Evolution and Distribution of Grasses

Recent developments in grass eg give a new insight into their : gy ae and poin a phylogenetic sequence which maps differences in suus internal metabolism.Corroboratory fossil evidence is unfortunately eae meager, but it can be supplemente d be examining the implications of present-day distributions.The M pies: are distributed in worldwide uu belts, but two-thirds of the genera are confined to single continents.Obviously, the genera are poor travellers, so how did the grasses become so widespread?Much depends on the probability of transoceanic transport.The evidence is inconclusive, but it seems likely that the tropical subfamilies spread during the first half of the Tertiary when the maximum water gap was 1200 km.Species distributions are likewise influenced by climatic differentiation and continental isolation.But they sometimes reveal the intervention of other factors, particularly the disruptive effect of climatic change in the Pleistocene.Data from the Afro-montane flora do not support the proposition that species from adjacent, but contrasting, ecological environments are distributed independently.Nor does a mapping of endemics encourage the concept of discrete centers CLASSIFICATION Fundamental to most biological disciplines is the need to identify the organisms they work with, and the primary purpose of taxonomy is to satisfy this need by devising a standardized nomenclature, differential diagnoses and techniques for identification.One of the powerful concepts it has developed for achieving these aims is that of hierarchical classification.