The revenge of history

Three papers today which look into the role of history in determining patterns of diversity, at the species and genetic level. I don’t have much time today, so descriptions will have to be quick and dirty for now.

In Molecular Ecology, Hoban et al. used microsatellites to genotype 29 populations of Juglans cinerea from throughout the eastern US.1 They wanted to know whether the observed pattern of genetic diversity was best explained by the spread of the species from refugia after the last glaciation, by its recent dramatic decline due to a fungal pathogen, or by a core-vs-periphery effect. It turned out to be the first of these. One of the consequences is that southern populations are the most diverse, and should be the ones to be targeted for ex situ conservation in the face of the depredations of the fungus.

Meanwhile, over at the Journal of Applied Ecology, Reitalu et al. looked at species diversity in Swedish grasslands in relation to various aspects of management.2 They found that distance to the nearest historical village was an excellent predictor of grassland diversity, integrating various management variables. Diversity peaked at 1-1.5 km from the nearest village, and declined thereafter with distance. This finding could be used to prioritize grasslands for conservation, and to devise appropriate management programmes, which should involve moderate grazing pressure.

Finally, again in the Journal of Applied Ecology, González-Varo et al. describe a somewhat retro study on the Mediterranean Shrub Myrtus communis in SW Spain using isozymes.3 Working not only on the actual natural populations but also on progenies, they wanted to know the relative importance of the past and the present effects of fragmentation of populations on fitness. The past effects were represented by the genetic diversity of populations, the present effects by outcrossing rates. In contrast to the previous two papers, they found that the present is a better guide to conservation that the past. It was outcrossing rates that had the strongest effect on the fitness of progenies. The recommendation is for honeybee hives to be controlled in the vicinity of these populations, to foster a diverse assemblage of local pollinators, and thus increased outcrossing.

Great to see very clear conservation recommendations being made in all cases, solidly based on the results. It is not always so.

  1. HOBAN, S., BORKOWSKI, D., BROSI, S., McCLEARY, T., THOMPSON, L., McLACHLAN, J., PEREIRA, M., SCHLARBAUM, S., & ROMERO-SEVERSON, J. (2010). Range-wide distribution of genetic diversity in the North American tree Juglans cinerea: a product of range shifts, not ecological marginality or recent population decline Molecular Ecology DOI: 10.1111/j.1365-294X.2010.04834.x []
  2. Reitalu, T., Johansson, L., Sykes, M., Hall, K., & Prentice, H. (2010). History matters: village distances, grazing and grassland species diversity Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01875.x []
  3. González-Varo, J., Albaladejo, R., Aparicio, A., & Arroyo, J. (2010). Linking genetic diversity, mating patterns and progeny performance in fragmented populations of a Mediterranean shrub Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01879.x []

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