As editors, we spend a lot of time putting some words into italics and removing italics from other words. You might wonder why all the bother with all these slanted letters, but carefully and consistently used, italics can make your paper clear, easy to read, and even more concise. Haphazard and inconsistent italics can confuse the reader and make your paper look sloppy, so it’s worth your while to check carefully.

How do you know what words should be in italics? General guides on writing offer some help, but a lot of examples that are not relevant for scientific writing. For example, it’s great to know that boat names should be in italics, although we have yet to edit any papers about the Titanic—and if someone writes a plant biology paper based on research from Boaty McBoatface, we want to be the first to edit that. Also, many guides suggest using italics for emphasis. Our suggestion for using italics for emphasis in scientific writing: Don’t do it. It’s just a bit too informal, like using contractions.

In addition to things not done, scientific writing has a lot of specific, specialized uses for italics and it’s important to get these right—as you will see below, correct usage of italics can make your meaning clear and might help impress the reviewers. For a comprehensive list of italics usage, check a style guide. In this post and the following posts in the series, we offer some tips on italics for biologists.

Tip #1
Use italics for genus and species, not for other classifications (kingdom, phylum, class, order, or family.) So, Zea mays belongs to the family Poaceae. If you mention the subspecies, that should be in italics. The variety should also be in italics thus:
A Draft Sequence of the Rice Genome (Oryza sativa L. ssp. indica)
Note that the “L” for “Linnaeus” and the “ssp.” for “subspecies” are not italicized.

Also, when you are writing about a genus, it should be in italics thus:
Sequencing of the genus Arabidopsis identifies a complex history of nonbifurcating speciation and abundant trans-specific polymorphism

Arabidopsis: Italics or No?
Now, you might ask, what about “Arabidopsis” not as the genus, but as the common name for Arabidopsis thaliana? Many people hold that when the genus is used as a common name, it should not be italicized (ditto for Drosophila), but some journals do italicize Arabidopsis. For example, some of our favorite journals use Arabidopsis in italics, thus:
NaKR1 regulates long-distance movement of FLOWERING LOCUS T in Arabidopsis

But others do not, thus:
Histone H3 Dynamics Reveal Domains with Distinct Proliferation Potential in the Arabidopsis Root

The best bet is to check your target journal and follow their style. Most importantly, whichever style you choose, be consistent. The worst of both worlds is to mix Arabidopsis and Arabidopsis in your manuscript!

The Twist!
But there’s a twist to this consistency rule! When the regular manuscript text is italicized, as is often the case for subheadings, be sure to use a different font type for genus, species, and variety. Therefore, on a background of italicized text, do not italicize these terms. For example:
Sequencing the Titanica magnificosa L. spp. tragicosa genome

More to Come
Thanks for checking out this post; please tune in soon for more tips on italics, including gene names and how the proper use of italics can make your manuscript more concise.