Groeters Francis R, Shaw David D
Molecular and Population Genetics Group, Research School of Biological Sciences, The Australian National University, P.O. Box 475, Canberra, A.C.T. 2601, AUSTRALIA.
Evolution. 1992 Feb;46(1):245-257. doi: 10.1111/j.1558-5646.1992.tb01999.x.
From southeastern Queensland to southern Victoria, over a transect of 11° latitude, the Moreton taxon of the Australian grasshopper Caledia captiva exhibits a cline in chromosome structure that involves change from a metacentric to an acrocentric genome. In this study, we show that embryonic development time covaries with chromosome structure along the transect. Both development time and chromosome short arm length exhibit an overall negative correlation with latitude, but with maxima just south of the northern limit of the taxon's distribution. Selection for such a pattern appears to arise from changes in voltinism along the cline in season length that exists along the transect. Populations with the highest temperature thresholds for avoidance of embryonic diapause also have the slowest development time and probably represent the northern extreme of a primarily univoltine life cycle. North of this region bivoltinism increases in frequency and, as expected from a split of the season length, development time decreases. Maximum chromosome short arm length occurs in the vicinity of the northern univoltine populations, rather than at the limit of distribution where bivoltinism prevails. We conclude that variation in chromosome structure could be contributing to the heritable variation for development time that forms the basis for adaptive change in this trait. These results provide justification for investigating causal relationships between chromosome structure and development time, with an ultimate aim of understanding the adaptive significance of chromosomal variation in C. captiva.
从昆士兰东南部到维多利亚州南部，跨越11°纬度的区域，澳大利亚蝗虫Caledia captiva的摩顿分类群在染色体结构上呈现出渐变群，涉及从中间着丝粒基因组到近端着丝粒基因组的变化。在本研究中，我们表明胚胎发育时间沿着该区域与染色体结构共同变化。发育时间和染色体短臂长度均与纬度呈现出总体负相关，但在该分类群分布北界以南达到最大值。这种模式的选择似乎源于沿着该区域存在的季节长度渐变群中化性的变化。避免胚胎滞育的温度阈值最高的种群发育时间也最慢，可能代表了主要为一化性生命周期的北部极端情况。在该区域以北，二化性的频率增加，并且正如季节长度划分所预期的那样，发育时间缩短。最大染色体短臂长度出现在北部一化性种群附近，而非二化性占主导的分布界限处。我们得出结论，染色体结构的变化可能有助于发育时间的可遗传变异，而发育时间变异是该性状适应性变化的基础。这些结果为研究染色体结构与发育时间之间的因果关系提供了依据，最终目的是了解Caledia captiva染色体变异的适应性意义。
