Comparative morphological and anatomical studies of the dispersal mechanisms
characterizing the wheat complex (Triticum L. and Aegilops L.) have documented
patterns of adaptive radiation which may have significance for evolutionary
relationships. These patterns, which form an array of diverse types of diaspores
among the diploid taxa, appear conceptually to have a starting point in the
dimorphic inflorescence of Ae. speltoides. Separate dispersal trends, centered
primarily in features of rachis disarticulation, lead in the direction of novel diaspore
types for Aegilops and in the direction of domestication for Triticum. With respect
to the taxonomy, this structural evidence supports the traditional Linnaean generic
circumscriptions and suggests a need for a monographic revision of Triticum. In
documenting the dispersal mechanisms, these studies have clarified conventional
interpretations and have offered new insights on the developmental relationships
linking the wild and domesticated taxa of the wheat complex. Although genetic
studies were not encompassed within this research, a consideration of the genetic
explanations for rachis disarticulation and glume closure suggests that the phenotypic
traits typically used in genetic studies are not well understood. Given that the
reticulate nature of genomic relationships in the wheats is coupled with intergrading
variation and polymorphic species, a proposal is made for a broader evolutionary
view than is found in the strict cladistic concept. This proposal emphasizes the need
of an improved understanding of fundamental structural traits and an inclusion of
these traits in evolutionary analyses. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35198 |
| Date | 21 October 1994 |
| Creators | Morrison, Laura A. |
| Contributors | Chambers, Kenton L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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