 |
| Titel |
Experimental insights into angiosperm origins. |
| VerfasserIn |
Barry Lomax, Alex Lee, Ian Smilie, Charles Knight, Garland Upchurch |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148968
|
| Publikation (Nr.) |
 EGU/EGU2017-13277.pdf |
|
|
|
|
|
| Zusammenfassung |
| The angiosperms occupy almost every habitat type on Earth and comprise nearly 90% of
extant plant species. Yet this ascendency is a relatively recent (geological) phenomenon.
Palaeobotanical evidence indicates a likely first occurrence in the Early Cretaceous followed
by a relatively rapid increase in diversity with their rise to dominance marking the onset of
modern world. Understanding this diversification event has been a key research question
since Darwin commented on this “abominable mystery”, and it remains one of the most
significant unanswered questions in plant biology. Sequencing work shows that the
diversification and radiation was accompanied by successive whole genome duplication
(WGD) events. Furthermore proxy data and predictions from long-term carbon
cycle models indicate that the angiosperm diversification was accompanied by a
decline in atmospheric CO2. These observation raise the intriguing possibility that
declining atmospheric CO2 concentration and capacity to undergo polyploidy could
have given angiosperms a competitive advantage when compared to other plant
groups.
Using comparative ecophysiology we set out to test the effects of declining
atmospheric CO2 by growing a six species (Ranunculus acris and Polypodium
vulgare, chosen to represent Cretaceous understorey angiosperms and pteridophytes
respectively. Liquidambar styraciflua and Laurus nobilis represented canopy angiosperms
and Ginkgo biloba and Metasequoia glyptostroboides canopy gymnosperms) in
controlled conditions across a CO2 gradient (2000, 1200, 800 and 400 ppm) to
simulate Cretaceous CO2decline. To test for WGDs we use the relationship between
guard cell size and genome size to reconstruct angiosperm genome size as they
radiated.
Analysis of our fossil dataset shows that earliest angiosperms had a small genome size.
Our experimental work shows that angiosperms have a greater capacity for acclimation
suggesting that declining CO2 could have acted as a trigger for the angiosperm rise to
dominance. When viewed collectively our data indicate that within angiosperms there is a
close coupling of genome size to physiological and reproductive processes that is
absent in other plant groups. Consequently the ability of angiosperms to alter key
processes as genome size changes might explain a proportion of Darwin’s “abominable
mystery”. More broadly, these data highlight the benefits of developing approaches
that allow the integration of palaeobotanical observation with experimental data. |
|
|
|
|
|
|