The Earliest Remains of Grasses in the Fossil Record

Crepet, William L.; Feldman, Gwen D.

doi:10.1002/j.1537-2197.1991.tb14506.x

Cited by 94 publications

(41 citation statements)

References 23 publications

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“…Earliest unambiguous grass macrofossils date back to the Palaeocene/Eocene boundary (55 Myr [44]). Otherwise, the Tertiary sediments are very poor in grass macrofossils [44]–[46].…”

Section: Discussionmentioning

confidence: 99%

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Rapid and Recent World-Wide Diversification of Bluegrasses (Poa, Poaceae) and Related Genera

et al. 2013

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Rapid species diversifications provide fascinating insight into the development of biodiversity in time and space. Most biological radiations studied to date, for example that of cichlid fishes or Andean lupines, are confined to isolated geographical areas like lakes, islands or island-like regions. Using DNA sequence data of the ribosomal internal transcribed spacer (ITS) for many species of the Poa alliance, a group comprising about 775 C3 grass species, revealed rapid and parallel diversifications in various parts of the world. Some of these radiations are restricted to isolated areas like the Andes, whereas others are typical of the lowlands of mainly the northern hemisphere. These radiations thus are not restricted to island-like areas and are seemingly actively ongoing. The ages of the diversifying clades are estimated to be 2.5–0.23 million years (Myr). Conservative diversification rates in the Poa alliance amount to 0.89–3.14 species per Myr, thus are in the order of, or even exceeding, other instances of well-known radiations. The grass radiations of the mainly cold-adapted Poa alliance coincide with the Late Tertiary global cooling, which resulted in the retreat of forests and the subsequent formation of cold-adapted grasslands especially in the northern, but also in parts of the southern hemisphere. The cold tolerance, suggested to be one of the ecological key innovations, may have been acquired during the early diversification of the subfamily Pooideae, but became significant millions of years later during the Pliocene/Pleistocene radiation of the Poa alliance.

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“…Earliest unambiguous grass macrofossils date back to the Palaeocene/Eocene boundary (55 Myr [44]). Otherwise, the Tertiary sediments are very poor in grass macrofossils [44]–[46].…”

Section: Discussionmentioning

confidence: 99%

“…Otherwise, the Tertiary sediments are very poor in grass macrofossils [44]–[46]. The discrepancy between the early fossil record and a subsequent paucity in fossils may be due to a long lag-phase in the family's diversification.…”

Section: Discussionmentioning

confidence: 99%

Rapid and Recent World-Wide Diversification of Bluegrasses (Poa, Poaceae) and Related Genera

et al. 2013

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“…Results from these runs were compared using Bayes factors in Tracer version 1.5 (Rambaut and Drummond 2007a). A single calibration point of 55 million years ago (mya) for the major diversification of the grass groups (Wolfe et al 1989; Crepet and Feldman 1991), modeled as a lognormal distribution with offset of 55 million years and log mean of 0 and log standard deviation of 1, was used to estimate divergence dates throughout the tree. Runs were performed for 30 million generations, with trees sampled every 3000 generations.…”

Section: Methodsmentioning

confidence: 99%

Haplotype Analysis and Linkage Disequilibrium at Five Loci inEragrostis tef

Smith

Yuan

Doust

et al. 2012

G3 Genes|Genomes|Genetics

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Eragrostis tef (Zucc.), a member of the Chloridoideae subfamily of grasses, is one of the most important food crops in Ethiopia. Lodging is the most important production problem in tef. The rht1 and sd1 dwarfing genes have been useful for improving lodging resistance in wheat and rice, respectively, in what has been known as the “Green Revolution.” All homologs of rht1 and sd1 were cloned and sequenced from 31 tef accessions collected from across Ethiopia. The allotetraploid tef genome was found to carry two rht1 homologs. From sequence variation between these two putative homologs, an approximate ancestral divergence date of 6.4 million years ago was calculated for the two genomes within tef. Three sd1 homologs were identified in tef, with unknown orthologous/paralogous relationships. The genetic diversity in the 31 studied accessions was organized into a relatively small number of haplotypes (2−4) for four of these genes, whereas one rht1 homeologue exhibited 10 haplotypes. A low level of nucleotide diversity was observed at all loci. Linkage disequilibrium analysis demonstrated strong linkage disequilibrium, extending the length of the five genes investigated (2−4 kb), with no significant decline. There was no significant correlation between haplotypes of any of these genes and their recorded site of origin.

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“…The great radiation of species occurs in the ‘crown group’ of grasses, whose members diverged from one another approx. 60 million years ago (mya) (Crepet and Feldman, 1991). One large clade (the BEP clade) comprises the basal subfamily Bambusoideae (bamboos) sister to the Ehrhartoideae (including rice and wild rice) and the Pooideae (including wheat, oats, barley, etc.).…”

Section: Phylogeny Of Grassesmentioning

confidence: 99%

“…The age of the separation of the BEP and PACCAD clades (‘crown group’) has been estimated at 55–60 mya, based on fossil pollen (Crepet and Feldman, 1991), but a recent report of grass phytoliths in dinosaur dung may push back the crown group age to 80 mya (Prasad et al , 2005) (Fig. 1).…”

Section: Phylogeny Of Grassesmentioning

confidence: 99%

Architectural Evolution and its Implications for Domestication in Grasses

2007

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BackgroundThe cereal crops domesticated from grasses provide a large percentage of the calories consumed by humans. Domestication and breeding in individual cereals has historically occurred in isolation, although this is rapidly changing with comparative genomics of the sequenced or soon-to-be sequenced genomes of rice, sorghum, maize and Brachypodium. Genetic information transferred through genomic comparisons is helping our understanding of genetically less tractable crops such as the hexaploid wheats and polyploid sugarcane, as well as the approx. 10 000 species of wild grasses. In turn, phylogenetic analysis helps put our knowledge of the morphology of cereal crops into an evolutionary context.Grass ArchitectureDomestication often involves a change in the pattern and timing of branching, which affects both vegetative and inflorescence architecture, and ultimately yield. Cereal grasses exhibit two main forms of vegetative architecture: the pooid and erhartoid cereals such as wheat and rice have multiple basal tillers, while panicoid cereals such as maize, sorghum and the millets have few tillers or even only a single main stem. These differences are reflected in the differences between the wild species of pooid and some erhartoid grasses, which emphasize basal branching over axillary branching, and the panicoid grasses, where axillary branching is more frequently found. A combination of phylogenetic and genomic analysis is beginning to reveal the similarities and differences between different cereal crops, and relate these to the diversity of wild grasses to which they are related. Recent work on genes controlling branching emphasizes that developmental genetics needs to be viewed in both an evolutionary and ecological framework, if it is to be useful in understanding how morphology evolves. Increasingly, exploring the phylogenetic context of the crop grasses will suggest new ways to identify and create combinations of morphological traits that will best suit our future needs.

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The Earliest Remains of Grasses in the Fossil Record

Cited by 94 publications

References 23 publications

Rapid and Recent World-Wide Diversification of Bluegrasses (Poa, Poaceae) and Related Genera

Rapid and Recent World-Wide Diversification of Bluegrasses (Poa, Poaceae) and Related Genera

Haplotype Analysis and Linkage Disequilibrium at Five Loci inEragrostis tef

Architectural Evolution and its Implications for Domestication in Grasses

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