Phylogenomics of Bony-Tongue Fishes (Osteoglossomorpha) Shed Light on the Craniofacial Evolution and Biogeography of the Weakly Electric Clade (Mormyridae).

Bonytongues (Osteoglossomorpha) constitute an ancient clade of teleost fishes distributed in freshwater habitats throughout the world. The group includes well-known species such as arowanas, featherbacks, pirarucus, and the weakly electric fishes in the family Mormyridae. Their disjunct distribution, extreme morphologies, and electrolocating capabilities (Gymnarchidae and Mormyridae) have attracted much scientific interest, but a comprehensive phylogenetic framework for comparative analysis is missing, especially for the species-rich family Mormyridae. Of particular interest are disparate craniofacial morphologies among mormyrids which might constitute an exceptional model system to study convergent evolution. We present a phylogenomic analysis based on 546 exons of 179 species (out of 260), 28 out of 29 genera, and all six families of extant bonytongues. Based on a recent reassessment of the fossil record of osteoglossomorphs, we inferred dates of divergence among transcontinental clades and the major groups. The estimated ages of divergence among extant taxa (e.g., Osteoglossomorpha, Osteoglossiformes, and Mormyroidea) are older than previous reports, but most of the divergence dates obtained for clades on separate continents are too young to be explained by simple vicariance hypotheses. Biogeographic analysis of mormyrids indicates that their high species diversity in the Congo Basin is a consequence of range reductions of previously widespread ancestors and that the highest diversity of craniofacial morphologies among mormyrids originated in this basin. Special emphasis on a taxon-rich representation for mormyrids revealed pervasive misalignment between our phylogenomic results and mormyrid taxonomy due to repeated instances of convergence for extreme craniofacial morphologies. Estimation of ancestral phenotypes revealed contingent evolution of snout elongation and unique projections from the lower jaw to form the distinctive Schnauzenorgan. Synthesis of comparative analyses suggests that the remarkable craniofacial morphologies of mormyrids evolved convergently due to niche partitioning, likely enabled by interactions between their exclusive morphological and electrosensory adaptations. [Africa; ancestral state estimation; diversity; exon capture; freshwater fishes; Phylogenomics.].

Phylogenomics and Historical Biogeography of Seahorses, Dragonets, Goatfishes, and Allies (Teleostei: Syngnatharia): Assessing Factors Driving Uncertainty in Biogeographic Inferences.

The charismatic trumpetfishes, goatfishes, dragonets, flying gurnards, seahorses, and pipefishes encompass a recently defined yet extraordinarily diverse clade of percomorph fishes-the series Syngnatharia. This group is widely distributed in tropical and warm-temperate regions, with a great proportion of its extant diversity occurring in the Indo-Pacific. Because most syngnatharians feature long-range dispersal capabilities, tracing their biogeographic origins is challenging. Here, we applied an integrative phylogenomic approach to elucidate the evolutionary biogeography of syngnatharians. We built upon a recently published phylogenomic study that examined ultraconserved elements by adding 62 species (total 169 species) and one family (Draconettidae), to cover ca. 25% of the species diversity and all 10 families in the group. We inferred a set of time-calibrated trees and conducted ancestral range estimations. We also examined the sensitivity of these analyses to phylogenetic uncertainty (estimated from multiple genomic subsets), area delimitation, and biogeographic models that include or exclude the jump-dispersal parameter ($j)$. Of the three factors examined, we found that the $j$ parameter has the strongest effect in ancestral range estimates, followed by number of areas defined, and tree topology and divergence times. After accounting for these uncertainties, our results reveal that syngnatharians originated in the ancient Tethys Sea ca. 87 Ma (84-94 Ma; Late Cretaceous) and subsequently occupied the Indo-Pacific. Throughout syngnatharian history, multiple independent lineages colonized the eastern Pacific (6-8 times) and the Atlantic (6-14 times) from their center of origin, with most events taking place following an east-to-west route prior to the closure of the Tethys Seaway ca. 12-18 Ma. Ultimately, our study highlights the importance of accounting for different factors generating uncertainty in macroevolutionary and biogeographic inferences.[Historical biogeography; jump-dispersal parameter; macroevolutionary uncertainty; marine fishes; syngnathiformes; ultraconserved elements].

Evolutionary determinism and convergence associated with water-column transitions in marine fishes.

Repeatable, convergent outcomes are prima facie evidence for determinism in evolutionary processes. Among fishes, well-known examples include microevolutionary habitat transitions into the water column, where freshwater populations (e.g., sticklebacks, cichlids, and whitefishes) recurrently diverge toward slender-bodied pelagic forms and deep-bodied benthic forms. However, the consequences of such processes at deeper macroevolutionary scales in the marine environment are less clear. We applied a phylogenomics-based integrative, comparative approach to test hypotheses about the scope and strength of convergence in a marine fish clade with a worldwide distribution (snappers and fusiliers, family Lutjanidae) featuring multiple water-column transitions over the past 45 million years. We collected genome-wide exon data for 110 (∼80%) species in the group and aggregated data layers for body shape, habitat occupancy, geographic distribution, and paleontological and geological information. We also implemented approaches using genomic subsets to account for phylogenetic uncertainty in comparative analyses. Our results show independent incursions into the water column by ancestral benthic lineages in all major oceanic basins. These evolutionary transitions are persistently associated with convergent phenotypes, where deep-bodied benthic forms with truncate caudal fins repeatedly evolve into slender midwater species with furcate caudal fins. Lineage diversification and transition dynamics vary asymmetrically between habitats, with benthic lineages diversifying faster and colonizing midwater habitats more often than the reverse. Convergent ecological and functional phenotypes along the benthic-pelagic axis are pervasive among different lineages and across vastly different evolutionary scales, achieving predictable high-fitness solutions for similar environmental challenges, ultimately demonstrating strong determinism in fish body-shape evolution.