International Commission on Zoological Nomenclature
 INTERNATIONAL CODE OF ZOOLOGICAL NOMENCLATURE online

Article 27. Diacritic and other marks. No diacritic or other mark (such as an apostrophe), or ligature of the letters a and e (æ) or o and e (œ) is to be used in a scientific name; the hyphen is to be used only as specified in Article 32.5.2.4.3.