Peer K, Taborsky M.. Outbreeding depression, but no inbreeding depression in haplodiploid ambrosia beetles with regular sibling mating. Evolution 59: 317-323

Department of Behavioural Ecology, Institute of Zoology, University of Bern, Wohlenstrasse 50A, CH-3032 Hinterkappelen, Switzerland.
Evolution (Impact Factor: 4.61). 03/2005; 59(2):317-23. DOI: 10.1111/j.0014-3820.2005.tb00992.x
Source: PubMed


In sexual reproduction the genetic similarity or dissimilarity between mates strongly affects offspring fitness. When mating partners are too closely related, increased homozygosity generally causes inbreeding depression, whereas crossing between too distantly related individuals may disrupt local adaptations or coadaptations within the genome and result in outbreeding depression. The optimal degree of inbreeding or outbreeding depends on population structure. A long history of inbreeding is expected to reduce inbreeding depression due to purging of deleterious alleles, and to promote outbreeding depression because of increased genetic variation between lineages. Ambrosia beetles (Xyleborini) are bark beetles with haplodiploid sex determination, strong local mate competition due to regular sibling mating within the natal chamber, and heavily biased sex ratios. We experimentally mated females of Xylosandrus germanus to brothers and unrelated males and measured offspring fitness. Inbred matings did not produce offspring with reduced fitness in any of the examined life-history traits. In contrast, outcrossed offspring suffered from reduced hatching rates. Reduction in inbreeding depression is usually attributed to purging of deleterious alleles, and the absence of inbreeding depression in X. germanus may represent the highest degree of purging of all examined species so far. Outbreeding depression within the same population has previously only been reported from plants. The causes and consequences of our findings are discussed with respect to mating strategies, sex ratios, and speciation in this unusual system.

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    • "The mating system precludes the need for long - range sex pheromones , as males cannot fly . The ability of females to invade new hosts rapidly is likely a reason for the dominance of xyleborine ambrosia beetles as adventive species , particularly as their inbreeding mating system seems to have minimal adverse effects that typically arise from inbreeding depression ( Peer and Taborsky 2005 , Kirkendall and Jordal 2006 ) . Ethanol is broadly associated with dead or dying host material of numerous taxa and correspondingly , broadly attractive to ambrosia beetles ( Coyle et al . "
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    ABSTRACT: In 2013, we examined the effects of conophthorin on flight responses of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to multiple-funnel traps baited with ethanol in Georgia, Michigan, New Hampshire, and Oregon. Adventive species (=exotic, nonnative, immigrant, introduced) accounted for 91.4% of total catches of ambrosia beetles. Conophthorin increased catches of Xyleborinus saxesenii (Ratzeburg) in Georgia, New Hampshire, and Oregon. Catches of Cyclorhipidion pelliculosum (Eichhoff) were increased by conophthorin in New Hampshire but not in Michigan. In Oregon, conophthorin decreased catches of Xylosandrus germanus (Blandford) to ethanol-baited traps but not in Michigan and New Hampshire. In Georgia, conophthorin increased catches of Gnathotrichus materiarius (Fitch), Xyleborus spp., and Xylosandrus crassiusculus (Motschulsky) but decreased catches of Cnestus mutilatus (Blandford), Dryoxylon onoharaensum (Murayama), and Cyclorhipidion bodoanum (Reitter). Conophthorin had no effect on catches of Ambrosiophilus atratus (Eichhoff), Anisandrus dispar (F.), Anisandrus sayi (Hopkins), Gnathotrichus sulcatus (Leconte), Monarthrum fasciatum (Say), Monarthrum mali (Fitch), and Xylosandrus compactus (Eichhoff). Attraction of the bark beetle, Hypothenemus rotundicollis (Eichhoff), was interrupted by conophthorin in Georgia. Our results suggest that adding conophthorin lures to traps baited with ethanol may have utility in detection programs in North America and overseas. However, traps baited with ethanol alone should also be used due to interruption in attraction for some species of ambrosia beetles.
    Full-text · Article · Feb 2015 · Journal of Economic Entomology
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    • "Bacteria have also been found in the ovarian epithelial tissue of Pityogenes calcographus L. (Arthofer et al., 2010), on the exoskeleton of over 20 bark beetle species (Streptomyces; Hulcr et al., 2011), and on the gallery walls (Hulcr et al., 2011). Wolbachia species, responsible for skewed sex ratios favoring females in many insects as well as other organisms, have been reported in Coccotrypes dactyliperda F. (Zchori- Fein et al., 2006), Hypothenemus hampei (Ferrari) (Vega et al., 2002), Ips typographus (Stauffer et al., 1997), Pityogenes chalcographus L. (Arthofer et al., 2009), and Xylosandrus germanus Blandford (Peer and Taborsky, 2005). Wolbachia is described in more detail in Chapter 3 as these bacteria likely influence bark beetle mating systems and evolution. "
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    ABSTRACT: Symbiotic interactions are prevalent in all bark beetle communities. For many species, the ability to associate with multiple partners enables species to persist through fluctuations in climate, resources, predation, and partner availability. Symbionts, particularly mutualistic species associated with bark beetles, can increase bark beetle fitness by providing nutrition or protection, exhaust or detoxify tree defenses, enhance communication, and promote or discourage other organisms. Alternatively, symbiotic species that are antagonistic to bark beetles can negatively affect bark beetle fitness directly (e.g., pathogens of bark beetles) or indirectly (e.g., competing with mutualistic microbes within trees). Symbionts associated with bark beetles have also been used to better understand the basic field of science such as mutualism theory, evolutionary and ecology adaption (e.g., horizontal gene transfer), and drivers of population dynamics. In general, bark beetle symbionts are known to affect mechanisms of evolution, coadaptation and speciation, tree defenses, chemical communication, population dynamics, range expansion, and pest management. Symbionts can have multiple roles, and interactions can change as species and environments change. Thus, simply categorizing symbionts as mutualistic, antagonistic, commensal etc. can be misleading. The combinations of genomic, behavioral, and ecological research approaches that incorporate symbionts will help us better understand how symbionts affect bark beetles. These interactions and effects will be discussed in more detail in this chapter.
    Full-text · Chapter · Jan 2015
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    • "However , outbreeding depression will be more important in the second generation (F2) after a BP cross due to the breakdown of co-adapted genes complexes in parental lineages after recombination events (Edmands 1999, 2007). Outbreeding depression has been mainly described in plants and invertebrates (Waser and Price 1994; Burke and Arnold 2001; Peer and Taborsky 2005; Escobar et al. 2008) but more rarely in vertebrates (Marr et al. 2002; Edmands 2007; McClelland and Naish 2007; Granier et al. 2011; Huff et al. 2011). Few studies on outbreeding depression have been carried through to the second (Palmer and Edmands 2000; Smoker et al. 2004; Dann et al. 2010; Houde et al. 2011; Huff et al. 2011; Willett 2012) or third generation (Edmands 1999, Fenster and Galloway 2000). "
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    ABSTRACT: The fitness consequences of outbreeding in wild populations are extremely variable. Heterosis and outbreed-ing depression can both be observed but the effect of envi-ronmental stressors on the occurrence of these phenomena is still poorly understood. We tested the influence of oxygen stress during embryonic development on consequences of outbreeding in wild populations of Atlantic salmon (Salmo salar). We used a common garden experiment and performed crosses within and between salmon populations to study performances of embryos reared under normal and hypoxic conditions. We detected both heterosis and outbreeding depression depending on traits but irrespective of divergence between parental populations. Nevertheless, outbreeding depression was observed almost exclusively under hypoxic conditions and prevailed over heterosis regarding survival during the whole embryonic development. Notably, the post-hatching survival of all between population crosses was approximately 15 % lower than the survival of within-pop-ulation crosses under hypoxic conditions. Different hypoxia reaction norms for post-hatching survival, length and time to hatch were also noticed among within and between popula-tions crosses further indicating outbreeding depression. These results demonstrate that consequences of outbreeding can dramatically vary depending on environmental conditions with outbreeding depression being possibly stronger under stressful conditions.
    Full-text · Article · Dec 2014 · Evolutionary Biology
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