Spatial Scales of Pollen and Seed-Mediated Gene Flow in Tropical Rain Forest Trees

University of Michigan Department of Ecology and Evolutionary Biology and Herbarium 830 North University Avenue Ann Arbor MI 48109 USA
Tropical Plant Biology (Impact Factor: 1.52). 04/2008; 1(1):20-33. DOI: 10.1007/s12042-007-9006-6


Gene flow via seed and pollen is a primary determinant of genetic and species diversity in plant communities at different
spatial scales. This paper reviews studies of gene flow and population genetic structure in tropical rain forest trees and
places them in ecological and biogeographic context. Although much pollination is among nearest neighbors, an increasing number
of genetic studies report pollination ranging from 0.5–14km for canopy tree species, resulting in extensive breeding areas
in disturbed and undisturbed rain forest. Direct genetic measures of seed dispersal are still rare; however, studies of fine
scale spatial genetic structure (SGS) indicate that the bulk of effective seed dispersal occurs at local scales, and we found
no difference in SGS (Sp statistic) between temperate (N = 24 species) and tropical forest trees (N = 15). Our analysis did find significantly higher genetic differentiation in tropical trees (F
ST = 0.177; N = 42) than in temperate forest trees (F
ST = 0.116; N = 82). This may be due to the fact that tropical trees experience low but significant rates of self-fertilization and bi-parental
inbreeding, whereas half of the temperate tree species in our survey are wind pollinated and are more strictly allogamous.
Genetic drift may also be more pronounced in tropical trees due to the low population densities of most species.

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    • "2 , Lowe et al . 2005 ) . En general los árboles tropicales suelen tener poblaciones con alta diversidad genética y bajos índices de diferenciación ( Tabla 1 ) , que se explican por la interacción con polinizadores , altas tasas de entrecruza , sistemas reproductivos dioicos y amplios rangos de dispersión de polen ( Dick 2001 , Ward et al . 2005 , Dick et al . 2008 ) ."
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    DESCRIPTION: En este estudio se evaluó la estructura genética de la caoba en México a partir del análisis de cuatro poblaciones separadas por hasta 1000 km. El estudio tiene como marco contextual la hipótesis de que la caoba pudo originarse en Sudamérica y colonizar hacia el norte alcanzando el sur de México, proceso que determina que las poblaciones mexicanas sean consideradas como periféricas. El uso de cuatro primers de microsatélites reveló que las poblaciones mexicanas mantienen en promedio, niveles bajos de diversidad genética. En general, los resultados derivados de este estudio son compatibles con la hipótesis de que la caoba se originó en Sudamérica llegando subsecuentemente a México. Un escenario de evolución reciente con expansión del área de distribución geográfica y asociado con efecto fundador pueden explicar la disminución de la diversidad genética registrada a lo largo de toda la distribución geográfica.
    • "The conclusion from these studies is that physically isolated trees are not necessarily reproductively isolated and thus the genetic diversity within the population can be maintained to a certain degree (reviewed in Ashley, 2010). On the other hand, this effect could also have negative consequences on the conservation of wild species, because it is expected that hybridization is not prevented due to spatial separation between related species since it may be compensated by longer pollen dispersal distances (Dick et al., 2008; Vranckx et al., 2012). Particularly, the extensive cultivation of domesticated crops greatly increases the likelihood of contact between domesticated and related wild species (Cornille et al., 2012). "
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    ABSTRACT: Knowledge of pollen movement and frequency of interspecific hybridization in fragmented populations of rare species is a prerequisite for the implementation of conservation measures. In a large-scale study area (14,000 hectares) we analysed 297 Malus sylvestris trees with nine nuclear microsatellite markers. After open pollination of 564 offspring from 51 mother trees located in seven harvesting sites were investigated and genetic paternity analysis was performed. The paternal parent was identified for 213 offspring and the pollen dispersal distances between mother and pollen source were calculated. A large proportion of detected pollination events (42.4%) were observed within a radius of 50 m of the mother tree. The comparison of different tree densities indicated that with decreasing density the pollen dispersal distances increase. We observed pollination over long distances with a maximum of 10.7 km which is probably one of the reasons for a low spatial genetic structure within the M. sylvestris population and a stable genetic diversity in the offspring. Incorporating microsatellite data of 21 apple cultivars, a hybridization frequency of nearly 8% was determined. With decreasing tree density the number of hybridization events increased. Based on the results of our study an enhancement of the density of existing M. sylvestris populations is recommend to reduce the likelihood of hybridization. The production of young plants originated from seeds collected after open pollination is not advisable. Instead of that the seedlings for further reintroduction measures should be produced by controlled crossings in seed orchards to ensure ‘true type’ M. sylvestris individuals.
    Plant Genetic Resources 06/2015; DOI:10.1017/S1479262115000301 · 0.58 Impact Factor
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    • "Brenan Arbóreo 10 de sp, br sp, lo pequeno camp actino creme - mel ane Quirino & Machado (2014) Balizia pedicellaris (DC.) Barneby & Grimes Arbóreo 11 pe an, in an, lo pequeno camp actino creme - esf aut Dick et al. (2008) "
    01/2015; 15. DOI:10.13102/scb438
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