Brian G. Murray

The cosmopolitan plant genus Plantago contains species with a wide range of chromosome numbers in its New Zealand endemic representatives. These species are diploid, tetraploid, octoploid, decaploid, dodecaploid and 16‐ploid. Using genomic in situ hybridization, we have shown that some of these polyploids contain at least three different genomes, confirming their allopolyploid status. Fluorescence in situ hybridization with 5S and 45S rDNA probes showed a wide variety of species‐specific patterns of distribution in the polyploid species, suggesting that polyploidy has been accompanied by genomic reorganization.

Chromosome numbers were determined for plants of five species and seven additional entities of uncertain taxonomic status of Brachyscome . We confirmed the chromosome numbers of several species but found new numbers in plants related to B. humilis , B. montana and B. radicata . Karyotype analysis showed a common karyotype in the diploids and suggested that the polyploids are autopolyploids. There is some evidence of aneuploidy in plants related to B. sinclairii and B. radicata. Karyotype analysis suggests that structural chromosome changes may have accompanied polyploidy in tetraploid B. humilis.

Chromosome numbers are reported for 112 endemic or indigenous vascular plants from New Zealand. Ninety one of these are new and the remainder provide confirmation of previous counts. Many of the counts fill gaps in the available record of chromosome numbers of New Zealand plants and a summary table provides a list of the genera where numbers remain to be determined. With the publication of these numbers, c. 85% of the indigenous vascular flora of New Zealand now has a documented chromosome number.

Chromosome numbers have been determined for plants of five species and one unnamed entity of Hydrocotyle , mostly from the Chatham Islands. The chromosome number of H. bowlesioides is reported for the first time, the numbers for H. heteromeria , H. microphylla and H. moschata agree with previously published counts from plants from the New Zealand mainland. Four chromosome races were found in H. robusta , this adds to the list of New Zealand endemic species that show intraspecific chromosome number variation.

Artificial pollinations were made between five New Zealand species of Schoenus (Cyperaceae) to determine whether they could form interspecific hybrids. No hybrids were produced and the site of the interspecific incompatibility was investigated using fluorescence microscopy. The site of pollen inhibition varied in the different cross combinations. No relationship was observed between pollen size and subsequent pollen germination and tube growth in the style. The results do not support the claim that S. concinnus and S. nitens form hybrids in nature.

Chromosome numbers have been determined for plants of Hibiscus trionum L. s.l. from nine locations: two inNew Zealand, five in Australia, and two in Africa. Two different numbers were obtained, one diploid with 2n = 28 and the other tetraploid with 2n = 56. The diploids were found in New Zealand and coastal New South Wales, all the other populations were tetraploid. Based on these observations, and plant morphology, especially flower shape and pigmentation patterns, the recent (1988) conclusion that all New Zealand m orphs of H trionum are naturalised is challenged and the morphs present different conservation options.

And C. ruamahanga have been taxonomically controversial. Here their distinctiveness is assessed so that their taxonomic and conservation status can be clarified. Populations of these two species were analysed using morphological, chromosomal and DNA sequence data. It proved impossible to differentiate between these two species using 12 key morphological characters. Populations were found to be chromosomally variable with 11 different chromosome numbers ranging from 2n = 42 to 2n = 100. Meiotic behaviour and levels of pollen stainability were both variable. Phylogenetic analyses showed that differences exist in both nuclear and plastid DNA sequences between individual plants, sometimes from the same population. The results suggest that these plants are a species complex that has evolved through interspecific hybridization and polyploidy. Their high levels of chromosomal and DNA sequence variation present a problem for their conservation.