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1. CHD chromatin remodeling protein diversification yields novel clades and domains absent in classic model organisms

   https://doi.org/10.1093/gbe/evac066  

   Trujillo, Joshua T.; Long, Jiaxin; Aboelnour, Erin; Ogas, Joseph; Wisecaver, Jennifer H. (May 2022, Genome Biology and Evolution)

   Hoffmann, Federico (Ed.)

   Chromatin remodelers play a fundamental role in the assembly of chromatin, regulation of transcription, and DNA repair. Biochemical and functional characterization of the CHD family of chromatin remodelers from a variety of model organisms have shown that these remodelers participate in a wide range of activities. However, because the evolutionary history of CHD homologs is unclear, it is difficult to predict which of these activities are broadly conserved and which have evolved more recently in individual eukaryotic lineages. Here, we performed a comprehensive phylogenetic analysis of 8,042 CHD homologs from 1,894 species to create a model for the evolution of this family across eukaryotes with a particular focus on the timing of duplications that gave rise to the diverse copies observed in plants, animals, and fungi. Our analysis confirms that the three major subfamilies of CHD remodelers originated in the eukaryotic last common ancestor, and subsequent losses occurred independently in different lineages. Improved taxon sampling identified several subfamilies of CHD remodelers in plants that were absent or highly divergent in the model plant Arabidopsis thaliana. Whereas the timing of CHD subfamily expansions in vertebrates correspond to whole genome duplication events, the mechanisms underlying CHD diversification in land plants appears more complicated. Analysis of protein domains reveals that CHD remodeler diversification has been accompanied by distinct transitions in domain architecture, contributing to the functional differences observed between these remodelers. This study demonstrates the importance of proper taxon sampling when studying ancient evolutionary events to prevent misinterpretation of subsequent lineage-specific changes and provides an evolutionary framework for functional and comparative analysis of this critical chromatin remodeler family across eukaryotes. 

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2. Macroevolutionary inference of complex modes of chromosomal speciation in a cosmopolitan plant lineage

   https://doi.org/10.1111/nph.20353  

   Tribble, Carrie_M; Márquez‐Corro, José_Ignacio; May, Michael_R; Hipp, Andrew_L; Escudero, Marcial; Zenil‐Ferguson, Rosana (December 2024, New Phytologist)

   Summary The effects of single chromosome number change—dysploidy – mediating diversification remain poorly understood. Dysploidy modifies recombination rates, linkage, or reproductive isolation, especially for one‐fifth of all eukaryote lineages with holocentric chromosomes. Dysploidy effects on diversification have not been estimated because modeling chromosome numbers linked to diversification with heterogeneity along phylogenies is quantitatively challenging.We propose a new state‐dependent diversification model of chromosome evolution that links diversification rates to dysploidy rates considering heterogeneity and differentiates between anagenetic and cladogenetic changes. We apply this model toCarex(Cyperaceae), a cosmopolitan flowering plant clade with holocentric chromosomes.We recover two distinct modes of chromosomal evolution and speciation inCarex. In one diversification mode, dysploidy occurs frequently and drives faster diversification rates. In the other mode, dysploidy is rare, and diversification is driven by hidden, unmeasured factors. When we use a model that excludes hidden states, we mistakenly infer a strong, uniformly positive effect of dysploidy on diversification, showing that standard models may lead to confident but incorrect conclusions about diversification.This study demonstrates that dysploidy can have a significant role in speciation in a large plant clade despite the presence of other unmeasured factors that simultaneously affect diversification. 

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3. Longer telomeres during early life predict higher lifetime reproductive success in females but not males

   https://doi.org/10.1098/rspb.2021.0560  

   Heidinger, Britt J.; Kucera, Aurelia C.; Kittilson, Jeff D.; Westneat, David F. (May 2021, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   The mechanisms that contribute to variation in lifetime reproductive success are not well understood. One possibility is that telomeres, conserved DNA sequences at chromosome ends that often shorten with age and stress exposures, may reflect differences in vital processes or influence fitness. Telomere length often predicts longevity, but longevity is only one component of fitness and little is known about how lifetime reproductive success is related to telomere dynamics in wild populations. We examined the relationships between telomere length beginning in early life, telomere loss into adulthood and lifetime reproductive success in free-living house sparrows ( Passer domesticus ). We found that females, but not males, with longer telomeres during early life had higher lifetime reproductive success, owing to associations with longevity and not reproduction per year or attempt. Telomeres decreased with age in both sexes, but telomere loss was not associated with lifetime reproductive success. In this species, telomeres may reflect differences in quality or condition rather than the pace of life, but only in females. Sexually discordant selection on telomeres is expected to influence the stability and maintenance of within population variation in telomere dynamics and suggests that any role telomeres play in mediating life-history trade-offs may be sex specific. 

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4. Does gene flow aggravate or alleviate maladaptation to environmental stress in small populations?

   https://doi.org/10.1111/eva.12768  

   Fitzpatrick, Sarah W.; Reid, Brendan N. (February 2019, Evolutionary Applications)

   Abstract Environmental change can expose populations to unfamiliar stressors, and maladaptive responses to those stressors may result in population declines or extirpation. Although gene flow is classically viewed as a cause of maladaptation, small and isolated populations experiencing high levels of drift and little gene flow may be constrained in their evolutionary response to environmental change. We provide a case study using the model Trinidadian guppy system that illustrates the importance of considering gene flow and genetic drift when predicting (mal)adaptive response to acute stress. We compared population genomic patterns and acute stress responses of inbred guppy populations from headwater streams either with or without a recent history of gene flow from a more diverse mainstem population. Compared to “no‐gene flow” analogues, we found that populations with recent gene flow showed higher genomic variation and increased stress tolerance—but only when exposed to a stress familiar to the mainstem population (heat shock). All headwater populations showed similar responses to a familiar stress in headwater environments (starvation) regardless of gene flow history, whereas exposure to an entirely unfamiliar stress (copper sulfate) showed population‐level variation unrelated to environment or recent evolutionary history. Our results suggest that (mal)adaptive responses to acutely stressful environments are determined in part by recent evolutionary history and in part by previous exposure. In some cases, gene flow may provide the variation needed to persist, and eventually adapt, in the face of novel stress. 

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5. Differential effects of pollen nutritional quality on male and female reproductive success within a diverse co‐flowering community

   https://doi.org/10.1111/1365-2435.14703  

   Russo, Laura; Carneiro, Liedson Tavares; Williams, Jessica N; Barker, Daniel A; Murray, Anne; Arceo‐Gómez, Gerardo (January 2025, Functional Ecology)

   Abstract Pollen protein content has been demonstrated to be an essential nutritional component for bees and thus important in mediating plant–pollinator interactions. However, little is known on the drivers and consequences of among‐species variation in pollen protein content and how this can impact male and female reproductive success across plant species. Among‐species variation in resources allocated to pollen nutrition could further be constrained by life‐history strategies (e.g. survival‐reproduction trade‐offs) or evolutionary history.Here, we surveyed pollen protein content for 29 species within a diverse co‐flowering community and evaluated the effect of pollen protein on male and female reproductive success. We also tested the role of life history (annuals vs. perennials) and phylogeny in mediating differences in resource allocation to pollen nutrition.We found that pollen protein content influences components of male (bee visitor abundance and pollen dispersal) but not female (conspecific pollen deposition and pollen tube growth) reproductive success, suggesting this trait affects plants only via male function. This sex‐specific effect further suggests the potential for sexual conflicts driven by differential investment on this trait. We found no phylogenetic signal on pollen protein content. However, pollen protein content was higher in annual compared to perennial species suggesting survival versus reproduction trade‐offs also contribute to variation in pollen protein at the community level.Our study underscores the importance of understanding the ecological and evolutionary drivers of pollen protein content across plant species. Our results further suggest the existence of sexual conflicts and ecological trade‐offs mediated by differential investment in pollen nutritional quality, with important implications for community assembly and the structure of plant–pollinator interactions. Read the freePlain Language Summaryfor this article on the Journal blog. 

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