Parallel patterns of development between independent cases of hybrid seed inviability in Mimulus

Abstract

6 7 Author Contributions: JMC designed this project design, performed data collection and 8 analysis, and wrote the manuscript. JHW contributed substantially to the ideas presented here 9 and the project design. Summary 25 Rationale: Hybrid seed inviability (HSI) is a common reproductive barrier in angiosperms, yet the 26 evolutionary and developmental drivers of HSI remain largely unknown. We test whether conflict 27 between maternal and paternal interests in resource allocation to developing offspring (i.e. 28 parental conflict) are associated with HSI and determine the degree of developmental parallelism 29 between independent incidences of HSI in Mimulus. 30 Methods: We quantified HSI between M. guttatus and two clades of M. decorus with oppositely 31 asymmetric incompatibilities and surveyed development of hybrid and parental seeds.32 Key Results: Crosses between M. guttatus and both clades of M. decorus show parent-of-origin 33 effects on reciprocal F1 seed development, but in opposing directions. Inviable hybrid seeds exhibit 34 paternal excess phenotypes, wherein endosperm is large and chaotic while viable hybrid seeds 35 produce endosperm cells that are smaller and less prolific (i.e. maternal-excess phenotypes).36 Main Conclusions: We find strong parent-of-origin effects on development in reciprocal F1s in 37 multiple incidences of HSI in Mimulus. These patterns suggest that parental conflict may be an 38 important force generating HSI in this group, and mismatches between maternal and paternal 39 contributions to developing seeds result in repeatable developmental defects in hybrids. 40 41 42 43 44 45 46 47 3 48

Asymmetric reinforcement inLucaniakillifish: assessing reproductive isolation when both sexes choose

“…In addition to the effects of classic sexual selection/mating system biology, the nature of postzygotic isolation can also create costs and benefits of choosing and courting that are unique to hybridization between species ( Coyne and Orr 2004 ). Asymmetric postzygotic isolation is common and occurs when hybrids in one direction (e.g., female A × male B) have lower fitness than hybrids in another direction (e.g., female B × male A), and empirical examples of these types of costs have been documented in insects ( Shapiro 2006 ; Hochkirch and Lemke 2011 ; Sánchez-Guillén et al 2012 ; Yukilevich 2012 ), fish ( Crow et al 2007 ; Van Der Sluijs et al 2008 ; Martin and Mendelson 2013 ), mammals ( Smadja and Ganem 2005 ; Beysard et al 2015 ; Shipley et al 2016 ), amphibians ( Pfennig and Simovich 2002 ; Arntzen et al 2009 ), and plants ( Tiffin et al 2001 ; Ramsey et al 2003 ; Coughlan and Willis 2018 ). In these scenarios, the expectation is that BI will be concordant with the direction of postzygotic isolation (i.e., females of species A and males of species B will be less likely to engage in hybrid matings than females of species B and males of species A).…”