Bactrocera tryoni and Bactrocera neohumeralis mate asynchronously; the former mates exclusively around dusk while the latter mates during the day. The two species also differ in the colour of the post-pronotal lobe (callus), which is predominantly yellow in B. tryoni and brown in B. neohumeralis. We have examined the genetic relationship between the two characters in hybrids, backcrosses and multigeneration hybrid progeny. Our analysis of the mating time of the parental species revealed that while B. tryoni mate exclusively at dusk, B. neohumeralis females pair with B. neohumeralis males during the day and with B. tryoni males at dusk. We found considerable variance in mating time and callus colour among hybrid backcross individuals of both sexes but there was a strong although not invariant trend for callus colour to co-segregate with mating time in both sexes. To genetically separate these two phenotypes we allowed the interspecific F1 hybrids to propagate for 25 generations (F25) without selection for mating time or callus colour, finding that the advanced hybrid population had moved towards B. tryoni phenotypes for both traits. Selection for day mating in replicate lines at F25 resulted in significant phenotypic shifts in both traits towards B. neohumeralis phenotypes in F26. However, we were unable to completely recover the mating time profile of B. neohumeralis and relaxation of selection for day mating led to a shift back towards dusk mating, but not yellow callus colour, by F35. We conclude that the inheritance of the two major species-defining traits is separable but tightly linked and involves more than one gene in each case. It also appears that laboratory conditions select for the B. tryoni phenotypes for mating time. We discuss our findings in relation to speciation theory and the likely effects of domestication during the generation of mass release strains for sterile insect control programmes.

中文翻译：

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分离两个紧密连锁的物种限定表型实蝇与杂交分析重组

try小食杆菌和新人小食杆菌异步交配。前者只在黄昏时交配，而后者白天则交配。两种物种的前胸膜后叶（愈伤组织）的颜色也不同，在Try。B. tryoni中主要为黄色，在B. neohumeralis中为棕色。我们已经检查了杂交，回交和多代杂交后代的两个性状之间的遗传关系。我们对亲本物种交配时间的分析表明，虽然B. tryoni雄性仅在黄昏时交配，但B. neohumeralis雌性在白天与B. neohumeralis雄性成对，而B. tryoni雄性在黄昏时成对。我们发现两性交回交个体之间的交配时间和愈伤组织颜色存在相当大的差异，但在两性中，愈伤组织颜色与交配时间共分离的趋势很强，尽管并非不变。为了遗传分离这两个表型，我们允许种间F1杂种繁殖25代（F25），而没有选择交配时间或愈伤组织颜色，发现先进的杂种群体已经朝着B. tryoni表型转移了这两个性状。在F25的复制品系中进行日交配的选择导致F26的两个性状均向B.neurohumeralis表型发生显着的表型转变。但是，我们无法完全恢复新肱骨芽孢杆菌的交配时间，而选择日间交配的放宽导致了向黄昏交配的转变，但没有黄色的愈伤组织颜色，由F35。我们得出的结论是，两个主要物种定义性状的遗传是可分离的，但紧密相关，并且在每种情况下都涉及多个基因。还似乎在实验室条件下为交配时间选择了B. tryoni表型。我们讨论与物种形成理论有关的发现以及不育昆虫控制程序的大量释放菌株产生过程中驯化的可能影响。