Developmental constraints

Based on their findings as well as those of others for ascidians, Lindquist et al.53 question the adequacy of the autotoxicity, energetic, or developmental constraints suggested by Orians and Janzen59 to explain a presumed lack of chemical defenses in the eggs and embryos of animals. Coupled with other reports of chemical defenses in the eggs and embryos of amphibians,66 insects,67 and additional marine invertebrates,44 43 52 54 68470 there appears to be ample evidence to question the validity of these presumed constraints. However, Slattery et al.70 recently suggested that the lack of chemical defenses in the larvae of the soft coral Sinularia polydactyla may be attributable to autotoxicity constraints. 

J. Maynard Smith et al. Developmental constraints and evolution. Quarterly Review of Biology, 60 (1985), 265-87. 

Maynard Smith, J., Burian, R., Kauffman, S. et al. (1985). Developmental constraints and evolution a perspective from the Mountain Lake Conference on Development and Evolution. Quarterly Review of Biology, 60, 265-87. 

The chapter is divided into two sections. The first section focuses on procurement as an industrial policy in African pharmaceutical markets. It takes a detailed microeconomic look at procurement design from the perspective of local pharmaceutical firms, for whom access to working capital is a major developmental constraint. Using illustrative data from Zimbabwe, the chapter shows that procurement can be either a source of finance or a serious drain on the finances of firms that operate in the context of high bank charges and interest rates, and in highly competitive markets. Careful procurement redesign can have a substantial impact on firms cash flow and investment prospects. 

It has been noted that the lack of basic health data is a major constraint at all stages of planning, monitoring and evaluation of health services. Consequently it is not possible to make an accurate assessment of the health status of Nigerians. In fact, the system of collecting basic health data on births, deaths, the occurrence of major diseases and other health indicators on a countr5nvide basis is still developmental. 

In the field, natural selection acts to optimize the adaptations of a plant so as to maximize individual fitness. In triazine resistant weeds, coevolution of the less productive chloroplast with the nuclear genome could have resulted in compensatory mechanisms not present in susceptible plants. These mechanisms could optimize productivity and maximize the fitness of those individuals, within the constraints imposed by impaired PSII. Even slight differences in the chloroplast genome between susceptible and resistant biotypes could result in different responses to the same selection pressures in the environment, perhaps in the direction of overcoming limitations caused by the resistance mutation. Thus, after several generations of selection, many nuclear-genome controlled traits are likely to appear that could mask intrinsic differences between biotypes due to the chloroplast mutation. It is also possible that the alteration in PSII in resistant plants triggers developmental events that compensate in some way. Effects of the resistance mutation may be compensated for by other aspects of plant performance such as carbon allocation or rate of development. Resistant plants may not necessarily be less productive than susceptible ones when traits not directly linked with triazine resistance are considered. 

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