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Pt-Qtr Calculations Datasheet of Excel FieldTripData2007 file.

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Presentation on theme: "Pt-Qtr Calculations Datasheet of Excel FieldTripData2007 file."— Presentation transcript:

1 Pt-Qtr Calculations Datasheet of Excel FieldTripData2007 file

2 Plot Calculations Datasheet of Excel FieldTripData2007 file

3 The sea palm Postelsia colonizes gaps in mussel beds, and coexists by ephemeral occupation of these patches - but coexist only if high rates of gap formation Poorer competitors but better colonizers

4 Early germinating and growing plants % Bromus depends on when germinates Physa snails reproduce earlier and survive better in ephemeral ponds than superior competitor Lymnaea First come, first served

5 Experimental plantings from seeds in different mixtures of 3-4 coexisting annual plant species Three competitive inferiors grew better when aggregated than randomly planted …but competitively superior Stellaria plants grew less well when seeds were aggregated illustrates coexistence in heterogeneous environments Aggregated distributions can deflect superior species towards intraspecific competition

6 Evolutionary effects of interspecific competition Limiting similarity: how differentiated must niches be to allow coexistence? - note: selection favors individuals with less overlap with competing species - coexistence easier when individuals compete more with conspecifics d>w, narrow niches & little competition d<

7 Character displacement: evidence of the “ghost of competition past” -competitive release on islands male & female Indian mongoose canine size (H. javanicus) H.j. H.e. Distribution of 3 Herpestes species

8 Character displacement: Stickleback fish in freshwater lakes (British Columbia) - if two species, feeding apparatus morphology diverges

9 Species “packing” in communities structured by competition: Phytoplankton diversity associated with number of limiting resources (nitrogen, phosphorus, silicon & light) n=221 samples from 3 Wyoming lakes Species diversity increased with no. resources limiting growth

10 Predation, Grazing & Parasitism Definitions of these species interactions Negative effects on vital rates and fitness of prey or host species Compensatory responses by individual prey Effects on prey or host populations Foraging behavior by predators & grazers Predator -prey population cycles Parasite-host population dynamics

11 Predation & Grazing - animal foraging behavior determines intensity and population consequences - negative interaction for prey or plant Predation: The consumption of one organism, in whole or in part, by another, where the consumed organism is alive when the consumer first attacks it. Predator: An organism that consumes other organisms, divisible into true predators, grazers, parasites and parasitoids. NO- too broad not fruits, nectar Herbivory: The consumption of living plant material.--NO Grazer: A consumer which attacks large numbers of large prey during its lifetime, but removes only a part of each prey individual, so that the effect, although often harmful, is rarely lethal in the short term, and never predictably lethal.

12 Parasitism Parasite: An organism that obtains its nutrients from one or a very few host individuals, causing harm but not causing death immediately. Parasitoid: Insects (mostly flies & wasps) in which the adults are free-living, but eggs are laid in, on or near an insect host after which the larvae develops in the host, eventually killing it before or during the pupal stage.

13 a)epiphytic flowering plant (Spanish moss) b)hemiparasite (mistletoe) c)parasite (dodder) Also- hemiepiphytes (many tropical figs) & lianas (= woody climbers) Distinguish parasites from commensuals--which use tree architecture for structural support but do not harm

14 Trees as hosts - structural support for epiphytes, hemiepiphytes and lianas Are these commensuals or parasites?

15 Are these parasites or commensuals? - do they affect host fitness? (e.g., vital rates of growth, survival and reproduction) 12 species of protozoa and rotifers live on the water louse Asellus, filtering food from moving water a)Polychaete worm on brown seaweed Fuscus b)Red seaweed commensual w/Ascophyllum c)Clava colonies on Ascophyllum

16 Ectoparasites Of plants: aphids, fungi which form a phyllospere of species living on plant leaf surfaces Of animals: fleas, lice, blood-sucking flies, etc.. (see Table 7.2 for % single or 2-host specialists of birds and mammals) Many are specialized to a single host species, so if host goes extinct, so do many of its ectoparasites

17 Endoparasites Dipsersal can involve secondary hosts & complex life cycles

18 Grazing influences plant vital rates: growth rates in the sand dune willow Salix cordata 1990: ample rain, no effect, but 1991: drought + high herbiv. = 80% mortality, vs. 0% & 40%

19 Effect of disease on fitness Late arriving male pied flycatchers reproduce poorly, and have a higher incidence of worm infection

20 Control of host population by parasitoid wasp Long-term population dynamics of laboratory host- parasitoid system (Venturia wasp & Indian meal moth) -the wasp controlled the moth at 1/10th of its abundance (note log scale)

21 Competition & parasitisim influence salt marsh community - Salicornia competitive ability affected by the parasite dodder

22 Nematode worm makes red grouse more susceptible to predation a) grouse shot for sport (+/- unbiased sample of pop) b) killed by predators Trichostongylus tenuis

23 Grazing & Competition Interactions - enhanced effect of herbivory Effect of beetle grazing and competition, alone and in combination, on Rumex crispus plant performance (as measured by leaf area) R. obtusifolius R. crispus (left) Gastrophysa

24 - simulated herbivory (clipping) of gentian plants change architecture & flowering… but note potential to compensate for herbivory depended on developmental stage during July Compensation for herbivory within plants: reallocation of nutrients

25 Compensatory production of defensive chemicals - grazers may have different effects: snails vs. isopods Ascophyllum

26 -Caterpillar induced production of defensive chemicals in wild radishes reduced leaf damage and led to higher fitness Benefit of reduced grazing comes at cost of resource allocation for defenses… net benefit to fitness over longer term?

27 Antipredator chemical defenses in animals - especially sedentary species - marine sponges seem defenseless, but suffer little herbivore damage

28 Anti-predator defense through mast fruiting & predator satiation - recall Borneo seed predation examples - New Zealand grasses of Chionochloa

29 Effects of predation on prey population dynamics - unpredictable outcomes 1) individuals killed may not contribute much to reproduction (very young or old) 2)compensatory changes in growth, reproduction or survivorship a)Reduced woodpigeon hunting: reduced food abundance & immigration maintained similar winter mortality b)Prey not food limited: spiders & grasshoppers

30 Imperfect compensatory mortality with reduced predation -Predator mortality may be replaced by other source of mortality -Reduction in vertebrate seed predation is not proportionally matched by increase in survival in Doug fir seeds (seedling survivorship doubled)

31 Effect of predators on prey population size depends on which age/sex classes killed Left: proportion Thompson gazelle killed different from availability Right: zig-zagging escape behavior by adults effective Result: predation on young & old may not much effect pop

32 Foraging Behavior - sit & wait predators vs. active predators - caddisfly larvae make nets (sit & wait) if fed (high density) b)Aggregative response to prey density

33 Foraging decisions a) which habitat? b) foraging vs. predation risk c) how long to stay in a food patch? d) patch quality vs. competition e) what foods to include in the diet (diet breadth)? Optimal Foraging Theory:

34 Predators select most profitable prey (high e/t) - not prefer those with greatest e -- but rate of return (net e/time spent feeding)

35 Optimal Diet Width How many food species to eat? Preference determined by e/(h+s) for each item- the net energy return from searching for and handling a food type Evolutionary ecology perspective: to foraging optimally, select a diet that maximizes E/t, where t = h+s If long handling times & short search times, then specialize (e.g., lions) If long search times, but short handling times, then generalize (e.g., insectivorous birds)

36 The Diet Width (or Breadth) Problem Broaden diet to less-preferred (lower e/t) foods if environment less productive; specialize as density of preferred food type increases

37 Specialize as habitat quality improves Black & brown bears consume more of each salmon when at low density; at high densities, specialize on energy-rich parts

38 Predator Switching to more common food type - effect can be to allow rare prey to recover or coexist

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