Dear Klaus, Thank you for your response. I was wondering if you could expand on how to do this with phangorn::pml_bb(). Here's a small tree I made in Raxml with the cytochrome b gene of a few species of birds: library(ape) tree <- read.tree(text = "(Nesillas_typica:0.04793543089316195,(((A_schoenobaenus:0.043980600360374364,A_melanopogon:0.06481521246716708):0.022244127250028972,(((I_caligata:0.08810019775981455,I_pallida:0.062476654152826855):0.017350459234948976,(((A_newtoni:0.033344055105229795,A_sechellensis:0.01792648331103279):0.021283417245643144,(A_rufescens:0.05238658747602984,A_gracilirostris:0.044877312044462714):0.013125661916305195):0.022403450749406223,((A_arundinaceus:0.04093765705229456,A_stentoreus:0.01826146619561772):0.015107695382970854,A_griseldis:0.0972067122912957):0.011211088579910683):0.02819743631258305):0.007869067285886489,(H_icterina:0.058362559770475525,H_polyglotta:0.033259000190850735):0.05342630181117944):0.005148698839842897):0.006239321505491391,((A_palustris:0.05185723350471064,(A_scirpaceus:0.014053067606248151,A_baeticatus:0.008365145972302118):0.045911856091680914):0.023773812432215297,(A_dumetorum:0.08560190754497965,A_agricola:0.07765117111045171):0.000001):0.013260470881828468):0.04793543089316195);")
If we assume that the divergence rate for cytochrome b for these species is 2.21% per million years, how could we rescale the tree with a strict clock? Do we need to start with a DNA alignment and re-estimate the tree topology or can this be done just with the ML tree I already estimated and the rate? Thank you, Vincenzo On Mon, Mar 4, 2024 at 7:57 PM Klaus Schliep <klaus.schl...@gmail.com> wrote: > Dear Vincenzo, > For ML estimates the edge length are the expected number of substitutions > per site, which depends on the product of rate and time. So you need either > a rate estimate or calibration points to estimate the time. If you divide > the edge length by the rate the edges should be proportional to time. > With pml_bb you can estimate ultrametric or tip dated trees with a strict > molecular clock model. > Kind regards, > Klaus > > > > > Von meinem iPhone gesendet > > > Am 04.03.2024 um 21:06 schrieb Vincenzo Ellis <vael...@udel.edu>: > > > > Dear Liam, > > > > Thank you for your answer. Yes, I have a hypothesized average clock rate > > and no explicit calibration points. > > > > If I use ape::chronos() with default values it gives me a depth of 1 at > the > > root. So I suppose to rescale the branch lengths I just need to multiply > > all of the branch lengths by a value (i.e., tree$edge.length * value), is > > that right? > > > > Thanks again, > > > > Vincenzo > > > >> On Mon, Mar 4, 2024 at 11:43 AM Liam J. Revell <liam.rev...@umb.edu> > wrote: > >> > >> Dear Vincenzo. > >> > >> If I understand your problem problem, you do not have any explicit > >> calibration points -- but you have a hypothesized average clock rate? > >> > >> If so, then you can obtain an ultrametric tree from* ape::chronos* for > >> any value of the smoothing parameter (*lambda*) and then simply re-scale > >> it to have the desired total depth (based on your hypothesized clock > rate). > >> > >> To choose a "correct" value of *lambda* one can use cross-validation as > >> described in Sanderson (2002; > doi:10.1093/oxfordjournals.molbev.a003974). > >> > >> Others should feel welcome to weigh in if this is not right. > >> > >> All the best, Liam > >> Liam J. Revell > >> Professor of Biology, University of Massachusetts Boston > >> Web: http://faculty.umb.edu/liam.revell/ > >> Book: Phylogenetic Comparative Methods in R > >> < > https://press.princeton.edu/books/phylogenetic-comparative-methods-in-r> > >> (*Princeton University Press*, 2022) > >> > >> > >> On 3/4/2024 11:09 AM, Vincenzo Ellis wrote: > >> > >> [You don't often get email from vael...@udel.edu. Learn why this is > important at https://aka.ms/LearnAboutSenderIdentification ] > >> > >> CAUTION: EXTERNAL SENDER > >> > >> Dear Emmanuel, > >> > >> Thank you very much for your response. I cannot see how to provide the > >> substitution rate to the phangorn::pml_bb() function, but I was looking > at > >> the ape::node.dating() function and it appears that I could provide the > >> substitution rate to the "mu" argument and then set the "node.dates" > >> argument to NA or zero for all tips (I'm not sure if NA or zero would be > >> preferable to force the tips to all be from a single time point). Do you > >> think that would work? I'm not sure how to make ape::node.dating() > accept a > >> substitution rate rather than try to estimate one. Maybe an option > could be > >> added to allow mu to equal a user-specified number rather than the > output > >> of ape::estimate.mu()? > >> > >> Another option might be to calculate an estimated age for every node > >> connecting sister taxa in the tree by converting the genetic distances > >> between sister pairs to divergence times using the substitution rate and > >> then use those as priors in ape::chronos(). I suppose I could also apply > >> that logic to date all of the nodes by using the mean pairwise distances > >> between taxa on either side of a node and converting that to divergence > >> times (although the R code for such a calculation would likely take me a > >> while to figure out). Would that be another option? > >> > >> Thanks again, > >> > >> Vincenzo > >> > >> On Sat, Mar 2, 2024 at 5:44 AM Emmanuel Paradis < > emmanuel.para...@ird.fr> <emmanuel.para...@ird.fr> > >> wrote: > >> > >> > >> Hi Vincenzo, > >> > >> There's no direct way to do this with ape::chronos(). You may have a > look > >> at the function phangorn::pml_bb() but I'm not sure it can estimate the > >> dates if the rate is provided in a model object given as main > argument(?) > >> > >> That said, I expect that estimating so many dates to be very challenging > >> (unless you have a lot of known dates for calibration). This implies > that > >> you are certainly right to look for an approach where you don't need to > >> estimate the rates. > >> > >> Best, > >> > >> Emmanuel > >> > >> ----- Le 27 Fév 24, à 22:40, Vincenzo Ellis vael...@udel.edu a écrit : > >> > >> > >> Dear R-sig-phylo members, > >> > >> I've made a maximum likelihood tree in Raxml for several thousand taxa > >> using a single gene that has an estimated substitution rate of 0.006 > >> substitutions/nucleotide/My. Is there a way to use chronos in ape to > >> > >> apply > >> > >> that substitution rate as a fixed clock rate and generate an ultrametric > >> time-scaled version of the tree? > >> > >> Thank you, > >> > >> Vincenzo > >> > >> [[alternative HTML version deleted]] > >> > >> _______________________________________________ > >> R-sig-phylo mailing list - R-sig-phylo@r-project.orghttps:// > nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstat.ethz.ch%2Fmailman%2Flistinfo%2Fr-sig-phylo&data=05%7C02%7Cliam.revell%40umb.edu%7C94e522b834f94ff6aa7c08dc3c659399%7Cb97188711ee94425953c1ace1373eb38%7C0%7C0%7C638451654193183565%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=wV2IJEHNPpbc2a7Erg%2F14jVmDcIqLshVohWaKa6vG6U%3D&reserved=0 > <https://stat.ethz.ch/mailman/listinfo/r-sig-phylo> > >> Searchable archive at > >> > >> > https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.mail-archive.com%2Fr-sig-phylo%40r-project.org%2F&data=05%7C02%7Cliam.revell%40umb.edu%7C94e522b834f94ff6aa7c08dc3c659399%7Cb97188711ee94425953c1ace1373eb38%7C0%7C0%7C638451654193196126%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=d4fLpFetiQDBjHKTmdlDijgx%2F360Z2oPddHLdCqrrUQ%3D&reserved=0 > <http://www.mail-archive.com/r-sig-phylo@r-project.org/> > >> > >> [[alternative HTML version deleted]] > >> > >> _______________________________________________ > >> R-sig-phylo mailing list - R-sig-phylo@r-project.orghttps:// > nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstat.ethz.ch%2Fmailman%2Flistinfo%2Fr-sig-phylo&data=05%7C02%7Cliam.revell%40umb.edu%7C94e522b834f94ff6aa7c08dc3c659399%7Cb97188711ee94425953c1ace1373eb38%7C0%7C0%7C638451654193201324%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=XV4ICgm3xswIObonT8pYZcEHsQVSImxPcKHqefo8zuk%3D&reserved=0 > <https://stat.ethz.ch/mailman/listinfo/r-sig-phylo> > >> Searchable archive at > https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.mail-archive.com%2Fr-sig-phylo%40r-project.org%2F&data=05%7C02%7Cliam.revell%40umb.edu%7C94e522b834f94ff6aa7c08dc3c659399%7Cb97188711ee94425953c1ace1373eb38%7C0%7C0%7C638451654193205831%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=dbdnzYPubwMiyqGLncCCl8P5bPDQ%2Bn3QPUUEAt4sQZQ%3D&reserved=0 > <http://www.mail-archive.com/r-sig-phylo@r-project.org/> > >> > >> > > > > [[alternative HTML version deleted]] > > > > _______________________________________________ > > R-sig-phylo mailing list - R-sig-phylo@r-project.org > > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > > Searchable archive at > http://www.mail-archive.com/r-sig-phylo@r-project.org/ > [[alternative HTML version deleted]] _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/
