Stable isotopes in early Eocene mammals as indicators of forest canopy structure and resource partitioning

The three dimensional structure of vegetation is an important component of ecosystems, yet it is difficult to reconstruct from the fossil record. Forests or woodlands prevailed at mid-latitudes in North America during the early Eocene but tree spacing and canopy structure are uncertain. Here we use...

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Bibliographic Details
Published in:Paleobiology 2008-03, Vol.34 (2), p.282-300
Main Authors: Secord, Ross, Wing, Scott L, Chew, Amy
Format: Article
Language:English
Subjects:
atmosphere
Atmospheric circulation
Bighorn Basin
C-13/C-12
Canopies
carbon
Carbon isotopes
Cenozoic
Chordata
Diet
enamel
Eocene
Fauna
Forest canopy
Forest habitats
Forests
Fossils
Geochemistry
habitat
Habitats
herbivorous taxa
isotope ratios
Isotopes
lower Eocene
Mammalia
Mammals
Mass spectrometry
Microhabitats
O-18/O-16
oxygen
Oxygen isotopes
Paleoecology
paleoenvironment
Paleogene
Paleontology
Plants
Resource partitioning
s
Stable isotopes
statistical analysis
teeth
Terrestrial ecosystems
terrestrial environment
Tertiary
Tetrapoda
Understory
United States
Vegetation
Vertebrata
vertebrate
Water availability
Willwood Formation
Woodlands
Wyoming
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Summary:The three dimensional structure of vegetation is an important component of ecosystems, yet it is difficult to reconstruct from the fossil record. Forests or woodlands prevailed at mid-latitudes in North America during the early Eocene but tree spacing and canopy structure are uncertain. Here we use stable carbon isotope values (δ13C ) in early Eocene mammalian faunas to infer canopy structure. We compare δ13C values in two diverse fossil assemblages from the central Bighorn Basin to values predicted for mammals in a variety of open and closed habitats, based on modern floras and faunas. We conclude that these early Eocene faunas occupied an open canopy forest. We also use carbon and oxygen isotopes to infer diet and microhabitat. Three higher level taxa have significantly different mean δ13C values, and values are negatively correlated with body mass. The pattern suggests diets high in leaves for larger mammals, and fruit or other non-foliar plant organs for small ones. A preference in the larger mammals for wetter habitats with high water availability to plants may also have contributed to the pattern.
ISSN:0094-8373
1938-5331
DOI:10.1666/0094-8373(2008)034[0282:SIIEEM]2.0.CO;2