Yom-Tov, Y., and Geffen, E. 2011. Recent spatial and temporal changes in in body size of terrestrial vertebrates: probable causes and pitfalls. Biological Reviews 86: 531-541.
Blog author: Maria Goller
1st author: Dr. Yoram Yom-Tov
Bachelors, Masters, PhD at Tel Aviv
Emeritus zoology professor at Tel Aviv University
Also was curator of terrestrial vertebrates at the museum as well as academic director of zoological garden
2nd author: Dr. Eli Geffen
Professor at Tel Aviv University
Has worked on a lot of different things, including visual communication in chameleons, sociality in carnivores, and parasite loads in rodents...
Studies vocal communication in rock hyraxes and tries to understand song syntax (which is what I do, yay!)
This is a review paper of how variation in various abiotic and biotic factors shapes changes in body size.
Overview and Major Points
1. Body size varies with space and time
· In some taxa, food availability during development plays a major role in determining body size
· Food availability changes with weather/climate, and from season to season
· Climate proxies for food availability - such as ambient temperature - are used because food availability is difficult to measure
· Both year and latitude affect body size indirectly
· Competition also affects body size
· Resource rule = mammal body size variation depends on resource fluctuation
· Species may vary widely in the pattern of change in body size
· Lumping body size patterns across species may mask variation
· Depending on the spatial or temporal scale of sampling, you may see different patterns in changes in body size
2. Rate of change
· Body size trends are fluid, even at short temporal scales
3. Time span, sample size, and the possibility of detecting a trend
· As number of samples increases, likelihood of detecting a trend in body size increases
· Also, as time of sampling increases, the likelihood increases
· So just because you don't see a trend, doesn't mean there isn't one
4. Sources of variation
· Not useful to measure body mass because it changes daily/seasonally/etc...
· Both body length and skull length vary annually
· Wing length is thought to be the best measure of avian body size, but it doesn't yield clear-cut results
· Birth year of sampled organisms matters due to differences in food availability/climate/etc…
· Continuous data are better than discrete
· Need to test climatic variables separately because they're all interrelated and lead to messy trends
5. Linear, non-linear, and cyclic effects on body size
· Environmental predictors vary cyclically
· Have found linear trends in body size with change in temperature
· Different trends in migratory and nonmigratory birds
· Body size changes correlated with precipitation, food availability, and biomass productivity, which are all influenced by temperature
· Temperature fluctuates among years, so taking a one-year snapshot isn't very revealing
6. Food supply and body size
· Climate and short-term changes in food availability (due to weather) shape body size patterns
· Various relationships between temperature and body size based on local conditions
· Climate change also may cause an increase/decrease in competition => changes in body size
· Also, humans may shape food availability and influence body size patterns
· Body size may change over short time periods if habitats change
7. Phenotypic and genetic variation
· A lot of the recent trends seem phenotypic in nature
· Genetics may play a role in some cases
Main Message:
· Body size is variable and fluctuates across time and space
· Although many predictors are correlated with body size, it is difficult to untangle which factors directly, and which indirectly, drive changes in body size
I like review papers because they give an overview of the state of the field.
I think this review reiterates the trend in the papers we’ve read this semester about everything being much more complicated than one might at first assume.
This was a great review paper that addressed the benefits and issues with observing body size. I would be interested in reading a paper that expanded on the subject of humans impacting body size of mammals through factors other than hunting, like the need to disperse longer distances due to fragmented habitat.
ReplyDeleteGreat article! This was a lot easier to follow along with and I like how informative this paper is. It talked about everything we’ve been going over in class, plus more so I feel like I have a slightly better understanding how body mass is so important to ecology.
ReplyDeleteI appreciated the section on the sources of variation and discussing different potential methods used to collect data. More on fragmentation would be an interesting addition, as smaller patches directly impacts food source, availability, and quality.
ReplyDeleteI really like this paper. First of all, it is easy to follow and distinguish important parts laid out in an organized manner. I like the phenomenon of how body size can be a predictor/indicator of certain temperature and other abiotic fluctuations at a different time. I always wondered how would they figure out the optimal body size to compare the changes in size but this review answered my question. I wonder how much that rat will grow if the direct and indirect effects favor its growth.
ReplyDeletePretty interesting to see just how many factors can go into one variable. A lot of these I hadn't thought of in terms of body size, like birth year or latitude, so that was cool.
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ReplyDeleteI agree with the previous comments: I liked that they explained their ideas clearly and it was easy to follow. I liked that they pointed, as Maria said, to how one thing might be influenced by many different factors, instead of showing how one particular thing is correlated to body size.
ReplyDeleteLike most other comments, I really liked this review paper! So interesting all of the things that have been since linked to body size. Figure 1 especially shows that and I think anyone who wants to use body size as a proxy for something should be aware of all of the various things that go into it.
ReplyDeleteI like that this paper takes in a lot of variables: temperature, food, climate,etc. I'm working on an experiment involving change in body size, so I'm glad I saw this paper.
ReplyDeleteI agree, it was good to read this paper. I found specially interesting the fact that brown bear body size is closely related to the nearest salmon site run, which is a good example of the main argument of the authors that key aspect of the traditionally used predictors is their relation to resources needed by the species or population
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