Colombo P C, Pensel S, Isabel R M
Depto. Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Ciudad Universitaria, Buenos Aires, Argentina.
Genetica. 2004 May;121(1):25-31. doi: 10.1023/b:gene.0000019924.96257.97.
The South-American species Leptysma argentina Bruner is polymorphic for a centric fusion between chromosomal pairs 3 and 6 (fusion 3/6). Cytogenetic and morphological studies revealed that fusion 3/6 significantly increases some morphometric variables in males. A selection components study showed that the fusion is positively selected for longevity, the direct effect being exerted on thorax height. Moreover, a unisexual approach revealed that sexual male selection acts by increasing third femur length. In the present study the effect of fusion 3/6 on morphometric variables and the effect of body size and karyotype on mating success in both males and females were analysed through a bisexual approach. Total body length (TL) and third femur length (FL) were significantly larger amongst the fusion carrier females. Besides, the largest females and the carriers of the fusion have increased mating success. The selection differential suggests that directional sexual selection favours the females with increased TL and fusion dosage; however, the selection gradient revealed that none of the variables here analysed is a direct target of sexual selection. The male sexual selection study agrees with previous results, showing the importance of the third pair of legs in male mating success among grasshoppers.
南美物种阿根廷瘦蝗（Leptysma argentina Bruner）存在3号和6号染色体对之间着丝粒融合（3/6融合）的多态性。细胞遗传学和形态学研究表明，3/6融合显著增加了雄性的一些形态测量变量。一项选择成分研究表明，该融合因寿命而受到正向选择，直接作用于胸部高度。此外，单性研究表明，雄性性选择通过增加第三股骨长度来起作用。在本研究中，通过两性研究方法分析了3/6融合对形态测量变量的影响以及体型和核型对雄性和雌性交配成功率的影响。融合携带者雌性的总体长（TL）和第三股骨长度（FL）显著更大。此外，体型最大的雌性和融合携带者的交配成功率有所提高。选择差异表明，定向性选择有利于总体长增加和融合剂量增加的雌性；然而，选择梯度表明，这里分析的变量都不是性选择的直接目标。雄性性选择研究与先前结果一致，表明第三对腿在蝗虫雄性交配成功中的重要性。
