Variation in flower biomass among nearby populations of Impatiens textori (Balsaminaceae): effects of population plant densities

Abstract

Although most of the previously detected variation in flower biomass was among populations that were far apart from each other, differences in population characteristics (population size, area, and plant density) may bring the variation in flower biomass to a more local scale. To examine the variation in flower biomass among nearby populations of Impatiens textori Miq. (Balsaminaceae), field studies were conducted on six natural populations located along a stream in Japan. We also examined the dependence of flower biomass and outcrossing rate on population characteristics, as well as the differences in plant size and pollinator behavior among populations. We conducted pollination experiments with potted plants, in which plant density and flower size were independently manipulated. Mean flower mass varied among populations, being negatively dependent on plant density. One-factor ANCOVA showed that both plant size and the other population-level factor affected flower biomass variation. Experiments with potted plant arrays showed that geitonogamous pollination more likely occurred in sparse populations, but in field studies, the population outcrossing rate was not significantly dependent on plant density of the population. Thus, the variation in flower biomass cannot be fully explained by these commonly considered factors. Our results show that the flower biomass of populations may evolve locally in response to plant density or other population characteristics.Key words: variation, flower biomass, population, Impatiens textori, plant density, local scale.

Pattern of flower size variation along an altitudinal gradient differs between Impatiens textori and Impatiens noli-tangere

“…Iwaizumi and Sakai (2004) suggested that pollinators visit small flowers of I. textori less frequently than they visit large flowers. These facts suggest that the higher altitude populations of I. textori may suffer from pollen limitation.…”

“…Although this species can produce chasmogamous and cleistogamous flowers, the frequency of cleistogamous flowers is very low (Sugita 2001). Iwaizumi & Sakai (2004) reported that the chasmogamous flower biomass in I. textori negatively correlates with the density of individuals, a finding that implies that flower biomass is influenced by resource competition (i.e. decreasing availability of resources).…”

“…They have similar vegetative and flower shapes (Tokuda et al 2015) and produce both chasmogamous and cleistogamous flowers (Sugita 2001). In I. noli-tangere, however, the chasmogamous flowers are protandrous and always need pollen transfer from other flowers for fertilization, whereas in I. textori they are homogamous and do not always need pollen transfer (Sugita 2001;Hatcher 2003;Iwaizumi & Sakai 2004;Masuda et al 2004). Therefore, although in central Japan these species are reported to be pollinated by the same pollinator, namely, Bombus diversus (Miyamoto 1961;Kato 1988;Tokuda et al 2015), the importance of the pollinator to seed set may differ between them.…”

Variations of flower size and reproductive traits in self-incompatible Trollius ranunculoides (Ranunculaceae) among local habitats at Alpine Meadow

“…The flower biomass or size of individuals varies between natural populations of single species (Galen et al 1987; Morgan and Barrett 1989;Kudo and Molau 1999;Caruso 2000;Iwaizumi and Sakai 2004). For example, it has been reported that flower size was larger in populations at higher altitudes than in those at lower altitudes (Galen et al 1987;Kudo and Molau 1999), but reverse results also existed, i.e., smaller flower size and plant size at higher altitudes than lower altitudes in Alpine Meadow (Zhao et al 2006).…”

“…For example, it has been reported that flower size was larger in populations at higher altitudes than in those at lower altitudes (Galen et al 1987;Kudo and Molau 1999), but reverse results also existed, i.e., smaller flower size and plant size at higher altitudes than lower altitudes in Alpine Meadow (Zhao et al 2006). These variations in flower biomass are considered to be due to differences in environmental or ecological factors, such as plant size, pollinator behavior and out-crossing rate (Iwaizumi and Sakai 2004). For plants that rely on animals for pollination, the ability to attract the animals to their flowers can be a crucial component of fitness (Darwin 1877;Waser 1983;Stanton et al 1986;Galen 1989).…”