Developmental Instability in Fragmented Populations of Prairie Phlox: A Cautionary Tale

Abstract: Considerable attention has recently been focused on using levels of developmental instability among members of a population to detect environmental or genetic stresses on animals or plants. It is not yet clear, however, that high developmental instability in a sample of individuals always indicates environmental stress or poor genetic quality. We studied 13 fragmented populations of prairie phlox (   Phlox pilosa L.) to test the hypothesis that developmental instability should decrease with increasing population size—as expected if small populations suffer genetic problems associated with inbreeding or are exposed to more environmental stress than larger populations. We used two different measures of developmental instability, each calculated for two different traits: radial asymmetry of flowers (for petal width and petal length) and modular fluctuating asymmetry of leaves (  for leaf widths at two points along the leaf  ). There were weak but significant correlations among individuals for four of six pairwise combinations of these measures. Surprisingly, three of our four measures of developmental instability showed strong population size effects that were opposite to those expected: developmental instability increased with population size. We conclude that measures of developmental instability cannot be applied uncritically for biomonitoring without considerable knowledge of developmental mechanisms, natural history, and population biology of the species in question.     

Migration,markets, and mangrove resource use on Kosrae,Federated States of Micronesia

Kosrae, Federated States of Micronesia, is a prototype of an island economy prone to economic crowding. Average family size is large, the habitable land area is small, economic activity is limited, and household dependence on natural resources for fuel and food is high. We analyze how economic crowding--and its mitigation through trade and migration policies--affects mangrove resource use. A comparison of household survey data from 1996 and 2000 indicates that despite decreases in US aid and public-sector jobs, average household consumption of mangrove resources has not increased. Migration and remittances have allowed the purchase of imported fuel and building materials substituting for mangrove wood. Despite changing preferences and shifts toward import consumption, population growth and further declines in US financial support will likely cause aggregate demand for mangrove and upland wood to rise. Moreover, continued emigration may accelerate the export of mangrove crabs to off-island Kosraeans.     

密克罗尼西亚联邦科斯雷岛上的人口迁徙、市场及红树林资源利用

密克罗尼西亚联邦(FSM)的科斯雷岛是易发生经济活动聚集的岛屿经济的典型.家庭平均人口多,可居住土地面积小,经济活动有限,家庭依赖自然资源作为燃料和食物的程度高.我们分析了经济活动聚集--及其通过贸易和人口迁徙得到缓和--是如何影响红树林资源利用的.对1996年和2000年的家庭调查进行比较的结果表明,尽管美国援助和公营部门就业机会的减少,家庭对红树林资源的平均消费并未增加,人口迁徙和汇款收入使得人们可能通过购买进口燃料和建筑材料来取代红树林木材.尽管人们的偏爱发生了变化,重点转向对进口品的消费,人口增长以及美国经济援助的进一步减少将可能造成对红树林和高地木材的总需求上升.此外,持续的移民出境现象,可能会加速锯缘青蟹向岛外科斯雷人居住地的出口.