Animal Ecology (Bartolomeus) PDF

Population → collection of individuals of a species that share the same restricted area at the same time (criterion of continuity) and that are spatially and temporarily separated from other populations of the same species (criterion of discontinuity). Within a population mating depends on density...

Population → collection of individuals of a species that share the same restricted area at the same time (criterion of continuity) and that are spatially and temporarily separated from other populations of the same species (criterion of discontinuity). Within a population mating depends on density and dispersal → both lead to gradients in genetic patterning that may cause subpopulations. Species generally consist of population. Within each area, interindividual genetic variability is lower in the centre than in the periphery. Overlapping areas of distribution allow gene flow between population. Gene flow within populations is higher than gene flow between populations of a given species. Dispersion (spatial patterns of distribution): Clumped (aggregated) → positive interdependencies, inhomogeneous resources; Uniform (homogeneous) → negative interdependencies; Random → no interdependencies. Land-use by ants: Colonies with strict territories. Mounds and streets of two American harvester ants Pogonomyrmex barbatus and Pogonomyrmex rugosus; Contact results in intraspecific and interspecific aggression; Aggressive behaviour is a negative interdependence that causes a homogeneous dispersion of the ant populations. How to estimate population size: Estimation based on random sampling: o Quadrate sampling: ▪ Nest = number of counted/proportion of habitat sampled; ▪ Grid mapping; Estimation based on mark-recapture method: 𝑀2 𝑀1 o = 𝑛𝑒𝑠𝑡 ; 𝑛2 𝑀1 𝑥 𝑛2 o 𝑛𝑒𝑠𝑡 = 𝑀2 ; ▪ M1 → number of individuals marked and released; ▪ M2 → number of individuals recaptured in sample 2; ▪ n2 → total number of individuals un sample 2;  ▪ nest → estimated population size. ACA → accumulation curve analysis: o Genotyping faecal piles. Age structure in populations: Time dependant parameters influence the structure of a population; Demographic factors, like age-dependant birth and death rates play an important role; In perennial species with an infertile juvenile phase, age structure is crucial to estimate prospective population dynamics. Survival curves; Type 1 (physiological survival curve) → in species with high parental investment into offspring (yolk, brood care) and low fecundity; Type-2 (ecological survival curve) → in species that face a constant risk to die over the entire life span; Type-3 → in species in which survival is very low in the larval and juvenile stage. These species have high number of offspring, but show low parental investment (rare or no brood care, yolk-poor eggs). Life history strategies → when and how often an organism reproduces, depends on its like history: Semelparity → mostly in annual species with single reproductive period. There are, however, a few perennial species that reproduce only once in their life (salmons, certain annelids): o Mostly type-3 survival curve; Iteroparity → in perennial organisms with several reproductive periods: o Mostly type-1 or 2 survival curves: ▪ Can exhibit seasonal or perennial fertility; Semelparous organisms allocate resources during their entire life time to produce gametes that are shed all at once. Iteroparous organisms must be able to find a balance between own survival and investment into gametes. r-adapted populations or species show: High fecundity (large number of offspring);  A single or a very few reproductive periods per generation; Short generation time; Use generally temporary habitat with high productivity (ephemeral biotopes). K-adapted populations or species show: Low fecundity; Several reproductive periods per generation; Long generation time; Tend to use very constant resources with low productivity (stable biotopes). Reproductive strategies: Body mass, life span and reproduction are correlation parameters: o Whales (K-adapted): ▪ Need 9 years to become fertile; ▪ Pregnancy lasts 2 years; ▪ 1 calf per birth; ▪ Time between two birth events is 3-6 years; o Mice (r-adapted): ▪ Need 6-8 weeks to become fertile; ▪ Pregnancy lasts 3 weeks; ▪ Up to 10 young are born per birth; ▪ Time between two birth event is 3 weeks. Different outcome of offspring during adulthood is influenced by growth and other physiological factors. Energy is spent both on growth and gamete production in early adulthood, this causes a lower outcome. Each life history strategy is always related/connected to resource use: Each resource serves in fulfilling two needs: o Investment into growth and survival; o Investment into gametes and reproduction (including brood care). Animals have to find a trade-off between number and quality of offspring: In general, body size of offspring and number if offspring are negatively correlated. Predation pressure and recruitment: General strategy in animals and plants: o Investment into growth; o Investment into reproduction. General rules: Any higher investment into offspring lowers the number of offspring, but increases the probability of their survival; Little investment into offspring rises the number of offspring; but lowers their individual chance to survive. Each life history strategy is a trade-off between investment into the actual fecundity and the chance to survive (in the sense of minimising the probability to die), and, thus, into the prospective production. Simplified life cycle showing interdependency between fertilisation, pregnancy and birth in mammals living in temperate biomes. Life cycle or large mammals of temperate biomes. Life cycle of egg laying animals in temperate biomes. Cerastoderma edule has a bentho-pelagic lifestyle (benthic adult, pelagic larvae): During ontogenesis (benthic phase) predator pressure on Cerastoderma edule decreases; From the third year onward humans are the only predators on cockles. 3 types of survival curves: There is always a progeny surplus in biological systems; In survival curves the number of surviving individuals must be plotted logarithmically against the age; To minimise failure of the paternal investment basically two extremes exist. Resource availability and seasonality. Impact of life history strategy on the population structure: Magicicada septemdecim → spends 17 years as larval instant in soil; In Clunio marinus, mating, egg-laying and death of the adults happen within the first hour after the final moult → which completes the larval phase; In mayflies, mating, egg-laying and death of the adults happen within a few hours after final hatching from the last larval instar after an aquatic larval phase that lasts several years. Predator saturation hypothesis → strategy in which organisms appear suddenly in such great densities that they overwhelm their predators' ability to consume them: Predator eats 7 prey items; If there are 10 individuals, 30% will survive; If there are 100 individuals, 99.3% will survive. Under which condition is a certain life history favoured? Differential evolution of semelparity and iteroparity can be explained by the trade-off between offspring produced and offspring foregone. This can be modelled using cost-benefit functions derived from economical studies. In such a model, produced offspring is equivalent to a benefit function, while not-produced offspring or foregone offspring is comparable to a cost function in terms of reproductive success. The reproductive effort of an organism (the amount of resources an organism can invest into reproduction) is optimal at maximal distance between offspring produced and offspring foregone;  If each additional offspring is less "expensive" than the average of all previous offspring, the marginal costs for offspring produced are decreasing. If this is the case and the marginal cost of offspring is increasing, an organism only devotes a portion of its resources to reproduction. The rest of its resources can be used for growth and survivorship, so that it can reproduce again in the future. In such a case iteroparity will be positively selected; If marginal cost of offspring produced increase with each additional offspring and marginal cost of offspring foregone decrease, it is favourable for the organism to reproduce a single time. The organism devotes all of its resources to that one episode of reproduction, so it then dies. Reproductive effort: Proportion of energy that an organism puts into reproducing, as opposed to growth or survivorship or the amount of resources an organism can invest into reproduction: o Semelparity is favoured when reproductive success initially increases slowly with reproductive effort, but then increases rapidly with high reproductive effort; o Iteroparity is favoured when reproductive success initially increases very rapidly with reproductive effort, but then levels off with higher reproductive effort.  𝑁(𝑡+1) Growth: 𝜆 = 𝑁(𝑡) λ = 1 → population is stable; λ > 1 → population grows; λ < 1 → population shrinks. Population growth: N1 = N0 + (B – D). Grey wolf (Canis lupus): Iteroparous species with seasonal reproduction; Reproduce 1 time a year; Fertile after 2 years; 9 weeks pregnancy; 4-6 newborn (max 11); Life span 10 to 13 years; Increase of population after X days: 𝑁(𝑡+𝑥)−𝑁(𝑡) o 𝑋 Under ideal conditions: o rm = maximal per capita growth rate or intrinsic growth rate: ▪ rm = bmax – dmin. Changes in population size N are caused by new born (B) minus dead (D) members and by the number of immigrating (I) minus emigrating (E) animals: N1 = N0 + (B – D) + (I – E); Generally immigration and emigration rates are assumed to be identical so that: o N1 + N0 + (B – D). 𝑑𝑁 Growth rate of population → 𝑑𝑡 𝑑𝑁 1 𝑑𝑁 Intrinsic growth rate → rm = 𝑑𝑡 ⋅𝑁→ 𝑑𝑡 = 𝑟𝑚 ⋅ 𝑁 𝑑𝑁 = 𝑟𝑚 ⋅ 𝑁 transforms into Nt = N0 x erm+t 𝑑𝑡 In theory a population can grow endlessly in an environment with limited resources: Change (dN/dt) of the number (N) of individuals in a population is caused by birth (b), death (d), immigration and emigration. If immigration and emigration are identical, the specific growth rate is → r = b – d: A population growth with a rate of dN/dt = bN – dN = rN; The size of any population at any moment t (N t) depends on r and on its initial size N0: o Nt = N0ert; o A population grows exponentially as long as the birth rate exceeds mortality. Increase in density causes lowering of the birth rate (b) and increasing the death rate (d). At the intersection of both curves, death rate and birth rate are in an equilibrium. This equilibrium marks the carrying capacity (K). It is reached at the population size where both curves cross. If the population size is increasing, size dependent factors also increase (limitation of resources, pollution, predation pressure, mortality). Basically, the birth rate decreases and the mortality increases with increasing population density. The more population size narrows the carrying capacity (K), the more decreases the intrinsic growth rate. Changes in population size limited resources depends in the carrying capacity: 𝑑𝑁 (𝐾−𝑁) 𝑑𝑡 = 𝑟𝑁 𝐾 ; Changes in population size end, if N equals K. Then: 𝑑𝑁 (𝐾−𝐾) 𝑑𝑁 o 𝑑𝑡 = 𝑟𝑁 𝐾 and 𝑑𝑡 = 0. Population ecology: Phase I → λ>1 (population grows): 𝑑𝑁 𝑑𝑡 = 𝑟𝑚 𝑥 𝑁; Phase II → λ=1 (population stable): 𝑑𝑁 (𝐾−𝑁) o 𝑑𝑡 = 𝑟𝑚 𝑥 𝑁 𝐾 ; Phase III → λ K2 x α12 and K2 < K1 x α21: 𝐾2 𝐾1 ▪ Transforms into 𝐾1 > 𝛼21 𝑎𝑛𝑑 𝐾2 < 𝛼12;  o No co-existence, species 1 survives; Scenario 2 → carrying capacity of species 1 is lower than the carrying capacity of species 2 multiplied by the impact of species 2 on species 1 (α12): o K1 < K2 x α12 and K2 > K1 x α21: 𝐾2 𝐾1 ▪ Transforms into 𝐾1 > 𝛼21 𝑎𝑛𝑑 𝐾2 < 𝛼12; o No co-existence, species 2 survives; Scenario 3 → carrying capacity of both species is lower than the carrying capacity of the competitor multiplied by its impact on the competing species (α21 or α12); o K1 < K2 x α12 and K2 < K1 x α21: 𝐾2 𝐾1 ▪ Transforms into 𝐾1 > 𝛼21 𝑎𝑛𝑑 𝐾2 > 𝛼12; o No co-existence, one species becomes extinct if the other one increases;  Scenario 4 → carrying capacity of both species is higher than the carrying capacity of the competitor multiplied by its impact on the competing species (α21 or α12): o K1 > K2 x α12 and K2 > K1 x α21: 𝐾2 𝐾1 ▪ Transforms into 𝐾1 < 𝛼21 𝑎𝑛𝑑 𝐾2 < 𝛼12; o Co-existence possible at intercept of isoclines, both species survive. Summary; In three out of four theoretical scenarios, co-existence is impossible and one of two competing species will disappear. Only in one out of four theoretical scenarios co-existence of two species is possible; Co-existence requires that the carrying capacities of both species are higher than the carrying capacity of the respective other species multiplied by their impact factor: 𝐾2 𝐾1 o If 𝐾1 < 𝛼21 𝑎𝑛𝑑 𝐾2 < 𝛼12 is given. Examples: The role and impact factor α: The impact of one species on the other is the decisive factor in the Lodka- Volterra model of competition. Even if the carrying capacity of two species is almost identical, they will be able to coexist, as long as the impact factor α is ≤ 1, as can be seen in this example; Two competing species will survive, if they are able to minimise the impact on each other; This generally leads to niche separation and specialisation among competing species. Niche concepts: Co-existence by niche shift → fundamental (black) and realised (red) miches of two species A and B. Niche dimensions: One dimensional resource-usage diagram (blue, green) and resulting niches (black) of five hypothetical species; The number of niches increases the more generalistic species are. Niches are species-specific: Co-existence by niche differentiation: Zonation of the balanid species Semibalanus balanoides and Chthamalus stellatus on the intertidal rocky shore of the North Atlantic; NN normal null (standard zero), mHT, sHT and mNT, sNT mean and spring high tides and low tide; Semibalanus balanoides overgrows Chthamalus stellatus, but is less tolerant against desiccation. Niche formation: Euryoecious: o Animals with a large range of tolerance and preferences; Stenoecious: o Animals with a narrow range of tolerance and preferences. From competition to exploitation; From a population standpoint, exploiters have a negative effect on the abundance of their prey or hosts, while the prey or hosts have a positive effect on the abundance of their exploiters. Prey-predator and host-parasite interaction → Lotka-Volterra predation model: Prey-predator relations and host-parasite interactions can be regarded as a special kind of competition. The partners, however, do not compete for a limited resource, instead one of the partners is the limiting resource: o c → efficiency with which the predator/parasite captures/infects the prey/host; o f → efficiency to convert prey/host into predator/parasite offspring; o rph → growth rate of the prey/host; o Nh → number of host or prey individuals, bh and dh birth and death rate of host/prey; o Np → number of predators or parasites, bp and dp birth and death rate of predator/parasite; Changes in population size can be calculated: o For prey/hosts: 𝑑𝑁 ▪ ℎ = Nh x (bh – dh) = rph x Nh – c x Np x Nh = Nh x (rph – c x Np); 𝑑𝑡 o For predators/parasites: 𝑑𝑁 ▪ 𝑃 = Np x (bp – dp) = d x c Np x Nh – dp x Np = Np x (f x c x Nh – 𝑑𝑡 dp); o Zero growth (prey/host): 𝑑𝑁 ▪ ℎ = 0 = rph x Nh – c x Np x Nh; 𝑑𝑡 𝑟𝑝ℎ ▪ Transforms into 𝑁𝑝 = 𝑐 :  𝑟𝑝ℎ Rph and c are constant factors so that 𝑐 is a constant, which means that the host isocline is a straight line parallel to the x axis and intersects with the y axis at 𝑟𝑝ℎ 𝑐 ; o Zero growth (predator/parasite): 𝑑𝑁 ▪ 𝑝 = 0 = f x c x Np x Nh – dp x Np; 𝑑𝑡 𝑑𝑝 ▪ Transforms into 𝑁ℎ = 𝑓𝑐. 4 scenarios; o Scenario A: ▪ Prey population at its maximum, predator population at its average value; ▪ Prey density will decline, predator density will increase; o Scenario B: ▪ Prey population at its average, predator population at its maximum; ▪ Prey density will decline, predator density will decline; o Scenario C:  ▪ Prey population at its minimum value, predator population at its average value; ▪ Prey density will increase, predator density will decline; o Scenario D: ▪ Prey population at its average value, predator population at its minimum value; ▪ Prey density will increase, predator density will increase; The number of individuals of prey and predators vary periodically and with temporal delay if conditions are stable; Lotka-Volterra rule:  o The population curve meanders with time-shifted extremes, whereby the curve of prey precedes that of the predator; o If the number of preys is high, the predator will benefit from a better access to nutrients and will excel in a higher rate of reproduction; o Since the offspring of predators need some time for growth, the maximum of predators will be active with some delay. An increasing number of predators will cause the prey population to decline. With decreasing population density of the prey successful hunting of the predator will also decrease and the predator density will decrease. The reduced predation pressure causes an increase of the prey population; o The mean size of prey and predator populations in a prey-predator relation remains constant for a longer period of time, as far as the environmental conditions remain stable; Predators are successful if they can focus on a single individual that it attacks; Clustering or shoaling us a defensive strategy, since the predator cannot focus on a single individual; Defence by shoaling is a function of the number of cluster/shoal members. Mytilus edulis distribution in the intertidal zone: Water coverage and thus time for feeding determines the upper limit of Mytilus in the intertidal; The lower limit is defined by the upper limit of the predator. Predation pressure delimits distribution → the influence of the sea star Pisaster ochraceus: Biomass production by primary and secondary producers in the North Atlantic: Primary producers and consumers show a Lotka-Volterra relation: o Primary production increases in spring, because the daylength and intensity of solar radiation increase towards the summer. This increase of primary producers is followed by an increase of consumers, basically by larvae, because most marine organisms of the North Atlantic reproduce in spring; o A temporary warm water lense in summer blocks the upper water layers from mineralisation. All minerals are used by primary producers in July to August and primary production declines; o With decreasing light intensities in August, the warm water lense becomes thinner. In some years early autumn storms cause the warm water lense to break apart, so that deeper water layers rich in minerals mix with surface waters; o If there are still sufficient light intensities, these storms may cause a second, shallow increase of primary producers, followed by an increase in consumers; o Declining light intensities in late autumn and winter decrease primary production. Energy flow across trophic levels and biomass: Bottom up – top-down regulation → size of circles indicates population size: Effects of overexploitation: Given the system consists of 2 competitors (K1a and K1b) and one consumer (K2);  Removing one competitor (K1a) and consumer (K2) increases the population size of the second competitor (K1b). The fishery's problem: Position of the economically relevant fish species within the trophic hierarchy. Expansion of the oceans: 71% of our plant's surface is covered by water. If there were no mountains nor any abyssal plains a 2000m water column would cover the entire planet; The entire ocean and shelf sea surface measure 361.1 million square kilometres. The entire volume of oceans and marine shelf areas is approximately 1.37 billion cubic kilometres (1.32x1015 m3); This enormous amount of water forms three oceans, the Pacific Ocean, the Atlantic Ocean and the Indian Ocean. Waves: Transport of energy; Sea floor structure influences wave amplitude and frequency. Abiotic factors: Solar radiation: o About 50% hits the sea surface, some of it is reflected. Only 50% of the remaining solar radiation can be used for photosynthesis. This is less than 25% of the solar radiation. In water its intensity decreases with increasing depth;  o Photosynthesis can be performed only in small zone below the oceans' surface. Production in terms of standing crop strongly depends on the degree of suspended matter in the water. In the North Sea, primary production is possible up to 20m, in the clear tropical oceans primary production occurs up to a depth of 100m; o Algae are unable to photosynthesise along the entire region → those adapted to living in deeper water are stressed by higher light intensities close to the surface; o Photosystems of algae are adapted to certain light intensities. Each species has a specific compensation depth, a depth in which the rate of respiration is compensated by the rate of photosynthesis. Below this depth, energy consumption is higher than energy gain by photosynthesis. Without certain polymeric carbohydrates, oil or other ways of energy the algae will die below the compensation depth; o Close to the surface algae that are adapted to low light conditions will suffer from light stress; Light: o Visible light ranging between 450-470 nm wavelength has the lowest amount of energy loss in water and still has 10% of its original intensity in 90m depth; o Maximal absorption is at 438nm in chlorophyll a and 470nm in chlorophyll b; o 4 scenarios: ▪ Northern spring → maximal solar radiation is recorded at the equator at equinox (21st of March); ▪ Northern summer → the sun is in the tropic Cancer (23° north) at midsummer (21st of June); ▪ Northern autumn → maximal solar radiation is recorded at the equator at equinox (21st of September); ▪ Northern winter → the sun is in the tropic Capricorn (23° south) at midwinter (21st of December); o Intensity of solar radiation: ▪ The angle of incident light or angle of radiation influences the area illuminated, reflection and depth of penetration; o Total solar radiation at the sea surface → changes with latitude and season in the northern and southern hemisphere. Water: Thermal capacity and density: o The effective heat capacity of a substance is equivalent to that heat quantity (J) needed to warm up 1g of substance to 1°C. For water the heat quantity is: ▪ 4.2 x g-1 x K-1 → 1 cal x g-1 x K-1; o Thermal capacity of the air is merely one fourth of this value and in most metals it is lesser than one tens of this value; The absorbed thermal energy has to break down the hydrogen bonds, before the H2O molecules can move faster. This faster movement involved more kinetic energy which again rises the temperature; Frozen water has a lower density than water measuring 4°C, because ice H2O molecules form hexagonal crystals and each water molecule has the same distance to four neighbouring water molecules. When water freezes, it increases in volume (about 9% for fresh water). Temperature and the oceans; There are warm water masses forming a permanent lense-like layer between 45°-35° south and 35°-45° north. This layer isolates deeper cold water from the surface and prevents any exchange. This water layer lacks nutrients (phosphates and nitrates) → these regions of the oceans form the ocean deserts. Physical processes influencing the distribution of water masses: Temperature: o Solar radiation is the driving force behind the continuous movement of air on our planet, essential for atmospheric circulation; o The sun consistently heats the upper water layer, creating temperature variations in adjacent aeras. As warm air rises into higher atmospheric layers, it cools down and descends to the Earth's surface, completing the cycle;  Climate; Coriolis force: o The Coriolis force, an inertial force, comes into play when a structure moves within a rotating reference system. This force becomes evident when the movement is not parallel to the axis of rotation or the vector of angular velocity; o Perpendicular to the instantaneous direction of movement in the rotating reference system, the Coriolis force induces a deflection to the side: ▪ An object moving in a straight line to the south will be deflected to the left in the northern hemisphere; ▪ deflected to the right in the southern hemisphere; Oceanic currents. Temperature, Coriolis force and oceanic currents: Solar radiation remains relatively constant between 20° south and 26° north, leading to the formation of a warm water lens in the oceans. This lens, in turn, induces the ascent of air near the equator, which flows poleward at an altitude of 10-15km, descends in the subtropics, and returns to its point of origin. This atmospheric circulation is known as the Hadley cell and serves as driving force behind the Trade winds; The Coriolis force causes air flowing southward or northward to turn clockwise (in the northern hemisphere) and counterclockwise (in the southern hemisphere). These winds continuously cause water masses to follow them and are an essential force for the formation of large oceanic currents. They form large clockwise-rotating gyres in the northern oceans and counterclockwise-rotating gyres in the southern oceans. Algae can only grow close to the surface, and only if there is sufficient PAR (photosynthetically active radiation) and sufficient supply with nutrients (nitric derivates, phosphate, silicate). The major proportion of results from re- mineralisation, which generally occurs on the ocean floor. A smaller portion of the nitric derivates originates from the atmosphere via the microbial loop. Standing crop in the oceans: Colour coded chlorophyll concentration in the oceans as indicator for primary production: o Purple → low; o Red → high. Antartica: Ice desert; 21.2 million km2. Polar seas: Shelf ice → terrestrial, freshwater; Icebergs are always pieces of the shelf ice; Pancake ice → aggregation of ice crystals; Pack ice → plates of sea water ice (can be condensed). Primary production: Ice algae are the basis for phytoplankton bloom in the Antarctic summer; Sea water ice is formed by H2O crystallisation. This process increases salt concentration in the remaining water. Channels containing this high salt sea water remain and are included into the sea water ice. These brine channels are unique ecosystems based on primary production of algae inside the brine channels. Upon melting of the ice these algae are set free and form the starting point for the Antarctic plankton bloom. The large polar mammals primarily feed on the consumers I: Global currents of surface and deep-sea masses: Deep sea: The oceanic water masses cover the continental slope, over the abyssal plane at 4,000m depth, the mid-ocean ridges and the deep-sea trenches; Optical sense: o Large eyes to see prey either visualised by background illumination caused by bioluminescent bacteria or by bioluminescence of the prey; o Long teeth to form a cage that prevents prey from escaping after having been caught. Shelf seas of the oceans: Shelf seas are flooded parts of the continental shelf;  During the last 100,000 years they were repeatedly flooded by marine water masses; Continental islands like England, Ireland or some Indonesian islands are part of the same continental plate, but were isolated from the mainland by a postglacial increase of the ocean level.