1. Life history and longevity Population ecology Life history evolution Reproductive value Longevity and senescence

2. Discussion Readings Kirkwood, T.B.L. and Austad, S.N. 2000 Why do we age? Nature 408:233-238. Perez-Campo, R., M. Lopez-Torres, S. Cadenas, C. Rojas and G. Barja 1998 The rate of free radical production as a determinant of the rate of aging: evidence from the comparative approach. Journal of Comparative Physiology B 168:149-158. Brunet-Rossinni AK 2004. Reduced free-radical production and extreme longevity in the little brown bat (Myotis lucifugus) versus two non-flying mammals. Mechanisms of Aging and Development 125: 11-20.

3. Exponential population growth b = birth rate d = death rate r = intrinsic rate of population growth dN/dt = (b-d)N = rN “r-selected”

4. Logistic population growth Addition of a density dependent term results in logistic growth K = carrying capacity dN/dt = rN (K-N)/K “K-selected”

5. Age-specific population growth Age-specific survivorship (l x ) Age specific reproduction (m x ) Net reproductive rate: R o =  l x m x –Stable population: R o = 1 –Growing population: R o > 1 –Declining population: R o < 1

6. The age-specific survival (l x ) and fertility (m x ) pattern specifies an organism’s life history pattern.

7. Fertility (m x ) patterns

8. Estimating Survivorship (l x ) (l x )

9. Survivorship types

10. Survivorship curve examples

11. Bat survivorship curves

12. r vs K selected

13. Life history trade-offs expected with limited resources Lizards Birds Due to allocation of resources between maintenance and reproduction

14. Reproductive value Age-specific expectation of offspring (how much is a female worth in terms of future offspring?) Assuming a stable population (R = 1) V x = (  t=x m t l t )/l x –the number of female offspring produced at this moment by females of age x or older / the number of females which are age x at this moment Reproductive value peaks near puberty in human populations

15. Reproductive value curves Lizards Beetle Crustacea

16. Evolutionary theory of aging The risk of extrinsic mortality should influence life span because the force of natural selection declines with age Consequently, mutations with late-acting deleterious effects will not be eliminated (antagonistic pleiotropy) Senescence should result and shorten life span in proportion to mortality risk Expect that investing in early reproduction will detract from survival - the “disposable soma” idea

17. Bat Methuselahs Rhinolophus ferrumequinum (31 yrs, 24 g) Plecotus auritus (30 yrs, 7 g) Myotis brandti (38 yrs, 8 g) Myotis lucifugus (34 yrs, 7 g) Myotis blythii (33 yrs, 23 g) Pteropus Giganteus (31 yrs, 1 kg)

18. Aging studies and bats Bats are long-lived because they save energy by going into torpor or hibernate (Bouliere 1958) But, nonhibernating tropical bat species live as long as temperate species (Herreid 1964) Furthermore, bats live longer than expected for their body size even after adjusting for metabolic differences (Jurgens and Prothero 1987) And, marsupials, which have lower metabolic rates than bats, have much shorter life spans (Austad and Fischer 1991) Flying mammals live longer than nonflying mammals (Holmes and Austad 1994)

19. Possible factors influencing extrinsic mortality risk in bats Body size Group size Cave roosting Diet Hibernation (Latitude) Reproductive rate

20. Longevity records for bats Distribution by family Pteropidae - 5 Emballonuridae - 1 Megadermatidae - 1 Rhinolophidae - 4 Noctilionidae - 1 Phyllostomidae - 8 Molossidae - 2 Vespertilionidae - 42 ANOVA (log long): F 7, 56 = 2.1, P = 0.064 Distribution by source Captive - 16 Field - 48 ANOVA: F 1, 62 = 1.3, P = 0.25 Data sources on longevity 56 from publications 8 from unpublished studies

21. Phylogenetically independent contrasts were used to infer correlated evolution

22. Longevity and body mass in nonflying eutherian mammals (Austad & Fischer, 1991)

23. Longevity and body mass in bats Body mass (g) Change in body mass (log g) Change in longevity (log y) Longevity (y) Species meansIndependent contrasts F 1,62 = 1.5, P = 0.23 F 1,40 = 7.3, P = 0.01 Allometric relationship for 463 spp of nonflying placental mammals (Austad & Fischer 1991)

24. Roosting and group size variation

25. Colony size and longevity Colony sizeChange in log colony size Change in longevity (log y) Longevity (y) F 1,60 = 1.5, P = 0.22F 1,38 = 0.4, P = 0.52

26. Roosting habits and longevity Cave roostingChange in cave roosting Change in longevity (log y) Longevity (y) (a)(b) F 2,61 = 4.6, P = 0.014 F 1,11 = 5.9, P = 0.033

27. Bat diets

28. Frugivory and longevity DietChange in fruit eating Change in longevity (log y) Longevity (y) F 1,2 = 0.1, P = 0.81F 1,62 = 0.04, P = 0.84

29. Reproductive effort variation 1 pup/yr1 pup/4-6 mos2 pups/yr Rhinolophus darlingiNyctophilus gouldiCarollia perspicillata

30. Reproductive effort and longevity Reproductive rateChange in reproductive rate Change in longevity (log y) Longevity (y) (a)(b) F 1,62 = 23.6, P = < 0.0001F 1,40 = 19.4, P = < 0.0001

31. Hibernation Twente et al. 1985

32. Hibernation and longevity HibernationChange in hibernation Change in longevity (log y) Longevity (y) F 1,60 = 13.7, P = 0.0005 F 1,5 = 10.3, P = 0.024

33. Latitude and longevity Species mid-range latitudeChange in latitude Change in longevity (log y) Longevity (y) F 1,62 = 14.6, P = 0.0003F 1,41 = 8.4, P = 0.006

34. Multivariate analysis of longevity (independent contrasts) Source (controlled*) dfFP Repro. rate (body mass) 1,5616.90.0002 Hibernation (rep. rate) 1,5614.30.013 Body mass (rep. rate) 1,565.40.025 Cave roosting (rep. rate) 2,565.20.043 *indicates the independent variable used to generate residual longevities for the contrast analyses, r 2 = 0.58

35. Conclusions Bats live 3.5 times as long as other mammals of comparable size. From an evolutionary perspective, extrinsic mortality risk could account for the effects of body size, cave roosting, reproductive rate and hibernation on longevity From a physiological perspective, the effects of reproductive rate and hibernation on longevity are consistent with allocation of finite resources to the soma.

36. Implications Caloric restriction is the only method for experimentally increasing lifespan in mammals Calorie restricted (and hibernating!) rodents show –Decreased blood glucose –Decreased glycolytic enzyme activity –Increased gamma globulin levels –Increased antioxidant defenses Hibernation could act to conserve resources much like caloric restriction

37. Proposed studies on big brown bats Big brown bats are the most common NA bat Big brown bats exhibit variation in litter size and hibernation across the species range

38. Aims - compare four sites Estimate field metabolic rate, as a proxy for oxygen consumption, using doubly-labeled water and temperature sensitive radio telemetry Compare seasonal survival at each site using transponder records Quantify oxidative damage in collagen using flourescent microscopy Determine if oxygen exposure influences the accumulation of mtDNA damage

39. Geographic range

40. Proposed study sites

41. mtDNA replication

42. Bat mtDNA control region