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Morphometric and Osteological Methods in Ichthyology

Morphometric and Osteological Methods in Ichthyology. Brian Sidlauskas National Evolutionary Synthesis Center Durham, NC bls16@duke.edu. Three main types of morphological study. Study of discrete character variation among species Phylogenetics Species delimitation

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Morphometric and Osteological Methods in Ichthyology

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  1. Morphometric and Osteological Methods in Ichthyology Brian Sidlauskas National Evolutionary Synthesis Center Durham, NC bls16@duke.edu

  2. Three main types of morphological study • Study of discrete character variation among species • Phylogenetics • Species delimitation • Quantification of shape and size variation • Species delimitation • Age and growth studies • Studies of character evolution • Phylogenetic comparative methods

  3. Phylogeny Reconstruction Laemolyta taeniata Systematics of Anostomidae (Characiformes) Sidlauskas and Vari 2008, Zoological Journal of the Linnean Society

  4. Anostomidae & Chilodontidae (~140 spp.) High Morphological Diversity Image credits: B. Chernoff, T. Clark, J. Gery, M. Sabaj, B. Sidlauskas

  5. Leporinus cf. ecuadorensis Anatomical differences reveal evolutionary patterns Fifth upper pharyngeal tooth plate Schizodon fasciatus Rhytiodus argenteofuscus

  6. Leporinus mormyrops Leporinus fasciatus Illustrations by Tamara Clark

  7. 123 morphological characters variable among ingroup or informative as to anostomid monophyly Additional 35 informative among outgroups 29 multistate, all unordered strict consensus of 1312 trees CI = 0.425 RI = 0.805 Parsimony From Sidlauskas and Vari, 2008

  8. Leporellus most basal • Leporinus paraphyletic (and difficult to resolve with morphology) • Hypomasticus (in Leporinus) monophyletic • Abramites within Leporinus • Rhytiodus with Schizodon • Laemolyta monophyletic and sister to Anostominae sensu Winterbottom (1980) • Anostominae very strongly supported • Monophyly of Pseudanos uncertain • Anostomus paraphyletic • New genus Petulanos Parsimony From Sidlauskas and Vari, 2008

  9. 1 2 3 4 4 5 6 7 8

  10. Consensus Phylogeny from Supermatrix Analysis ANOSTOMOIDEA Synthesis of 463 morphological characters from 14 studies 171 Species Analyzed using Parsimony Ratchet via PaupRat (Sikes and Lewis, 2001) and PRAP (Müller 2004) CURIMATOIDEA From Sidlauskas, in press, Evolution

  11. Species Discovery and Delineation B A From Sidlauskas et al. 2005, Copeia

  12. Schizodon scotorhabdotus new species Schizodon isognathus Schizodon knerii From Sidlauskas et al. Copeia 2007

  13. Leporinus sp. nov. 1? (Brazil, Southern Amazon tributaries) Leporinus sp. Nov. 2? (Suriname) Leporinus cylindriformis, holotype (Brazil, Main Amazon channel)

  14. ALLOMETRY

  15. Traditional and Geometric Techniques Often Yield Complementary Answers Traditional Linear Morphometrics Geometric Morphometrics

  16. PCA for comparing individuals and testing group membership CVA for recognizing difference between known groups From Sidlauskas, Vari and Mol, in prep

  17. Highland fishes measurably more streamlined than lowland fishes • Differing allometric trajectories • Consistent with induction by growth in fast water Sidlauskas, Chernoff and Machado-Allison 2006, Ichthyological Research

  18. Measuring Morphological Diversity Curimatidae Curimatella alburna • 21 skull landmarks • 171 species, ca. 1200 specimens • Analyzed with geometric morphometrics From Sidlauskas, 2007, Evolution

  19. Phylomorphospaces • Relative Warp Analysis of skull shapes yields positions of species in morphospace • Phylogeny links species • Squared-change parsimony or likelihood infers position of internal nodes and morphometric distances (Euclidean) between them. • Species sorted into diet classes based on literature accounts (Herbivore, Invertivore, Detritivore, etc.) and color coded • Reconstruction of diet at internal nodes Relative Warp 2 Relative Warp 1 Sidlauskas, in press, Evolution

  20. Plotting phylogenies into a morphospace Sidlauskas in press, Evolution

  21. ECOPHYLOMORPHOSPACE

  22. Significance Testing via Simulation • Simulate morphological evolution • Many possible phylogenies • constant tempo and mode (e.g. single rate Brownian motion) • Reconstruct distribution of possible phylomorphospaces • Determine how often one generates two clades that differ as greatly as the observed • If A/Cobserved > A/C simulated 95% of the time, then reject the null hypothesis of equal tempo or mode • Otherwise, real world consistent with two random outcomes of the same process Unequal tempo?: P from 0.29 to 0.65 Unequal modes?: P from 0.01 to 0.05

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