Flexible mating system in a logged population of Swietenia macrophylla King (Meliaceae): implications for the management of a threatened neotropical tree species

Abstract

Microsatellites were used to evaluate the mating system of the remaining trees in a logged population of Swietenia macrophylla, a highly valuable and threatened hardwood species, in the Brazilian Amazon. A total of 25 open pollinated progeny arrays of 16 individuals, with their mother trees, were genotyped using eight highly polymorphic microsatellite loci. Genotypic data analysis from the progeny arrays showed that 373 out of the 400 seedlings (93.25%) were unambiguously the result of outcrossed matings and that the remaining 6.75% had genotypes consistent with self-fertilisation. Apomixis could be ruled out, since none of the 400 seedlings analysed had a multi-locus genotype identical to its mother tree. The high estimate of the multi-locus outcrossing rate (t m = 0.938 ± 0.009) using the mixed mating model also indicated that the population in this remnant stand of S. macrophylla was predominantly allogamous. The relatively large difference between the multi-locus and single-locus outcrossing estimates (t m Àt s = 0.117 ± 0.011) provides evidence that, in spite of the high outcrossing rate, a considerable degree of biparental inbreeding has contributed to the genetic structure of this population. Levels of outcrossing were not evenly distributed among maternal trees (t m ranging from 0.39 to 1.00), suggesting the occurrence of a variable degree of selfincompatibility and/or dichogamy among individual trees of this monoecious species. Due to its generalist pollination system and some level of tolerance for selfing, S. macrophylla seems to be resilient to environmental disturbances such as those caused by logging, since it sets fruits with predominantly outcrossed seeds even at low stand densities. Therefore, the remaining individuals in logged areas or in relict fragments may be very important for long-term population recovery and genetic conservation programmes.

Leaf age affects the quality of DNA extracted from Dimorphandra mollis (Fabaceae), a tropical tree species from the Cerrado region of Brazil

“…Plant biodiversity research using molecular markers has increased for species from Brazil (Lemes et al, 2007;Moreira et al, 2009;Novaes et al, 2010;Souza and Lovato, 2010). These studies have used leaves of plants as the DNA source.…”

Mating system parameters at hierarchical levels of fruits, individuals and populations in the Brazilian insect-pollinated tropical tree, Tabebuia roseo-alba (Bignoniaceae)

“…If inbreeding conditions persists over successive generations, heterozygosity is expected to decrease resulting in the increased expression of deleterious recessive alleles and ultimately decreased fitness in the population due to inbreeding depression. In the long term, this process may reduce a population's ability to respond to future environmental change (such as climate change) and drive populations to extinction Aguilar et al 2008, Leimu et al 2010.…”

Biparental inbreeding depression, genetic relatedness and progeny vigour in a wind-pollinated treeline species in Argentina

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