applications of c in animals: diet and resource partitioning, resource allocation all using...
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Applications of C in animals:Diet and resource partitioning,
resource allocation
All using differences in 13C C3 and C4 plants
Renewable and nonrenewable resources: Amino acid turnover and allocation to
reproduction in Lepidoptera
O’Brien et al. (2002 )
Hawkmoth (Amphion floridensis)
Percentage of adult dietary carbon
O’Brien et al. (2000):
Egg 13C increased rapidly from a value similar to larval 13C and reached an asymptotic value, lower than diet 13C carbon contributed to eggs should come from two different pools: larval and adult
How do nectar nutrients relate to fecundity?
NectarC3 or C4
Grape leaves
Natural variation in 13C in food sources was used for tracing sources of egg amino acid carbon
Larvae Adult
Vitis (normal C3 host)13C = -30.11
Depleted in 13C
Sucrose solution: (1)C3 beet sugar (13C= -24.76)(2)C4 cane sugar (13C = -11.25 )
Experiment
p = proportion of aa’s carbon derived from adult diet1 – p = proportion of aa’s 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
Compound-specific 13C analysis of amino acids13 amino acids were resolved:
-6 were nonessential (i.e. carbon skeletons can be synthesized from sugars in nectar, and therefore adult source)
Ala ProGly AspSer Glu
-6 were essential (i.e. cannot be synthesized by animals) + 1 “sort of” essential because animals cannot synthesize its ring structure from scratch.
Thr Iie (Tyr)Val PheLeu Lys
Young females eggs = Old female’s eggs in amino acid composition (no sign of senescence)
Adult diet had a significant effect on non-essential 13C indicating substantial incorporation of carbon from adult diet
Day’s significant effect extent to which adult dietary carbon is incorporated varied
Adult dietary carbon was not incorporated into any of the essential amino acids
Variation of the proportion of aa’s carbon derived from adult diet over time
Non-essential amino acids
Allocation of essential and non-essential aa’s into the egg differs
Essential aa’s (~50% egg aa’s) derive exclusively from larval sources (contribute 35% of total egg carbon)
Non-essential aa’s increasingly derive from adult diet, accesing endogenous sources of amine nitrogen (explains asymptotic behavior)
Bottom line: Essential amino acids come from larval carbon sources
Ecosystem Collapse in Pleistocene Australia and a Human Role in Megafaunal Extinction
Miller et al. (2005)
Emu - Dromaius novaehollandieGenyornis newtoni
Humans colonized Australia between 55 and 45 ka
Most of Aussie’s 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)
Eggshell analysis
Dated eggshells: 14C ; 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 > 106 years)
Ccarb = Calcite Carbon - from blood
Corg = Carbon from Organic residues - from protein sources
Used a general bird diet (feeding trials of Ostriches) -> egg shell organic offset (fractionation) 3 ‰
Fractionation diet to egg – 13Corg ~ 3 ‰
AVERAGE offset between 13Ccarb & 13Corg :
~ 10.4 ‰ (Emu)
~ 11.1 ‰ (Genyornis)
these averages were used to approximate the fractionation between the two types of carbon sources and thus 13Ccarb can be adjusted to the same scale as 13Corg and using the 3 ‰ fractionation value they can be plotted as diet….
Winter nester
50-45ka mean dietary d13C 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
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)
-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
Ancient Diets, Ecology, and Extinction of 5-Million-Year-Old Horses from Florida
MacFadden et al. (1999)
Short-crowned teeth:Browsing diet
High-crowned teeth (Hypsodonty):
Grazing on abrasive plants
Not quite…
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
3 independent methods for determining diet:
-Tooth crown height
-Carbon isotopic ratios from fossil tooth enamel (C3 vs C4 plants)
13C C3 plants ~ -27 ‰ (-36 - -22‰)13C C4 plants ~ -13 ‰ (-16 - -9‰)
-Tooth Wear:browsing tends to produce pits, while grazing leads to parallel scratches
Microwear on enamel from a horse tooth. Magnification x 50
Species/taxon HI* Estimated Clade history after ~4.8 Mabody mass (kg)
N. eurystyle 2.4 141 ExtinctP. simpsoni >3.5 51 ExtinctN. minor 2.4 63 N. peninsulatusC. emsliei 2.1 105 C. emsliei in FloridaA. stockii 3.1 101 ExtinctD. mexicanus 2.3 268 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
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
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
medium
small