Evolution and Distribution of Grasses

A comprehensive world classification of the Poaceae is presented in which 720 currently accepted genera are distributed among five subfamilies (Pooideae, Bambusoideae, Arundinoideae, Chloridoideae, Panicoideae) and six supertribes (Triticanae and Poanae, in Pooideae; Bambusanae and Oryzanae, in Bambusoideae; Panicanae and Andropogonanae, in Panicoideae). Synonyms in recent use are listed under appropriate groups. The classification reflects a variety of numerical analyses of generic descriptions, accounting for original observations and compiled data on nearly 300 characters concerning mainly morphology, anatomy, physiology and cytology. The detailed group descriptions are fully comparative, and include statistical information on character state distributions. * Vulpiella (Trabut) Burollet, Wangenheimia Moench, Zingeria Smirnow Classification of the Poaceae Synonyms Anachortus V . Jirr.

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“…Clayton 1981;Campbell 1985). In terms of group contents, it is consistent with the results of our various analyses of the data (e.g.…”

Section: Taxonomic Interpretation Of Resultssupporting

confidence: 90%

The Classification of Poaceae: Subfamilies and Supertribes

Watson¹,

Clifford²,

Dallwitz³

1985

Aust. J. Bot.

132

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“…Evolution of the Poacae led to a reduced morphology and uncomplicated geometry, growth of vegetative tissues from intercalary menstems, evolution of the leaf sheath as an envelope of floral structures and stem-reinforcing structural ele-ment of vegetative tissues, and depauperate secondary chemistry (McNaughton 1979a, 1983a, Clayton 1981, Stebbins 1981, McNaughton and Tarrants 1983. Almost all pharmacologically active plants are products of that radiation.…”

Section: Introductionmentioning

confidence: 99%

Silica as a Defense against Herbivory and a Growth Promotor in African Grasses

McNaughton¹,

Tarrants²,

McNaughton³

et al. 1985

Ecology

268

207

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Grasses and dung were collected in the Serengeti National Park and analyzed for silica content by wet ashing. Grasses from grasslands differing in the grazing intensities experienced were grown in the laboratory in a factorial experiment to determine factors controlling tissue silicification. Concentrations of silica in tissues of plants collected in the field were higher than have been reported for any other plants abundant in grazing ecosystems. Silica contents in the field were higher in more heavily grazed grasslands and in tissue produced earlier in the growing season. Animal dung contained substantial quantities of silica. Laboratory experiments indicated that tissue silicification was increased by defoliation, was higher in plants from more heavily grazed grasslands, varied in different organs and species in patterns confirming current hypotheses about plant defense, and was affected by the availability of soluble silica in the nutrient medium. Silica in the nutrient medium promoted the yield of unclipped plants substantially. Total yield was 18% higher than that of control plants, although hydroponic experiments with solutions prepared and handled in plastic indicated that silica was not a growth requirement, except, perhaps, at the ecologically unrealistic concentrations that might result from reagent contamination. Yield stimulation by silica was differentially distributed among organs, tending to promote photosynthetically active tissues and crowns. Flowering of one species was promoted by silica. Leaves of silica-fed plants were larger. Leaf blade chlorophyll concentrations were 15% higher in silica-fed plants from the more heavily grazed grasslands. The results suggest that complex patterns of grass silicification had a role in the radiation of grazing animals and grasses and may contribute to maintaining the biotic diversity of contemporary grassland-savanna ecosystems by influencing the partitioning of forage species and organs among grazers. Growth promotion by silica may be due to the substitution of mineral support for carbon-based support associated with the deposition of silica in the intercellular spaces of aerial tissues. Since soils of the Serengeti region commonly have pH levels above neutrality, where the availability of silica is low, silica supply could influence primary productivity and resultant energy and nutrient flow through the trophic web in the native environments of the plants.

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“…The danthonioid grasses essentially occupy warm‐temperate habitats and, in that sense, are analogous to the pooid grasses of the Northern Hemisphere (Clayton, ; Inda et al ., ). The absence of the Danthonioideae from tropical and equatorial climates, and the only occasional penetration into arid and cold‐temperate climates, is not due to lack of opportunity, as the geographical range of Danthonioideae has been adjacent to these biomes over much of the evolutionary history of the clade.…”

Section: Discussionmentioning

confidence: 99%

What determines biogeographical ranges? Historical wanderings and ecological constraints in the danthonioid grasses

Linder

Antonelli

Humphreys

et al. 2013

Journal of Biogeography

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Aim We sought to understand the variables that limit the distribution range of a clade (here the danthonioid grasses). We tested time, area of origin, habitat suitability, disjunction width and nature, and wind direction as possible range determinants. Location Global, but predominantly the Southern Hemisphere. Methods We mapped the range of the subfamily Danthonioideae, and used 39,000 locality records and an ensemble modelling approach to define areas with suitable danthonioid habitat. We used a well‐sampled, dated phylogeny to estimate the number and direction of historical dispersal events, based on parsimony optimization. We tested for the impact of wind direction on dispersal rate using a likelihood approach, and for the effects of barrier width with a regression approach. Results We found 17 geographically isolated areas with suitable habitats for danthonioids. All currently suitable Southern Hemisphere areas have been occupied, but three apparently suitable areas in the Northern Hemisphere have not. We infer that southern Africa was first occupied in the Oligocene and that dispersal to the other areas was initiated in the middle Miocene. Inferred dispersal rate was correlated with the width of the disjunctions, up to a distance of 5000 km. There was no support for wind direction having influenced differences in dispersal rate. Main conclusions The current range of the Danthonioideae can be predicted ecologically (areas with suitable habitat) and historically (the width of the disjunctions separating the areas with suitable habitat and the area of origin). The direction of dispersal is dictated by the area of origin and by serendipity: there is no evidence for general patterns of dispersal, for example for dispersal occurring more frequently over land than over sea or in an easterly versus a westerly direction around the Southern Hemisphere. Thus the range and range‐filling of Danthonioideae can be accounted for by surprisingly few variables: habitat suitability, distance between suitable areas, and area of origin.

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Evolution and Distribution of Grasses

Cited by 77 publications

References 15 publications

The Classification of Poaceae: Subfamilies and Supertribes

The Classification of Poaceae: Subfamilies and Supertribes

Silica as a Defense against Herbivory and a Growth Promotor in African Grasses

What determines biogeographical ranges? Historical wanderings and ecological constraints in the danthonioid grasses

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