Evolution of gametophytic apomixis in flowering plants: an alternative model from Maloid Rosaceae |
| |
Authors: | Nadia Talent |
| |
Institution: | (1) Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, M5S 2C6, Canada |
| |
Abstract: | 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.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
| |
Keywords: | Apospory Asexual reproduction Crataegus Diplospory Endosperm Gametophytic apomixis Polyploid evolution Rosaceae |
本文献已被 SpringerLink 等数据库收录! |
|