1. On the analysis of populations in time and space: Forest Hymenoptera

3. A fresh beech forest in spring and later in the year

4. Basic population parameters: Species densities (m -2 ) SpeciesStudy year 1981198219831984198519861987 Acoelius erythronotus1212250.5 Anacharis eucharioides1310.5 32 Aphelopus melaleucus35415121 Aspilota GW24470.512718 Basalys pedisequa40.51381094 Charitopes gastricus27310.1206 Chrysocharis prodice6511391 Cleruchus spec.21319185010 Eretmocerus mundus049990.5 0.1 Eustochus atripennis34536192 Exallonyx quadriceps120.50.10.552 Exallonyx subserratus0.10.510.1110.5 Gastrancistrus walkeri287390.5726 Glauraspidia microptera4545231 Ismarus dorsiger0.1 5520.5 Lagynodes pallidus110.12711 Litus cynipseus6402180.52224 Mesopolobus GW10.1 66430.5 Phygadeuon ursini12120.50.1572 Synopeas GW111476587700.5 Tetrastichus ?brachycerus72517830.5659 Tetrastichus fageti533121031 Tetrastichus luteus0.5 2191281 Trichogramma embryophagum0.580.10.50.140.5 Trichopria aequata11610.511 Trichopria evanescens0.5 10.1 90.5

6. Familie Number of species Total catch Average density (m -2 ) Anacharitidae42601.8 Andrenidae11< 0.1 Aphelinidae4443830.8 Apidae7-- Braconidae123407528.3 Ceraphronidae307185 Charipidae5840.6 Cynipidae113802.6 Diapriidae69174312.1 Dryinidae47765.4 Embolemidae11< 0.1 Encyrtidae143842.7 Eucoilidae56454.5 Eulophidae55629343.7 Eupelmidae11< 0.1 Eurytomidae180.1 Figitidae1370.3 Formicidae9-- Heloridae13< 0.1 Ichneumonidae179313221.8 Familie Number of species Total catch Average density (m -2 ) Megachilidae11< 0.1 Megaspilidae165093.5 Mymaridae26420529.2 Ormyridae11< 0.1 Platygasteridae34504935.1 Proctotrupidae157415.1 Pteromalidae56223315.5 Scelionidae132511.7 Sphecidae11< 0.1 Tenthredinidae20480.3 Torymidae6740.5 Trichogrammatidae2650.5 Vespidae4-- Sum72036157251.1 Basic population parameters: Species richness and densities Hymenoptera is the most species rich taxon in temperate terrestrial ecological systems.

7. The question of coexistence Population versus community ecology

9. The magnitude of population fluctuations in forest Hymenoptera SpeciesStudy year 1981198219831984198519861987 Acoelius erythronotus1212250.5 Anacharis eucharioides1310.5 32 Aphelopus melaleucus35415121 Aspilota GW24470.512718 Basalys pedisequa40.51381094 Charitopes gastricus27310.1206 SpeciesR 198219831984198519861987 Acoelius erythronotus 2.00.52.01.02.50.1 Anacharis eucharioides 3.00.30.51.06.00.7 Aphelopus melaleucus 1.70.83.80.12.00.5 Aspilota GW2 1.01.80.12.027.00.7 Basalys pedisequa 0.12.038.00.30.90.4 Charitopes gastricus 3.50.40.30.1200.00.3 N(1982)/N(1981) We calculate population increase and decrease R from the observed species abundances.

10. SpeciesR 198219831984198519861987 Acoelius erythronotus 2.00.52.01.02.50.1 Anacharis eucharioides 3.00.30.51.06.00.7 Aphelopus melaleucus 1.70.83.80.12.00.5 Aspilota GW2 1.01.80.12.027.00.7 Basalys pedisequa 0.12.038.00.30.90.4 Charitopes gastricus 3.50.40.30.1200.00.3 The net reproductive rate Rs 2 (R)r 1.510.760.41 1.924.130.65 1.461.480.38 5.4193.601.69 6.96193.141.94 34.115505.263.53 The net rate of population growth was independent of average density. Most species increased in density. The net rate of population growth increased with variability in density. Is this correct? Średnia() N(1982)/N(1981) The values are too precise

11. RrDmeans 2 (Dmean) 0.89-0.121.51.89 1.120.121.21.03 0.83-0.182.920.53 1.280.254.384.99 1.000.004.3146.64 1.200.182.440.09 Rs 2 (R)r 1.510.760.41 1.924.130.65 1.461.480.38 5.4193.601.69 6.96193.141.94 34.115505.263.53 Średnia.geo metriczna() R was independent of average density and density fluctuations. Net reproductive rates scattered equally around the equilibrium value of R = 1. CV 0.896 0.819 1.553 2.144 2.814 2.603

12. SpeciesR 198219831984198519861987 Acoelius erythronotus2.0 2.5 Anacharis eucharioides3.0 6.0 Aphelopus melaleucus1.7 3.8 2.0 Aspilota GW2 1.8 2.027.0 Basalys pedisequa 2.038.0 Charitopes gastricus3.5 200.0 The theoretical upper boundary of R denotes the average number of eggs layed by each female. The effective maximum net rate of population growth High maximum reproductive rates were linked to high absolute fluctuations according to Taylor’s power law. max Rs 2 (R)rDmeans 2 (Dmean) 2.500.060.771.51.89 6.002.251.451.21.03 3.750.830.842.920.53 27.00140.291.524.384.99 38.00324.002.174.3146.64 200.009653.063.282.440.09

13. Maximum Hymenoptera reproduction rates were not significantly linked to averge species densities Maximum Hymenoptera reproduction rates increased with the observed variability in density. The probability of this relation was P(H1) > 0.95. (Significance of the regression is P(H0) < 0.05) Species with larger fluctuations in abundance had higher capacities for recruitment.

14. Density regulation SpeciesStudy year 1981198219831984198519861987 Acoelius erythronotus1212250.5 Anacharis eucharioides 1310.5 32 SpeciesStudy year 1981198219831984198519861987 Acoelius erythronotus1103-4.5 Anacharis eucharioides 2-2-0.502.5 Time N K If a population is regulted in a density dependent manner the correlation between  N t and N t should be negative.

15. Are populations really density dependent regulated? Bulmer’s (1975) test for density dependence Time N K In random walk time series we expect negative correlations of  N and N. Trichogramma embryophagum Density regulation Only one of the 26 parasitoid species passed the test. At least 20 generations are needed to detect density dependence

16. J >> 1: chaotic density fluctuations J = 1: Poisson random fluctuations <J << 1: densities at equilibrium The variance - mean ration in the form of the Lloyd index Variability in population size of forest Hymenoptera was positively linked to geometric mean density. Nearly all Lloyd values are far above 1.0. Populations are not regulated. Are populations in equilibrium?

17. The band model of density dependence Density dependence Density independence N K N min N max Random walk Most species fluctuate randomly with certain upper and lower boundaries of population density At lower density, the Allee effect might cause a positive density dependence, that means populations have even less ability for recruitment. Factors that cause density dependence: Factors that cause density independence: predator – prey cycles cyclic weather conditions (el Nino, el Nina, NAO) density dependent mortality and reproduction unpredictable weather conditions unstable habitats high degrees of dispersal t

18. Intrinsic rates of increase Speciesmax RRR0s 2 (R)rDmean s 2 (Dmean ) CV Acoelius erythronotus2.500.890.560.76-0.121.51.890.896 Anacharis eucharioides6.001.121.784.130.121.21.030.819 Aphelopus melaleucus3.750.830.401.48-0.182.920.531.553 Aspilota GW227.001.283.5093.600.254.384.992.144 Basalys pedisequa38.001.00 193.140.004.3146.642.814 Charitopes gastricus200.001.202.505505.260.182.440.092.603 Phygadeuon ursini Parasitoid of Cheilosia fasciata on Allium ursinum Outbreak species

19. Population outbreaks Four of 26 abundant Hymenopteran species increased abundances duig two years by a factor of more than 1000. Circles mark years of zero abundance. After the outbreak populations collapsed

20. On the probability of extinction In the case of random walks extinction probabilities are given by Annual extinction probability Species4 ha study arears 2 (r)Dmeans 2 (Dmean)LloydTP(annual) 198219831984198519861987 Acoelius erythronotus40000800004000080000 200000-0.121.251.51.891.150117.10.01 Anacharis eucharioides400001200004000020000 1200000.121.031.21.030.864131.40.01 Aphelopus melaleucus1200002000001600006000004000080000-0.181.692.920.533.069103.10.01 Aspilota GW2160000 280000200004000010800000.253.074.384.995.36261.70.02 Basalys pedisequa160000200004000015200004000003600000.003.414.3146.648.68457.90.02 Charitopes gastricus800002800001200004000040008000000.186.352.440.097.36328.20.03