| Summary: | The Asian lineage of Zika virus (ZIKV), a mosquito-borne pathogen originally from Africa, caused an epidemic into Brazil in 2015 and subsequently spread throughout the Americas. Local transmission in the U.S. is a public health concern, especially for Florida where the mosquito vectors <i>Aedes aegypti</i> and <i>Ae. albopictus</i> are widespread, abundant, and there is a high potential for virus introduction due to imported cases. Here we evaluate relative susceptibility to infection and transmission of Zika virus among geographic populations of <i>Ae. aegypti</i> and <i>Ae. albopictus</i> in Florida. Both species have been implicated as ZIKV vectors elsewhere, but both virus and vector genotype are known to influence transmission capacities and, hence, the risk of outbreaks. We test the hypothesis that <i>Ae. aegypti</i> and <i>Ae. albopictus</i> show geographic differences in midgut and salivary gland barriers that limit ZIKV transmission, using local populations of the two vector species recently colonized from three regions of Florida to compare their susceptibility to ZIKV infection, disseminated infection, and transmission potential. Susceptibility to infection was higher in <i>Ae. aegypti</i> (range 76–92%) than <i>Ae. albopictus</i> (range 47–54%). <i>Aedes aegypti</i> exhibited 33–44% higher susceptibility to infection than <i>Ae. albopictus</i>, with <i>Ae. aegypti</i> from Okeechobee, FL having 17% higher susceptibility to infection than <i>Ae. aegypti</i> from Miami, FL. Similarly, disseminated infection was higher in <i>Ae. aegypti</i> (range 87–89%) than <i>Ae. albopictus</i> (range 31–39%), although did not vary by region. Enhanced infection and disseminated infection in <i>Ae. aegypti</i> were associated with higher viral loads in mosquito samples than in <i>Ae. albopictus</i>. Transmission rates did not vary by species or region (range 26–47%). The results support the hypothesis that <i>Ae. aegypti</i>, but not <i>Ae. albopictus</i>, exhibited regional differences in midgut infection barriers. Our observation of higher vector competence for <i>Ae. aegypti</i> than <i>Ae. albopictus</i>, together with this species greater propensity to feed on humans, lends support to the notion that <i>Ae. aegypti</i> is regarded as the primary vector for ZIKV and public health concern in continental U.S.
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