Biology subjects

Orti, G.

Publications and source records attributed to Orti, G..

7 recordsLinked to original sources

bioRxiv2026

Ecological axes of skull diversification in a massive 1 vertebrate radiation

Eupercarian spiny-rayed fishes are one of the largest vertebrate radiations, rivaling mammals and occupying nearly every aquatic habitat. We present a densely sampled, time-calibrated phylogenomic framework for Eupercaria, supporting a revised classification, combined with the largest cranial phenomics dataset for fishes. Habitat and trophic ecology make independent, complementary contributions to skull shape. Most species cluster around a conserved generalized architecture, the Percomorph Pile, from which one clade of pufferfishes, anglerfishes, butterflyfishes, and surgeonfishes repeatedly invaded novel morphospace; exceptionally high rates on its deep branches indicate that rapid skull evolution arose early in this clade. Freshwater lineages converge on the ancestral condition, reflecting late arrival into systems occupied by older otophysans, whereas durophages show the greatest disparity and converge on derived forms. Cranial diversity was partitioned among subclades during the Cretaceous and later within them across the Cenozoic, showing that clade-level differences in evolutionary rates and ecological opportunity jointly shaped skull diversification.

evolutionary biology↗

bioRxiv2026

Whole-genome phylogenomics and synteny resolve a single origin of body-plan asymmetry in flatfishes

Flatfishes display the most dramatic asymmetric body plan in vertebrates, yet whether this rare innovation evolved once (flatfish monophyly, FM) or multiple times (flatfish polyphyly, FP) has remained contentious. A recent genome-wide study supported FP by placing Psettodes, the earliest-diverging flatfish lineage, among symmetric relatives within Carangaria, the clade that also includes billfishes, jacks, mahi-mahi, and barracudas. Subsequent work traced this to base-composition artifacts and inadequate substitution modeling. Here we revisit the question using whole-genome phylogenomic and synteny data from 17 carangarian species spanning flatfishes and carangarian relatives. We contribute three new chromosome-level assemblies, including the first for Psettodes. Nucleotide-based coalescent analyses (e.g., ROADIES, CASTER) yield strong support for FM, with Psettodes sister to all other flatfishes. Microsynteny analyses built from conserved gene-order blocks corroborate this result: topology tests, cluster-profile counts, and rearrangement-based trees favor FM over two competing FP topologies. Macrosynteny, based on chromosome-scale rearrangements, yields a more mixed signal, with support for FM depending on the metric and taxon-sampling scheme. We interpret this scale-dependent pattern in the context of the explosive post-Cretaceous radiation of Carangaria. The short intervals between speciation events that characterize rapid radiations appear to have left sufficient signal in fine-grained microsyntenic rearrangements, while chromosome-scale rearrangements were too rare to consistently resolve these closely spaced splits. When integrated with evidence from conserved developmental mechanisms active during metamorphosis, the stage at which flatfish asymmetry first emerges, and from the exceptionally complete fossil record, our multi-scale genomic evidence supports a single evolutionary origin of flatfish asymmetry.

evolutionary biology↗

bioRxiv2026

Phylogenomics, Biogeography, and a New Family-level Classification of Silversides, Rainbowfishes, and Allies (Teleostei: Atheriniformes)

The order Atheriniformes (silversides, rainbowfishes, and blue-eyes) is a globally distributed group of fishes with frequent evolutionary transitions between marine and freshwater ecosystems. However, understanding the tempo and mode of these transitions has been hampered by poor phylogenetic resolution and limited taxonomic sampling, particularly within the suborder Atherinoidei. We generated a phylogenomic dataset of 1,100 exon loci for 150 species to resolve interfamilial relationships and reconstruct the groups biogeographic history. We were also able to incorporate a large number of existing GenBank sequences, producing a phylogeny with 265 species sampled for at least some genetic data (67% of known species diversity). While the New World suborder Atherinopsidae is well-resolved, we found that the family Atherinidae is polyphyletic across all analyses. We propose a revised classification that restricts Atherinidae to the genus Atherina and recognizes Atherinomoridae and Craterocephalidae as separate families. Our biogeographic inferences using explicit geographic areas suggests more frequent marine-to-freshwater transitions than previously inferred with simplified binary (marine vs. freshwater) coding, and uncover habitat transitions where marine ancestors may have gone extinct. These results highlight how explicit geographic modeling can uncover marine ancestry erased by extinction, providing a robust phylogenetic framework for future evolutionary studies of Atheriniformes.

evolutionary biology↗

bioRxiv2023

Dissecting Factors Underlying Phylogenetic Uncertainty Using Machine Learning Models

Phylogenetic inference can be influenced by both underlying biological processes and methodological factors. While biological processes can be modeled, these models frequently make the assumption that methodological factors do not significantly influence the outcome of phylogenomic analyses. Depending on their severity, methodological factors can introduce inconsistency and uncertainty into the inference process. Although search protocols have been proposed to mitigate these issues, many solutions tend to treat factors independently or assume a linear relationship among them. In this study, we capitalize on the increasing size of phylogenetic datasets, using them to train machine learning models. This approach transcends the linearity assumption, accommodating complex non-linear relationships among features. We examined two phylogenomic datasets for teleost fishes: a newly generated dataset for protacanthopterygians (salmonids, galaxiids, marine smelts, and allies), and a reanalysis of a dataset for carangarians (flatfishes and allies). Upon testing five supervised machine learning models, we found that all outperformed the linear model (p < 0.05), with the deep neural network showing the best fit for both empirical datasets tested. Feature importance analyses indicated that influential factors were specific to individual datasets. The insights obtained have the potential to significantly enhance decision-making in phylogenetic analyses, assisting, for example, in the choice of suitable DNA sequence models and data transformation methods. This study can serve as a baseline for future endeavors aiming to capture non-linear interactions of features in phylogenomic datasets using machine learning and complement existing tools for phylogenetic analyses.

evolutionary biology↗

bioRxiv2021

Deterministic shifts in molecular evolution correlate with convergence to annualism in killifishes

The repeated evolution of novel life histories correlating with ecological variables offer opportunities to test scenarios of convergence and determinism in genetic, developmental, and metabolic features. Here we leverage the diversity of aplocheiloid killifishes, a clade of teleost fishes that contains over 750 species on three continents. Nearly half of these are "annual" or seasonal species that inhabit bodies of water that desiccate and are unfeasible for growth, reproduction, or survival for weeks to months at a time. We present a large-scale phylogenomic reconstruction of aplocheiloid killifish evolution using newly sequenced transcriptomes from all major clades. We show that developmental dormancy (diapause) and annualism have up to seven independent origins in Africa and America. We then measure evolutionary rates of orthologous genes and show that annual life history is correlated with higher dN/dS ratios. Many of these fast-evolving genes in annual species constitute key developmental genes and nuclear-encoded metabolic genes that control oxidative phosphorylation. Lastly, we compare these fast-evolving genes to genes associated with developmental dormancy and metabolic shifts in killifishes and other vertebrates and thereby identify molecular evolutionary signatures of repeated evolutionary transitions to extreme environments.

evolutionary biology↗

bioRxiv2020

Phylogenomics of piranhas and pacus (Serrasalmidae) uncovers how convergent diets obfuscate traditional morphological taxonomy.

The Amazon and neighboring South American river basins harbor the worlds most diverse assemblages of freshwater fishes. One of the most prominent South American fish families are the Serrasalmidae (pacus and piranhas), found in nearly every continental basin. Serrasalmids are keystone ecological taxa, being some of the top riverine predators as well as the primary seed dispersers in the flooded forest. Despite their widespread occurrence and notable ecologies, serrasalmid evolutionary history and systematics are controversial. For example, the sister taxon to serrasalmids is contentious, the relationships of major clades within the family are obfuscated by different methodologies, and half of the extant serrasalmid genera are suggested to be non-monophyletic. We used exon capture to explore the evolutionary relationships among 64 (of 99) species across all 16 serrasalmid genera and their nearest outgroups, including multiple individuals per species in order to account for cryptic lineages. To reconstruct the timeline of serrasalmid diversification, we time-calibrated this phylogeny using two different fossil-calibration schemes to account for uncertainty in taxonomy with respect to fossil teeth. Finally, we analyzed diet evolution across the family and comment on associated changes in dentition, highlighting the ecomorphological diversity within serrasalmids. We document widespread non-monophyly within Myleinae, as well as between Serrasalmus and Pristobrycon, and propose that reliance on traits like teeth to distinguish among genera is confounded by ecological convergence, especially among herbivorous and omnivorous taxa. We clarify the relationships among all serrasalmid genera, propose new subfamily affiliations, and support hemiodontids as the sister taxon to Serrasalmidae.

evolutionary biology↗

bioRxiv2020

Exon probe sets and bioinformatics pipelines for all levels of fish phylogenomics

Exon markers have a long history of use in phylogenetics of ray-finned fishes, the most diverse clade of vertebrates with more than 35,000 species. As the number of published genomes increases, it has become easier to test exons and other genetic markers for signals of ancient duplication events and filter out paralogs that can mislead phylogenetic analysis. We present seven new probe sets for current target-capture phylogenomic protocols that capture 1,104 exons explicitly filtered for paralogs using gene trees. These seven probe sets span the diversity of teleost fishes, including four sets that target five hyper-diverse percomorph clades which together comprise ca. 17,000 species (Carangaria, Ovalentaria, Eupercaria, and Syngnatharia + Pelagiaria combined). We additionally included probes to capture exon markers that have been commonly used in fish phylogenetics, despite some being flagged for paralogs, to facilitate integration of old and new molecular phylogenetic matrices. We tested these probes and merged new exon-capture sequence data into an existing data matrix of 1,105 exons and 300 ray-finned fish species. We provide an optimized bioinformatics pipeline to assemble exon capture data from raw reads to alignments for downstream analysis. We show that loci with known paralogs are at risk of assembling duplicated sequences with target-capture, but we also assembled many useful orthologous sequences. These probe sets are a valuable resource for advancing fish phylogenomics because they can be easily extracted from increasingly available whole genome and transcriptome datasets, and also may be integrated with existing PCR-based exon and mitochondrial datasets.

evolutionary biology↗