Expanding the View of Emergence in Individuals, Populations, and Species of Stipoid Grasses: A Comparison Including Achnatherum occidentale
Dedicated to the memory of Mareen S. Kruckeberg, friend to people and plants.
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In our ongoing studies of emergent
properties at different hierarchical levels in the grass tribe Stipeae, an
additional species, Achnatherum occidentale, is included to broaden the
comparison. The degree of emergence seen parallels that of previous studies, an
increasing trend from populations to individuals and species to related groups
of species. The degree of emergence in species pairs that hybridize, A. hendersonii and A.
lemmonii, or A. occidentale and A. lemmonii, is lower than in non-hybridizing
species pairs of Achnatherum, including the closely related pair of A.
wallowaensis and A. hendersonii. The degree of emergence assesses the
relationship among variables. This relationship, in turn, is the end product of
integrated developmental pathways; a lower degree of emergence reveals similar
responses among developmental pathways. Similar developmental responses may
facilitate hybridization since hybrid survival requires
coordinated development. The different developmental pathways inferred for A. hendersonii and A.
wallowaensis argue for the existence of different
developmental ways to very similar ends, the spikelets in the two species. The
outcome of speciation, as viewed from a developmental perspective, seems best
accounted for through theories that relate the dissipation of energy to the
transformation of matter along with conceptualizing a species as a virtual code
that achieves material expression only when an individual appears. This view of
a species is explored through structural relationships within and among grass
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