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Naoki Kachi – 1st expert on this subject based on the ideXlab platform
change in spatial distribution patterns of a Biennial Plant between growth stages and generations in a patchy habitatAnnals of Botany, 2005Co-Authors: Ryo Suzuki, Junichirou Suzuki, Naoki KachiAbstract:
• Background and Aims The aim of the study was to evaluate factors causing change in spatial distribution patterns of Plants between growth stages and generations for a monocarpic Biennial Plant, Lysimachia rubida. It was assumed that habitat heterogeneity was a primary factor determining spatial patterns of Plants, and a randomization procedure was developed for testing the null hypothesis that only spatial association with ground surface conditions determined spatial patterns of Plants.
• Methods A 5-year demographic census was conducted on an open dry habitat that was heterogeneous with regard to the ground surface conditions.
• Key Results There was significant habitat association in that Plants at vegetative and reproductive stages were denser in areas with smaller gravel than with larger gravel. Point process analyses rejected the null hypothesis of the spatial association with ground surface conditions.
• Conclusions The results suggest that other factors, such as patchy seed dispersal, secondary dispersal of the seeds and life-history variation at various spatial scales, also affected spatial patterns of individuals in a population of L. rubida. Spatial structures and dynamics of a local population in a patchy habitat represent various performances of Plants within patches and seed dispersal within a patch and beyond the patch.
spatial and temporal variations in mortality of the Biennial Plant lysimachia rubida effects of intraspecific competition and environmental heterogeneityJournal of Ecology, 2003Co-Authors: Ryo Suzuki, Hiroshi Kudoh, Naoki KachiAbstract:
We studied mortality, growth and spatial distribution of individuals of Lysimachia rubida to elucidate causes and consequences of temporal and spatial variations in mortality. This short-lived monocarpic Biennial grows in open dry habitats on rocky coastal cliffs of the subtropical Bonin (Ogasawara) Islands, Japan.
All individuals of two successive cohorts that appeared in a 8 × 8-m quadrat were mapped, and their fate and size were recorded at 2–3 month intervals from March 1998 to July 2000. We analysed spatial and temporal changes in the relative importance of Plant size, local densities of neighbouring Plants and ground surface conditions to determine Plant mortality. We also examined spatially non-random mortality and its spatial scales.
Patchy seed dispersal from scattered mother Plants resulted in a clumped distribution of seedlings. During the growth cycle of L. rubida, we recognized two growth stages that differed in the relative importance of the factors affecting Plant mortality.
At the earlier growth stage, after germination in March until July, mortality was caused mainly by local density. Smaller Plants within areas of high local densities were more likely to die. The spatial patterns of surviving and dead Plants tended to be regular and aggregated, respectively, in comparison with those expected from random mortality. The spatial scale of aggregation of the dead Plants was 5–25 cm, corresponding to the distance of direct interactions between neighbours.
At the later growth stages, in October until May of the following year, mortality was affected mainly by ground surface conditions. Both surviving and dead Plants were spatially aggregated at spatial scales of 20–100 cm. Plants tended to survive in microhabitats of smaller gravel, which had a greater water-holding capacity.
This study also showed the consequence of spatial variations in mortality on population structures of L. rubida. Patchy seed dispersal and subsequent temporal and spatial variations in mortality are likely to contribute to the scattered distribution of L. rubida individuals observed at the study site.
Germination traits and seed-bank dynamics of a Biennial Plant,Oenothera glazioviana MicheliEcological Research, 1990Co-Authors: Naoki KachiAbstract:
A study was conducted on the germination traits and seed-bank dynamics of Oenothera glazioviana (=O. erythrosepala ), which sets seed in August in sand-dune systems in Japan. More than 90% of freshly matured seeds germinated over a wide range of temperature in light, but less than 10% did so in continuous darkness. Stratification (chilling under moist conditions) was ineffective in diminishing the light-requirement for germination. When fresh seeds were imbibed for 24 h including a 12-h light period, followed by 7-day air-drying, 94% of them became germinable in the dark at 25°C, but remained dormant at less than 15°C. of seeds collected in March from capsules of dead Plants, 58% germinated in the dark at 25°C. After four cycles of alternatc 1-day wetting followed by 2-day drying or 1.5-day wetting followed by 1.5-day drying under a 12-h photoperiod, the fraction of viable seeds declined from 76% to 40% and 22%, respectively, due to germination during the wet periods. Seed-bag experiments were conducted in the field, using seeds given and not given a light-stimulus. Forty percent of the light-stimulated seeds germinated in the soil, whereas the seeds without a light-stimulus remained dormant throughout the experiment. When seeds were placed on the soil surface or at a depth of 0.5-1 cm, the proportion of germinable seeds declined during late spring and autumn, but not during winter and early spring. The seed-bank size of a natural population just prior to current seed dispersal was 2–3% of the seed production in the previous year, suggesting a high turnover rate of the seed-bank.
Lorne M Wolfe – 2nd expert on this subject based on the ideXlab platform
the genetics and ecology of seed size variation in a Biennial Plant hydrophyllum appendiculatum hydrophyllaceaeOecologia, 1995Co-Authors: Lorne M WolfeAbstract:
The goal of this study was to elucidate the sources of seed size variation in Hydrophyllum appendiculatum, an outcrossing, Biennial Plant. The genetic basis of seed size variation was examined with a diallel breeding design. The analysis did not reveal any evidence for additive genetic variance, suggesting that seed size could not evolve in response to natural selection. A series of greenhouse experiments was conducted to determine the sensitivity of seed weight to a number of ecological variables. Seed weight was affected by inbreeding depression: seeds produced by self-pollinations were significantly lighter that outcrossed seeds. Maternal Plants did not differentially provision seeds that were the result of crosses between subpopulations (separated by 300 m) or between populations (separated by 1.7 km). Mean seed size was independent of the number of outcrossed pollen donors (one vs. many) that sired seeds on an inflorescence; however, the variance was greater on inflorescences pollinated by multiple donors. Direct manipulations of the abiotic environment showed that seed size was greater on Plants growing under full sunlight compared to shaded Plants. Seed size was unaffected by soil type, fertilizer addition, or defoliation. Finally, I determined the effect of varying pollination intensity at the level of a single inflorescence, and at the whole Plant level. Seed weight was greatest on Plants that had only 1 and 5 inflorescences pollinated, and least on those that had 10 and 20 pollinated. At the inflorescence level, seed weights were greatest on those where all flowers were pollinated, compared to inflorescences where only half of the flowers were pollinated. Perhaps the greatest contributor to variance in seed size in this species was the temporal decline within Plants through the flowering season. These results indicate that maternal Plants are not capable of producing uniform seed crops. Rather, the final distribution of seed size produced by Plants within a population will necessarily vary and be the result of pollination effects, heterogeneity in the abiotic environment, and developmental constraints.
Francisco Perfectti – 3rd expert on this subject based on the ideXlab platform
inter annual maintenance of the fine scale genetic structure in a Biennial PlantScientific Reports, 2016Co-Authors: Javier Valverde, Jose M Gomez, Cristina Garcia, Timothy F Sharbel, M N Jimenez, Francisco PerfecttiAbstract:
: Within Plant populations, space-restricted gene movement, together with environmental heterogeneity, can result in a spatial variation in gene frequencies. In Biennial Plants, inter-annual flowering migrants can homogenize gene frequencies between consecutive cohorts. However, the actual impact of these migrants on spatial genetic variation remains unexplored. Here, we used 10 nuclear microsatellite and one plastid genetic marker to characterize the spatial genetic structure within two consecutive cohorts in a population of the Biennial Plant Erysimum mediohispanicum (Brassicaceae). We explored the maintenance of this structure between consecutive flowering cohorts at different levels of complexity, and investigated landscape effects on gene flow. We found that cohorts were not genetically differentiated and showed a spatial genetic structure defined by a negative genetic-spatial correlation at fine scale that varied in intensity with compass directions. This spatial genetic structure was maintained when comparing Plants from different cohorts. Additionally, genotypes were consistently associated with environmental factors such as light availability and soil composition, but to a lesser extent compared with the spatial autocorrelation. We conclude that inter-annual migrants, in combination with limited seed dispersal and environmental heterogeneity, play a major role in shaping and maintaining the spatial genetic structure among cohorts in this Biennial Plant.