Abstract
Bed bugs (Cimex lectularius) provide a unique opportunity to understand speciation and host-associated divergence in parasites. Recently, two sympatric but genetically distinct lineages of C. lectularius were identified: one associated with humans and one associated with bats. We investigated two mechanisms that could maintain genetic differentiation in the field: reproductive compatibility (via mating crosses) and aggregation fidelity (via two-choice sheltering assays). Effects were assessed at the intra-lineage level (within human-associated bed bugs), inter-lineage level (between human- and bat-associated bed bugs), and inter-species level (between C. lectularius and Cimex pipistrelli [bat bug]). Contrary to previous reports, bed bugs were found to be reproductively compatible at both the intra- and inter-lineage levels, but not at the inter-species level (although three hybrids were produced, one of which developed into an adult). Lineage- and species-specific aggregation fidelity was only detected in 8% (4 out of 48) of the aggregation fidelity assays run. These results indicate that under laboratory conditions, host-associated lineages of bed bugs are reproductively compatible, and aggregation pheromones are not capable of preventing gene flow between lineages.
Highlights
The common bed bug, Cimex lectularius L., offers a unique system for studies of incipient speciation for several reasons
Wawrocka et al.[11] showed that interbred HA and BA bed bugs were incapable of producing hybrids, suggesting complete reproductive isolation, no gene flow, and that C. lectularius has differentiated into two species
Three C. lectularius-C. pipistrelli hybrid nymphs were observed, one of which was dead during the initial observation
Summary
The common bed bug, Cimex lectularius L., offers a unique system for studies of incipient speciation for several reasons. Despite being found in the same environment, there is little to no apparent gene flow between the two lineages across Europe[8,9,10] These factors – small propagule size, extensive inbreeding, recurrent bottlenecks and founder effects, pressure to adapt to changes in host culture, behavior and physiology, and the existence of differentiated host-associated lineages in sympatry – produce an optimal scenario for sympatric speciation[4]. The apparent lack of gene flow between the HA and BA C. lectularius lineages suggests that complete or incomplete reproductive isolation might have evolved. Wawrocka et al.[11] showed that interbred HA and BA bed bugs were incapable of producing hybrids, suggesting complete reproductive isolation, no gene flow, and that C. lectularius has differentiated into two species. The extent species-level aggregation fidelity need to be considered given the co-habitation of BA C. lectularius and Cimex pipistrelli in bat roosts (O.B. field collection, 2014)
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