Karyotype analyses were carried out on 73taxa of Brachyscm and Btaxa of its allied genera, Australian Astereae. Statistical tests regarding correlations between changes in chromosome number, total chromosome length, mean chromosome length, karyotypic asymmetry and chromosome length heterogeneity and changes in habd were performed based on the matK molecular phylogenetic tree. The reductions in chromosome number and total chromosome length, and the increases in mean chromosome length, chromosome length heterogeneity and karyotypic asymmetry were found to be correlated with the change in habit from perennial to annual. A reduction in total chromosome length is favored to shorten the mitotic cell cycle and to produce smaller cells conducive to more rapid development of smaller annuals under the time-limited environment. Stepwise dysploidal reductions in chromosome number were achieved through the translocation of large chromosome segments onto other chromosomes, followed by the loss of a centromere, resulting in one fewer linkage group and one fewer haploid chromosome. The correlations between the dysploidal reduction in chromosome number and the increases in mean chromosome length, length heterogeneity and asymmetry in karyotype can be attributed to this mode of chromosomal change. These changes occurred independently in several different lineages in Brachyscom.

Aim Floristic differentiation in the Ryukyu Archipelago has been explained primarily by geohistory, specifically landbridge formation and vicariance at the Tokara and Kerama Gaps, two deep-sea channels through the island arc. This ignores current environmental effects, which may also be important. We therefore tested whether the floristic differentiation pattern is explained primarily by the historical effect of the gaps as barriers, or whether a better understanding of floristic differentiation is achieved when both historical and current environmental factors are incorporated.Location Ryukyu Archipelago, Japan: an assemblage of continental islands.Methods We compiled a presence-absence matrix of 1815 plant species on 26 islands. Floristic dissimilarity distances between islands were calculated using Simpson's similarity index and analysed using cluster analysis. We also conducted multiple regression on distance matrices (MRM) to examine the significance of the historical factors of the gaps and current environmental factors: geographical distance among islands and differences in island area and maximum elevation. ResultsWe detected clear patterns of floristic differentiation across the gaps. Using the two gaps as explanatory variables, the MRM showed that both had significant effects on floristic dissimilarity distance. However, when geographical distance was added to the explanatory model, the Kerama Gap effect disappeared. When all five explanatory variables were used, the Tokara Gap and geographical distance had positive effects, but area difference had a negative effect. The Kerama Gap and difference in maximum elevation had no effect. Main conclusionsThe geographical pattern of floristic differentiation appears to indicate the influence of both gaps. However, the MRM indicates that the floristic differentiation across the Kerama Gap is no more than could be explained solely by geographical distance. Across the Tokara Gap, however, floristic differentiation is larger than geographical distance alone can explain. This additional differentiation is attributable to the effect of the historical barrier. To verify the significance of historical effects of vicariance on island biota, the confounding effects of geographical distance must be considered. The distance decay of floristic similarity and negative effect of area difference on floristic differentiation demonstrate that floristic differentiation is better understood by incorporating both historical and current environmental factors.

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Sonerileae/Dissochaeteae (Melastomataceae) comprises ca. 50 genera, two thirds of which occur in Southeast Asia. Phylogenetic relationships within this clade remain largely unclear, which hampers our understanding of its origin, evolution, and biogeography. Here, we explored the use of chloroplast genomes in phylogenetic reconstruction of Sonerileae/Dissochaeteae, by sampling 138 species and 23 genera in this clade. A total of 151 complete plastid genomes were assembled for this study. Plastid genomic data provided better support for the backbone of the Sonerileae/Dissochaeteae phylogeny, and also for relationships among most closely related species, but failed to resolve the short internodes likely resulted from rapid radiation. Trees inferred from plastid genome and nrITS sequences were largely congruent regarding the major lineages of Sonerileae/Dissochaeteae. The present analyses recovered 15 major lineages well recognized in both nrITS and plastid phylogeny. Molecular dating and biogeographical analyses indicated a South American origin for Sonerileae/Dissochaeteae during late Eocene (stem age: 34.78 Mya). Two dispersal events from South America to the Old World were detected in late Eocene (33.96 Mya) and Mid Oligocene (28.33 Mya) respectively. The core Asian clade began to diversify around early Miocene in Indo-Burma and dispersed subsequently to Malesia and Sino-Japanese regions, possibly promoted by global temperature changes and East Asian monsoon activity. Our analyses supported previous hypothesis that Medinilla reached Madagascar by transoceanic dispersal in Miocene. In addition, generic limits of some genera concerned were discussed.

Chromosome number determinations from 152 collections representing 42 genera and 106 species of the Australian Gnaphalieae and Plucheeae are reported. The chromosome numbers of 75 of these species have not been previously counted or differ from those previously reported for species. Chromosome numbers have been documented for the first time for 14 genera: Argyroglottis (n = 12), Cephalosorus (2n = 24), Decazesia (n = 14), Dielitzia (2n = 26), Eriochlamys (n = 14), Erymophyllum (n = 11 and 14), Gilruthia (n = 13), Leucochrysum (n = 9), Myriocephalus s. str. (n = 14, 2n = 24), Polycalymma s. str. (n = 14), Pterocaulon (n = 10), Pterochaeta (n = 12), Quinetia (2n – 24) and Sondottia (2n = 6). Remaining counts augment and agree with previously reported determinations. Some problems with generic delimitation and interpretation of chromosome data are outlined. There is an array of karyotypes within the Australian Gnaphalieae and dysploidy is widespread. Polyploidy has also played an important role in the evolution of some taxa. Evidence suggests that the base number for Australian Gnaphalieae is x = 14. This may be the base number for the entire tribe.

Mucuna macrocarpa is a plant found in tropical and subtropical regions that requires an "explosive opening." Explosive opening is the process that exposes the stamen and pistil from the opening of the carina. This process is needed for cross pollination; however, the plant cannot open itself and opening by an animal is needed. The most common opener of Mucuna flowers is several nectar-eating bats (e.g., Syconycteris), but the flying fox, Pteropus dasymallus, is the only opener of M. macrocarpa on the subtropical island of Okinawajima. Here, we present the explosive openers and possible pollinators in the northernmost and temperate Kamae region, Kyushu, Japan, where nectar-eating bats are absent. The Japanese macaque, Macaca fuscata, and the Japanese marten, Martes melampus, were the explosive openers observed during our survey in Kamae. Martens opened flowers using their snout in a manner similar to that of the flying fox, whereas macaques opened flowers using their hands. This is the first time that an animal has been observed opening these flowers with its hands rather than snout. In total, 97% (n = 283) of explosively opened flowers were opened by macaques, and the macaque largely contributed to the overall flower opening. Because many pollen grains become attached to the explosive openers, they are considered to be primary pollinators. Furthermore, two bee species, Apis cerana japonica and Bombus ardens ardens, also visited opened flowers and collected pollen, and they were possibly secondary pollinators. Fig. 1 Distribution of Mucuna macrocarpa (shaded area) and the study area.

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Aim Phylogeographical patterns in the Ryukyu Archipelago have been explained primarily by landbridge formation and the opening of two straits in the Pliocene, namely the Tokara and Kerama gaps. These old straits have been considered to be the barriers most likely to determine genetic boundaries. To test this, we conducted a molecular analysis of the herb Ophiorrhiza japonica. We discuss the causes of and processes involved in its phylogeographical structure and explore aspects of island separation other than the duration of the straits to explain genetic boundaries at the gaps.Location Ryukyu Archipelago, Japan.Methods Plants were collected from 40 localities in the archipelago and vicinity. Non-coding regions of chloroplast DNA were sequenced. The genealogical relationships among haplotypes were estimated using a statistical parsimony network. To examine the phylogeographical structure, we compared two parameters of population differentiation, namely G ST and N ST , and conducted correlation analysis of genetic and geographical distances. Genetic boundaries were identified using Monmonier's maximum difference algorithm. To test vicariance-dispersal hypotheses, that is, vicariance after migration via the Pliocene landbridge or over-sea dispersal in the Pleistocene, molecular dating analysis was conducted.Results A statistical parsimony network revealed that the haplotypes from the Ryukyu Archipelago and northwards coalesce to one ancestral haplotype in Taiwan. A clear phylogeographical structure was observed: plants within the same population and populations in geographical proximity were phylogenetically close. A genetic boundary was recognized across the Kerama Gap, but not across the Tokara Gap. Dating analysis suggested that population divergence across the Kerama Gap occurred in the early to late Pleistocene. Main conclusionsThe statistical parsimony network suggests migration from Taiwan and northward range expansion in the archipelago. Based on the divergence time, over-sea dispersal in the Pleistocene is likely, although migration via a Pliocene landbridge is not totally rejected. Negligible genetic differentiation across the Tokara Gap suggests recent over-sea dispersal, possibly facilitated by the small geographical width of the gap. Conversely, the large genetic differentiation across the Kerama Gap is probably explained by the large geographical distance across it. The past splitting of a landbridge would have had a significant influence on population differentiation after a certain geographical distance was reached.