The species has two
subspecies including
A. semialata subsp.
semialata, which uses the
C4 photosynthetic pathway, and
A. semialata subsp.
eckloniana, which uses the
C3 photosynthetic pathway. As the only plant species known to use both pathways, it is an important model for the study of the evolution of
photosynthesis. There are a wide range of intermediate phenotypes, including that of
C2 photosynthesis. The species has been found in a
polyploid series with
diploid,
tetraploid,
hexaploid,
octoploid and
dodecaploid individuals. All members of the C3 subspecies are diploid and there are no diploid individuals outside of that subspecies. == Distribution and habitat ==