title: Outbreeding effects in an inbreeding insect, Cimex lectularius.
abstract: In some species, populations with few founding individuals can be resilient to extreme inbreeding. Inbreeding seems to be the norm in the common bed bug, Cimex lectularius, a flightless insect that, nevertheless, can reach large deme sizes and persist successfully. However, bed bugs can also be dispersed passively by humans, exposing inbred populations to gene flow from genetically distant populations. The introduction of genetic variation through this outbreeding could lead to increased fitness (heterosis) or be costly by causing a loss of local adaptation or exposing genetic incompatibility between populations (outbreeding depression). Here, we addressed how inbreeding within demes and outbreeding between distant populations impact fitness over two generations in this re-emerging public health pest. We compared fitness traits of families that were inbred (mimicking reproduction following a founder event) or outbred (mimicking reproduction following a gene flow event). We found that outbreeding led to increased starvation resistance compared to inbred families, but this benefit was lost after two generations of outbreeding. No other fitness benefits of outbreeding were observed in either generation, including no differences in fecundity between the two treatments. Resilience to inbreeding is likely to result from the history of small founder events in the bed bug. Outbreeding benefits may only be detectable under stress and when heterozygosity is maximized without disruption of coadaptation. We discuss the consequences of these results both in terms of inbreeding and outbreeding in populations with genetic and spatial structuring, as well as for the recent resurgence of bed bug populations.
authors.affiliation: Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Department of Biosciences, University of Helsinki PO Box 65 (Viikinkaari 1), FI-00014, Helsinki, Finland.
authors.forename: Toby
authors.initials: T
authors.lastname: Fountain
authors.affiliation: Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Sven Lovén Centre - Tjärnö, University of Gothenburg SE, 452 96, Strömstad, Sweden.
authors.forename: Roger K
authors.initials: RK
authors.lastname: Butlin
authors.affiliation: Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Institute for Evolution and Ecology, University of Tübingen Auf der Morgenstelle 28, D-72076, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Reinhardt
authors.affiliation: Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Animal Population Ecology, Animal Ecology I, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth Universitätsstrasse 30, 95440, Bayreuth, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Otti
keywords: Cimex lectularius; colonization; inbreeding; metapopulation dynamics; outbreeding depression