An official website of the United States government
Abstract Baobabs (Adansonia) are a cohesive group of tropical trees with a disjunct distribution in Australia, Madagascar, and continental Africa, and diverse flowers associated with two pollination modes. We used custom-targeted sequence capture in conjunction with new and existing phylogenetic comparative methods to explore the evolution of floral traits and pollination systems while allowing for reticulate evolution. Our analyses suggest that relationships in Adansonia are confounded by reticulation, with network inference methods supporting at least one reticulation event. The best supported hypothesis involves introgression between Adansonia rubrostipa and core Longitubae, both of which are hawkmoth pollinated with yellow/red flowers, but there is also some support for introgression between the African lineage and Malagasy Brevitubae, which are both mammal-pollinated with white flowers. New comparative methods for phylogenetic networks were developed that allow maximum-likelihood inference of ancestral states and were applied to study the apparent homoplasy in floral biology and pollination mode seen in Adansonia. This analysis supports a role for introgressive hybridization in morphological evolution even in a clade with highly divergent and geographically widespread species. Our new comparative methods for discrete traits on species networks are implemented in the software PhyloNetworks. [Comparative methods; Hyb-Seq; introgression; network inference; population trees; reticulate evolution; species tree inference; targeted sequence capture.]
more »
« less
This content will become publicly available on March 1, 2026
Phylogenetic relationships and the repeated loss of traits associated with sicklebill pollination in Centropogon subgenus Centropogon (Campanulaceae)
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
- Award ID(s):
- 2055525
- PAR ID:
- 10611498
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 112
- Issue:
- 3
- ISSN:
- 0002-9122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
PremiseMultiple transitions from insect to wind pollination are associated with polyploidy and unisexual flowers inThalictrum(Ranunculaceae), yet the underlying genetics remains unknown. We generated a draft genome ofThalictrum thalictroides, a representative of a clade with ancestral floral traits (diploid, hermaphrodite, and insect pollinated) and a model for functional studies. Floral transcriptomes ofT. thalictroidesand of wind‐pollinated, andromonoeciousT. hernandeziiare presented as a resource to facilitate candidate gene discovery in flowers with different sexual and pollination systems. MethodsA draft genome ofT. thalictroidesand two floral transcriptomes ofT. thalictroidesandT. hernandeziiwere obtained from HiSeq 2000 Illumina sequencing and de novo assembly. ResultsTheT. thalictroidesde novo draft genome assembly consisted of 44,860 contigs (N50 = 12,761 bp, 243 Mbp total length) and contained 84.5% conserved embryophyte single‐copy genes. Floral transcriptomes contained representatives of most eukaryotic core genes, and most of their genes formed orthogroups. DiscussionTo validate the utility of these resources, potential candidate genes were identified for the different floral morphologies using stepwise data set comparisons. Single‐copy gene analysis and simple sequence repeat markers were also generated as a resource for population‐level and phylogenetic studies.more » « less
-
Abstract PremiseA central goal of pollination biology is to connect plants with the identity of their pollinator(s). While predictions based on floral syndrome traits are extremely useful, direct observation can reveal further details of a species' pollination biology. The wildflowerPhlox drummondiihas a floral syndrome consistent with pollination by Lepidoptera. We tested this prediction using empirical data. MethodsWe observed each step of pollination inP. drummondii. First, we observed 55.5 h of floral visitation across the species range. We used temporal pollinator exclusion to determine the contribution of diurnal and nocturnal pollination to reproductive output. We then quantifiedP. drummondiipollen transfer by the dominant floral visitor,Battus philenor. Finally, we tested the effect ofB. philenorvisitation onP. drummondiireproduction by quantifying fruit set following single pollinator visits. ResultsBattus philenoris the primary pollinator ofP. drummondii. Pollination is largely diurnal, and we observed a variety of lepidopteran visitors during the diurnal period. However,B. philenorwas the most frequent visitor, representing 88.5% of all observed visits. Our results show thatB. philenoris an extremely common visitor and also an effective pollinator by demonstrating that individuals transfer pollen between flowers and that a single visit can elicit fruit set. ConclusionsOur data are consistent with the prediction of lepidopteran pollination and further reveal a single butterfly species,B. philenor, as the primary pollinator. Our study demonstrates the importance of empirical pollinator observations, adds to our understanding of pollination mechanics, and offers a specific case study of butterfly pollination.more » « less
-
Abstract PremiseThe ~140 species ofLoniceraare characterized by variously fused leaves, bracteoles, and ovaries, making it a model system for studying the evolution and development of organ fusion. However, previous phylogenetic analyses, based mainly on chloroplast DNA markers, have yielded uncertain and conflicting results. A well‐supported phylogeny ofLonicerawill allow us to trace the evolutionary history of organ fusion. MethodsWe inferred the phylogeny ofLonicerausing restriction site–associated DNA sequencing (RADSeq), sampling all major clades and 18 of the 23 subsections. This provided the basis for inferring the evolution of five fusion‐related traits. ResultsRADSeq data yielded a well‐resolved and well‐supported phylogeny. The two traditionally recognized subgenera (PericlymenumandChamaecerasus), three of the four sections (Isoxylosteum,Coeloxylosteum, andNintooa), and half of the subsections sampled were recovered as monophyletic. However, the large and heterogeneous sectionIsikawas strongly supported as paraphyletic.Nintooa, a clade of ~22 mostly vine‐forming species, includingL. japonica, was recovered in a novel position, raising the possibility of cytonuclear discordance. We document the parallel evolution of fused leaves, bracteoles, and ovaries, with rare reversals. Most strikingly, complete cupules, in which four fused bracteoles completely enclose two unfused ovaries, arose at least three times. Surprisingly, these appear to have evolved directly from ancestors with free bracteoles instead of partial cupules. ConclusionsWe provide the most comprehensive and well‐supported phylogeny ofLonicerato date. Our inference of multiple evolutionary shifts in organ fusion provides a solid foundation for in depth developmental and functional analyses.more » « less
-
Abstract PremiseTo date, phylogenetic relationships within the monogeneric Brunelliaceae have been based on morphological evidence, which does not provide sufficient phylogenetic resolution. Here we use target‐enriched nuclear data to improve our understanding of phylogenetic relationships in the family. MethodsWe used the Angiosperms353 toolkit for targeted recovery of exonic regions and supercontigs (exons + introns) from low copy nuclear genes from 53 of 70 species inBrunellia, and several outgroup taxa. We removed loci that indicated biased inference of relationships and applied concatenated and coalescent methods to inferBrunelliaphylogeny. We identified conflicts among gene trees that may reflect hybridization or incomplete lineage sorting events and assessed their impact on phylogenetic inference. Finally, we performed ancestral‐state reconstructions of morphological traits and assessed the homology of character states used to define sections and subsections inBrunellia. ResultsBrunelliacomprises two major clades and several subclades. Most of these clades/subclades do not correspond to previous infrageneric taxa. There is high topological incongruence among the subclades across analyses. ConclusionsPhylogenetic reconstructions point to rapid species diversification in Brunelliaceae, reflected in very short branches between successive species splits. The removal of putatively biased loci slightly improves phylogenetic support for individual clades. Reticulate evolution due to hybridization and/or incomplete lineage sorting likely both contribute to gene‐tree discordance. Morphological characters used to define taxa in current classification schemes are homoplastic in the ancestral character‐state reconstructions. While target enrichment data allows us to broaden our understanding of diversification inBrunellia, the relationships among subclades remain incompletely understood.more » « less
