The accepted scientific name of thickspike wildrye is Elymus macrourus
(Turcz.) Tsvel. [
1]. There is some disagreement over this placement,
however, as is apparent from the number of synonyms. There are no
subspecies, varieties, or forms.
Thickspike wildrye forms hybrids with Siberian wildrye (E. sibiricus)
where they occur together. The sterile hybrid, xAgroelymus palmerensis
Lepage, has become increasingly abundant and is common along road
systems of south-central Alaska [
8]. Thickspike wildrye also forms
hybrids with foxtail barley (Critesion jubatum); the resulting sterile
hybrid is named Elytesion pilosilemma (Mitchell & Hodgson) Barkw. & D.
R. Dewey [
1,
9]. Hybrids with meadow barley (Critesion brachyantherum),
named xAgrohordeum jordalii Melderis, also occur [
6].