ALBERT

Notizen: Two aroid congeners, Alocasia odora and Alocasia cucullata, grow on Okinawa Island, Japan. Two floricolous species of Colocasiomyia alocasiae and Colocasiomyia xenalocasiae (Diptera: Drosophilidae), previously known to be specific pollinators for A. odora, were found pollinating A. cucullata. We collected the floral volatiles of A. odora and A. cucullata and compared them using gas chromatography and mass spectrometry because floral volatiles act as attractive signals for these pollinators. The volatile compositions detected were similar and dominated by methyl salicylate, 4,8-dimethyl-1,3,7-nonatriene, β-caryophyllene, bicyclogermacrene, methyl benzoate and α-humulene, which means it is likely that the flies cannot discriminate between the two plant species when they search for hosts. Interspecific hybridization did not occur when A. odora was hand pollinated with A. cucullata pollen, suggesting that the movement of flies from one host species to another will result in wastage of pollen. Adults of both Colocasiomyia flies emerged from A. cucullata inflorescences collected in the field, suggesting that their larvae can also develop on A. cucullata. We did not find any difference in larval performance of C. alocasiae on A. cucullata or A. odora. C. alocasiae does not appear to suffer any ill effects when using A. cucullata as a host plant. The partnership between A. cucullata and the two Colocasiomyia flies may be an example of exaptation, although other possibilities cannot be excluded.

Notizen: The effects of pollination competition between related species on pollen limitation, selfing ability and heterospecific incompatibility were studied in the alpine snowbed shrubs, Phyllodoce caerulea and Phyllodoce aleutica (Ericaceae) along local snowmelt gradients. The flowering season of these species highly overlapped and they shared the same method of pollination (via bumblebees). The floral density and nectar production were higher in P. caerulea in the early snowmelt habitat, but they were higher in P. aleutica in the late snowmelt habitat, reflecting the species-specific sensitivity to a short growing season. Bumblebee preference shifted from P. caerulea to P. aleutica along the snowmelt gradient, reflecting the changes in the relative reward level between the species. The extent of pollen limitation of P. caerulea was severe in the late snowmelt habitat, whereas that of P. aleutica was obvious in the early snowmelt habitat. A pollination experiment revealed that P. caerulea showed a consistently low selfing ability, whereas P. aleutica showed a high selfing ability in the early snowmelt habitat and shifted to an obligate outcrosser in the late snowmelt habitat. The frequency of interspecific bumblebee movement for P. caerulea from P. aleutica increased in the late snowmelt habitat. To the contrary, the frequency of interspecific movement for P. aleutica from P. caerulea decreased along the snowmelt gradient. P. caerulea did not indicate heterospecific incompatibility to P. aleutica pollen. In contrast, P. aleutica indicated heterospecific incompatibility to P. caerulea pollen, reflecting the high risk of receiving heterospecific pollen as a result of interspecific bumblebee movement. However, heterospecific compatibility of P. aleutica disappeared in the late snowmelt habitat, where the risk of heterospecific pollen receipt was low. Therefore, changes in interspecific bumblebee movement might have been responsible for the variation in heterospecific incompatibility among P. aleutica populations. The local snowmelt gradient creates diverse biological interactions and mating system evolution in the alpine ecosystem.

Notizen: Common wild rice (Oryza rufipogon Griff.), known as the ancestor of Asian cultivated rice (Oryza sativa L.), is the most important germplasm for rice improvement. The first male sterility gene was found in the wild rice, and introduced to the cultivated rice, which launched the fast development of the high-yielding hybrid rice. Other agronomically beneficial traits in the wild rice, such as rice tungro virus resistance, bacterial leaf blight (Xa21 gene) resistance and acid sulfate soil tolerance, have played important roles in rice breeding. China has the northernmost distribution area of wild rice possessing great genetic diversity. However, most of the populations of this species have disappeared in China over the last three decades, mainly caused by habitat loss, fragmentation and other human disturbances. Unfortunately, the decline of existing populations still continues. In the present study, we reviewed studies on genetic diversity and conservation of this wild rice in China, concentrating on population structure, pollen competition, pollen/gene flow from cultivated rice to wild rice, and ecological restoration in relation to in situ conservation. The relatively high genetic diversity of populations of O. rufipogon in China suggests that there is great value for conservation. Considerable gene flow from cultivated rice to wild rice may alter the genetic structure of natural populations of O. rufipogon and eventually lead to its genetic erosion. Pollen competition between wild and cultivated rice has caused a low rate of crop-to-wild gene flow, but it does not completely prevent gene flow from the crop. Effective isolation measures should be undertaken in the regions where in situ conservation of O. rufipogon is carried out. Reintroduction is an important alternative for the in situ conservation of wild rice species. As wild rice is an important genetic resource, both in situ and ex situ conservation strategies are needed.

Notizen: In current quantitative genetic models, the trade-off is viewed as a dynamic relationship between competing fitness components, which will evolve as a consequence of selection. Selection can change both the intercept and slope of the trade-off function, although it changes the former more strongly than the latter. We tested these predictions by examining two relationships among three clonal life-history traits (ramet number per plant and ramet production rate as a function of leaf number per ramet) in Iris pumila plants originating from an open and a shaded habitat. Our results support the hypothesis that the trade-off function will vary over environments, but not the expectation that the changes in the intercept are more likely than in the slope.

Notizen: Plantago asiatica L. (Plantaginaceae) is a perennial herb that is distributed over a wide range of habitats from exposed to shaded sites in lowlands to the subalpine zone in Japan. We investigated the patterns of biomass allocation and population structures based on the frequency distribution of individual plants in order to clarify the extent of plasticity in significant life-history traits and also population dynamics of this plantain species, which occurs under two contrasting light regimes—in exposed and shaded habitats—at Numappara, 1230 m a.s.l., Tochigi Prefecture, central Honshu. The plants at the shaded site allocated more biomass to leaves, but less to rhizomes than those at the exposed site. Increasing the biomass of the reproductive organs resulted in a reduction of the leaf and rhizome fractions. This trend is clearer in the shaded plants than in the exposed plants. In both exposed and shaded populations, the number of seedlings was greater in the first year, but the population structure was skewed more negatively in the second year during two consecutive study years. The possible effects of allocation traits of individuals on the population structures and regeneration mechanisms of P. asiatica at elevated habitats are discussed in terms of cyclic changes in population structure with the fluctuations of seeding activity over some years.

Notizen: Abstract  Although positive interactions among plants are believed to be common in primary succession, they have rarely been demonstrated on glacial moraines. In Patagonia, the prostrate shrub Empetrum rubrum is dominant in early succession in recently deglaciated valleys, eventually being replaced by the small tree Nothofagus antarctica. This study experimentally evaluates the effects of E. rubrum shrubs on density, biomass, growth and survival of N. antarctica seedlings. The initial density of the seedlings was significantly higher under the canopy of Empetrum than in open areas. A removal experiment was performed to evaluate the influence of Empetrum on survival and growth of seedlings that germinated naturally beneath the canopy of this species. The shrub cover was removed from half of a sample of randomly selected seedlings, and left intact above the remainder. One year later, seedlings with an intact cover of E. rubrum showed significantly higher survival, growth and leaf number than seedlings which had been exposed. The results suggest that the presence of E. rubrum facilitates the establishment of N. antarctica in post-glacial succession, mainly as a result of more favourable microclimatic conditions under the shrub canopy.