Genetic diversity and thermal performance in invasive and native populations of African fig flies

During biological invasions, invasive populations can suffer losses of
genetic diversity that are predicted to negatively impact their
fitness/performance. Despite examples of invasive populations harboring
lower diversity than conspecific populations in their native range, few
studies have linked this lower diversity to a decrease in fitness. Using
genome sequences, we show that invasive populations of the African fig
fly, Zaprionus indianus, have less genetic diversity than conspecific
populations in their native range and that diversity is proportionally
lower in regions of the genome experiencing low recombination rates. This
result suggests that selection may have played a role in lowering
diversity in the invasive populations. We next use interspecific
comparisons to show that genetic diversity remains relatively high in
invasive populations of Z. indianus when compared to other closely related
species. By comparing genetic diversity in orthologous gene regions, we
also show that the genome-wide landscape of genetic diversity differs
between invasive and native populations of Z. indianus, indicating that
invasion not only affects amounts of genetic diversity, but also how that
diversity is distributed across the genome. Finally, we use parameter
estimates from thermal performance curves measured for 13 species of
Zaprionus to show that Z. indianus has the broadest thermal niche of
measured species, and that performance does not differ between invasive
and native populations. These results illustrate how aspects of genetic
diversity in invasive species can be decoupled from measures of fitness,
and that a broad thermal niche may have helped facilitate Z. indianus’s
range expansion.