Mixed evidence for the erosion of intertactical genetic correlations through intralocus tactical conflict

Ríos-Cardenas

2019

Preprint

Alternative reproductive tactics occur when individuals of the same sex have a suite of morphological and/or behavioural traits that allow them to pursue different reproductive strategies. A common pattern is e.g. the existence of “courter” and “sneaker” tactics within males. We have previously argued that alternative reproductive tactics should be subject to genetic conflict over the phenotypic expression of traits, similar to sexual antagonism. In this process, which we called intra-locus tactical conflict, genetically determined tactics experience conflicting selection on a shared phenotypic trait, such as body size, but a positive genetic correlation between tactics in body size prevents either tactic from reaching its optimum. Recently, other authors have attempted to extend this idea to developmentally plastic alternative reproductive tactics, with mixed results. However, it is not clear whether we should expect intra-locus tactical conflict in developmentally plastic tactics or not. We have therefore run a series of simulation models investigating under what conditions we should expect to see positive estimates of the inter-tactical genetic correlation, since a positive genetic correlation is a prerequisite for the existence of intra-locus tactical conflict. We found that for autosomal, X-linked, and Y-linked genetically-determined tactics, estimated inter-tactical genetic correlations were generally high. However, for developmentally plastic tactics, the genetic correlation depends on the properties of the switching threshold between tactics. If it is fixed, then estimated genetic correlations are positive, but if there is genetic variation in the switch-point, then any sign and magnitude of estimated genetic correlation is possible, even for highly heritable traits where the true underlying correlation is perfect. This means that caution should be used when investigating genetic constraints in plastic phenotypes.

Section: Conclusion 313supporting

confidence: 86%

Section: Introduction 46mentioning

confidence: 99%

Genetic correlations across genetically determined and developmentally plastic alternative reproductive tactics

Ríos-Cardenas

2019

Preprint

“…genetically fixed, developmentally plastic), but in general we suggest these should involve multigenerational half-sib breeding designs to obtain the different components of the genetic variance (see Abbott and Svensson 2010 for an example using a full-sib design). In cases where the environment influences the development of the ARTs, this component may need to be included in the design (Buzatto et al 2015, Pike et al 2017. Artificial selection regimes have also been used to indirectly detect genetic correlations (Buzatto et al 2018).…”

Section: When To Expect and How To Detect Iatcmentioning

confidence: 99%

“…) simulations. Pike et al (2017) examined genetic correlations between traits in two species with developmentally plastic ARTs, the acarid mite Rhizoglyphus echinopus (Fig. 1a) and the European earwig Forficula auricularia.…”

Section: When To Expect and How To Detect Iatcmentioning

confidence: 99%

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Insights from intralocus tactical conflict: adaptive states, interactions with ecology and population divergence

Ríos-Cardenas

2019

Oikos

Alternative reproductive tactics (ARTs) have improved our understanding of the evolution of adaptive variation; for instance, their study has led us to understand that the best phenotype (e.g. large and flashy) for a tactic that uses one mating behavior (e.g. court females) is often not the best phenotype (e.g. small and inconspicuous) for a tactic that uses a different mating behavior (e.g. chase and force‐copulate females). However, genetic correlations of shared traits across ARTs can constrain ARTs from reaching their optimal states, resulting in intralocus tactical conflict (IATC). While constraints on evolution in general have been well‐established and studied, there are some important implications of constraints due to intralocus tactical conflict on ARTs that have not been incorporated into the field of evolutionary ecology. Here we describe how an appreciation of IATC, including how to detect it and when to expect it, can change our perspectives in three areas: 1) adaptive states for traits associated with ARTs (e.g. growth rates, behavioural plasticity); 2) how selection due to ecological variation across populations can produce patterns of divergence between ARTS; 3) and the evolutionary stability of polymorphisms (e.g. how IATC can explain losses of one ART, and why this can lead to rapid speciation).

Antagonistic selection on body size and sword length in a wild population of the swordtail fish, Xiphophorus multilineatus: Potential for intralocus tactical conflict

Liotta

et al. 2021

Ecology and Evolution