The Neotropics harbor the most species-rich freshwater fish fauna on the planet, but the timing of that exceptional diversification remains unclear. Did the Neotropics accumulate species steadily throughout their long history, or attain their remarkable diversity recently? Biologists have long debated the relative support for these museum and cradle hypotheses, but few phylogenies of megadiverse tropical clades have included sufficient taxa to distinguish between them. We used 1,288 ultraconserved element loci (UCE) spanning 293 species, 211 genera and 21 families of characoid fishes to reconstruct a new, fossil-calibrated phylogeny and infer the most likely diversification scenario for a clade that includes a third of Neotropical fish diversity. This phylogeny implies paraphyly of the traditional delimitation of Characiformes because it resolves the largely Neotropical Characoidei as the sister lineage of Siluriformes (catfishes), rather than the African Citharinodei. Time-calibrated phylogenies indicate an ancient origin of major characoid lineages and reveal a much more recent emergence of most characoid species. Diversification rate analyses infer increased speciation and decreased extinction rates during the Oligocene at around 30 million years ago (Ma) during a period of mega-wetland formation in the proto-Orinoco-Amazonas. Three species-rich and ecomorphologically diverse lineages (Anostomidae, Serrasalmidae, and Characidae) that originated more than 60 Ma in the Paleocene experienced particularly notable bursts of Oligocene diversification and now account collectively for 68% of the approximately 2,150 species of Characoidei. In addition to paleogeographic changes, we discuss potential accelerants of diversification in these three lineages. While the Neotropics accumulated a museum of ecomorphologically diverse characoid lineages long ago, this geologically dynamic region also cradled a much more recent birth of remarkable species-level diversity.

The characiform fishes of the Neotropics and Africa radiated remarkably in ecomorphology, but the macroevolutionary processes responsible for their biodiversity remain unexplored, and the degree to which their continental diversification parallels classic adaptive radiations remains untested. We reconstruct their diversification using a new fossil‐calibrated molecular phylogeny, dietary information, and geometric morphometrics. Though body shape diversified early in a manner consistent with an ancient continental adaptive radiation, trophic shifts did not always coincide with shape changes. With the notable exception of piscivores, lineages that converged in diet did not converge closely in body shape. Shifts in habitat or other variables likely influenced body shape evolution in addition to changes in diet, and the clade's history departs from many classic adaptive radiations in lakes or on islands, in which trophic convergence drives morphological convergence. The contrast between the Neotropical radiation's exhaustive exploration of morphospace and the more restrained diversification in Africa suggests a major role for contingency in characiform evolution, with the presence of cypriniform competitors in the Old World, but not the New, providing one possible explanation. Our results depict the clearest ecomorphological reconstruction to date for Characiformes and set the stage for studies further elucidating the processes underlying its diversification.

While intertidal habitats are often productive, species-rich environments, they are also harsh and highly dynamic. Organisms that live in these habitats must possess morphological and physiological adaptations that enable them to do so. Intertidal fishes are generally small, often lack scales, and the diverse families represented in intertidal habitats often show convergence into a few general body shapes. However, few studies have quantified the relationship between phenotypes and intertidal living. Likewise, the diversity of reproductive traits and parental care in intertidal fishes has yet to be compared quantitatively with habitat. We examine the relationship of these characters in the sculpin subfamily Oligocottinae using a phylogenetic hypothesis, geometric morphometrics, and phylogenetic comparative methods to provide the first formal test of associations between fish phenotypes and reproductive characters with intertidal habitats.We show that the ability to live in intertidal habitats, particularly in tide pools, is likely a primitive state for Oligocottinae, with a single species that has secondarily come to occupy only subtidal habitats. Contrary to previous hypotheses, maximum size and presence of scales do not show a statistically significant correlation with depth. However, the maximum size for all species is generally small (250mm or less) and all show a reduction in scales, as would be expected for an intertidal group. Also contrary to previous hypotheses, we show that copulation and associated characters are the ancestral condition in Oligocottinae, with copulation most likely being lost in a single lineage within the genus Artedius. Lastly, we show that body shape appears to be constrained among species with broader depth ranges, but lineages that occupy only a narrow range of intertidal habitats display novel body shapes, and this may be associated with habitat partitioning, particularly as it relates to the degree of wave exposure. 17 Abstract 18 While intertidal habitats are often productive, species-rich environments, they are also harsh and 19 highly dynamic. Organisms that live in these habitats must possess morphological and 20 physiological adaptations that enable them to do so. Intertidal fishes are generally small, often 21 lack scales, and the diverse families represented in intertidal habitats often show convergence 22 into a few general body shapes. However, few studies have quantified the relationship between 23 phenotypes and intertidal living. Likewise, the diversity of reproductive traits and parental care 24 in intertidal fishes has yet to be compared quantitatively with habitat. We examine the 25 relationship of these characters in the sculpin subfamily Oligocottinae using a phylogenetic 26 hypothesis, geometric morphometrics, and phylogenetic comparative methods to provide the first 27 formal test of associations between fish phenotypes and reproductive characters with intertidal 28 habitats. We show that the ability to live in intertidal habitats, particularly in tide pools,...

Migration is a widespread phenomenon among animals and has a profound influence on the evolution of species traits. Diadromous fishes provide an extreme example of migration, moving between marine and freshwaters, often travelling thousands of kilometres for feeding and reproduction. Diadromy has been linked to changes in feeding ecology, body size and various life-history attributes. However, most studies have focused on intraspecific variation and associated mechanisms. In this study, we use phylogenetic comparative methods to analyse body size and trophic position across Clupeiformes (anchovies, herring, shad and allies), a large clade of fishes that includes both diadromous and non-diadromous species. We found that diadromous species are larger than non-diadromous species, but there is no difference in trophic position, and that these patterns are not attributable to common ancestry. Diadromous species show a decoupling of body size and trophic position, whereas non-diadromous clupeiforms have a positive relationship between body size and trophic position. Using a model-fitting approach, we detected a signal of strong selection driving diadromous fishes to different adaptive peaks from non-diadromous fishes for body size, but a single adaptive peak for trophic position. We suggest that diadromous fishes have evolved larger body size than obligate marine and freshwater species as an adaptation to maximize energy expenditure during long-distance migration.

An investigation of the aqueous chlorination (NaOCl) of resorcinol is reported. The following intermediates were detected in moderate to high yield at different pH values and varying percentages of chlorination: 2-chloro-, 4-chloro-, 2,4-dichloro-, 4,6-dichloro-and 2,4,6-trichlororesorcinol. Only trace amounts of the intermediates were detected when the chlorination was conducted in the presence of phosphate buffer. This result has significant implications since resorcinol in phosphate buffer has been used as a model compound in several recent studies on the formation of chlorinated hydrocarbons during chlorination of drinking water. Relative rates of chlorination were determined for resorcinol and several of the chlorinated resorcinols. Resorcinol was found to chlorinate only three times faster than 2,4,6-trichlororesorcinol. The structure 2,4,6-trichlororesorcinol was established as a monohydrate even after sublimation. A tetrachloro or pentachloro intermediate was not detected, suggesting that the ring-opening step of such an intermediate must be rapid.

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Migratory animals respond to environmental heterogeneity by predictably moving long distances in their lifetime. Migration has evolved repeatedly in animals, and many adaptations are found across the tree of life that increase migration efficiency. Life-history theory predicts that migratory species should evolve a larger body size than non-migratory species, and some empirical studies have shown this pattern. A recent study analysed the evolution of body size between diadromous and non-diadromous shads, herrings, anchovies and allies, finding that species evolved larger body sizes when adapting to a diadromous lifestyle. It remains unknown whether different fish clades adapt to migration similarly. We used an adaptive landscape framework to explore body size evolution for over 4500 migratory and non-migratory species of ray-finned fishes. By fitting models of macroevolution, we show that migratory species are evolving towards a body size that is larger than non-migratory species. Furthermore, we find that migratory lineages evolve towards their optimal body size more rapidly than non-migratory lineages, indicating body size is a key adaption for migratory fishes. Our results show, for the first time, that the largest vertebrate radiation on the planet exhibited strong evolutionary determinism when adapting to a migratory lifestyle.