C-Value And Chromosome Variation In The New Zealand Grass Flora

BG Murray1, PJ de Lange2, AR Ferguson3 and J Dixon3

1School of Biological Sciences, University of Auckland, New Zealand;
2Department of Conservation, Auckland, New Zealand
3Horticulture and Food Research Institute of New Zealand, Auckland, New Zealand

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    The New Zealand botanical region covers an area that extends from 30oS to 50oS and includes a number of islands of varying size and topography. It therefore contains a wide range of habitats, from sub-tropical to sub-antarctic and coastal to high alpine, all of which are colonized by grasses. The NZ grass flora consists of 157 endemic, 31 indigenous, 226 naturalised and 46 transient species. We have concentrated our investigations on the endemic and indigenous species and have determined C-values and chromosome numbers for 132 named species and 12 other taxa of uncertain status. The great majority of the species are polyploid; only 12 are diploid (7.7%), and the highest chromosome number recorded in the Poaceae is found in Poa litorosa, 2n = c.266, 38-ploid. The C-values for these species also show a wide range of values, from 0.97pg in Zoysia pauciflora to 32.32pg in Poa litorosa, an approximately 33-fold range. No clear difference was found in C-value between the NZ species and those from the rest of the world in the ten genera common to both areas. A comparison of the ‘tropical’ and ‘temperate’ elements in the grass flora shows that the tropical species have smaller C-values than the temperate ones, on average. In most NZ genera there is a reduction in genome size (C-value/ploidy level) with an increase in ploidy level. The exceptions to this trend are seen in Festuca and Lachnagrostis.