More Like this

1. Flower morphology as a predictor of pollination mode in a biotic to abiotic pollination continuum

   https://doi.org/10.1093/aob/mcad069  

   Martínez-Gómez, Jesús; Park, Seongjun; Hartogs, Samantha R; Soza, Valerie L; Park, SeonJoo; Di Stilio, Verónica S (May 2023, Annals of Botany)

   Abstract Background and Aims Wind pollination has evolved repeatedly in flowering plants, yet the identification of a wind pollination syndrome as a set of integrated floral traits can be elusive. Thalictrum (Ranunculaceae) comprises temperate perennial herbs that have transitioned repeatedly from insect to wind pollination while also exhibiting mixed pollination, providing an ideal system to test for evolutionary correlation between floral morphology and pollination mode in a biotic to abiotic continuum. Moreover, the lack of floral organ fusion across this genus additionally allows to test for specialization to pollination vectors in the absence of this feature. Methods We expanded phylogenetic sampling in the genus from a previous study using six chloroplast loci, which allowed us to test whether species cluster into distinct pollination syndromes based on floral morphology. We then used multivariate analyses on floral traits, followed by ancestral state reconstruction of the emerging flower morphotypes and determined whether these traits are evolutionarily correlated under a Bayesian framework with Brownian motion. Key Results Floral traits fell into five distinct clusters, which were reduced to three after considering phylogenetic relatedness, and were largely consistent with flower morphotypes and associated pollination vectors. Multivariate evolutionary analyses found a positive correlation between the lengths of floral reproductive structures (styles, stigmas, filaments, and anthers). Shorter reproductive structures tracked insect-pollinated species and clades in the phylogeny while longer structures tracked wind-pollinated ones, consistent with selective pressures exerted by biotic vs. abiotic pollination vectors, respectively. Conclusions While detectable suites of integrated floral traits across Thalictrum correlated with wind or insect pollination at the extremes of the morphospace distribution, a presumed intermediate, mixed pollination mode morphospace was also detected. Thus, our data broadly support the existence of detectable flower morphotypes from convergent evolution underlying pollination mode evolution in Thalictrum, presumably via different paths from an ancestral mixed pollination state. 

   more » « less
2. Ancient and recent introgression shape the evolutionary history of pollinator adaptation and speciation in a model monkeyflower radiation (Mimulus section Erythranthe)

   https://doi.org/10.1371/journal.pgen.1009095  

   Nelson, Thomas C.; Stathos, Angela M.; Vanderpool, Daniel D.; Finseth, Findley R.; Yuan, Yao-wu; Fishman, Lila (February 2021, PLOS Genetics)

   Buerkle, Alex (Ed.)

   Inferences about past processes of adaptation and speciation require a gene-scale and genome-wide understanding of the evolutionary history of diverging taxa. In this study, we use genome-wide capture of nuclear gene sequences, plus skimming of organellar sequences, to investigate the phylogenomics of monkeyflowers in Mimulus section Erythranthe (27 accessions from seven species ) . Taxa within Erythranthe , particularly the parapatric and putatively sister species M . lewisii (bee-pollinated) and M . cardinalis (hummingbird-pollinated), have been a model system for investigating the ecological genetics of speciation and adaptation for over five decades. Across >8000 nuclear loci, multiple methods resolve a predominant species tree in which M . cardinalis groups with other hummingbird-pollinated taxa (37% of gene trees), rather than being sister to M . lewisii (32% of gene trees). We independently corroborate a single evolution of hummingbird pollination syndrome in Erythranthe by demonstrating functional redundancy in genetic complementation tests of floral traits in hybrids; together, these analyses overturn a textbook case of pollination-syndrome convergence. Strong asymmetries in allele sharing (Patterson’s D-statistic and related tests) indicate that gene tree discordance reflects ancient and recent introgression rather than incomplete lineage sorting. Consistent with abundant introgression blurring the history of divergence, low-recombination and adaptation-associated regions support the new species tree, while high-recombination regions generate phylogenetic evidence for sister status for M . lewisii and M . cardinalis . Population-level sampling of core taxa also revealed two instances of chloroplast capture, with Sierran M . lewisii and Southern Californian M . parishii each carrying organelle genomes nested within respective sympatric M . cardinalis clades. A recent organellar transfer from M . cardinalis , an outcrosser where selfish cytonuclear dynamics are more likely, may account for the unexpected cytoplasmic male sterility effects of selfer M . parishii organelles in hybrids with M . lewisii . Overall, our phylogenomic results reveal extensive reticulation throughout the evolutionary history of a classic monkeyflower radiation, suggesting that natural selection (re-)assembles and maintains species-diagnostic traits and barriers in the face of gene flow. Our findings further underline the challenges, even in reproductively isolated species, in distinguishing re-use of adaptive alleles from true convergence and emphasize the value of a phylogenomic framework for reconstructing the evolutionary genetics of adaptation and speciation. 

   more » « less
3. Phylogenetic relationships and the repeated loss of traits associated with sicklebill pollination in Centropogon subgenus Centropogon (Campanulaceae)

   https://doi.org/10.1002/ajb2.70016  

   Mansaray, Janet K; Bedoya, Ana M; Frost, Laura A; Degreenia, Olivia C; Lagomarsino, Laura P (March 2025, American Journal of Botany)

   Abstract PremiseCentropogonsubgenusCentropogoncomprises 55 species found primarily in midelevation Andean forests featuring some of the most curved flowers among angiosperms. Floral curvature is linked to coevolution with the sicklebill hummingbird, which pollinates most species. Despite charismatic flowers, there is limited knowledge about the phylogenetic relationships and floral evolution. MethodsWe conducted the first densely sampled phylogenomic analysis of the clade using methods that account for incomplete lineage sorting on a sequence capture dataset generated with a lineage‐specific probe set. Using phylogenetic comparative methods, we test for correlated evolution of two traits central to sicklebill pollination. ResultsWe improve understanding of species relationships by more than doubling past taxon sampling. We confirm the monophyly of the subgenus and two sections, and the non‐monophyly of remaining sections. The subgenus is characterized by high gene tree discordance. Three widespread species display contrasting phylogenetic dynamics, withC. cornutusforming a clade andC. granulosusandC. solanifoliusforming non‐monophyletic, biogeographically clustered lineages. Correlated evolution of floral curvature and inflorescence structure has led to multiple putative losses of sicklebill pollination. ConclusionsCentropogonsubgenusCentropogonadds to a growing body of literature of Andean plant clades with high gene tree discordance. This phylogeny serves as a foundational framework for further macroevolutionary investigations into the environmental and biogeographic factors shaping the evolution of pollination‐related traits. 

   more » « less
4. Ecological Diversification in an Adaptive Radiation of Plants: The Role of De Novo Mutation and Introgression

   https://doi.org/10.1093/molbev/msae007  

   Stone, Benjamin W; Wessinger, Carolyn A (January 2024, Molecular Biology and Evolution)

   Josephs, Emily (Ed.)

   Abstract Adaptive radiations are characterized by rapid ecological diversification and speciation events, leading to fuzzy species boundaries between ecologically differentiated species. Adaptive radiations are therefore key systems for understanding how species are formed and maintained, including the role of de novo mutations versus preexisting variation in ecological adaptation and the genome-wide consequences of hybridization events. For example, adaptive introgression, where beneficial alleles are transferred between lineages through hybridization, may fuel diversification in adaptive radiations and facilitate adaptation to new environments. In this study, we employed whole-genome resequencing data to investigate the evolutionary origin of hummingbird-pollinated flowers and to characterize genome-wide patterns of phylogenetic discordance and introgression in Penstemon subgenus Dasanthera, a small and diverse adaptive radiation of plants. We found that magenta hummingbird-adapted flowers have apparently evolved twice from ancestral blue-violet bee-pollinated flowers within this radiation. These shifts in flower color are accompanied by a variety of inactivating mutations to a key anthocyanin pathway enzyme, suggesting that independent de novo loss-of-function mutations underlie the parallel evolution of this trait. Although patterns of introgression and phylogenetic discordance were heterogenous across the genome, a strong effect of gene density suggests that, in general, natural selection opposes introgression and maintains genetic differentiation in gene-rich genomic regions. Our results highlight the importance of both de novo mutation and introgression as sources of evolutionary change and indicate a role for de novo mutation in driving parallel evolution in adaptive radiations. 

   more » « less
5. Within-species floral evolution reveals convergence in adaptive walks during incipient pollinator shift

   https://doi.org/10.1038/s41467-025-57639-3  

   Wenzell, Katherine E; Neequaye, Mikhaela; Paajanen, Pirita; Hill, Lionel; Brett, Paul; Byers, Kelsey_J_R P (March 2025, Nature Communications)

   Abstract Understanding how evolution proceeds from molecules to organisms to interactions requires integrative studies spanning biological levels. Linking phenotypes with associated genes and fitness illuminates how adaptive walks move organisms between fitness peaks. Floral evolution can confer rapid reproductive isolation, often converging in association with pollinator guilds. Within the monkeyflowers (Mimulussect.Erythranthe), yellow flowers within red hummingbird-pollinated species have arisen at least twice, suggesting possible pollinator shifts. We compare two yellow-flowered forms ofM. cardinalisandM. verbenaceusto their red counterparts in floral phenotypes, biochemistry, transcriptomic and genomic variation, and pollinator interactions. We find convergence in ongoing adaptive walks of both yellow morphs, with consistent changes in traits of large effect (floral pigments, associated gene expression), resulting in strong preference for yellow flowers by bumblebees. Shifts in scent emission and floral opening size also favor bee adaptation, suggesting smaller-effect steps from hummingbird to bee pollination. By examining intraspecific, incipient pollinator shifts in two related species, we elucidate adaptive walks at early stages, revealing how convergent large effect mutations (floral color) may drive pollinator attraction, followed by smaller effect changes for mechanical fit and reward access. Thus, ongoing adaptive walks may impact reproductive isolation and incipient speciation via convergent evolution. 

   more » « less