Revisiting old bones: coupled carbon isotope analysis of bioapatite and collagen as an ecological and palaeoecological tool

Abstract

Isotopic studies of palaeoecological and ecological questions often use bone collagen or bioapatite as substrates, but rarely both. Substantial new information can be gained from the incorporation of isotopic values from both the organic and inorganic fractions of bone. Here we show that combining isotopic data from both substrates provides valuable and unique insights into (1) trophic relationships and dietary interactions; (2) differences in digestive physiologies and (3) identification of palaeontological or archaeological remains that lack diagnostic morphological characters. We present a range of new isotopic data collected from modern and fossil mammals, and investigate patterns within several published datasets. We define carbon isotope spacing variables, and then explore four diverse palaeoecological and ecological case studies.

Rewriting the history of an extinction—was a population of Steller's sea cows ( Hydrodamalis gigas ) at St Lawrence Island also driven to extinction?

“…As DNA confirmed the identity of these bones as originating from Steller [8]. Specimen ID for samples not from this study is detailed in table 2; numbers correspond to the latter part of the specimen ID.…”

“…C can indicate changes in trophic level [8,9,11]. As DNA confirmed the identity of these bones as originating from Steller [8].…”

“…The mass of the ions is separated using electric and magnetic fields. The numbers of N collagen values for six new samples, from Bering and St Lawrence Island, were added to 10 samples from Clementz et al [8], from Bering Island only (figure 2), and a Mann -Whitney U-test was conducted on the stable isotope data for nitrogen.…”

“…N can indicate geographical variation in feeding location [8][9][10][11][12][13][14][15][16][17][18], including in marine mammals [12,13], whereas small changes in d…”

Resource partitioning among top predators in a Miocene food web

“…Trophic fractionation of carbon isotopes between mammalian carnivores and their prey results in slightly lower d 13 C values in carnivoran tooth enamel relative to that of their prey [27 -29]. To account for this trophic fractionation, we adjusted carnivoran d 13 C values by þ1.3‰, following the trophic discrimination factor proposed by Clementz et al [27]. Because the carnivoran teeth analysed here were found as isolated fossils in Batallones-1 and it was not possible to group the teeth by individuals, we treated each carnivoran tooth as a different individual and compared their d 13 C values to the average d 13 C values of feasible prey in terms of body size (see below).…”