Whole Genome Duplication and the Evolution of the Land Plant Body Plan

Abstract

The evolution of the land plant body plan has shaped the evolution of
terrestrial ecosystems, human economics and the Earth’s biosphere. The body
plan has arisen through a series of innovations or ‘jumps’ that have in turn
facilitated a greater diversity of architecture, reproductive complexity and the
ability to occupy increasingly inhospitable environments. The evolution of
novelty through gene duplication is a hypothesis that was first developed in
the animal kingdom, though the more recent discovery of multiple whole
genome duplication (WGD) events throughout plant evolutionary history has
sparked a goldrush to identify and characterise WGD events, and to relate
them to macroevolutionary hypotheses. As it stands, plants represent the best
opportunity to establish a natural system in which to determine the outcomes
of WGD events across disparate lineages. However, a fundamental
requirement to studying WGD in a phylogenetic context is to first establish
on which branch it occurred. Secondly, an accurate estimate of the absolute
timing of the event can aid in providing a geological context. Finally, an effort
must be made to capture and quantify the macroevolutionary outcome and
determine the relative contribution of WGD. Studies of WGD to date have
taken a ‘tip down’ approach, focussing solely on extant taxa and ignoring the
wealth of information presented in the fossil record. In this thesis, I aim to
establish and progress methods for the identification, dating and
characterisation of WGD events in a palaeontological context. I establish a
timescale for several of the most ancient duplication events in the most
species rich lineages and the lineages on which we are most economically
dependent. I demonstrate a means of measuring phenotypic diversity
(disparity) at the kingdom level and use this to determine the relationship
between WGD and morphological evolution. Ultimately, I show that the best
approach to studying WGD in land plants is a holistic one, considering
phylogenetic, developmental and palaeontological evidence.

Date of Award	23 Jan 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Philip C J Donoghue (Supervisor) & Simon Hiscock (Supervisor)