Species boundaries, phylogeography and conservation genetics of the red-legged frog (Rana aurora/drytonii) complex - PowerPoint PPT Presentation

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Species boundaries, phylogeography and conservation genetics of the red-legged frog (Rana aurora/drytonii) complex. Presented by: Chris Burton & Matt Meyer. Presentation Overview. Introduction – Matt Materials and Methods – Chris Results – Chris Discussion and Implications - Matt.

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Species boundaries, phylogeography and conservation genetics of the red-legged frog (Rana aurora/drytonii) complex

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Species boundaries, phylogeography and conservation genetics of the red-legged frog (Rana aurora/drytonii) complex

Presented by: Chris Burton & Matt Meyer


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Presentation Overview

  • Introduction – Matt

  • Materials and Methods – Chris

  • Results – Chris

  • Discussion and Implications - Matt


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R. Aurora

  • Originally classified as two distinct species: R. aurora (Northern red-legged frog) and R. draytonii (California red-legged frog)

  • Reclassified R. aurora as a single polytypic species with two subspecies, R. a. aurora & R. a. draytonii

  • Currently R. a. aurora and R. a. draytonii are conspecific subspecies

R. a. aurora

R. a. draytonii


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R. aurora

  • Once widespread in Sierra Nevada and San Joaquin Valley

  • Currently only 6 known, recently discovered, populations still in existence in these areas

  • R. a. draytonnii – threatened under US Endangered Species Act. – Enormous economic and ecological consequences

  • Mark Twain’s – “The Celebrated Jumping Frog of Calaveras County”


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Range

Restricted to Pacific Coast of North America from southern British Columbia to northern Mexico.

  • Broad Zone of Intergradation – several hundred kilometers in northern California

http://www.californiaherps.com/anurans/maps/rauroramap.jpg


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Materials and Methods

Specimen

  • 108 Specimen from six taxa

  • Sample 50 sites that span the range of aurora and draytonii – (1 to 4 from each site)

  • Included three outgroup taxa

    • R. boylii

    • R. muscosa

    • R. catesbeiana


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Molecular Methods

  • DNA was extracted

  • Primers were developed to amplify a fragment of cytochrome b mtDNA from all taxa

  • Species specific Primers

    • cytb1-ra

    • cytb1-rm

    • cytb1-rb

    • cytb2-ra

  • Individual were sequenced in both directions

  • Sequences ranged from 297 to 397bp (most ~ 350bp)


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    Analysis

    • Parsimony analysis was ran on both short and full fragments

    • Likelihood analysis used MODELTEST for a common 287bp fragment

    • Bootstrap proportions (BP) were used to asses the strength of the trees

    • Parametric bootstrapping used to test a prior hypthesis of relationships


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    Results

    • 47of 107 sequnces were unique

    • All individuals showed low frequency of guanine. – f(G)=0.15

    • Optimal Model selection HKY+G

    Sequence

    Variance


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    Phylogeny

    • Several well supported clades

    • Demonstrate a sister-group between aurora and cascadae

    • aurora and cascadae are not a monophyletic group


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    Bootstrap Likelihood of Subset of Unique Sequences

    • 15 sequences – 3 of each major group

    • Show monophyly of individual taxon and the monophyly of aurora and cascadea clade


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    Parametric Bootstrap Analysis

    • Test Hypothesis that Rana a. aurora and R. a. draytonii are sister taxa

    • Search for a model tree, with aurora + draytonii forming an exclusive clade


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    The aurora/draytonii contact zone

    • Sample effort was supplemented

      • To approximate the width of the contact zone

      • To identify biogeographical barriers

    • Found that the two over lap over a several-km region

    • Pure aurora found from Big River north

    • Pure draytonii from Mills Creek south

    • In between both were found

    • Breeding dynamics or restriction of overlap zone can not be determined due to only one or a few indiviuals being sequenced per site

    • However, mtDNA contact zone can be determined to be narrow with no obvious barriers to gene flow


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    Discussion and Conclusions

    • mtDNA data supports the separate species hypothesis based on:

      • Relatively deep differentiation and reciprocal monophyly of aurora and draytonii

      • The sister group relationship of aurora and cascadae and the exclusion of draytonii

  • Assuming the data reflects the correct order of speciation:

    • Split 1 – between northern (aurora & cascadae) and southern frogs (draytonii)

    • Split 2 – between coast range (aurora) and interior cascade mountains (cascadae)


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    Biogeography

    • Past studies have shown two distinct phylogeographical splits along the Pacific Coast in California

      • North/South break

      • Northern California break

    • These phylogeographic boundaries relatively coincide with the north and south ends of the aurora and draytonii contact zone

    • Data reflects history of species, not just mitochondrion


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    Species Conservation / Implications

    • As a result of the data, many of the population that were thought to be intergrades are not.

      • draytonii (protected species) extends farther north

      • Confirmation with nuclear markers could result in a conservation status adjustment

    • Single draytonii population in southern California

      • Only 3 adult males

      • Captive breeding

      • Data suggests more closely related to distant draytonii populations rather than closest ones


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    Questions???


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