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NAPC 2014 Constraint and Convergence on a Graptoloid Supertree

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Information about NAPC 2014 Constraint and Convergence on a Graptoloid Supertree
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Published on February 20, 2014

Author: dwbapst

Source: slideshare.net

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My talk for NAPC 2014 with co-author Charles Mitchell
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NAPC 2014 David W. Bapst (SDSMT, UC Davis) & Charles E. Mitchell (SUNY Buffalo)

Functional Constraint in Graptoloid Morphology? Figures from Bulman, 1970; Mitchell, 1990; Maletz et al., 2009; etc.

Using Phylogeny to Test for Constraints  Convergent traits give opportunity to study biotic and abiotic drivers of trait acquisition across clades  Convergence alone indicates potential  …but isn’t evidence of ecomorph. function or other constraints  Randomly evolving traits will converge Wagner and Erwin, 2006  Simulate characters on the phylogeny  Test how often some aspect of the observed data occurs in simulations

Major Features  Primary Stipe Number  Many, 4, 2, 1.5, 1  Scandency  Not Scandent, Partly, Scandent  Reduced Periderm  Extrathecal Threads  Determinant Growth  Cladia Figures from Bulman, 1970; Mitchell, 1990; Maletz et al., 2009; etc.

Graptoloid Phylogenetics  3D preservation provides detailed characters for cladistics  …but only some taxa: ~49% of genera are on published cladograms  Missing lots of unique colony morphologies

Informal Supertree of 117 Genera  Adding extra taxa to cladistic ‘skeleton’  Summarize our current knowledge of relationships using all types of evidence Trees from: Maletz et al., 2009 Mitchell et al., 2007 Storch et al., 2011 Melchin et al., 2011 Bates et al., 2005  Hierarchical placing of unanalyzed taxa  First, synapomorphies in cladistic analyses  If not, most recent taxonomic placement

Poorly preserved early graptoloids: mostly unresolved Use soft polytomies (multifurcating nodes) for uncertainty in morphology or taxonomy Inclusive Summary of Relationships among 245 Graptoloid Genera The under-analyzed Monograptidae: one single polytomy

Character Analyses  Minimum number of gains and losses: How much convergence?  Parsimony ancestral trait reconstruction  Resolve polytomies to minimize character gains under parsimony  Simulation Analyses of constraint  Simulate character evolution on observed phylogeny (randomly-resolved)  Use estimated transition matrices for each trait (assuming indep evolving)  …but no time-scaling?

Character Analyses  Minimum number of gains and losses: How much convergence?  Parsimony ancestral trait reconstruction  Resolve polytomies to minimize character gains under parsimony  Simulation Analyses of constraint  Simulate character evolution on observed phylogeny (randomly-resolved)  Use estimated transition matrices for each trait (assuming indep evolving)  …but no time-scaling? Really?

Character Analyses  Minimum number of gains and losses: How much convergence?  Parsimony ancestral trait reconstruction  Resolve polytomies to minimize character gains under parsimony  Simulation Analyses of constraint  Simulate character evolution on observed phylogeny (randomly-resolved)  Use estimated transition matrices for each trait (assuming indep evolving)  Analyzing Not Time-scaled Trees  # of character changes / evolutionary ‘length’ per branch: minimal reversals  Are we willing to assume relatively uniform sampling of taxa, nodes

Minimum Number of Transitions ‘Gains’ Reversals  Polytomies resolved to minimize # of Primary Stipes 15 0 number of character transitions Scandency 6 4  Minimally, many indep ‘gains’ to Reduced Periderm 6 0 derived states with few reversals Extrathecal Threads 3 0 Determinant Growth 6 0 Cladia 3 0 Relative to Primitive State:  High evolvability?  Lack of reversals an indicator of species sorting for some traits? (Sort of a reversal for stipe #)

Nonrandom Associations Between Characters Reduced Extrathecal Determinant Scandency Cladia Periderm Threads Growth # of Primary Stipes Scandency Reduced Periderm Extrathecal Threads Determinant Growth  Imbalance of by-genus contingency table for pairs of discrete traits (Cramer’s V) 0.03 0.23 0.14 0.55 0.19 - 0.32 0.09 0.39 0.81 - - < 0.01 0.15 0.25 - - - 0.03 0.34  Some traits aren’t evolving - - - - 0.4  Proportion of simulations with imbalance as high or higher than observed value independent of each other  # of stipes and scandency  Extrathecal threads with red. periderm and det. growth  Constraints on trait change?

But are these ecomorphological constraints?  W&E ‘06: Paleozoic Wagner and Erwin (2006) gastropod taxa distributed among fewer morphotypes than in simulations  Even when the number of Observed potential char combos in simulation limited to the observed # of combos  Implies ecomorpological constraints, not ‘biotic’ architectural constraints

Ecomorphological Constraint on Graptoloids?  Using same traits except treating cladia as a return to many-stipes…  Observed frequencies are slightly higher than simulations without constraining the number of character combinations 95% Quantile

Ecomorphological Constraint on Graptoloids  But when we constrain simulations to observed number of combinations…  Simulations match observed frequency distribution almost perfectly  I.e., the distribution of taxa among combinations of these traits is closely predicted by a null model where some morphologies are simply unavailable  …But not rejecting null ≠ accepting null 95% Quantile

Conclusions  Large scale summaries of what we think we know about relationships in a group can be useful, if we adequately explore phylogenetic uncertainty in our analyses  Derived states of these major morph innovations in graptoloids were repeatedly ‘gained’ independently, implying evolvability  Rarely reverse back… may reflect species sorting (for some)  We can reject these characters evolve independently  But based on the obs frequency of morphotypes, we can’t reject that convergence are due to intrinsic biotic constraints such as construnctional or developmental factors Thanks to M. Foote, P. Smits, M. Pennell, E. King for useful discussions.

Characters Tied Across Branches…?  Sets of traits ( ) seem to repeat in Retiolitids Spinograptus Glossograptids Corynoides Cryptograptus certain clades … but not always in the same taxon in those clades  Some invisible ‘predictor’ trait? Extrathecal Threads Reduced Periderm Extrathecal Threads Determinant Growth Determinant Growth Cladia  Use mean patristic distance of < 0.01 0.09 0.31 taxon with one character to closest relative with other trait - 0.16 0.33 - - Hard to reject null? 0.32  Only works for binary traits  Proportion of simulations with low or lower mean pairwise patristic distance than observed

Informing Our Functional Morphology Analyses  Use physics to test a supposed function for morphology  Can test that X could do function Y  Cannot test whether X had any function  Need to start with a carefully chosen specific hypothesis of a specific function  Larger patterns of evolution can be useful for informing what we should investigate

Cladia-like abnormal Amplexograptus latus

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