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Applications of C in animals: Diet and resource partitioning, resource allocation All using differences in 13 C C3 and C4 plants.

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Presentation on theme: "Applications of C in animals: Diet and resource partitioning, resource allocation All using differences in 13 C C3 and C4 plants."— Presentation transcript:

1 Applications of C in animals: Diet and resource partitioning, resource allocation All using differences in 13 C C3 and C4 plants

2 Renewable and nonrenewable resources: Amino acid turnover and allocation to reproduction in Lepidoptera OBrien et al. (2002 ) Hawkmoth (Amphion floridensis)

3 Percentage of adult dietary carbon OBrien et al. (2000): Egg 13 C increased rapidly from a value similar to larval 13 C and reached an asymptotic value, lower than diet 13 C carbon contributed to eggs should come from two different pools: larval and adult How do nectar nutrients relate to fecundity?

4 Nectar C3 or C4 Grape leaves Natural variation in 13 C in food sources was used for tracing sources of egg amino acid carbon LarvaeAdult Vitis (normal C3 host) 13 C = Depleted in 13 C Sucrose solution: (1)C3 beet sugar ( 13 C= ) (2)C4 cane sugar ( 13 C = ) Experiment

5 p = proportion of aas carbon derived from adult diet 1 – p = proportion of aas carbon derived from larvae diet Calculating the Proportion of Adult and Larval Carbon in TOTAL Egg Amino Acids Fractionation effects associated with amino acid synthesis or import from adult and larval diets should be the same for C3 fed and C4 fed females

6 Compound-specific 13 C analysis of amino acids 13 amino acids were resolved: -6 were nonessential (i.e. carbon skeletons can be synthesized from sugars in nectar, and therefore adult source) AlaPro GlyAsp SerGlu -6 were essential (i.e. cannot be synthesized by animals) + 1 sort of essential because animals cannot synthesize its ring structure from scratch. ThrIie(Tyr) ValPhe LeuLys

7 Young females eggs = Old females eggs in amino acid composition (no sign of senescence) Adult diet had a significant effect on non-essential 13 C indicating substantial incorporation of carbon from adult diet Days significant effect extent to which adult dietary carbon is incorporated varied Adult dietary carbon was not incorporated into any of the essential amino acids

8 Variation of the proportion of aas carbon derived from adult diet over time Non-essential amino acids Allocation of essential and non-essential aas into the egg differs Essential aas (~50% egg aas) derive exclusively from larval sources (contribute 35% of total egg carbon) Non-essential aas increasingly derive from adult diet, accesing endogenous sources of amine nitrogen (explains asymptotic behavior)

9 Bottom line: Essential amino acids come from larval carbon sources

10 Ecosystem Collapse in Pleistocene Australia and a Human Role in Megafaunal Extinction Miller et al. (2005) Emu - Dromaius novaehollandie Genyornis newtoni

11 Humans colonized Australia between 55 and 45 ka Most of Aussies large animals became extinct between 50 and 45 ka Ecosystem change Large browsers were disproportionally affected Changed fire regime beginning in 45ka recorded in terrestrial & marine sediments Is the arrival of humans related to these extinctions? Approach: Isotopic traces of diet from eggshells & marsupial teeth were used to monitor ecosystem before and after human colonization Eggshells of two contemporaries species of big-flightless birds were analyzed: Emu, Dromaius novaehollandie (extant species) Genyornis newtoni (extinct ~45ka)

12 Eggshell analysis Dated eggshells: 14 C ; sandgrain age, amino acid racemization in egg shells Paleodiet: Bird eggshells are a calcite biomineral containing 3% organic matter sequestered within calcite crystals. (Stable for > 10 6 years) C carb = Calcite Carbon - from blood C org = Carbon from Organic residues - from protein sources Used a general bird diet (feeding trials of Ostriches) -> egg shell organic offset (fractionation) 3

13 Fractionation diet to egg – 13 C org ~ 3 AVERAGE offset between 13 C carb & 13 C org : ~ 10.4 (Emu) ~ 11.1 (Genyornis) these averages were used to approximate the fractionation between the two types of carbon sources and thus 13 C carb can be adjusted to the same scale as 13 C org and using the 3 fractionation value they can be plotted as diet….

14 Winter nester 50-45ka mean dietary d 13 C decreased by 3.4 Prior to 50ka - variable diet (C4 & C3 plants) Wet years C4 (grasslands) Dry years C3 (shrubs and trees) 45ka - present restricted to C3 plants More restrictive diet Only 40% of the isotope variance observed in Emu Always includes some C4 diet sources Emu

15 Is this change a regional phenomena? Samples were collected from 3 widely separated regions of the Aussie continent Can we find the same change in other animal groups?? Wombat tooth enamel samples were analyzed (also a strict herbivore)

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17 -An abrupt ecological shift occurred about 50 to 45 ka in Australia -Climatic forcing is unlikely (previous major climatic shift did not result in such massive extinctions), and climate change between 60 to 40 ka was not large change was seen at the base of the food web -a change in fire regime caused ecosystem reorganization: C4 dominated grasslands C3 fire-adapted grasslands and chenopod/desert scrub Or Did over hunting of a number of species lead to this change in food web structure. Emu Genyornis

18 Ancient Diets, Ecology, and Extinction of 5-Million- Year-Old Horses from Florida MacFadden et al. (1999)

19 Short-crowned teeth: Browsing diet High-crowned teeth (Hypsodonty): Grazing on abrasive plants Not quite…

20 Horses in Bone Valley - - Excellent fossil record -6 species -two diverse clades of advanced hypsodonts with similar dental morphologies (and similar yet varying body sizes!) -Existed during a time of major global change -Preceded a terrestrial massive extinction event at ~ 4.8 Ma. The similar dental morphology implies same food source and potential competition Corresponds to a horse from an older level that shows short-crowned (i.e. browsing) tooth

21 3 independent methods for determining diet: -Tooth crown height -Carbon isotopic ratios from fossil tooth enamel (C3 vs C4 plants) 13 C C3 plants ~ -27 ( ) 13 C C4 plants ~ -13 ( ) -Tooth Wear: browsing tends to produce pits, while grazing leads to parallel scratches Microwear on enamel from a horse tooth. Magnification x 50

22 Species/taxonHI * Estimated Clade history after ~4.8 Ma body mass (kg) N. eurystyle Extinct P. simpsoni>3.5 51Extinct N. minor2.4 63N. peninsulatus C. emsliei C. emsliei in Florida A. stockii Extinct D. mexicanus Equus spp. Modern grazers¶>1-- Modern browsers#<1-- Hypsodonty Index Short crowned teeth = Browsers High crowned teeth = Grazers *HI = molar crown height / anteroposterios occlusal length

23 Figure 2. Microwear is analyzed by plotting the mean number of scratches versus pits per unit area (0.5 mm2). Abbreviations of modern browsers (shaded circles) and grazers (open circles) are given in the footnotes to Table 1. Extant grazers have, on average, more scratches and less pits than browsers. Equines (medium and large) 3-toes hipparionines tiny & small medium

24 Figure 3. Mean d13C versus MI for the Bone Valley horses (large symbols with vertical lines, data from Table 1; individual d13C sample data are indicated by small symbols). Almost exclusively C4- grass feeder C3 = C4 ??? – Mixed feeder, but with both browse (low MI) and C4 plants (rarely found) Medium & large tiny medium small


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