Mercer S J, Wallace B M, Searle J B
Department of Zoology, University of Oxford, UK.
Cytogenet Cell Genet. 1992;60(1):68-73. doi: 10.1159/000133298.
Two chromosomal races of common shrews (Sorex araneus) were crossed in captivity to generate chain VII-forming complex Robertsonian heterozygotes. Meiosis and gametogenesis were studied in three male hybrids. Regular chain VII configurations were observed at both pachytene and diakinesis/metaphase I, although in many pachytene spreads the chain configuration was incomplete (the basis of this peculiarity is unknown). From metaphase II counts, the frequency of anaphase I nondisjunction in the complex heterozygotes was estimated to be 13%. Germ-cell death in the chain VII-forming complex heterozygotes was 22% greater than it was in controls, but this difference is unlikely to have greatly influenced the capacity of the heterozygotes to sire offspring. Thus, the fecundity of these complex heterozygous common shrews would probably have been only slightly reduced relative to homozygous or simple heterozygous shrews. These results call into question the generality of speciation models based on the presumed sterility of complex heterozygotes.
在圈养条件下，将两种普通鼩鼱（Sorex araneus）的染色体族进行杂交，以产生形成VII链的复合罗伯逊杂合子。对三只雄性杂种鼩鼱的减数分裂和配子发生进行了研究。在粗线期和终变期/中期I均观察到规则的VII链构型，尽管在许多粗线期铺片中，链构型并不完整（这种特殊性的原因尚不清楚）。根据中期II的计数，估计复合杂合子中减数分裂I后期不分离的频率为13%。形成VII链的复合杂合子中的生殖细胞死亡比对照组高22%，但这种差异不太可能对杂合子生育后代的能力产生重大影响。因此，相对于纯合或简单杂合的鼩鼱，这些复合杂合普通鼩鼱的繁殖力可能只会略有降低。这些结果对基于复合杂合子假定不育性的物种形成模型的普遍性提出了质疑。
