In recent years, increased global trade and travel have provided potent invasion pathways for ever-increasing numbers of alien species. Alien species may not only harm local biodiversity but also may impact genetic diversity of local fauna as a result of intercrossing with native species. Allee effects arising from mate-location failure often limit the ability of an invading species to establish during the early, low-density phase of invasions. However, if the invading species can mate with a native species, producing viable hybrids, the presence of this native species may diminish Allee effects and thereby facilitate establishment. Furthermore, introgression of invader genes may significantly alter the genome of the native species. We formulated a mathematical model of two-species and their hybrid system in which both larval competition and mating behavior are described. As a first step, we assumed the simplest case in which mate preference in the adult stage and fitness in the larval stage are located on a single locus and there are only a single native allele and a single alien allele.

Results/Conclusions

Simulations demonstrated several possible outcomes of invader hybridization depending upon the parameter conditions: competitive exclusion  of the native species, exclusion of the invading species and coexistence of both species with prevalence of hybrids. Similar to the classic theoretical work of Gause, the phenotype of largest initial population always excluded others when competition among phenotypes was more severe than that within phenotypes. In addition, Allee effects associated with the invading species were diminished when the fitness of hybrids was greater than or substantially competitive to the fitness of either species. We discuss the role of hybridization during early phases of invasions referring and provide examples of interbreeding among native and invasive species.