Acres Defoliated Maine 500000 1000000 1500000 2000000 Acres Defoliated New Hampshire 2500000 20000 40000 60000 80000 100000 120000 140000 Acres Defoliated Vermont Lymantria dispar 500000 1000000 1500000 2000000 2500000 Acres Defoliated Massachusetts Year 20 30 40 50 60 70 80 90 3000000 Gradation: The massive increase in density Data from Williams and Liebhold (1995)

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

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

Evolutionary time scales 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. 100% Body size Female body length Sex dimorphism How much variance in important niche dimensions of European plants is explained by taxonomc relatedness? Male body length Dietary range Colours Migratory behaviour 50% Shading preference Abundance Moisture preference German range size Shading tolerance Moisture tolerance Habitat tolerance European range size 0% Spiders Birds Entling et al. 2007, Gl. Ecol. Biogeogr. 16: 440-448 Prinzing et al. 2001. Proc. R. Soc. B 268: 1.

Taxon species richness and local abundances The case of Hymenoptera Continental taxon species richness of Hymenoptera is correlated to mean local abundances Species rich hymenopteran taxa contain more locally rare and fewer locally abundant species 1 2 3 4 5 10 100 1000 10000 Number of species Mean density per species 0.2 0.4 0.6 0.8 1 10 100 1000 10000 Number of species Fraction of singletons Ulrich W. 2005c. Regional species richness of families and the distribution of abundance and rarity in a local community of forest Hymenoptera. Acta Oecol. 28: 71-76. 0.2 0.4 0.6 0.8 1 10 100 1000 10000 Number of species Fraction of abundant species

Species richer sites contain relatively less higher taxa. Numbers of families and species scale allometrically to floral species richness y = 1.78x 0.77 R 2 = 0.94 10 20 30 40 50 60 80 Number of species in a flora Number of genera 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) y = 1.9x 0.61 R 2 = 0.70 5 10 15 20 25 30 35 40 60 80 Number of species in a flora Number of families Darwin’s competition hypothesis: Closely related species should be ecologically more similar and under higher selection pressure than more distantly related species An example how to study the relation between evolutionary history and phylogeny is the work of Enquist et al. (2002) about allometric scaling of higher taxer of woody plants on local species number. Larger sites (4 to 45 myr ago) contained significantly less higher taxa than expected by chance. (Figures modified from Enquist B. J., Haskell J. P., Tiffney B. H. (2002) General patterns of taxonomic and biomass partitioning in extant and fossil plant communities. Nature 419: 610-613. Enquist et al. 2002. Nature 419: 610-613

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