Abstract
Senna multijuga is a pioneer tropical tree species that occurs mainly in the Brazilian Atlantic forest. We investigated the mating system of two populations of S. multijuga, one located in a reserve area (RD1) and the other (RD2) about 15 km away. The mating system parameters were estimated using the mixed mating model (software MLTR). The two populations had significantly different outcrossing rates, with population RD2 having a high rate (t m = 0.838) and population RD1, a lower rate (t m = 0.540). The values of t s were different between the two populations and also lower than those of t m. Significant t m - t s estimates indicated that biparental inbreeding contributed to the apparent selfing rate in these populations. The correlation of paternity was significant in population RD2 (r p = 0.309), suggesting that the progeny were more closely related than inferred by the observed outcrossing rate. The estimates of correlation of paternity, biparental inbreeding and the significant differences in pollen and ovule allele frequencies indicated that population RD2 is genetically substructured. For a pioneer species such as S. multijuga, selfing can be an important strategy for occupying open areas.
Highlights
The long-term survival of a species depends on the ability of populations to respond to environmental changes and is related to the amount of genetic variation present in the species (Beardmore, 1983)
The mating system has an important influence on the amount and distribution of genetic variation within and among populations of plant species (Hamrick et al, 1979; Loveless and Hamrick, 1984; Hamrick and Godt, 1989)
Some species have a similar or lower tm than that observed in population RD1, e.g. Ceiba pentandra, Eucalyptus rhodantha, Cavanillesia platanifolia (Murawski, 1995), Helicteres brevispira
Summary
The long-term survival of a species depends on the ability of populations to respond to environmental changes and is related to the amount of genetic variation present in the species (Beardmore, 1983). The mating system has an important influence on the amount and distribution of genetic variation within and among populations of plant species (Hamrick et al, 1979; Loveless and Hamrick, 1984; Hamrick and Godt, 1989). Neel et al (2001) studied six populations of Eriogonum ovalifolium and found no significant relationship between mating system parameters and environmental conditions or plant density. Collevatti et al (2001) reported outcrossing rates of 1 for four Caryocar brasiliense populations analyzed, which suggested that this species had an efficient self-incompatibility mechanism. In another study, Hall et al (1996) found no difference in the outcrossing rates among populations of Pithecollobium elegans that differed in their proportion of flowering trees in two consecutive years
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