Transcript Slide 1
Species boundaries, phylogeography and conservation genetics of the redlegged 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 R. Aurora • Originally classified as two distinct species: R. aurora (Northern redlegged frog) and R. draytonii (California redlegged 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 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” 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 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 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) 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 Results Sequence Variance • 47of 107 sequnces were unique • All individuals showed low frequency of guanine. – f(G)=0.15 • Optimal Model selection HKY+G Phylogeny • Several well supported clades • Demonstrate a sistergroup between aurora and cascadae • aurora and cascadae are not a monophyletic group 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 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 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 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) 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 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 Questions???