Is mahogany dysgenically selected?

Environmental Conservation - Tập 32 Số 2 - Trang 129-139 - 2005
Jonathan Cornelius1,2, Carlos Navarro1, Kevyn E. Wightman3, Sheila Ward4,5
1Center for Research and Higher Education in Tropical Agriculture (CATIE), Turrialba 7170, Costa Rica
2Current address: World Agroforestry Centre (ICRAF), c/o CIP, Apartado 1558, Lima 12, Peru
3Hardwood Tree Improvement and Regeneration Center, Purdue University, Department of Forestry and Natural Resources, 715 West State Street, West Lafayette, IN 47907-2061, USA
4Current address: Mahogany for the Future, Inc., 265 Calle Sorbona Apt 2, Urb. University Gardens, San Juan, Puerto Rico 00927
5Sheila Ward, International Institute of Tropical Forestry, PO Box 25000, San Juan, Puerto Rico 00928-50

Tóm tắt

One concern in the ongoing debate over the conservation status of mahogany has been the possibility that selective logging, as a form of negative phenotypic selection, might have led to deterioration in the genetic quality of populations. The incidence and degree of such ‘dysgenic’ effects is discussed, based on a consideration of mahogany logging practices, their expected genetic effects and empirical data on phenotypic selection in forest trees. Loggers have tended to avoid diseased, small, very large and poorly-formed individuals, and consequently logging has tended to increase the proportion of poor quality phenotypes relative to that before logging; in at least some conditions, selection differentials have been strongly negative. However, the upper limit for heritability of logger-selected traits in naturally-regenerated mahogany is probably no more than c. 0.1. Consequently, and assuming relatively extreme but realistic negative selection differentials of 50%, the maximum negative dysgenic response to a single logging-mediated phenotypic selection event is expected to be relatively small, i.e. ≤5%. This expectation is consistent with the empirical information from mahogany and other taxa. The implications of any dysgenic effects depend very much on the use and the future of dysgenically-selected populations. In managed populations, dysgenic effects could be reversed through positive selection. In the case of exploited but currently unmanaged natural populations, dysgenic selection is primarily of importance insofar as it affects fitness. As a threat to mahogany conservation and long-term sustainable production, it is probably insignificant in comparison with other genetic and non-genetic factors.

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Environmental Conservation

Tập 32 Số 2

129-139

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