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Outbreeding effects in an inbreeding insect, Cimex lectularius.

Fountain T, Butlin RK, Reinhardt K, Otti O - Ecol Evol (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus

Egg number changes over time and treatment for G2 females. (A) total number of eggs, (B) proportion of inviable eggs laid each week.
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fig04: Egg number changes over time and treatment for G2 females. (A) total number of eggs, (B) proportion of inviable eggs laid each week.

Mentions: As in G1 individuals, weekly egg numbers decreased significantly over the laying period, (Fig.4A: likelihood ratio test: χ2 = 98.56, P-value < 0.001) with no differences between treatments (Fig.4A: likelihood ratio test: χ2 = 3.05, P-value = 0.08), and no interaction of treatment and week (likelihood ratio test: χ2 = 0.03, P-value = 0.86). In contrast to G1 females, paternal body size had a significant effect on egg number laid by G2 females (likelihood ratio test: χ2 = 50.80, P-value < 0.001), whereas maternal body size did not (likelihood ratio test: χ2 = 0.28, P-value = 0.60). As in G1 females, the proportion of inviable eggs laid by G2 females increased significantly over the laying period (Fig.4B: likelihood ratio test: χ2 = 3776.62, P-value < 0.001), with treatment (likelihood ratio test: χ2 = 0.65, P-value = 0.42), paternal body size (likelihood ratio test: χ2 = 0.12, P-value = 0.73), and the interaction between treatment and week (likelihood ratio test: χ2 = 0.02, P-value = 0.89) having no effect on the proportion of inviable eggs laid. However, in G2 females, there was a significant effect of maternal body size on weekly proportion of inviable eggs laid (likelihood ratio test: χ2 = 4.30, P-value < 0.05). All outbred crosses, except one in the G1 crosses and three in the G2 crosses, produced viable eggs.


Outbreeding effects in an inbreeding insect, Cimex lectularius.

Fountain T, Butlin RK, Reinhardt K, Otti O - Ecol Evol (2014)

Egg number changes over time and treatment for G2 females. (A) total number of eggs, (B) proportion of inviable eggs laid each week.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4314272&req=5

fig04: Egg number changes over time and treatment for G2 females. (A) total number of eggs, (B) proportion of inviable eggs laid each week.
Mentions: As in G1 individuals, weekly egg numbers decreased significantly over the laying period, (Fig.4A: likelihood ratio test: χ2 = 98.56, P-value < 0.001) with no differences between treatments (Fig.4A: likelihood ratio test: χ2 = 3.05, P-value = 0.08), and no interaction of treatment and week (likelihood ratio test: χ2 = 0.03, P-value = 0.86). In contrast to G1 females, paternal body size had a significant effect on egg number laid by G2 females (likelihood ratio test: χ2 = 50.80, P-value < 0.001), whereas maternal body size did not (likelihood ratio test: χ2 = 0.28, P-value = 0.60). As in G1 females, the proportion of inviable eggs laid by G2 females increased significantly over the laying period (Fig.4B: likelihood ratio test: χ2 = 3776.62, P-value < 0.001), with treatment (likelihood ratio test: χ2 = 0.65, P-value = 0.42), paternal body size (likelihood ratio test: χ2 = 0.12, P-value = 0.73), and the interaction between treatment and week (likelihood ratio test: χ2 = 0.02, P-value = 0.89) having no effect on the proportion of inviable eggs laid. However, in G2 females, there was a significant effect of maternal body size on weekly proportion of inviable eggs laid (likelihood ratio test: χ2 = 4.30, P-value < 0.05). All outbred crosses, except one in the G1 crosses and three in the G2 crosses, produced viable eggs.

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus