Heterozygosity patterning and its relation to fitness components in experimental populations of Liomys pictus from tropical forests in western Mexico

We investigated the relationship between individual heterozygosity and the utilization of food and water in experimental populations of Liomys pictus from the markedly seasonal tropical dry deciduous and semideciduous forests of Chamela, Jalisco, in western Mexico. Thirty presumptive genre loci were analysed using starch-gel electrophoresis to estimate levels of heterozygo sity. Mean body weight was used as a direct measure of the performance of i ndividuals under food and water stressful conditions. L. pictus individuals subjected to a sequentially decreasing food treatment showed high feeding efficiency, with a ratio of food absorbed/food consumed of almost one. The association between food utilization and heterozygosity was not statistical ly significant, despite the pattern observed that the more heterozygosity i ndividuals maintained their weight better during the food treatment. Water utilization was positively associated with heterozygosity. When deprived of water, the more heterozygous individuals lost less weight than die less he terozygous ones. The ability of the more heterozygous individuals to better conserve water and energy may contribute to their adaptation to the extrem e seasonality of the Chamela forests. (C) 1998 The Linnean Society of Londo n.