Opposing dominance within a color gene block is associated with maladaptive hybrid signal discordance

AbstractColor divergence is increasingly recognized as important for speciation in songbirds through its influence on social dynamics. However, the behavioral mechanisms underlying the eco-evolutionary feedback that acts across species boundaries is poorly understood. The hybrid zone between Setophaga occidentalis (SOCC) and S. townsendi (STOW) in the Cascade mountain ranges provides a natural observatory to test the interplay between genetics and social behaviour in maintaining species boundaries. Recently, we found that selection within a gene block underpinning color variation (ASIP-RALY) has maintained a stable and narrow hybrid zone. Here we investigated the social signaling roles of cheek darkness and flank streaking, two color traits linked to ASIP-RALY that reflect opposing dominance of SOCC and STOW alleles. We found that both traits act as honest badges of status, as they predicted male breeding quality. The opposing dominance effects of ASIP-RALY resulted in signal discordance for heterozygotes, which in turn was associated with inferior hybrid territorial performance, a fitness proxy quantified by vocal and physical responses of resident males to a decoy intruder. Taken together, this study highlights a potential behavioral mechanism underlying selection acting on a simple genetic architecture that has maintained a stable species boundary over decades despite significant gene flow.

Download Full-text

Formation of a recent hybrid zone offers insight into the geographic puzzle and maintenance of species boundaries in musk turtles

Molecular Ecology ◽

10.1111/mec.14983 ◽

2019 ◽

Vol 28 (4) ◽

pp. 761-771 ◽

Cited By ~ 1

Author(s):

Peter A. Scott ◽

Travis C. Glenn ◽

Leslie J. Rissler

Keyword(s):

Hybrid Zone ◽

Species Boundaries ◽

Insight Into

Download Full-text

Genomic Adaptations to Salinity Resist Gene Flow in the Evolution of Floridian Watersnakes

Molecular Biology and Evolution ◽

10.1093/molbev/msaa266 ◽

2020 ◽

Author(s):

Rhett M Rautsaw ◽

Tristan D Schramer ◽

Rachel Acuña ◽

Lindsay N Arick ◽

Mark DiMeo ◽

...

Keyword(s):

Gene Flow ◽

Isolation By Distance ◽

Species Boundaries ◽

Selective Pressures ◽

Nerodia Fasciata ◽

Isolation By Environment ◽

Significant Gene ◽

Candidate Loci ◽

Osmoregulatory Function ◽

Ecological Differences

Abstract The migration-selection balance often governs the evolution of lineages, and speciation with gene flow is now considered common across the tree of life. Ecological speciation is a process that can facilitate divergence despite gene flow due to strong selective pressures caused by ecological differences; however, the exact traits under selection are often unknown. The transition from freshwater to saltwater habitats provides strong selection targeting traits with osmoregulatory function. Several lineages of North American watersnakes (Nerodia spp.) are known to occur in saltwater habitat and represent a useful system for studying speciation by providing an opportunity to investigate gene flow and evaluate how species boundaries are maintained or degraded. We use double digest restriction-site associated DNA sequencing to characterize the migration-selection balance and test for evidence of ecological divergence within the Nerodia fasciata-clarkii complex in Florida. We find evidence of high intraspecific gene flow with a pattern of isolation-by-distance underlying subspecific lineages. However, we identify genetic structure indicative of reduced gene flow between inland and coastal lineages suggesting divergence due to isolation-by-environment. This pattern is consistent with observed environmental differences where the amount of admixture decreases with increased salinity. Furthermore, we identify significantly enriched terms related to osmoregulatory function among a set of candidate loci, including several genes that have been previously implicated in adaptation to salinity stress. Collectively, our results demonstrate that ecological differences, likely driven by salinity, cause strong divergent selection which promotes divergence in the N. fasciata-clarkii complex despite significant gene flow.

Download Full-text

The role of hybridization during ecological divergence of southwestern white pine (Pinus strobiformis) and limber pine (P. flexilis)

10.1101/185728 ◽

2017 ◽

Author(s):

Mitra Menon ◽

Justin C. Bagley ◽

Christopher Friedline ◽

Amy V. Whipple ◽

Anna W. Schoettle ◽

...

Keyword(s):

Gene Flow ◽

Hybrid Zone ◽

Ecological Niche Modeling ◽

Life History Strategies ◽

Species Boundaries ◽

Disruptive Selection ◽

Hybrid Index ◽

Extrinsic Factors ◽

Intrinsic Factors ◽

Demographic Modeling

AbstractInteractions between extrinsic factors, such as disruptive selection, and intrinsic factors, such as genetic incompatibilities among loci, can contribute to the maintenance of species boundaries. The relative roles of these factors in the establishment of reproductive isolation can be examined using species pairs characterized by gene flow throughout their divergence history. We investigated the process of speciation and the maintenance of species boundaries between Pinus strobiformis and P.flexilis. Utilizing ecological niche modeling, demographic modeling, and genomic cline analyses, we illustrated a history of divergence with continuous gene flow between these species. We found an abundance of advanced generation hybrids and a lack of loci exhibiting large allele frequency differences across the hybrid zone. Additionally, we found evidence for climate-associated variation in the hybrid index and niche divergence between parental species and the hybrid zone. Our results are consistent with extrinsic factors, such as climate, being an important isolating mechanism for these species. A buildup of intrinsic incompatibilities and of co-adapted gene complexes is also apparent in our results, although these appear to be in the earliest stages of development. This supports previous work in coniferous species demonstrating the importance of extrinsic factors in creating and enforcing species boundaries. Overall, we lend support to the hypothesis that varying strengths and directions of selection pressures across the long lifespans of conifers, in combination with their life history strategies, delay the evolution of strong intrinsic incompatibilities.

Download Full-text

Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zone

BMC Evolutionary Biology ◽

10.1186/s12862-016-0635-y ◽

2016 ◽

Vol 16 (1) ◽

Cited By ~ 21

Author(s):

Jennifer Walsh ◽

W. Gregory Shriver ◽

Brian J. Olsen ◽

Adrienne I. Kovach

Keyword(s):

Hybrid Zone ◽

Species Boundaries ◽

Advanced Generation

Download Full-text

HYBRID ZONE ORIGINS, SPECIES BOUNDARIES, AND THE EVOLUTION OF WING-PATTERN DIVERSITY IN A POLYTYPIC SPECIES COMPLEX OF NORTH AMERICAN ADMIRAL BUTTERFLIES (NYMPHALIDAE: LIMENITIS)

Evolution ◽

10.1111/j.1558-5646.2008.00366.x ◽

2008 ◽

Vol 62 (6) ◽

pp. 1400-1417 ◽

Cited By ~ 33

Author(s):

Sean P. Mullen ◽

Erik B. Dopman ◽

Richard G. Harrison

Keyword(s):

Hybrid Zone ◽

North American ◽

Species Complex ◽

Species Boundaries ◽

Wing Pattern ◽

Pattern Diversity

Download Full-text

The Fragility of Intergroup Relations

Psychological Science ◽

10.1111/j.1467-9280.2008.02236.x ◽

2008 ◽

Vol 19 (12) ◽

pp. 1272-1279 ◽

Cited By ~ 56

Author(s):

Adam R. Pearson ◽

Tessa V. West ◽

John F. Dovidio ◽

Stacie Renfro Powers ◽

Ross Buck ◽

...

Keyword(s):

Real Time ◽

Social Dynamics ◽

Minority Groups ◽

Intergroup Contact ◽

Delay Condition ◽

Response Delay ◽

Intergroup Communication ◽

Intergroup Interactions ◽

Behavioral Mechanism ◽

Practical Implications

Intergroup interactions between racial or ethnic majority and minority groups are often stressful for members of both groups; however, the dynamic processes that promote or alleviate tension in intergroup interaction remain poorly understood. Here we identify a behavioral mechanism—response delay—that can uniquely contribute to anxiety and promote disengagement from intergroup contact. Minimally acquainted White, Black, and Latino participants engaged in intergroup or intragroup dyadic conversation either in real time or with a subtle temporal disruption (1-s delay) in audiovisual feedback. Whereas intergroup dyads reported greater anxiety and less interest in contact after engaging in delayed conversation than after engaging in real-time conversation, intragroup dyads reported less anxiety in the delay condition than they did after interacting in real time. These findings have theoretical and practical implications for understanding intergroup communication and social dynamics and for promoting positive intergroup contact.

Download Full-text

Stable Species Boundaries Despite Ten Million Years of Hybridization in Tropical Eels

10.1101/635631 ◽

2019 ◽

Author(s):

Julia M. I. Barth ◽

Chrysoula Gubili ◽

Michael Matschiner ◽

Ole K. Tørresen ◽

Shun Watanabe ◽

...

Keyword(s):

Sequence Data ◽

F1 Hybrids ◽

Species Boundaries ◽

Hybrid Breakdown ◽

Genome Wide ◽

Dynamic Scenario ◽

Stable Species ◽

Species Pairs ◽

History Of ◽

Tropical Eels

AbstractGenomic evidence is increasingly underpinning that hybridization between taxa is commonplace, challenging our views on the mechanisms that maintain their boundaries. Here, we focus on seven catadromous eel species (genusAnguilla), and use genome-wide sequence data from more than 450 individuals sampled across the tropical Indo-Pacific, morphological information, and three newly assembled draft genomes to compare contemporary patterns of hybridization with signatures of past gene flow across a time-calibrated phylogeny. We show that the seven species have remained distinct entities for up to 10 million years, despite a dynamic scenario of incomplete isolation whereby the current frequencies of hybridization across species pairs (over 5% of all individuals were either F1 hybrids or backcrosses) contrast remarkably with patterns of past introgression. Based on near-complete asymmetry in the directionality of hybridization and decreasing frequencies of later-generation hybrids, we identify cytonuclear incompatibilities and hybrid breakdown as two powerful mechanisms that can support species cohesion even when hybridization has been pervasive throughout the evolutionary history of entire clades.

Download Full-text