Week 4 - Species, Niches, and Communities continued
Stable isotopes reveal seasonal competition for resources between late Pleistocene bison (Bison) and horse (Equus) from Rancho La Brea, southern California
Robert S. Feranec a,⁎, Elizabeth A. Hadly b, Adina Paytan c
Paleogeography, Paleoclimatology, Paleoecology
2009
In this paper, the authors use stable carbon and oxygen isotopes in fossil tooth enamel to compare dietary niches of late Pleistocene bison and horses in southern California. These isotopes are indicative of source of water source and diet, particularly percentage of C3 and C4 plants eaten. Data supports yearly bison migration to and from Rancho La Brea and no yearly migration for horses. It also indicates that, while both horses and bison ate primarily C3 plants, bison ate a significantly higher proportion of C4 plants than horses. Since both taxa are primarily grazers who also do a little browsing, this indicates niche partitioning.
Thoughts:
Is pressure to partition niches found more in the fact that bison migrate and horses do not, or in the fact that the two taxa have slightly different diets?
In the discussion they mention that previous studies on bison and horses indicate that bison are primarily grazers and that horses incorporate more browse. The findings of this study indicate the opposite: horses grazing and bison browsing more. I wonder why this would switch.
ReplyDeleteI also wonder how the range in C13 values compare between the bison from this study and previous studies; in other words, do the bison in this study exhibit greater or less niche breadth than in previous studies?
Interesting points, Mel. I also wonder if it can't be a combination of both slightly different diets and migration that allow the horses and bison to co-exist? Maybe that is something we will not be able to get at by looking at the fossil record, but will have to compare with diets of extant representatives. I would have liked to see this study go into how each are functioning in an ecosystem. It would be cool to see how the ecosystem has changed, and what (if anything) has replaced some of the vegetation and herbivores.
ReplyDeleteMel, I think you've misread the results of the earlier study they cite - they actually agree with this study's findings pretty well. I thought this was an elegant study, and a good example of the use of stable isotopes to study diet, which is an increasingly popular method in paleoecology. I would like to hear more about the plant communities at Rancho La Brea; they hint at the area having mostly C3 plants but don't explain further.
ReplyDeleteFred, we can discuss their discussion section this afternoon :-P
ReplyDeleteI also wanted to say, I personally love methods papers, and I like that they emphasize at the end the value of using the inorganic carbonate from enamel versus collagen for this kind of study.
I interpreted the findings of the previous study as Mel did; horses incorporating more browse than bison.
ReplyDeleteI would be interested in knowing a little more about the morphology of the bison and horse specimens the authors used in this study, especially concerning their ability to consistently obtain a specific food source. If bison are less able to reach C3 plants under snow than horses, might this cause them to simply consume more c4 plants in the same area? I don't quite understand how their results support migration rather than just utilizing different resources in the same area.
The study also states that the two genera did not exactly co-exist. If this is true, could changing environment have a roll to play in the differences in diet?
I had the same question as Kat, to what extent did these specimen coexist? The approach in the paper was extremely elegant and the results very concrete. I did really enjoy the explanation of the differences in collagen isotopic results vs enamel brought up in the study. But back to the question of competition between the genera I would like to know the method of identifying the relative ages of the specimens found in RLB and the error within the dating. Even if the two were not in direct competition of each other, the diet regime could be an indicator of the herd structure. I would imagine the larger herds would show are larger range of migration and a variety of vegetation ingestion based on the competition within the genera.
ReplyDeleteSorry this is late guys, crazy week... Anyway, I found this study pretty amazing. There are some problems I have with it, for starters it would make sense that horses would migrate as much or more than bison would. This is what mustangs try to do today, and it would make sense that their ancestors did the same or something similar. I have more thoughts on that. It is so cool that they were able to use isotopes to tell whether bison an horses ate C3 OR C4 plants. I find everyone's thoughts so far to bring up extremely valuable points about the paper. I'm slightly curious if there was some form of a barrier at the time that caused the horses to have a more restricted diet? This doesn't make any sense really because horses would be more mobile than bison?
ReplyDeleteSorry again for this being late and not a very good post, like I said long week... See you guys in class!!
I found this paper rather interesting. I also would like to know a little more about the morphology of both the horse and the bison as has been previously suggested. I also find it interesting that the authors attribute the differences in the diet to migration. I would like to know why they make this suggestion and what kept horses in the basin, I do not know much about horses but it seems that they would migrate from place to place. I also like the way they explained their methods. I have not done much with isotopes so It was very helpful for me to understand the paper.
ReplyDelete