Biomedical subjects

Richard A Ennos

Publications and source records attributed to Richard A Ennos.

3 recordsLinked to original sources

PubMed2006

Effective seed dispersal across a fragmented landscape.

The role of seed dispersal in maintaining genetic connectivity among forest fragments has largely been ignored because gene flow by pollen is expected to predominate. By using genealogical reconstruction, we investigated gene flow after establishment of seeds in a wind-pollinated, wind-dispersed tree. Our data show that seed dispersal is the main vector of gene flow among remnants and that long-distance dispersal is common across a chronically fragmented landscape. The relative importance of seed-mediated gene flow may have been underemphasized in other fragmented systems, and diagnosing the response of forest trees to current anthropogenic disturbances requires the assessment of phenomena after establishment.

Conservation of Natural Resources↗

PubMed2005

Conserving taxonomic complexity.

Traditional species-based conservation programmes are appropriate in situations where species are readily identifiable. However, in certain taxonomically complex groups of organisms, generally characterized by the presence of uniparental lineages and reticulate evolution, it is not possible to classify biodiversity into discrete and unambiguous species. Attempts to impose species-based conservation on such taxonomically complex groups are proving untenable, and threaten to divert scarce resources and taxonomic expertise from the conservation of other priority groups. We argue here that a new approach should be adopted for taxonomically complex groups. We advocate the conservation of evolutionary processes that generate taxonomic biodiversity, rather than the preservation of a limited number of poorly defined taxa arising from this evolution.

Journal Article↗

PubMed2005

Historical and contemporary mating patterns in remnant populations of the forest tree Fraxinus excelsior L.

Genetic variation at microsatellite markers was used to quantify genetic structure and mating behavior in a severely fragmented population of the wind-pollinated, wind-dispersed temperate tree Fraxinus excelsior in a deforested catchment in Scotland. Remnants maintain high levels of genetic diversity, comparable with those reported for continuous populations in southeastern Europe, and show low interpopulation differentiation (E = 0.080), indicating that historical gene exchange has not been limited (Nm = 3.48). We estimated from seeds collected from all trees producing fruits in three of five remnants that F. excelsior is predominantly outcrossing (t(m) = 0.971 +/- 0.028). Use of a neighborhood model approach to describe the relative contribution of local and long-distance pollen dispersal indicates that pollen gene flow into each of the three remnants is extensive (46-95%) and pollen dispersal has two components. The first is very localized and restricted to tens of meters around the mother trees. The second is a long-distance component with dispersal occurring over several kilometers. Effective dispersal distances, accounting for the distance and directionality to mother trees of sampled pollen donors, average 328 m and are greater than values reported for a continuous population. These results suggest that the opening of the landscape facilitates airborne pollen movement and may alleviate the expected detrimental genetic effects of fragmentation.

Biological Evolution↗