Simaba docensis, a new Brazilian species of Simaroubaceae

Simaba docensis, a new species of Simaroubaceae, is described and illustrated. Its geographical distribution seems to be restricted to semideciduous forest in the region of the Rio Doce basin, Minas Gerais, southeastern Brazil. Accordingly, it is likely to be a rare endemic and endangered species. It is very closely related to the only other Amazonian species of section Floribundae Engler, S. paraensis Ducke, from which it is basically distinguished by the number and shape of leaflets, leaf indument, and flower and fruit size.9334534

TAXONOMIC USE OF LEAF ANATOMICAL CHARACTERS IN THE GENUS SIMAROUBA-AUBLET (SIMAROUBACEAE)

Studies of the taxonomic value of leaf anatomical features in the neotropical genus Simarouba AUBLET (Simaroubaceae) revealed the occurrence of four types of leaf sclereids based on their shape, ramification and arrangement within the mesophyll. These leaf sclereid characteristics seem to be not influenced by environmental conditions and are useful to distinguish from one another the three morphologically very similar continental species, S. amara, S. glauca and S. versicolor, as do the three insular species, S. berteroana, S. tulae and S. laevis. Papillate trichomes on the abaxial leaf surface occur only in the continental species and are generally a good character to separate them from the insular species; however, they may be sometimes absent or reduced and scattered in S. amara, thus precluding its taxonomic use to separate papillate and non-papillate species groups. Overlapping values for the thickness of the adaxial leaf epidermis and of the sclereid cell wall among species were found, but extreme values for these characters may help the recognition of some species.188111712

Distinctions among three Simarouba species

Simarouba amara is frequently confused with two other continental species of the neotropical genus, S. glauca and S. versicolor. Cluster and Principal Component Analyses were applied to verify the distribution and variation of the main diagnostic characters proposed in early revisions: newer and anther size, stamen appendage indument, leaflet surface, and venation features. Simarouba glauca and S. versicolor were found to be morphologically closer to each other than to S. amara. Overlapping of characteristics in boundary populations of the three species was found. Geographical and morphological data other than leaf features also proved useful for species identification.23447948

The genetic diversity of Myrciaria floribunda (Myrtaceae) in Atlantic Forest fragments of different sizes

The genetic diversity of Myrciaria floribunda, a common Atlantic Forest tree, was investigated in six populations located in two small fragments (10 and 18 ha), two medium-sized fragments (36 and 44 ha) and one large fragment (3003 ha). Two populations occur in the large fragment. It is expected that smaller fragments should have lower genetic diversity and higher inbreeding. Distances between fragments varied from 0.66 to 10 km. On average 32 young trees smaller than 20 cm basal girth were sampled in each population. Allozyme electrophoresis was carried out, and six loci were scored. The effective number of alleles was lower for populations of the two small fragments (1.46 and 1.51) and higher for populations of the large (1.62 and 1.71) and medium ones (1.69 and 1.84). Small fragments showed lower values of expected and observed heterozygosities than large and medium fragments. Most of the genetic variability occurs within populations, and there was a moderate genetic variation among them (theta(p) = 0.097). Our findings show a tendency of lower genetic diversity within small and isolated fragments and higher genetic differentiation among them. But, few correlations between genetic diversity indices and fragment features (size and isolation) were significant.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.23336136

Limited pollen dispersal and biparental inbreeding in Symphonia globulifera in French Guiana

 In this paper, we report a study of the mating system and gene flow of Symphonia globulifera, a hermaphroditic, mainly bird-pollinated tree species with a large geographic distribution in the tropical Americas and Africa.Using three microsatellites, we analysed 534 seeds of 28 open pollinated families and 164 adults at the experimental site 'Paracou' in French Guiana. We observed, compared to other tropical tree species, relatively high values for the effective number of alleles. Significant spatial genetic structure was detected, with trees at distances up to 150 m more genetically similar than expected at random. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGener approach. The estimated multilocus outcrossing rate, tm, was 0.920. A significant level of biparental inbreeding and a high proportion of full-sibs were estimated for the 28 seed arrays. We estimated mean pollen dispersal distances between 27 and 53 m according to the dispersal models used. Although the adult population density of S. globulifera in Paracou was relatively high, the joint estimation of pollen dispersal and density of reproductive trees gave effective density estimates of 1.6 and 1.3trees/ha. The parameters of the mating system and gene flow are discussed in the context of spatial genetic and demographic structures, flowering phenology and pollinator composition and behaviour

Mating system in a neotropical tree species, Senna multijuga (Fabaceae)

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