Why Does Species Number Decrease with Smaller Body Mass?

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In summary, there are graphs comparing the number of species to body mass, and it's clear that smaller animals have a greater number of species. However, there seems to be a decrease in number of species for organisms with a mass of less than 100g. This may be due to missing species, particularly in the case of microbes which are difficult to culture in a lab. With the use of metagenomics, it is possible to get a distribution of species in an environment even without being able to culture them. Additionally, there is a wide range of sizes for dogs, but this is not mentioned in the graphs.
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farful
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# of species vs body mass

Here are some graphs:

http://en.wikipedia.org/wiki/File:Intercontinental_land_mammals.png
http://en.wikipedia.org/wiki/File:North_american_land_mammals_graph.png
http://en.wikipedia.org/wiki/File:May_slope_-2_line.png

It's obvious why the number of species that have smaller body sizes are greater in number.
However, once we get into organisms with mass smaller than 100g, it seems to decrease. Why? One would assume it'd keep increasing, no?
Furthermore, would the trend continue for microbials?

Edit: Thanks DaveC, links have been fixed
 
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There may be a problem with missing species. Most microbes are impossible to culture in lab (or at least we haven't figured out how to yet), so there are likely a great number of undiscovered microbial species.
 
  • #3


Ygggdrasil said:
There may be a problem with missing species. Most microbes are impossible to culture in lab (or at least we haven't figured out how to yet), so there are likely a great number of undiscovered microbial species.

The graph is for animals, not microbes, so I can't imagine there being missing species.

Also, with the advent of metagenomics, not being able to culture microbes is not a problem to get a distribution of species in an environment.
 
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  • #4


I couldn't see the graphs... does it mention the wide range of the size of dogs?
 
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farful said:
Edit: Thanks DaveC, links have been fixed
Uh, that's DaveC426913. I hate nicknames... :-p
 

FAQ: Why Does Species Number Decrease with Smaller Body Mass?

What is the relationship between the number of species and body mass?

The number of species and body mass have an inverse relationship, meaning that as body mass increases, the number of species decreases.

Why do larger animals tend to have a lower number of species compared to smaller animals?

This is because larger animals require more resources and space to survive, leading to fewer individuals of that species being able to coexist in a given environment.

How does the concept of niche specialization relate to the number of species and body mass?

Niche specialization refers to the specific role a species plays in its environment. Larger animals have a wider range of possible niches due to their size and physical capabilities, allowing them to occupy a larger range of habitats and resources. This can lead to a decrease in the number of species as they are able to fill multiple roles within an ecosystem.

Are there exceptions to the relationship between number of species and body mass?

Yes, there are exceptions. Some smaller animals may have a lower number of species due to competition with larger, dominant species. Additionally, environmental factors such as climate and habitat can also affect the number of species present regardless of body mass.

How does human activity impact the relationship between number of species and body mass?

Human activity, such as habitat destruction and climate change, can greatly disrupt the balance between number of species and body mass. This can lead to a decrease in the number of species, particularly for larger animals that are more susceptible to changes in their environment.

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