Abstract
Adaptation to different host plants is considered to be an important driver of the divergence and speciation of herbivorous insects. The application of molecular data and integrated taxonomic practices in recent years may contribute to our understanding of population divergence and speciation, especially for herbivorous insects considered to be polyphagous. Aphis aurantii is an important agricultural and forestry pest with a broad range of host plants. In this study, samples of A. aurantii feeding on different host plants in the same geographical area were collected, and their population genetic divergence and morphological difference were analyzed. Phylogenetic analysis and haplotype network analysis based on five genes revealed that the population on Ficus exhibited significantly genetic divergence from populations on other host plants, which was also supported by the statistical analysis based on measurements of 38 morphological characters. Our results suggest that A. aurantii has undergone specialized evolution on Ficus, and the Ficus population may represent a lineage that is experiencing ongoing sympatric speciation.
Highlights
The mechanism of speciation has been a hot research topic in biology from Darwin’s time to present day (Darwin, 1859; Futuyma and Mayer, 1980; McKinnon et al, 2004; Li et al, 2015; Taylor and Friesen, 2017)
The nucleotide composition of mitochondrial gene (COI and Cytb) and gnd fragments showed a strong bias toward A + T content (76, 77.5, and 75.3%, respectively), while EF-1α and 16S have no similar bias (Supplementary Table 3)
In the past three decades, the pea aphid A. pisum has been considered as a good model to investigate host specialization and sympatric speciation (Via, 1991a,b)
Summary
The mechanism of speciation has been a hot research topic in biology from Darwin’s time to present day (Darwin, 1859; Futuyma and Mayer, 1980; McKinnon et al, 2004; Li et al, 2015; Taylor and Friesen, 2017). During much of the twentieth century, sympatric speciation was considered to be more unreliable when compared with allopatric speciation (Futuyma and Mayer, 1980). Due to the in-depth research on biogeography and phylogeny in recent years, the concept of sympatric speciation has been accepted gradually (Via, 2001; Berlocher and Feder, 2002; Drès and Mallet, 2002; Bolnick and Fitzpatrick, 2007; Li et al, 2015). Complete sympatric speciation events in nature may take a long time (Mallet, 2008), and much fewer empirical studies have been reported (Savolainen et al, 2006; Bolnick and Fitzpatrick, 2007). Exploring divergence among sympatric populations, which may indicate ongoing sympatric speciation, can be helpful for understanding mechanisms of sympatric speciation (Drès and Mallet, 2002; Peccoud et al, 2009)
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