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    V: ASIH Symposium: Why are there so many kinds of fishes? A showcase of early-career ichthyologists, IV

    2021-07-27   14:30 - 16:00

    Moderator: Elizabeth Miller

    1.  14:30  VIRTUAL    Early Career: Addressing the Ancient Evolutionary Radiation of Tunas, Stromateoids, and Allies (Teleostei: Pelagiaria). Dahiana Arcila*, University of Oklahoma

    The use of high-throughput sequencing technologies to produce genome-scale data sets was expected to settle some long-standing controversies across the Tree of Life, particularly in areas where short branches occur at deep timescales. Instead, these data sets have often yielded many well-supported but con?icting topologies, and highly variable gene-tree distributions. We applied multiple branch-support metrics to an ancient group of marine ?shes (Teleostei: Pelagiaria) whose interfamilial relationships have proven dif?cult to resolve due to a rapid accumulation of lineages very early in its history. We analyzed hundreds of loci including published ultraconserved element data and newly generated exonic data along with their ?anking regions to represent all 16 extant families for more than 150 out of 284 valid species in the group. Branch support was lower for interfamilial relationships regardless of the type of marker used. Several nodes that were highly supported with bootstrap had a very low site and gene-tree concordance, revealing underlying con?ict. Despite this con?ict, we were able to identify four consistent interfamilial clades, each comprised of two or three families. Combining exons with their ?anking regions also produced increased branch lengths in the deep branches of the pelagiarian tree. Our results demonstrate the limitations of employing current metrics of branch support and species-tree estimation when assessing the con?dence of ancient evolutionary radiations and emphasize the necessity to embrace alternative measurements to explore phylogenetic uncertainty and discordance in phylogenomic data sets.

    2.  14:45  VIRTUAL    Early Career: Evolutionary Relationships of Anglerfishes (Lophiiformes) Reconstructed using Ultraconserved Elements. Pamela Hart*, Louisiana State University; Rachel Arnold, Northwest Indian College; Fernando Alda, University of Tennessee at Chattanooga; Prosanta Chakrabarty, Louisiana State University

    Species of Lophiiformes (anglerfishes) are considered to be among the most bizarre and mysterious fishes, as they inhabit some of the darkest depths of the oceans and have a variety of unique traits including bioluminescent lures, parasitic males, and even “elbows”. Despite their captivating nature, evolutionary relationships among the Lophiiformes, including the monophyly of the Antenariidae (frogfishes), remain unclear. To elucidate relationships within the order, we reconstructed evolutionary history using ultraconserved element (UCE) loci. We recovered the Lophioidei (monkfishes) as sister to the remaining Lophiiformes, a relationship shown in previous phylogenetic investigations. Our topologies suggest a sister-relationship between Ogcocephalioidei (batfishes) and Antennarioidei. The Chaunacoidei (coffinfishes) were recovered as the sister-group to the Ceratioidei (deep-sea anglerfishes). Frogfishes of the family Antennariidae were not recovered as monophyletic; instead, we found four groups of antennariids. Within Antennariidae, we propose two new subfamilies (Porophryninae and Tathicarpinae) based on genetic and morphological characters. Also, we re-evaluated Histiophryninae and retained Antennariinae. Relationships among the deep-sea ceratioids were much less straightforward: multiple families were found to be paraphyletic or polyphyletic. These genetic relationships correspond with previous morphological investigations, which also had difficulties recovering patterns among the suborders. We clarify the relationships among the Antennarioidei, but the Ceratioidei remain an enigma in terms of both their deep-sea biology and evolutionary history.

    3.  15:00  VIRTUAL    Early Career: A Dive into Deep-sea Fish Diversity and the Growing Work of Early Career Scientists. Rene Martin*, University of Kansas

    Research on deep-sea fish biodiversity and evolution has historically been hard to pursue due to the extreme conditions in which they live. The deep sea is defined as oceanic water depths below 200 m, and it exhibits little-to-no light, nearly freezing temperatures, and extreme hydrostatic pressures. These abiotic factors have made it difficult to sample and preserve specimens in their natural state and has prevented researchers from documenting important behaviors like feeding, communication, and reproduction. Many of the fishes living in the deep sea share a similar habitat and are of a similar size, yet different fish lineages posses considerable variation in species numbers and abundances; from the species depauperate neoscopelids (blackchins, 6 spp.) to the comparatively species rich myctophids (lanternfishes, 254 spp.). Understanding the ‘why’ and ‘how’ of this diversity across deep-sea fish lineages continues to be an intriguing phenomenon for ichthyologists. Over the last few decades, there has been a proliferation of macroevolutionary studies by early career scientists aiming to better understand the evolution of deep-sea groups. Many of these studies combine methods including phylogenetics, niche modeling, and geometric morphometrics to gather information and test hypothesis about evolution in this stable yet extreme environment. The cumulative effort of these individuals and their research showcases the ability to explore and understand deep-sea fish diversity and the range of methods that can be used to understand the evolution of diversity in difficult to study taxa occurring in some of the remotest areas on Earth.

    4.  15:15  VIRTUAL    Early Career: Challenges and discoveries studying fishes on mesophotic coral ecosystems. Hudson Pinheiro*, Center for Marine Biology, University of São Paulo; Chancey MacDonald, California Academy of Sciences; Tyler Phelps, California Academy of Sciences; Bart Shepherd, California Academy of Sciences; Luiz Rocha, California Academy of Sciences

    The recent popularization of technical diving by scientists has yielded a large increase in the exploration of mesophotic coral ecosystems (MCEs), deep reefs found between 30 and 150 m depth. Our fish biodiversity assessments have disclosed rich MCE assemblages and many unknown species across the globe, with a current discovery rate around two new fish species per hour of technical diving exploration. We found a general pattern of species richness decreasing along the depth gradient, with substantial changes in coral reef fish assemblages with depth, a trend mainly driven by species turnover. Conversely, studies based on depth range datasets present high overlap of species between shallow and deep reefs, suggesting that MCEs could provide refuge to species of broad depth range that are threatened in shallow reefs; a concept known as Deep Reef Refuge Hypothesis (DRRH). Our empirical data, on the other hand, show low levels of similarity between depth zones, revealing unique assemblages on MCEs, with many endemic and undescribed species.

    5.  15:30  VIRTUAL    Early Career: Why Are There So Many Kinds of Fishes on Coral Reefs? Jennifer Hodge*, Clemson University; Samantha Price, Clemson University

    Marine fishes account for nearly a quarter of all vertebrate diversity. Rather than being distributed evenly throughout Earth’s oceans, marine fishes are highly concentrated within coral reef habitats that comprise less than 0.1% of marine environments. The composition and diversity of fishes on coral reefs is determined by the coalescence of high productivity, structural and spatial heterogeneity, and complex biotic interactions. While both competition and predation are thought to be important drivers of reef fish diversity, predation has received far less attention from ecologists and evolutionary biologists. Intense predation, typical of coral reefs, is hypothesised to regulate prey populations enough to lower the level of competition between and among them, thereby facilitating the co-existence of additional prey types, and consequently additional predators. How generally this applies to coral reef fishes remains unclear. Moreover, we are only beginning to understand how predator-prey interactions are influenced by the structural complexity and heterogeneity characteristic of coral reefs and how this in turn influences ecological and phenotypic diversity. Here, I present an initial assessment of the impacts of predation on species richness and the ecomorphological diversity of reef fishes. Overall, the evidence supports the notion that the structural complexity of coral reefs releases evolutionary constraints, thereby generating diverse assemblages of predators and prey.

    6.  15:45  VIRTUAL    Why are there so many cryptobenthic reef fishes? Luke Tornabene*, University of Washington; Elizabeth Miller, University of Washington

    Cryptobenthic reef fishes are small fishes (typically less than 10 cm) that are associated with coral reefs and live on, in, or immediately above substrate. Collectively they make up nearly 50% of fishes on coral reefs in terms of both abundance and species richness, and represent a critically important component of reef trophodynamics. Cryptobenthic reef fishes are asymmetrically distributed amongst the acanthomorph phylogeny, and are well represented in at least 17 major families. However, the vast majority of species belonging to just two main clades, the Gobiiformes, and the Blenniiformes and relatives. This study explores potential mechanisms explaining the high diversity and abundance of cryptobenthic reef fishes, including the possibility of higher rates of speciation relative to other acanthomorph lineages. We also discuss several biological traits possessed by some lineages of cryptobenthic fishes, but not all, and hypothesize about how combinations of these features may explain the asymmetrical distribution of species-richness among cryptobenthic reef fishes. Our findings hope to shed light as to how this guild of fishes have flourished over evolutionary timescales in the face of the strong selective pressures associated with a cryptobenthic lifestyle.

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