Department of Entomology and Acarology, University of Sao Paulo, Luiz de Queiroz College of Agriculture (USP/ESALQ), Piracicaba, SP, 13418-900, Brazil.
Department of Ecology and Evolutionary Biology, Graduate Program in Ecology and Evolution, Federal University of São Paulo, Diadema, SP, 09972-270Brazil.
J Econ Entomol. 2021 Dec 6;114(6):2346-2354. doi: 10.1093/jee/toab190.
Euschistus heros (Hemiptera: Pentatomidae) has two allopatric strains with a hybrid zone in central Brazil. Asymmetric dispersal and gene flow between these strains of E. heros have been observed, where the South strain (SS) moves more quickly to the northern regions of the country than the North strain (NS) to the southern areas. In addition, SS generally has a bigger body size and presents dark brown coloration, and NS is usually smaller in size and presents light brown coloration. Here, we studied the reproductive behavior and tested for the presence of assortative mating and reproductive barriers between the two allopatric strains of E. heros. Nonrandom mating was observed in the SS strain based on mating choice trials and the reproductive isolation indexes. SS females and males prefer to mate with their co-specific (same strain) partner, while NS insects showed no mating preference. The insect's pronotum width was positively associated with the mating choice suggesting size-assortative mating in E. heros. Reciprocal crosses between strains yielded similar reproductive outputs when compared with pure strain crosses, suggesting similar fitness of hybrid pure strains. The asymmetric gene flow in the hybridization zone that favors SS seems to be associated with the reproductive behavior of the species, which favors the typical phenotype found in the SS populations.
美洲芫菁（半翅目：芫菁科）在巴西中部有两个地理上隔离的种群，存在一个杂交区。观察到这些美洲芫菁种群之间存在不对称的扩散和基因流，南方种群（SS）比北方种群（NS）更快地向该国北部地区移动，而 NS 则向南部地区移动。此外，SS 通常体型较大，呈深棕色，而 NS 通常体型较小，呈浅棕色。在这里，我们研究了这两个地理隔离种群的繁殖行为，并测试了它们之间是否存在交配偏好和生殖隔离。基于交配选择试验和生殖隔离指数，观察到 SS 种群存在非随机交配。SS 雌、雄虫更喜欢与同种（同种群）的伙伴交配，而 NS 昆虫则没有交配偏好。昆虫的前胸宽度与交配选择呈正相关，表明美洲芫菁存在大小交配偏好。与纯系杂交相比，种群间的相互杂交产生了相似的繁殖效果，表明杂种纯系的适应性相似。在有利于 SS 的杂交区中，不对称的基因流似乎与该物种的繁殖行为有关，这种行为有利于在 SS 种群中发现的典型表型。
