Local adaptation for body color in Drosophila americana.

Pigmentation is one of the most variable traits within and between Drosophila species. Much of this diversity appears to be adaptive, with environmental factors often invoked as selective forces. Here, we describe the geographic structure of pigmentation in Drosophila americana and evaluate the hypothesis that it is a locally adapted trait. Body pigmentation was quantified using digital images and spectrometry in up to 10 flies from each of 93 isofemale lines collected from 17 locations across the United States and found to correlate most strongly with longitude. Sequence variation at putatively neutral loci showed no evidence of population structure and was inconsistent with an isolation-by-distance model, suggesting that the pigmentation cline exists despite extensive gene flow throughout the species range, and is most likely the product of natural selection. In all other Drosophila species examined to date, dark pigmentation is associated with arid habitats; however, in D. americana, the darkest flies were collected from the most humid regions. To investigate this relationship further, we examined desiccation resistance attributable to an allele that darkens pigmentation in D. americana. We found no significant effect of pigmentation on desiccation resistance in this experiment, suggesting that pigmentation and desiccation resistance are not unequivocally linked in all Drosophila species.

[Effects of growth regulator, full exposure and mist spray on the cutting of Eucommia ulmoides].

OBJECTIVE: To study the effects of growth regulator on the cutting method of Eucommia ulmoides seedlings. METHODS: Treated with H2O (CK), NAA, 6-BA and NAA + 6-BA for 4 hours, respectively, cuttings of 4-year and 20-year trees were cultured for 45-60 days under the shed or full exposure and mist spray. The growth of the cuttings was observed periodically. The number of the roots, the root length, the callus and the death rate were investigated after harvest. RESULTS: Compared with the cutting from 4-year-old tree, the cutting from 20-year-old tree developed better. The rate of stroking root in treated group was 14 times as much as CK group. Other agronomic traits such as the number of the roots, the root length, the callus, the number of the leaves and the death rate of the cuttings in treated group were all better than that of the cuttings in CK group. The cultural time in treated group reduced by 15 days than that of CK group. CONCLUSIONS: The present study shows that both full exposure mist spray and growth regulators have remarkable effects on cuttings of tree with different ages for rooting or forming callus.