Presentation on theme: "Microhabitat specialization in parasitic lice: lineage assortment or character displacement? Illinois Natural History Survey University of Illinois Campus."— Presentation transcript:
microhabitat specialization in parasitic lice: lineage assortment or character displacement? Illinois Natural History Survey University of Illinois Campus Champaign, Illinois USA Vincent S. Smith & Kevin P. Johnson The evolution of
…Niche Specialization Body lice Head lice Wing lice
Niche Specialization is Common Opisthocomiformes Passeriformes Galliformes Tinamiformes Charadriiformes Anseriformes Coraciiformes
Patterns of Niche Evolution Niche conservedNiche convergent WingWWWHeadHHHBodyBBB CI 1.00CI 0.33
Process of Niche Evolution - consider hosts Niche evolves early (niche assorts with host lineages) Niche evolves late (niche displaces within host lineages) ? GalliformesGGG Anseriformes A AA TinamouTTT
Louse Phylogeny MoleculesMorphology - 41 in-group taxa (~ 1/3rd ischnoceran genera) - mammal louse (trichodectid) outgroup - in-group span basal ischnoceran diversity - representatives from 18 bird orders - all but 4 bird orders host lice from 2 or more niches - include 8 body, 12 head, 10 wing & 11 generalist genera - focus on avian Ischnocera (Philopteridae)
Louse Phylogeny 4 genes (12s, COI, EF1-a, wingless) MrBayes (partitioned by gene) 4 chains, 5 million generations Molecules Posterior Prob. > 0.95 Morphology 138 characters PAUP* Parsimony, TBR Bootstrap > 0.85 Topologies Very Different! Principal coordinate analysis of partition metric scores ( subset of these taxa but including more genes) Combined Tree Mol. trees 2 islands morph. trees
Niche Evolution MorphologyMolecules RI 0.31 CI steps RI 0.65 CI steps
Randomization Tests - character fit Molecules RI steps Actual tree Sig. (P < 0.001) Niche shuffled across molecular phylogeny (1000 Randomizations, steps, RI ) RI steps Actual tree Not Sig. (P = 0.19) Host shuffled across molecular phylogeny (1000 Randomizations, steps, RI ) RI steps Actual tree Sig. (P < 0.001) Morphology Frequency Niche shuffled across morphological phylogeny (1000 Randomizations, steps, RI ) RI steps Actual tree Sig. (P=0.011) Host shuffled across morphological phylogeny (1000 Randomizations, steps, RI )
Randomization Tests (sister taxa occupying a different niche) No. of sister taxon pairs from the same host order occupying different ecological niches (1000 Randomized trees) Frequency Molecular Phylogeny Highly significant (P < 0.001) Morphological Phylogeny Not significant (P = 1.0) Same Host Order Diff. niche # sister taxa pairs
Niche Evolution - Recap MorphologyMolecules Sig.better than random Niche Not significant Host Sig.better than random (just)Sig.better than random Sister taxon niche pairs Not significantHighly significant
Niche evolves early (niche assorts with host lineages) Niche evolves late (niche displaces within host lineages) ? Morphology supports lineage assortment Molecules supports character displacement Lineage assortment or character displacement?
Which hypothesis is best supported? Molecules Niche evolves late (displaces within host lineages) Character displacement Mol. phylogeny well supported Especially terminal clades Mit. + nuclear genes agree Mol. data blind to niche There are only a few host niches We would expect to see strong selection & morphological character convergence
What use is morphology? Can we identify morphological characters that co-vary with niche? If so, what are they, and can we extract them to build the correct louse phylogeny i.e. one that is topologically more similar to the molecular tree - phylogenetically speaking
Identifying co-varying characters? MorphologyNiche Constraint Enforce backbone constraint Which characters fit the constraint tree better than the original? Exclude characters with increased RI Heuristic search Repeat until no more characters improve their fit 9 cycles, 61 characters excluded Almost half the dataset removed! Remaining characters very noisy We need a better method - any suggestions?
Is character displacement common? Common mammal lice Traditionally considered unrelated Morphologically very different Occupy different host niches Placed in different families Generic phylogeny of sucking lice Genera are sister taxa!
Is character displacement common? Generic phylogeny of sucking lice Human head louseHuman pubic louse
Character displacement - a general mechanism producing phenotypic diversity Radiation of Anolis lizards on the Greater Antilles UPGMA Morphology (clusters phenotype) Molecular Phylogeny (phenotype transitions common) Niche / Microhabitat Losos et al. Science
Character displacement - a general mechanism producing phenotypic diversity Fig wasps Weiblen & Bush Mol. Ecol Non pollinating Fig wasp parasites Fig Plant hosts Shared host use by wasp sister taxa promotes character displacement