Variation and Population Structure at Enzyme Gene Loci in Araucaria angustifolia (Bert.) O. Ktze

Abstract

We describe alloenzyme variation in A. angustifolia populations of three separate geographical areas in southern Brazil. The genetic structure of populations was examined in seedtrees, embryos and effective pollen. Seven out of 24 enzyme loci were polymorphic. The average number of alleles per locus (24 loci) was 1.54, with 2.44 alleles per polymorphic locus. Mean expected and observed heterozygosities at the polymorphic loci were H e = 0.128 and H o = 0.132 for seed-trees, and H e = 0.142 and H o = 0.161 for embryos. All measures of genetic variability were highest in the most northern populations. Differences among localities explained 84.14 % and 92.06 % of the total genetic diversity in embryos and seed trees, respectively. Sex ratio was 1:1 in almost all populations. Female and male gene pools differed in allele frequencies, most significantly at loci 6-Pgdh-B and Skdh-B. This explains the excess of heterozygotes detected among embryos. No inbreeding or excess of heterozygotes was detected among adult seed trees. Genetic variation in A. angustifolia revealed a latitudinal gradient.

Evidences of delayed size recovery in Araucaria angustifolia populations after post-glacial colonization of highlands in Southeastern Brazil

“…Sousa et al 2004, Stefenon et al 2007) has been explained as effect of post-glacial migration from different refugia, which in addition to the geographical isolation, resulted in temporal isolation of the southeastern populations (Stefenon et al 2007). Four populations analysed in this study belong to the southeastern region (CJ, CJm, CJs1 and CJs2 from São Paulo State; Fig.…”

“…Isozyme allelic frequencies were obtained from their original publications (Auler et al 2002, Sousa et al 2004, Mantovani et al 2006. Founded on the principle that rare alleles are lost in populations which experienced a strong reduction in effective size (Nei et al 1975), three methods were employed to search for signature of population bottlenecks.…”

“…Shimizu and Higa 1980, Auler et al 2002, Sousa et al 2004, Mantovani et al 2006, Stefenon et al 2007, Schögl et al 2007). However, little is known about the relationship between historical demography and the current genetic structure of this species.…”

“…Here, two coalescentbased methods (the heterozygosity excess and the Mratio analyses), a graphical analysis of allele frequency distribution and classical clustering analysis were applied to investigate molecular signature of demographic events based on individual microsatellite genotypes scored in six natural populations of A. angustifolia sampled in four States: São Paulo, Paraná, Santa Catarina and Rio Grande do Sul (see Table I). Additionally, allelic frequencies at isozyme loci scored in three populations from São Paulo State (Sousa et al 2004, Mantovani et al 2006, see Table II) and in eight populations from Santa Catarina State (Auler et al 2002, see Table II) were analysed using the heterozygosity excess and the allele frequency distribution approaches. The main goal of this study was to investigate molecular signatures of genetic bottleneck due to post-glacial establishment of A. angustifolia populations in the highlands of southeastern and southern Brazil.…”

Ontogenia de megaestróbilos de Araucaria angustifolia (Bert.) O. Kuntze (Araucariaceae)

“…Já as escamas férteis foram observadas nos megaestróbilos iniciais neste estudo a partir de dezembro de 2011, um pouco mais cedo do que foi relatado por Anselmini et al (2006), cuja presença das escamas férteis ocorreu somente a partir de março de 2003/2004. Variações na sazonalidade da produção de sementes são ocasionadas por fatores climáticos, como foi descrito por Sousa (2000) em seus estudos em diferentes anos em populações de A. angustifolia situadas em Caçador (SC), Irati (PR) e Campos do Jordão (SP). Outro fator que causa a alternância na produção de sementes é a formação irregular de megaestróbilos pelas plantas (MANTOVANI et al, 2004).…”