Influence of light and plant size on the reproduction and growth of small palm tree species: Comparing two methods for measuring canopy openness.

PREMISE OF THE STUDY: The reproduction and growth of large palms are influenced by many factors, including light and plant size, but few studies have examined smaller species (up to 2 m tall). We examined the effect of incident light and individual size on growth rates, the probability of reproduction, and the number of inflorescences of three small palm species and compared two methods for estimating canopy openness. METHODS: We measured canopy openness above the crowns of 132 adult plants and in the centers of 72 subplots (10 × 10 m) where individuals were sampled. We also recorded individual size and the number of leaves and inflorescences produced in two years. KEY RESULTS: Reproductive individuals of Butia paraguayensis tend to occur in illuminated microhabitats. Reproduction of Acrocomia emensis was correlated with stem diameter, but not with light. Reproduction was inversely related to individual size and light in Syagrus petraea, probably because this clonal palm invests heavily in sexual reproduction during its younger stages and clonal activity in older stages and may be adapted to the low-light conditions of the woodland understory. Growth was not predicted by light or individual size. Stronger correlations were found when incident light was measured directly above the crown, as opposed to the subplot center. CONCLUSIONS: The influences of light on reproduction are dependent on plant life histories, even among related and sympatric species. Light measurements directly above individual crowns provide better understanding of the reproductive effort rather than in subplot center.

Characterization of 10 microsatellite loci for Bathysa australis (Rubiaceae).

PREMISE OF THE STUDY: Bathysa australis is a common subcanopy tree from the Atlantic Forest that is pollinated by bees and wasps and produces autochoric seeds. This species exhibits great phenotypic plasticity along the elevational gradient of Serra do Mar in southeastern Brazil. We expect to assess the genetic diversity and gene flow between populations of this species along the elevational gradient. • METHODS AND RESULTS: We developed a microsatellite-enriched genomic library for B. australis, and 10 microsatellite loci were successfully amplified, ranging from one to 13 alleles per locus. The observed and expected heterozygosities ranged from 0.333 to 0.900 (average: 0.629) and 0.564 to 0.900 (average: 0.742), respectively. • CONCLUSIONS: These are the first microsatellite markers developed for the genus Bathysa and may be useful in other species of the Condamineeae tribe. These primers will be an important tool for studies of population ecology and conservation genetics.

Cytogenetics and characterization of microsatellite loci for a South American pioneer tree species, Croton floribundus.

Despite the recent advances in plant population genetic studies, the lack of information regarding pedigree, ploidy level, or mode of inheritance for many polyploids can compromise the analysis of the molecular data produced. The aim of this study was to examine both microsatellite and cytogenetic characteristics of the pioneer tree Croton floribundus Spreng. (Euphorbiaceae) to test for the occurrence of polyploidy in the species and to evaluate its implications for the appropriate use of SSR markers. Seven microsatellite markers were developed and screened for 62 individuals from a semi-deciduous tropical forest in Brazil. Chromosome number, meiotic behavior, and pollen viability were evaluated from male flower buds. All SSR loci were highly polymorphic. The number of bivalents observed in meiosis n = 56 (2n = 8× = 112) and the maximum number of alleles per individual (Ni = 8) demonstrated the occurrence of polyploidy in C. floribundus. The normal meiotic pairing and the high pollen viability suggested that C. floribundus is a regular and stable polyploid, most likely an allopolyploid. The combined SSR and cytogenetic data provided new evidence on the origin and evolution of the species as well as assured the accurate use of SSR loci for population genetic studies of the polyploid pioneer species.

Characterization of microsatellite loci in Himatanthus drasticus (Apocynaceae), a medicinal plant from the Brazilian savanna.

PREMISE OF THE STUDY: We developed a new set of microsatellite markers for studying the genome of the janaguba tree, Himatanthus drasticus (Mart.) Plumel, which is used in folk medicine in northeastern Brazil. These novel markers are being used to evaluate the effect of harvesting on the genetic structure and diversity of natural populations of this species. • METHODS AND RESULTS: Microsatellite loci were isolated from an enriched H. drasticus genomic library. Nine primer pairs successfully amplified polymorphic microsatellite regions, with an average of 8.5 alleles per locus. The average values of observed and expected heterozygosity were 0.456 and 0.601, respectively. • CONCLUSIONS: The microsatellite markers described here are valuable tools for population genetics studies of H. drasticus. The majority of the primers also amplified sequences in the genome of another species of the same genus. This new set of markers may be useful in designing a genetic conservation strategy and a sustainable management plan for the species.