Quality of Seeds Produced by Psychotria tenuinervis (Rubiaceae): Distance from Anthropogenic and Natural Edges of Atlantic Forest Fragment

Abstract

The aim of this study was to investigate whether there were differences in the genetic variability and rate and velocity of the seed germination produced by Psychotria tenuinervis located at anthropogenic edges, natural edges, and in the forest interior. The populations of P. tenuinervis showed no differences in genetic variability or structure among the three habitats. There was, however, an indication of inbreeding, which was significantly higher in natural edges than in anthropogenic edges and the forest interior. Within-habitat variation was considerable, but there were no differences in seed mass or rate and velocity of germination among the three habitats. These results suggest that seed characteristics were not influenced by the genetic pattern of P. tenuinervis and that other characteristics of the forest fragment, such as gaps, edge age, and type of matrix exert more influence on seed mass and germination than the distance from the edges.

Genetic Structure of Tree and Shrubby Species Among Anthropogenic Edges, Natural Edges, and Interior of an Atlantic Forest Fragment

“…Two species were used as models for this evaluation: Psychotria tenuinervis (shrub, Rubiaceae) and Guarea guidonia (tree, Meliaceae). These plant species were chosen for their high abundance in the study area Santos 2005, 2006;Ramos et al 2007Ramos et al , 2008, being present in all three habitats; both are pollinated by insects, and their seeds are dispersed by vertebrate animals. In addition, they represent different forest strata, the canopy and the subcanopy.…”

Mating Systems of Psychotria tenuinervis (Rubiaceae): Distance from Anthropogenic and Natural Edges of Atlantic Forest Fragment

“…Ramos et al (2007) supposed that the substantial inbreeding in P. tenuinervis populations in this forest fragment resulted from biparental inbreeding, since the reproductive biology (manipulating flower mating) of this species indicated predominance of outcrossing (Virillo et al in press). This article, however, demonstrates that the biparental inbreeding rate (t m -t s ) of P. tenuinervis in this forest fragment was low (\7%).…”

“…In this present study, there was no size effect in Psychotria populations in the fragment, because this species is very abundant and widespread throughout it. Ramos et al (2007) showed that gene flow among the three habitats in the fragment is high (low G ST ). Therefore, the P. tenuinervis native pollinators can visit both edges as interior flowers, and the exotic pollinator Apis mellifera, the most abundant flower visitant in the fragment (Ramos and Santos 2006a), has compensated when the native pollinator could not visit any of them.…”

“…Theoretically, reducing the population size of a normally outbreeding species will lead to inbreeding (Ellstrand and Elam 1993;Frankel et al 1995;Coates et al 2007;Ramos et al 2007), and decreases in outcrossing rates with decreasing population size have been reported in Clarkia exilis (Vasek and Harding 1976), Eichhornia paniculata (Barrett and Husband 1990), and Aquilegia canadensis (Routley et al 1999). Over much longer time frames, genetic erosion combined with elevated linkage owing to reduced panmixia can reduce a species' ability to respond to environmental challenges, increasing the probability of extinction, as the ability to generate novel recombinant multilocus genotypes is lost (Young et al 1996;Broadhurst and Young 2007).…”

Efeito do tamanho do fragmento na dispersão de sementes de Copaíba (Copaifera langsdorffii Delf.)

“…Isto pode estar comprometendo a manutenção local da população, por conseqüência da alta concentração espacial de indivíduos aparentados próximo à planta-mãe. Este tipo de distribuição espacial pode gerar um alto grau de endogamia nas gerações futuras (Ramos et al 2007). Cordeiro & Howe (2003) mostraram que as taxas de dispersão de sementes e recrutamento de plantas jovens nas redondezas da planta-mãe são maiores em áreas fragmentadas em comparação a florestas contínuas, devido à redução na dispersão por falta de dispersores como aves.…”