It is generally thought that behavioral flexibility, the ability to change behavior when circumstances change, plays an important role in the ability of a species to rapidly expand their geographic range. However, it is an alternative non-exclusive possibility that an increase in the amount of available habitat can also facilitate a range expansion. Great-tailed grackles (*Quiscalus mexicanus*) are a social, polygamous species that is rapidly expanding its geographic range and eats a variety of human foods in addition to foraging on insects and on the ground for other natural food items. They are behaviorally flexible and highly associated with human-modified environments, thus offering an opportunity to assess the role of behavior and habitat change over the course of their expansion. Here, we compare behavior in wild-caught grackles from two populations across their range (a more recent population in the middle of the northern expansion front in Arizona versus a very recent population on the northern edge of the expansion front in California) to investigate whether individuals in a more recently established population exhibit more dispersal behavior (i.e., individuals are more likely to move away from their parents). We find that levels of relatedness are lower in the population closer to the edge compared to the population nearer the core. In particular, we observe no closely related individuals at the edge, suggesting that individuals of both sexes disperse further in this population than in the population nearer the core. Our analyses also suggest that, in both populations, females generally move shorter distances from where they hatched than males. These results elucidate that the rapid geographic range expansion of great-tailed grackles is associated with individuals differentially expressing dispersal behaviors.
Genetic divergence and environment influence on speciation process are the great deal studies over recent decades. One of the best ways for exploring the interaction of geography and genetics is the evaluation of hybrids in a contact zone. To understand if there is one or more hybrid zone between house mouse subspecies in Iran and what are the differences comparing these zones with European well-known hybrid zone, we performed this approach. Samples were live-trapped from Ilam city in west for sensu lato M. m. domesticus subspecies, and Neishabur city in north-east of Iran for sensu lato M. m. musculus subspecies. In five experimental groups, male and female mice of the two subspecies were crossed reciprocally to generate F1 hybrids, and then F1 offspring males and females were crossed also reciprocally between siblings to generate F2 hybrids. In the same manner as seen in European hybrid zone, hybridization between female M. m. musculus and male M. m. domesticus of all five groups showed male sterility in F1 generation, but intact female offspring. These sterile males comparing with a parent or healthy males showed low count and more abnormal sperm percentage in morphological and testis histological section studies. Comparing the results from this study with numerous studies carried out during several years on the European hybrid zone showed an equal condition of contact between two subspecies. Genetical elements have kept their same influence on postzygotic reproductive isolation more than environmental effects far from the Europe, here in Iran.
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