Nadia Talent: Publication abstract
Talent, Nadia 2009. Evolution of gametophytic apomixis in flowering plants: an alternative model from Maloid Rosaceae. Theory in Biosciences. Published online 5 Mar 2009. doi:10.1007/s12064-009-0061-4
Gametophytic apomixis, asexual reproduction involving megagametophytes,
occurs in many flowering-plant families and as several variant
mechanisms. Developmental destabilization of sexual reproduction as a
result of hybridization and/or polyploidy appears to be a general
trigger for its evolution, but the evidence is complicated by
ploidy-level changes and hybridization occurring with facultative
apomixis. The repeated origins of polyploid apomictic complexes in the
palaeopolyploid Maloid Rosaceae suggest a new model of evolutionary
transitions that may have wider applicability. Two conjectures are
fundamental to this model: (1) that as previously suggested by
Rutishauser, like many sexual flowering plants the polyploid apomicts
require maternal--paternal balance in the second fertilization event that
gives rise to the endosperm, and (2) that the observed variation in
endosperm ploidy levels relates less to flexibility late in development
than to the known variation in developmental origin of the
megagametophyte between mechanisms loosely categorized as
diplospory and apospory. The model suggests explanations
for the relative frequencies of apospory and diplospory, and for the
wide but incomplete associations of apospory with a pollination
requirement (pseudogamy) and of diplospory with autonomous development
of the endosperm. It is suggested that pollination from other taxa may
provide some adaptive advantage to pseudogamous apospory.
Key Words:
Apospory, asexual reproduction, Crataegus, diplospory, endosperm,
gametophytic apomixis, polyploid evolution, Rosaceae
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Last modified 17 April 2014.