Abstract
The shaggy soldier [<i>Galinsoga ciliata</i> (Rafin) S. F. Blake], family Asteraceae] is an invasive species that poses a growing threat to crop production. This annual plant produces heteromorphic achenes in a capitulum type inflorescence. The objective of this study was to compare selected morphological and phenological parameters and the success of generative reproduction in plants developed from peripheral and central achenes of the capitulum. The somatic variability of <i>G. ciliata</i> diaspores contributed to differences in the growth rates, development and fertility of the resulting populations. The progeny of central diaspores developed at a slower rate than the individuals derived from peripheral achenes, but at the end of their life cycle, the offspring of dimorphic achenes formed homogenous groups as regards height values. On average, the initial phenophases of <i>G. ciliata</i> plants derived from central achenes began one day later, and they entered the flowering stage eight days later than the individuals developed from peripheral seeds. At the initial growth stage (experimental day 65 to 83), the progeny of central achenes produced fewer capitula. On day 133, the individual fertility of the plants derived from central diaspores was 10% higher on average in comparison with the offspring of peripheral achenes.
Highlights
Heteromorphism promotes the development of various ecological strategies of evolutionary significance
The initial phenophases in plants derived from central achenes commenced one day later in comparison with the individuals developed from peripheral achenes
Significant differences were noted in respect of the time of first flowering, and the progeny of central achenes began to flower eight days later than the individuals derived from peripheral achenes (Table 2)
Summary
Heteromorphism promotes the development of various ecological strategies of evolutionary significance. The production of seeds and fruits with different dispersal capacity, dormancy patterns and germination requirements is a specific feature of that strategy which enables species to survive under variable and unpredictable environmental conditions (Imbert , 2002; Matilla et al 2005; Venable , 1985). Achenes differ with regard to their size, shape, mass, depth of dormancy, germination and dispersion ability (Baskin and Baskin , 1998; Corkidi et al 1991; Flint and Palmblad, 1978; Imbert , 2002; Imbert et al 1996; Rocha , 1996; Tanowitz et al 1987). Selected representatives of Asteraceae adopt the strategy of weak dispersion and delayed germination of weakly dispersed peripheral achenes as well the strategy of strong dispersion, faster and fuller germination of widely dispersed central achenes (Rocha , 1996; Tanowitz et al 1987, Venable et al 1987). Dispersed achenes have been found to germinate more rapidly and fully than widely dispersed diaspores (Chmielewski , 1999; Ellner , 1986, Imbert et al 1996, Pitelka et al 1983)
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