ANT 154B Course notes- Lecture _11

ANT 154B Course notes- Lecture _11 - ANT 154BN Course notes...

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Unformatted text preview: ANT 154BN Course notes Lecture #11: Life history theory 11 February 2011 Key terms and concepts are indicated in blue Outline 1. (Very) basic life history theory 2. Some thoughts on primate life histories 3. Linking ecology, life history, and evolution: orangutans as a case study 1. (Very) basic life history theory Life history theory: trade offs Resources are limited. Life is a zero-sum game. Natural selection shapes allocation “decisions”. Life history decisions: how to allocate limited resources? Investment (time and resources) Somatic effort (growth, maintenance and repair) Reproductive effort Parental effort (offspring quality - survival, growth, learning, social connections, etc) Mating effort (copulations) Thursday, April 16, 2009 27 There are many examples of tradeoffs, the key is that these are shaped by natural selection to maximize inclusive fitness Life history trade offs: examples • we expect the nature of these tradeoffs growth vs.between sexes, in different environments, between to differ reproduction individuals, for the same individual at different portions of the life span. reproduce now vs. reproduce later • the study of how and why individuals and species invest in certain ways is the central focus of life long juvenile period vs. short juvenile period history theory little investment per offspring, many offspring (“r strategists”) vs. vs. intense investment a few offspring (“K strategists”) paternal investment * Thursday, April 16, 2009 mating effort Shaped by NS, allocate to * maximize inclusive fitness 28 ANT 154B Lecture #11 course notes Body weight page 2 of 10 Charnov & Berrigan 1993 37 Primates have relatively small litters 2. Some thoughts on primate life histories Primates typically have slow life histories Small litters Long pregnancy & juvenile period Long life span Thursday, April 16, 2009 Primates: life in the slow lane Average adult lifespan Age at maturity Primates: life in the slow lane Body weight Primates have long lifespans and mature late Number of offspring Charnov & Berrigan 1993 Thursday, April 16, 2009 38 Body weight Primates have relatively small litters Charnov & Berrigan 1993 Thursday, April 16, 2009 37 The puzzle of primate life histories: Why do primates live so long? Primates: life in the slow lane Average 1. “Rate of living” theory: high metabolic rate -> early death adult lifespan test: does low metabolic rate -> long life ? (e.g., turtles) Age at maturity 2. Large brains are homeostatic test: large brains -> long life (e.g., primates) Body weight Primates have long lifespans and mature late Charnov & Berrigan 1993 T rs ay, April 16, 2009 3.huSdenescence theory 38 low environmental hazard -> long life high environmental hazard = high extrinsic mortality when high extrinsic mortality, “faustian alleles” impose few costs Why do primates grow so slowly? 1. Brains demand energy (tradeoff brain vs. body) test: large brain correl. w/ slow growth ANT 154B Lecture #11 course notes 2. Brains demand learning logic: takes time to develop adult skills page 3 of 10 3. To reduce mortality risk Logic: • primate juveniles susceptible to starvation, predation • slow growth can reduce risk of starvation • protection of group living reduces predation risk, allowing slower growth 3. To reduce mortality risk e.g., juvenile capuchin monkeys use less exposed branches (reduces feeding efficiency, and therefore growth rate, but is safer) whitefronted 3. To reduce mortality risk slow juvenile growth rates +/- “fixed” captive wild brown juvenile Janson & van Schaik 1993 Thursday, February 11, 2010 Janson & van Schaik 1993 21 4. Low food abundance Logic: primate food too scarce to permit rapid growth Thursday, February 11, 2010 20 predict: species with lower quality, more abundant food, grow faster 4. Low food abundance Male Gorilla Velocity (kg/yr) high quality food = less food = slow growth relative age at female maturity relative diet quality Weight (kg) Chimp Bonobo Age (yrs) Age (yrs) female age at maturity diet quality Female Weight (kg) log Body weight log Body weight 23 Gorilla Velocity (kg/yr) Thursday, February 11, 2010 Chimp Bonobo Age (yrs) Age (yrs) Leigh & Shea 1998 24 Thursday, February 11, 2010 ANT 154B Lecture #11 course notes page 4 of 10 3. Linking ecology, life history, and evolution: orangutans as a case study West Morphology Thursday, February 11, 2010 East bigger Chewing apparatus smaller 27 Taylor JHE 2006 Thursday, February 11, 2010 West East smaller 30 Brains bigger Female brain size ANT 154B Lecture #11 course notes Diet page 5 of 10 Percent fruit in the diet 100 90 80 70 60 50 40 30 20 10 0 0.5 1 P. abelii 1.5 2 P. p. wurmbii 2.5 3 P. p. morio 3.5 Wich et al. 2006 Thursday, February 11, 2010 34 Thursday, February 11, 2010 Percent veg in the diet 80 70 60 50 40 30 20 10 0 0.5 P. abelii 1 1.5 P. p. wurmbii 2 2.5 P. p. morio 3 3.5 Wich et al. 2006 35 Fallback foods Sumatra: figs Borneo: cambium (inner bark) Percent cambium in the diet Fig stems per ha 60 50 40 30 20 10 0 0.5 1 P. abelii 1.5 2 3 P. p. wurmbii 2.5 P. p. morio 3.5 Wich et al. 2006 Thursday, February 11, 2010 37 14 12 10 8 6 4 2 0 0.5 P. abelii 1 1.5 P. p. wurmbii 2 2.5 P. p. morio 3 3.5 Marshall et al. 2006, 2009; Wich et al. 2006 38 Thursday, February 11, 2010 ANT 154B Lecture #11 course notes Population density Orangutan density on Sumatra and Borneo page 6 of 10 Sumatra West Pop. density Borneo high East low Thursday, February 11, 2010 41 Forest productivity In controlled comparisons, generally more fruit available in Sumatra Periods of fruit scarcity are less common on Sumatra van Schaik, Marshall, & Wich 2009 Thursday, February 11, 2010 42 Orangutan den 3 2 1 0 ANT 154B Lecture #11 course notes Marshall et al. FIGURE 3.4 8 Orangutan density (direct obs/km2) 1185 38 page 7 of 10 0 .5 1 1.5 Log (Total stems/ha LFP+1) 2 Less masting in Sumatra Comparative phenology of Borneo and Sumatra -1 1190 7 6 5 4 3 2 1 0 -1 a 1195 Orangutan density (direct obs/km2) 6 5 4 3 2 1 0 absent 1200 1205 0 .5 1 1.5 Log (Total stems/ha LFP+1) 2 b 0 50 100 150 Dipterocarp density (stems/ha) Orangutan density (direct obs/km2) 6 1210 5 4 3 2 1 0 Marshall et al. 2008 46 Thursday, February 11, 2010 foods more available on Sumatra important orangutan 1215 b 0 50 100 150 Dipterocarp density (stems/ha) Marshall et al. 2008 Thursday, February 11, 2010 47 ANT 154B Lecture #11 course notes Sociality & culture page 8 of 10 Female sociality (mean adult party size) 2 1.8 1.6 Culture Sociality sophisticated 1.4 1.2 limited low high 1 0.5 P. abelii 1 1.5 P. p. wurmbii 2 2.5 P. p. morio 3 3.5 Delgado & van Schaik 2000 Thursday, February 11, 2010 50 Life history Thursday, February 11, 2010 van Inter birth intervals (years) Schaik, Marshall, & Wich 2008 51 10 9 8 7 6 5 0.5 1 P. abelii 1.5 2 3 P. p. wurmbii 2.5 P. p. morio 3.5 Wich et al. 2008, Ancrenaz unpublished Thursday, February 11, 2010 53 ANT 154B Lecture #11 course notes Explanation: volcanic Sumatran soils are more fertile page 9 of 10 Mechanism? Phenotypic plasticity Local genetic adaptations Social learning: cultural repertoires differ due to learning ANT 154B Lecture #11 course notes page 10 of 10 Take home messages 1. Natural selection shapes allocation “decisions” among different life history strategies to maximize inclusive fitness. 2. Primate life histories are atypical compared to other mammals (e.g., live long, grow slowly). 3. Behavior, morphology, sociality, and life history show a clear west to east gradient among orangutan populations. 4. Patterns of resource availability appear to explain this pattern. 5. Mechanisms underlying these difference may be a complex interplay of phenotypic plasticity and local genetic adaptations, plus some social learning (but we don’t really know yet). Question to ponder There is considerable variation among orangutan taxa in their morphology, diet, life history, and social behavior that seems to map well onto variation in patterns of resource availability among sites (and ultimately, seems to depend on soil quality). Even if we assume that these differences are adaptive (i.e., ignoring genetic drift as a possible explanation), the extent to which these differences are evolved, genetic adaptations to local conditions or represent phenotypic plasticity is unclear. Briefly describe two ways that you might be able to tease these two alternatives apart, either through field studies, captive observations, or experiments. ...
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This note was uploaded on 04/05/2011 for the course ANT 154bn taught by Professor Debello during the Winter '10 term at UC Davis.

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