Species complex diversification by host plant use in an herbivorous insect: The source of Puerto Rican cactus mealybug pest and implications for biological control

Cryptic taxa have often been observed in the form of host‐associated
species that diverged as the result of adaptation to alternate host
plants. Untangling cryptic diversity in species complexes that encompass
invasive species is a mandatory task for pest management. Moreover,
investigating the evolutionary history of a species complex may help to
understand the drivers of their diversification. The mealybug
Hypogeococcus pungens was believed to be a polyphagous species from South
America and has been reported as a pest devastating native cacti in Puerto
Rico, also threatening cactus diversity in the Caribbean and North
America. There is neither certainty about the identity of the pest, nor
the source population from South America. Recent studies pointed to
substantial genetic differentiation among local populations, suggesting
that H. pungens is a species complex. In this study, we used a combination
of genome-wide SNPs and mtDNA variation to investigate species diversity
within H. pungens sensu lato to establish host plant ranges of each one of
the putative members of the complex, to evaluate whether the pattern of
host plant association drove diversification in the species complex, and
to determine the source population of the Puerto Rican cactus pest. Our
results suggested that H. pungens comprises at least five different
species, each one strongly associated with specific host plants. We also
established that the Puerto Rican cactus pest derives from southeastern
Brazilian mealybugs. This is an important achievement because it will help
to design reliable strategies for biological control using natural enemies
of the pest from its native range.