Mating system and pollen flow between remnant populations of the endangered tropical tree, <Emphasis Type="Italic">Guaiacum sanctum</Emphasis> (Zygophyllaceae) |
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Authors: | Eric J Fuchs J L Hamrick |
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Institution: | 1.Department of Plant Biology,University of Georgia,Athens,USA;2.Escuela de Biología,Universidad de Costa Rica,San Jose,Costa Rica |
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Abstract: | Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic
diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and
the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown
for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from
larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations
is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations
of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant
populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t
m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone
between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately
high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting
Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow
suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats
become available. |
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