The 'didymocarpoid Gesneriaceae' (traditional subfam. Cyrtandroideae excluding Epithemateae) are the largest group of Old World Gesneriaceae, comprising 85 genera and 1800 species. We attempt to resolve their hitherto poorly understood generic relationships using three molecular markers on 145 species, of which 128 belong to didymocarpoid Gesneriaceae. Our analyses demonstrate that consistent topological relationships can be retrieved from data sets with missing data using subsamples and different combinations of gene sequences. We show that all available classifications in Old World Gesneriaceae are artificial and do not reflect natural relationships. At the base of the didymocarpoids are grades of clades comprising isolated genera and small groups from Asia and Europe. These are followed by a clade comprising the African and Madagascan genera. The remaining clades represent the advanced Asiatic and Malesian genera. They include a major group with mostly twisted capsules. The much larger group of remaining genera comprises exclusively genera with straight capsules and the huge genus Cyrtandra with indehiscent fruits. Several genera such as Briggsia, Henckelia, and Chirita are not monophyletic; Chirita is even distributed throughout five clades. This degree of incongruence between molecular phylogenies, traditional classifications, and generic delimitations indicates the problems with classifications based on, sometimes a single, morphological characters.

Cyrtandra comprises at least 600 species distributed throughout Malesia, where it is known for many local endemics and in Polynesia and Micronesia, where it is present on most island groups, and is among the most successfully dispersing genera of the Pacific. To ascertain the origin of the oceanic Pacific island species of Cyrtandra, we sequenced the internal transcribed spacers of nuclear ribosomal DNA of samples from throughout its geographical range. Because all oceanic Pacific island species form a well-supported clade, these species apparently result from a single initial colonization into the Pacific, possibly by a species from the eastern rim of SE Asia via a NW-to-SE stepping stone migration. Hawaiian species form a monophyletic group, probably as a result of a single colonization. The Pacific island clade of Cyrtandra dispersed across huge distances, in contrast to the apparent localization of the SE Asian clades. Although highly vagile, the Pacific clade is restricted to oceanic islands. Individual species are often endemic to a single island, characteristic of the "supertramp" life form sensu Diamond (1974, Science 184: 803-806). The evolution of fleshy fruit within Cyrtandra provided an adaptation for colonization throughout the oceanic Pacific via bird dispersal from a single common ancestor.

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In this paper chromosome counts for 90 collections representing 67 native Hawaiian angiosperm species and eight hybrids in 22 families are presented and discussed. Included are the first records for 26 species, two subspecific taxa, eight natural hybrids, and the endemic genus Pteralyxia (Apocynaceae). In four families Hawaiian representatives have been investigated cytologically for the first time. For three species the investigations are the first on Hawaiian material. Seven counts differ from earlier reports in the literature. Implications of the results are discussed in the context of autochthonous chromosomal evolution and of colonization events for the Hawaiian Islands.

Oceanic islands are unique in their species composition, which is defined by arrival of colonizers via long distance dispersal followed by establishment of species followed in some cases by adaptive radiation. Evolutionary biologists identified traits facilitating successful colonization of islands as including polyploidy, self‐compatibility, herbaceousness and ability for long‐distance dispersal. Successful establishment and evolutionary diversification of lineages on islands often involves shifts to woodiness and shifts in methods of outcrossing as well as changes in dispersal ability. The genus Melicope colonized numerous archipelagos throughout the Pacific including the Hawaiian Islands, where the lineage comprises currently 54 endemic species and represents the largest radiation of woody plants on the islands. The wide distributional range of the genus illustrates its high dispersibility, most likely due to adaption to bird dispersal. Here we investigate ploidy in the genus using flow cytometry and chromosome counting. We find the genus to be paleopolyploid with 2n = 4x = 36, a ploidy level characterizing the entire subfamily Amyridoideae and dating back to at least the Palaeocene. Therefore Hawaiian Melicope have not undergone recent polyploidization prior to colonization of the islands. Thus Melicope retained colonization success while exhibiting a combination of traits that typically characterize well established island specialists while lacking some traits associated to successful colonizers.

Recent molecular systematic studies have significantly improved our understanding of the large, complex, and cosmopolitan plant family Rubiaceae, comprising about 13,000 species. Besides the obvious importance of DNA phylogenetic data, cytological studies have long added important basic information on the circumscription of clades and relationships within the family. In light of recent changes affecting a large number of tribes and genera, the current knowledge on the systematics of Neotropical Rubiaceae is reviewed with a focus on Costa Rica, which harbors an exceptionally rich Rubiaceae flora including most of the genera and biogeographic elements present in the Neotropics. Based on this systematic framework, previously published chromosome counts on Costa Rican taxa are reviewed and 49 new chromosome counts are reported. In total, 110 accessions of 75 species or infraspecific taxa representing 36 genera of Costa Rican Rubiaceae are discussed and supplemented by new counts for extraterritorial taxa when appropriate. Altogether the present study includes the first chromosome counts reported for the tribes Cordiereae and Hillieae, as well as for 10 genera and 27 species, providing new aspects of Rubiaceae systematics.