ORIGINAL PAPER Genetic effects of forest fragmentation in high-density Araucaria angustifolia populations in Southern Brazil Juliana Vitória Messias Bittencourt & Alexandre Magno Sebbenn Received: 25 February 2009 / Accepted: 1 April 2009 / Published online: 8 May 2009 # Springer-Verlag 2009 Abstract Araucaria angustifolia is an endangered tropical/ subtropical coniferous of great interest for conservation due its economical, ecological, and social value. Only 3% of original Araucaria forests remain, which are generally confined to small forest fragments. Forest fragmentation can have serious consequences on genetic process in tree population, affecting long-term fitness and adaptability. To investigate the effects of forest fragmentation on genetic diversity and the structure of A. angustifolia populations, the genetic diversity of eight microsatellite loci was compared in four small fragmented populations (<22 ha), four tree groups (five to 11 trees) occurring in pastures and in three plots in a large continuous population. The clearest effect of fragmentation was the loss of rare alleles (p ≤ 0.05) in fragmented populations (19.4% to 47.2%) and interme- diate frequency (0.05< p ≤ 0.25) and rare alleles (p ≤ 0.05) in tree groups (19% to 86.1%) in comparison to continuous populations. Fragmented populations have significant higher fixation index ( b F IS ¼ 0:121, P <0.05) than continuous populations ( b F IS ¼ 0:083, P <0.05). High genetic differenti- ation was detected among tree groups ( b G 0 ST ¼ 0:258, P <0.01) and low among fragments ( b G 0 ST ¼ 0:031, P <0.05) and continuous populations ( b G 0 ST ¼ 0:026, P <0.05), show- ing a significant bottleneck effect in tree groups. Evidence that forest fragments have experienced a recent bottleneck was confirmed in at least two studied fragments. The implications of the results for conservation of the fragmented A. angustifolia populations are discussed. Keywords Araucaria . Coniferous . Forest fragmentation . Genetic structure . Microsatellite markers Introduction Understanding the demographic and genetic consequences of forest fragmentation in tree species is of general interest. Forest fragmentation is a common phenomenon in practi- cally all habited regions of the planet as a result from human activities (Nason and Hamrick 1997; Young and Boyle 2000) and can result in smaller population size and increased isolation of populations and individuals (Bellington 1991; Young et al. 1996; Young and Boyle 2000; Rajora and Mosseler 2001; Cascante et al. 2002; Jump and Peñuelas 2006). Potentially, this can disrupt natural, ecological, and evolutionary processes such as mating system and gene flow, producing bottlenecks immediately after the fragmentation and genetic drift in subsequent generations and consequently affecting the genetic diversity, inbreeding, and structure of populations (Hamrick 2004; O´Connell et al. 2006). Frag- mented tree populations may experience inbreeding depression, reduction in heterozygosity, increased sus- ceptibility to diseases and pests, fixation of deleterious alleles, and loss of self-incompatible alleles (Isagi et al. 2007). Inbreeding can, in a short time, lead to reduced fitness, and the loss of genetic diversity can limit the ability of the population to adapt to environmental changes (Isagi et al. 2007). Moreover, with restricted gene flow, fragmentation is usually highly deleterious in the Tree Genetics & Genomes (2009) 5:573–582 DOI 10.1007/s11295-009-0210-4 J. V. M. Bittencourt Campus Dois Vizinhos (UTFPR, DV), Universidade Tecnológica Federal do Paraná, End.: Estrada para Boa Esperança, Km 4, Dois Vizinhos, PR 85660-000, Brazil A. M. Sebbenn (*) Instituto Florestal de São Paulo, CP 1322, São Paulo, SP 01059-970, Brazil e-mail: alexandre.sebbenn@pq.cnpq.com.br