applications of c in animals: diet and resource partitioning, resource allocation all using...

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