Direct and indirect genetic effects in life-history traits of flour beetles (Tribolium castaneum)

Abstract

Indirect genetic effects (IGEs) are the basis of social interactions among conspecifics, and can affect genetic variation of nonsocial and social traits. We used flour beetles (Tribolium castaneum) of two phenotypically distinguishable populations to estimate genetic (co)variances and the effect of IGEs on three life-history traits: development time (DT), growth rate (GR), and pupal body mass (BM). We found that GR was strongly affected by social environment with IGEs accounting for 18% of the heritable variation. We also discovered a sex-specific social effect: male ratio in a group significantly affected both GR and BM; that is, beetles grew larger and faster in male-biased social environments. Such sex-specific IGEs have not previously been demonstrated in a nonsocial insect. Our results show that beetles that achieve a higher BM do so via a slower GR in response to social environment. Existing models of evolution in age-structured or stage-structured populations do not account for IGEs of social cohorts. It is likely that such IGEs have played a key role in the evolution of developmental plasticity shown by Tenebrionid larvae in response to density. Our results document an important source of genetic variation for GR, often overlooked in life-history theory.

Indirect genetic effects in behavioral ecology: does behavior play a special role in evolution?

“…18% of heritable variation in growth rate in the flour beetle Tribolium castaneum was influenced by IGEs, while no such influence was documented for other life-history traits in the same study (Ellen et al 2016). A trait-based analysis of 5 antipredator and social behaviors in the guppy Poecilia reticulata found evidence for reciprocal IGEs on all traits, but only a limited number of nonreciprocal IGEs, and their directions and magnitudes varied (Bleakley et al 2009).…”

Female Density-Dependent Chemical Warfare Underlies Fitness Effects of Group Sex Ratio in Flour Beetles

“…Previous work suggests that quinones are toxic for Tribolium castaneum juveniles (Sokoloff 1977) and cause high adult mortality in related species such as Tribolium destructor (Palm 1946). Beetles also grow faster and larger in male-biased groups (Ellen et al 2016), possibly due to relatively lower amounts of toxic quinones. Hence, it may indeed be beneficial to avoid laying eggs under high quinone concentrations and wait to find a less crowded resource patch.…”

Increased developmental density decreases the magnitude of indirect genetic effects expressed during agonistic interactions in an insect

“…In animals, IGEs have been documented for a large number of phenotypic traits, including aggressiveness (Wilson et al 2009;Saltz 2013;Alemu et al 2014;Santostefano et al 2017), dominance (Moore et al 2002;Wilson et al 2011), parental care (Hunt and Simmons 2002;Head et al 2012;Ashbrook et al 2015), cooperation (Linksvayer 2006), sexual behavior (Petfield et al 2005 Marie-Orleach et al 2017), and timing of reproduction (Brommer and Rattiste 2008;Germain et al 2016). In plants and fungi, the role of IGEs has also been recognized in research focusing on the role of competition in growth and reproduction (Mutic and Wolf 2007;Wolf et al 2011;Costa e Silva et al 2013;Costa e Silva et al 2017;Rode et al 2017), while a key role of IGEs in trait evolution is widely recognized in evolutionary research on commercial livestock aimed at decreasing the adverse effects of competition (Camerlink et al 2013;Camerlink et al 2015;Ellen et al 2016;Canario et al 2017). Indeed, IGEs can greatly influence evolutionary trajectories because they change the proportion of heritable variation on which selection can act (Bijma et al 2007;Bijma and Wade 2008;Bijma 2011;Bijma 2014;Wilson 2014).…”