Ecologically-mediated selection against hybrids, caused by hybrid phenotypes fitting poorly into available niches, is typically viewed as distinct from selection caused by epistatic Dobzhansky-Muller hybrid incompatibilities. Here, we illustrate how selection against transgressive phenotypes in hybrids manifests as incompatibility.  After outlining our logic, we summarize current approaches for studying ecology-based selection on hybrids. We then quantitatively review QTL-mapping studies and find traits differing between parent taxa are typically polygenic. Next, we describe how verbal models of selection on hybrids translate to phenotypic and genetic fitness landscapes, highlighting emerging approaches for detecting polygenic incompatibilities. Finally, in a synthesis of published data, we report that trait transgression—and thus possibly extrinsic hybrid incompatibility—in hybrids escalates with the phenotypic divergence between parents. We discuss conceptual implications and conclude that studying the ecological basis of hybrid incompatibility will facilitate new discoveries about mechanisms of speciation.

Full methods / details about data collection are given in the supplementary materials (within repository).

The dataset contains raw data and analysis/simulation code for three quantitative 'vignettes' within the paper. Two are syntheses of existing data, and one is an original small-scale simulation study.

For the analysis of transgression, raw trait data for hybrids from each study are included. For the analysis of QTL, summary tables from papers are reproduced.

Other authors on the paper transcribed QTL tables and produced referential datasheets, but KAT curated and checked all data and bears sole responsibility for any and all inconsistencies.

'R' v 4.1.2
        package 'broom' v 0.7.12
        package 'cowplot' v 1.1.1
        package 'ggforce' v 0.3.3
        package 'metafor' v 3.8-1
        package 'tidyverse' v 1.3.1
Admix'em v 1.0.2.3