Herbivory is an ecological process that is known to generate different patterns of selection on defensive plant traits across populations. Studies on this topic could greatly benefit from the general ...framework of the Geographic Mosaic Theory of Coevolution (GMT). Here, we hypothesize that herbivory represents a strong pressure for extrafloral nectary (EFN) bearing plants, with differences in herbivore and ant visitor assemblages leading to different evolutionary pressures among localities and ultimately to differences in EFN abundance and function. In this study, we investigate this hypothesis by analyzing 10 populations of Anemopaegma album (30 individuals per population) distributed through ca. 600 km of Neotropical savanna and covering most of the geographic range of this plant species. A common garden experiment revealed a phenotypic differentiation in EFN abundance, in which field and experimental plants showed a similar pattern of EFN variation among populations. We also did not find significant correlations between EFN traits and ant abundance, herbivory and plant performance across localities. Instead, a more complex pattern of ant-EFN variation, a geographic mosaic, emerged throughout the geographical range of A. album. We modeled the functional relationship between EFNs and ant traits across ant species and extended this phenotypic interface to characterize local situations of phenotypic matching and mismatching at the population level. Two distinct types of phenotypic matching emerged throughout populations: (1) a population with smaller ants (Crematogaster crinosa) matched with low abundance of EFNs; and (2) seven populations with bigger ants (Camponotus species) matched with higher EFN abundances. Three matched populations showed the highest plant performance and narrower variance of EFN abundance, representing potential plant evolutionary hotspots. Cases of mismatched and matched populations with the lowest performance were associated with abundant and highly detrimental herbivores. Our findings provide insights on the ecology and evolution of plant-ant guarding systems, and suggest new directions to research on facultative mutualistic interactions at wide geographic scales.
Wallace's riverine barrier hypothesis postulates that large rivers, such as the Amazon and its tributaries, reduce or prevent gene flow between populations on opposite banks, leading to allopatry and ...areas of species endemism occupying interfluvial regions. Several studies have shown that two major tributaries, Rio Branco and Rio Negro, are important barriers to gene flow for birds, amphibians and primates. No botanical studies have considered the potential role of the Rio Branco as a barrier, while a single botanical study has evaluated the Rio Negro as a barrier. We studied an Amazon shrub, Amphirrhox longifolia (A. St.‐Hil.) Spreng (Violaceae), as a model to test the riverine barrier hypothesis. Twenty‐six populations of A. longifolia were sampled on both banks of the Rio Branco and Rio Negro in the core Amazon Basin. Double‐digest RADseq was used to identify 8,010 unlinked SNP markers from the nuclear genome of 156 individuals. Data relating to population structure support the hypothesis that the Rio Negro acted as a significant genetic barrier for A. longifolia. On the other hand, no genetic differentiation was detected among populations spanning the narrower Rio Branco, which is a tributary of the Rio Negro. This study shows that the strength of riverine barriers for Amazon plants is dependent on the width of the river separating populations and species‐specific dispersal traits. Future studies of plants with contrasting life history traits will further improve our understanding of the landscape genetics and allopatric speciation history of Amazon plant diversity.
Species of Tanaecium (Bignonieae, Bignoniaceae) are lianas distributed in the Neotropics and centered in the Amazon. Members of the genus exhibit exceptionally diverse flower morphology and ...pollination systems. Here, we sequenced, assembled, and annotated 12 complete and four partial chloroplast genomes representing 15 Tanaecium species and more than 70% of the known diversity in the genus. Gene content and order were similar in all species of Tanaecium studied, with genome sizes ranging between 158,470 and 160,935 bp. Tanaecium chloroplast genomes have 137 genes, including 80-81 protein-coding genes, 37 tRNA genes, and four rRNA genes. No rearrangements were found in Tanaecium plastomes, but two different patterns of boundaries between regions were recovered. Tanaecium plastomes show nucleotide variability, although only rpoA was hypervariable. Multiple SSRs and repeat regions were detected, and eight genes were found to have signatures of positive selection. Phylogeny reconstruction using 15 Tanaecium plastomes resulted in a strongly supported topology, elucidating several relationships not recovered previously and bringing new insights into the evolution of the genus.
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•First densely sampled, genome-based, time-calibrated phylogeny of Amphilophium.•First split was between an Amazonian and an Atlantic forest clades, ca. 28.4 Ma.•Atlantic forest clade ...diversified first, ca. 25.8 Ma, following multiple movements.•Amazonian clade diversified at ca. 7.2 Ma followed by in situ speciation events.•Late Paleogene/Neogene geological and climatic changes influenced diversification.
The mechanisms and processes underlying patterns of species distributions have intrigued ecologists and biogeographers for a long time. The Neotropics is the most species-rich region in the World, representing an excellent model for studying the drivers of diversification. In this study, we used a phylogenomic approach to infer relationships and examine the role of major geological and climatic events in shaping biogeographic patterns within Amphilophium (Bignonieae, Bignoniaceae), a genus of Neotropical lianas. Even though Amphilophium is broadly distributed across the Neotropics, it is centered in Amazonia and the Atlantic rainforest. We generated nearly-complete plastome sequences for 32 species of Amphilophium, representing 70% of the species diversity in the genus. The final dataset included 78 plastid-coding regions and was analyzed under Maximum Likelihood and Bayesian approaches to reconstruct the phylogeny of Amphilophium. We also used this dataset to estimate divergence times using a Bayesian relaxed-clock approach. We further inferred ancestral ranges, migration events, and shifts in diversification rates using a branch-specific diversification model and the Dispersal-Extinction-Cladogenesis (DEC) model implemented in a Bayesian phylogenetic framework. Overall, we obtained a well-resolved and strongly supported phylogeny for Amphilophium, with five main clades that are well characterized by morphological features. Amphilophium originated in the Early Oligocene, and started to diversify in the Late Oligocene. The first diversification event involved a split between Amazonian and Atlantic forest clades. These two clades showed very different diversification scenarios. Divergence within the Atlantic forest clade began in the Mid-Oligocene, while the Amazonian clade underwent rapid diversification starting in the Late Miocene. In-situ speciation characterized the Amazonian clade, whereas allopatric speciation driven by migration events into other Neotropical biomes were mostly inferred within the Atlantic forest clade. The diversification of Amphilophium in the Neotropics was triggered by major geological events and changes in landscape that occurred during the Late Paleogene and Neogene, with little influence of the climatic changes of the Pleistocene ice ages. The divergence times and range inferences support the role of the Western Amazonian “megawetlands” and the formation of the South American “dry diagonal” as key climatic and geological barriers that separated the Atlantic forest from the Amazonian lowlands. Timing of migration events agrees with a Mid-Miocene closure of the Central American Seaway.
Seed dispersal is crucial to gene flow among plant populations. Although the effects of geographic distance and barriers to gene flow are well studied in many systems, it is unclear how seed ...dispersal mediates gene flow in conjunction with interacting effects of geographic distance and barriers. To test whether distinct seed dispersal modes (i.e., hydrochory, anemochory, and zoochory) have a consistent effect on the level of genetic connectivity (i.e., gene flow) among populations of riverine plant species, we used unlinked single-nucleotide polymorphisms (SNPs) for eight co-distributed plant species sampled across the Rio Branco, a putative biogeographic barrier in the Amazon basin. We found that animal-dispersed plant species exhibited higher levels of genetic diversity and lack of inbreeding as a result of the stronger genetic connectivity than plant species whose seeds are dispersed by water or wind. Interestingly, our results also indicated that the Rio Branco facilitates gene dispersal for all plant species analyzed, irrespective of their mode of dispersal. Even at a small spatial scale, our findings suggest that ecology rather than geography play a key role in shaping the evolutionary history of plants in the Amazon basin. These results may help improve conservation and management policies in Amazonian riparian forests, where degradation and deforestation rates are high.
Bignoniaceae are woody, trees, shrubs, and lianas found in all tropical floras of the world with lesser representation in temperate regions. Phylogenetic analyses of chloroplast sequences (rbcL, ...ndhF, trnL-F) were undertaken to infer evolutionary relationships in Bignoniaceae and to revise its classification. Eight clades are recognized as tribes (Bignonieae, Catalpeae, Coleeae, Crescentieae, Jacarandeae, Oroxyleae, Tecomeae, Tourrettieae); additional inclusive clades are named informally. Jacarandeae and Catalpeae are resurrected; the former is sister to the rest of the family, and the latter occupies an unresolved position within the "core" Bignoniaceae. Tribe Eccremocarpeae is included in Tourrettieae. Past classifications recognized a large Tecomeae, but this tribe is paraphyletic with respect to all other tribes. Here Tecomeae are reduced to a clade of approximately 12 genera with a worldwide distribution in both temperate and tropical ecosystems. Two large clades, Bignonieae and Crescentiina, account for over 80% of the species in the family. Coleeae and Crescentieae are each included in larger clades, the Paleotropical alliance and Tabebuia alliance, respectively; each alliance includes a grade of taxa assigned to the traditional Tecomeae. Parsimony inference suggests that the family originated in the neotropics, with at least five dispersal events leading to the Old World representatives.
The history of classification of the tribe Bignonieae and its genera are reviewed as context for a comprehensive new genus-level classification of the tribe Bignonieae (Bignoniaceae, Lamiales). This ...new classification is based on a well-supported phylogeny based on multiple molecular markers from both chloroplast and nuclear DNA, a morphological survey, and a broad sampling of taxa. Genera are circumscribed here as clades that are well supported as monophyletic by molecular data and also recognizable by one or more morphological synapomorphies. Perianthomega Bureau ex Baill. is here transferred from Bignoniaceae tribe Tecomeae into Bignonieae, and 21 genera and a total of 393 species are recognized in Bignonieae: Adenoccdymma Mart, ex Meisn. (82 species), Amphilophium Kunth (47), Anemopaegma Mart, ex Meisn. (45), Bignonia L. (28), Callichlamys Miq. (1), Cuspidaria DC. (19), Dolichandra Cham. (8), Fridericia Mart. (67), Lundia DC. (13), Manaosella J. C. Gomes (1), Mansoa DC. (12), Martinella · Baill. (2), Neojobertia Baill. (2), Pachyptera DC. ex Meisn. (4), Perianthomega (1), Pleonotoma Miers (17), Pyrostegia C. Presl (2), Stizophyllum Miers (3), Tanaecium Sw. (17), Tynanthus Miers (15), and Xylopkragma Sprague (7). Several genera are here circumscribed differently from previous classifications, in particular Memora Miers and Sampaiella J. C. Gomes are synonymized with Adenocalymma; Distictella Kuntze, Dktictis Mart, ex Meisn., Glaziova Bureau, Pithecoctenium Mart. ex DC., and Urbanolophium Melch. are synonymized with Amphüophium; Cydista Miers, Clytostoma Miers ex Bureau, Macranthisiphon Bureau ex K. Schum., Mussatia Bureau ex Baill., Phryganocydia Mart, ex Bureau, Potamoganos Sandwith, Roentgenia Urb., and Saritaea Dugand are synonymized with Bignonia; Macfadyena A. DC, Melloa Bureau, and Parabignonia Bureau ex K. Schum. are synonymized with Dolichandra; Arrabidaea DC. is synonymized with Fridericia; Gardnerodoxa Sandwith is synonymized with Neojobertia; Leucocalantha Barb. Rodr. is synonymized with Pachyptera; and Ceratophytum Pittier, Periarrabidaea A. Samp., Paragonia Bureau, Pseudocatalpa A. H. Gentry, and Spathicalyx J. C. Gomes are synonymized with Tanaecium. The genera Adenocalymma, Amphilophium, Fridericia, Dolichandra, and Tanaecium are formally emended here as to diagnosis and circumscription. A natural key, complete morphological descriptions, and illustrations characterize the accepted genera, and full generic synonymy and a catalogue of their component species summarize their basic nomenclature and geographic range. Three new names are published: B. neouliginosa L. G. Lohmann replaces Phryganocydia uliginosa Dugand; B. neoheterophylla L. G. Lohmann replaces Cydista heterophytta Seibert; and Tanaecium neobrasiliense L. G. Lohmann replaces Sanhilaria brasiliensis Baill. Thirty-two generic names are newly synonymized, and 144 new nomenclatural combinations are made. A lectotype is designated for one genus, Periarrabidaea A. Samp., and 78 species names. One species name is neotypified, Memora campicola Pilg. (= Adenocalymma campicola (Pilg.) L. G. Lohmann).
Human impacts outpace natural processes in the Amazon Albert, James S; Carnaval, Ana C; Flantua, Suzette G A ...
Science (American Association for the Advancement of Science),
01/2023, Volume:
379, Issue:
6630
Journal Article
Peer reviewed
Amazonian environments are being degraded by modern industrial and agricultural activities at a pace far above anything previously known, imperiling its vast biodiversity reserves and globally ...important ecosystem services. The most substantial threats come from regional deforestation, because of export market demands, and global climate change. The Amazon is currently perched to transition rapidly from a largely forested to a nonforested landscape. These changes are happening much too rapidly for Amazonian species, peoples, and ecosystems to respond adaptively. Policies to prevent the worst outcomes are known and must be enacted immediately. We now need political will and leadership to act on this information. To fail the Amazon is to fail the biosphere, and we fail to act at our peril.
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