Heterostyly is a genetically controlled sexual polymorphism promoting outcrossing by animal pollinators. The occurrence of heterostyly in angiosperms was investigated, and 199 genera in 28 families in 15 orders were recognized as taxa that contain heterostylous species. A correlation between the occurrence of heterostyly and ploidy level was found in some limited groups in Primulaceae and Rubiaceae. In such taxa, individuals with a lower ploidy level tended to have heterostyly and individuals with a higher ploidy level tended to have monomorphic flowers. It appears reasonable that the first step of the breakdown of heterostyly was the recombination of the supergene in a diploid heterostylous plant, and then poyploidization incidentally occurred. Polyploidization itself does not necessarily appear to have direct effects on the breakdown of heterostyly.

Platycrater arguta (Hydrangeaceae) is a small deciduous shrub of the Sino­Japanese floristic region, where it occurs in montane sites mostly covered with warm­temperate deciduous forest. This sole representative of its genus contains two varieties disjunctly distributed between East China (var. sinensis) and South Japan (var. arguta). To illuminate the biogeographic and demographic history of this rare species, we conducted a survey of chloroplast DNA (cpDNA) sequence variation (trnD­trnE, trnH­psbA) within and among twelve populations (four from China, eight from Japan, 129 individuals in total) representing the overall distributional range of the species. Based on a total of 19 haplotypes identified, P. arguta was found to harbor surprisingly high levels of haplotype and nucleotide diversity (hT = 0.882;T = 0.00475), possibly associated with its long evolutionary history. Spatial analysis of molecular variance found two regional phylogroups, corresponding to var. sinensis and var. arguta, and supported by genealogical (unrooted network) analysis of haplotypes. Using a coalescent­based model of 'divergence by isolation with migration', the likely vicariant origin of these varieties was dated to the mid­Pleistocene (ca. 0.89 mya). Very similar haplotype mismatch distributions indicate that var. sinensis and var. arguta underwent past demographic growth almost simultaneously (dated to ca. 0.43 and 0.45 mya, respectively), suggesting climate­induced expansion. However, var. sinensis likely experienced a mere demographic expansion in a narrowly circumscribed mountain range, while var. arguta underwent a spatial northward expansion that might have consisted of a series of bottlenecks, leading to genetically impoverished populations that most likely derived from initial population(s) in southern Kyushu. Our results endorse the recognition of two 'evolutionarily significant units' within P. arguta, corresponding to var. sinensis from East China and var. arguta from South Japan.

The floral morphology and reproductive ecology of a scandent shrub species, Mussaenda parviflora Miq. (Rubiaceae), were studied on Iriomote and Amami Ohshima Islands, Japan. The morphological study demonstrated that M. parviflora was gynodioecious. Crossing experiments, however, revealed that it was functionally dioecious. The flowers were visited mainly by butterflies in the daytime and mainly by crepuscular hawkmoths in the evening. Dioecy in this species is thought to have evolved from distyly. Dioecy of this species, which is pollinated by long‐tongued Lepidoptera, is unusual as the evolution of dioecy from distyly in plants with long corolla tubes is thought to have been triggered by a pollinator shift from long‐ to short‐tongued insects. In this species, however, two floral morphological features may have caused the evolution. The first feature is the presence of many upward‐facing hairs covering the inner surface of the upper part of the corolla tube; these hairs appear to have impeded pollen flow from long‐ to short‐styled flowers. The second feature is the overlap in anther height between the two types of flowers, which may have reduced seed set by clogging stigma with incompatible pollen grains. Accordingly, male sterility in long‐styled plants may have evolved.

We examined variation in Cinnamomum camphora (L.) J. Presl (Lauraceae) leaf domatium morphology with respect to domatium inhabitants in the tree's natural habitats. Canonical discriminant analysis revealed that domatium morphology could be classified into four different types: pouch type, domatia with a narrow (about 0.06 mm) pubescent opening; pubescent pit type, domatia with a wider (about 0.21 mm) pubescent opening; glabrous pit type, domatia similar to the pubescent pit type but with a glabrous opening; and dish type, domatia with a wide (about 0.26 mm) glabrous opening. These four domatium types were found in different positions on a leaf, and domatia with narrower openings tended to occur in or near the position between the midrib and basal secondary veins. The four domatium types were associated, respectively, with herbivorous Eriophyidae mites and herbivorous or fungivorous Tarsonemidae mites; with carnivorous Stigmaeidae mites; with Stigmaeidae mites and egg shells or excuviae of carnivorous Phytoseiidae mites; and with egg shells or excuviae of Phytoseiidae mites. These results suggest that different mites use different domatia, even on the same C. camphora leaf. This conclusion may explain the different results in previous reports about domatium fauna. It suggests that ecological interactions within the plant–herbivore–carnivore system are complicated.Key words: carnivorous mite, Cinnamomum camphora, domatia, herbivorous mite, inhabitant, morphology.

Species radiations, despite immense phenotypic variation, can be difficult to resolve phylogenetically when genetic change poorly matches the rapidity of diversification. Genomic potential furnished by palaeopolyploidy, and relative roles for adaptation, random drift and hybridisation in the apportionment of genetic variation, remain poorly understood factors. Here, we study these aspects in a model radiation, Syzygium, the most species-rich tree genus worldwide. Genomes of 182 distinct species and 58 unidentified taxa are compared against a chromosome-level reference genome of the sea apple, Syzygium grande. We show that while Syzygium shares an ancient genome doubling event with other Myrtales, little evidence exists for recent polyploidy events. Phylogenomics confirms that Syzygium originated in Australia-New Guinea and diversified in multiple migrations, eastward to the Pacific and westward to India and Africa, in bursts of speciation visible as poorly resolved branches on phylogenies. Furthermore, some sublineages demonstrate genomic clines that recapitulate cladogenetic events, suggesting that stepwise geographic speciation, a neutral process, has been important in Syzygium diversification.