Macrofossils, cuticles, and phytoliths: an update on the paleoecology and biogeography of the grasses

GALLAHER, T.J.; PIPO, L.; CLARK, L.G.; ARI IGLESIAS; STRÖMBERG, C.

Natal

Congreso; VI Monocot International Conference on Comparative Biology of Monocotyledons, and 7th International Symposium on Grass Systematics and Evolution; 2018

Monocots

The timing of the origin anddiversification of the grass family has become the subject of intense debateparticularly with regards to the taxonomic placement of recently describedgrass phytoliths and cuticle from the Maastrichtian of India. Here, we reporton new quantitative analyses of phytoliths from multiple sources and a newlydiscovered early-mid Campanian fossil grass cuticle from James Ross Island,Antarctica. Time calibrated phylogenetic analyses and ancestral area estimationsusing macrofossils, fossil cuticles and phytoliths support an Early CretaceousGondwanan origin of the Poaceae. Ancestral habitat estimations using extanttaxa indicate that grasses first evolved in forest-associated habitats and mayhave occupied key positions in forest margins, allowing lineages to morereadily evolve into either deep shade or open habitats. In the Late Cretaceousor Paleocene, the PACMAD and Pooideae moved from forest associated ecosystemsto open habitats, more than 30 Ma before the spread of grass-dominatedvegetation in the Oligocene-Miocene. Our temporal estimations also suggest thatC4 photosynthesis evolved first in the Chloridoideae in the Eocene orOligocene, approximately 15-20 Ma earlier than other C4 PACMAD lineages and longbefore the rise to dominance of C4 grasslands within the last 10 Ma.