A comprehensive assessment of inbreeding and laboratory adaptation in Aedes aegypti mosquitoes.

Perran A. Ross,Ary A. Hoffmann,Nancy M. Endersby‐Harshman

doi:10.1111/eva.12740

Abstract

Modified Aedes aegypti mosquitoes reared in laboratories are being released around the world to control wild mosquito populations and the diseases they transmit. Several efforts have failed due to poor competitiveness of the released mosquitoes. We hypothesized that colonized mosquito populations could suffer from inbreeding depression and adapt to laboratory conditions, reducing their performance in the field. We established replicate populations of Ae. aegypti mosquitoes collected from Queensland, Australia, and maintained them in the laboratory for twelve generations at different census sizes. Mosquito colonies maintained at small census sizes (≤100 individuals) suffered from inbreeding depression due to low effective population sizes which were only 25% of the census size as estimated by SNP markers. Populations that underwent full‐sib mating for nine consecutive generations had greatly reduced performance across all traits measured. We compared the established laboratory populations with their ancestral population resurrected from quiescent eggs for evidence of laboratory adaptation. The overall performance of laboratory populations maintained at a large census size (400 individuals) increased, potentially reflecting adaptation to artificial rearing conditions. However, most individual traits were unaffected, and patterns of adaptation were not consistent across populations. Differences between replicate populations may indicate that founder effects and drift affect experimental outcomes. Though we find limited evidence of laboratory adaptation, mosquitoes maintained at low population sizes can clearly suffer fitness costs, compromising the success of “rear‐and‐release” strategies for arbovirus control.

Highlights

Aedes aegypti mosquitoes transmit some of the most important arbo‐ viruses in the world, including dengue, Zika, and chikungunya
Our study is the first to investigate the effects of inbreeding on Ae. aegypti fitness directly by compar‐ ing outbred and inbred lines derived from the same population, and the first that links fitness costs to reductions in effective population size as assessed through genomic markers
We look for evidence of adaptation by comparing laboratory populations to their direct an‐ cestor concurrently and use replicate populations to separate fitness changes due to adaptation from drift and founder effects, two ap‐ proaches which have not been previously applied in mosquitoes

Summary

| INTRODUCTION

& Carrieri, 2013; Benedict & Robinson, 2003) In this approach, male mosquitoes are irradiated or chemically treated and re‐ leased into the field in large numbers to sterilize the wild females. Transgenic Ae. aegypti males possessing a dominant lethal system have been released in multiple locations where they have reduced population sizes, at least in the short term (Carvalho et al, 2015; Garziera et al, 2017; Harris et al, 2012; Lacroix et al, 2012). There are numerous studies that compare life history, morphological, and physiological traits be‐ tween laboratory and field populations for evidence of laboratory adaptation (Supporting Information Table S1). Our research highlights potential issues with maintaining colonized insects that are des‐ tined for field release, and informs protocols for the maintenance of Ae. aegypti in the laboratory

| MATERIALS AND METHODS

| DISCUSSION

Findings

F27 Inbred