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I am a bioinformatician working with plant data. Therefore my formation on plant biology and botany is "ok" but not very strong.

When people talk about sections, I know that they talk about a phylogenetic rank that is lower than the genus but higher than the species. It groups subsets of species belonging to a genus together.

What is the thing that puts them together? Morphology, origin, geography, metabolism, genome identity, ...?

schmat_90
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    It depends. Sometimes people use it because there is monophyletic group within the genus which share a particular character, but which they don't want to (or can't) segregate into its own genus. Usually you will find sections in large genera which contain quite a lot of morphological diversity. – NatWH Oct 12 '18 at 11:58
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    For more discussion on what makes a "good" name, see comments on this answer: https://biology.stackexchange.com/a/77519/42697 – NatWH Oct 12 '18 at 12:04

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Taxonomic rankings above the species level are arbitrary—that is, they are created just to be a useful handle, much the way one might call the plants in one’s study “my study plants” and the plants in one’s kitchen “my kitchen plants” in order to convey information about them more easily. What makes a handle like “section” or “genus” useful is up to the botanist creating the handle, and, yes, he or she would likely consider many or all the things you mention (metabolism, origin, geography, etc.) while doing such creating. There are some rules, however—-such as respecting taxonomic hierarchy, giving such names only to clades, prioritizing earlier valid names for the same taxon, etc.

resplaine
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