Transcript PPT Presentation

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)
O’Brien et al. (2000):
How do nectar nutrients relate to fecundity?
Percentage
of adult
dietary
carbon
Egg d13C increased rapidly from a value similar to larval d13C and reached an asymptotic value,
lower than diet d13C  carbon contributed to eggs should come from two different pools:
larval and adult
Grape
leaves
Nectar
C3 or C4
Natural variation in d13C in food sources was used
for tracing sources of egg amino acid carbon
Experiment
Larvae
Vitis (normal C3 host)
d13C = -30.11
Depleted in d13C
Adult
Sucrose solution:
(1)C3 beet sugar (d13C= -24.76)
(2)C4 cane sugar (d13C = -11.25 )
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
p = proportion of aa’s carbon derived from adult diet
1 – p = proportion of aa’s carbon derived from larvae diet
Compound-specific d13C 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)
-6 were essential (i.e. cannot be
synthesized by animals) + 1 “sort of”
essential because animals cannot
synthesize its ring structure from
scratch.
Ala
Gly
Ser
Thr
Val
Leu
Pro
Asp
Glu
Iie
Phe
Lys
(Tyr)
Young females eggs = Old female’s eggs in amino acid composition (no sign
of senescence)
Adult diet had a significant effect on non-essential d13C  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)
Genyornis newtoni
Emu - Dromaius novaehollandie
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:
shells
14C
; sandgrain age, amino acid racemization in egg
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 – d13Corg ~ 3 ‰
AVERAGE offset between d13Ccarb & d13Corg :
~ 10.4 ‰ (Emu)
~ 11.1 ‰ (Genyornis)
these averages were used to approximate the
fractionation between the two types of carbon
sources and thus d13Ccarb can be adjusted to the same
scale as d13Corg and using the 3 ‰ fractionation value
they can be plotted as diet….
Emu
Winter nester
50-45ka mean dietary d13C decreased by 3.4
‰
Prior to 50ka - variable diet (C4 & C3 plants)
More restrictive diet
Only 40% of the isotope variance
observed in Emu
Wet years C4 (grasslands)
Dry years C3 (shrubs and trees)
45ka - present restricted to C3 plants
Always includes some C4 diet sources
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
Emu
Genyornis
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
Ancient Diets, Ecology, and Extinction of 5-MillionYear-Old Horses from Florida
MacFadden et al. (1999)
High-crowned teeth
(Hypsodonty):
Grazing on abrasive plants
Short-crowned teeth:
Browsing diet
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)
d13C C3 plants ~ -27 ‰ (-36 - -22‰)
d13C 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
Hypsodonty Index
Species/taxon
HI*
N. eurystyle 2.4
P. simpsoni >3.5
N. minor
C. emsliei
A. stockii
D. mexicanus
Modern grazers¶
Modern browsers#
141
51
2.4
2.1
3.1
2.3
>1
<1
Estimated
body mass (kg)
Clade history after ~4.8 Ma
Extinct
Extinct
63
105
101
268
-
*HI = molar crown height /
anteroposterios occlusal length
Short crowned teeth = Browsers
High crowned teeth = Grazers
N. peninsulatus
C. emsliei in Florida
Extinct
Equus spp.
-
Equines
(medium
and large)
medium
3-toes hipparionines
tiny & small
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.
C3 =
C4
tiny
medium
Almost exclusively C4grass feeder
small
medium
??? – Mixed feeder, but
with both browse (low MI)
and C4 plants (rarely
found)
Medium &
large
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).