Proposal (190) to South American Classification Committee
Merge Oceanodroma into Hydrobates Boie 1822
Background
The current SACC Checklist
recognises seven species within the genus Oceanodroma Reichenbach 1853.
Proposal
Penhallurick and Wink carried out
an analysis using Bayesian Inference (Mr Bayes3.1) of 95 taxa within the
Procellariiformes.
We used PAUP (Swofford 1998) and ModelTest
(Posada and Crandall 1998) to
analyse the substitution patterns in a cytochrome-b data set against 56 different models of DNA
evolution. We used the Akaike Information Criterion (AIC). The model selected
was GTR+I+G.
We used Bayesian inference and
Markov Chain Monte Carlo (mcmc) with Metropolis coupling for estimating
phylogenetic hypotheses from DNA data. The model of nucleotide substitution
used was the GTR model, following the results of ModelTest mentioned above.
Thus Nst was set to 6 and Rates to Invgamma. In relation to prior
distributions, we used a flat Dirichlet for both Revmatpr and Statefreqpr.
Ronquist et al. (2005) stated
that use of the default settings is appropriate if we want to estimate these
parameters from the data assuming no prior knowledge about their values. After
three million generations, the average standard deviation of split frequencies
was 0.008673. The mean of the 13 Potential Scale Reduction Factor (PSRF)
figures was 1.002 (SD 0.003). We give, as Figure 1, a plot of the generation
versus the log probability of the data (the log likelihood values). The plot
approximates "white noise". All the data just cited support the
validity of the analysis.
Figure 1 Plot of generation versus
the log probability of the data (the log likelihood values) for the MrBayes3.1
analysis of the data
Figure 2 Phylogeny of all
Procellariiformes
Bayesian Inference Tree. This
represents a 50% majority rule consensus tree. Posterior Probability values are
indicated, usually to the right of the nodes, but occasionally, for reasons of
space, to the left.
Figure 3 displays that section of
Figure 2 containing the storm-petrels
Note: All three figures are
available at the author's website.
Click on Enter, and then on
"SACC Documents" at the bottom of the menu on the left.
Figure 1 can be found under "Mr
Bayes Plot"
Figure 2 under "Mr Bayes tree
for Procellariiformes"
Figure 3 under "Mr Bayes
subtree for Storm-Petrels"
Figure 2 shows two subgroups:
Oceanitini and Hydrobatini, both with posterior probability values of 1.00 in
Figure 2. Clearly in Figure 2, the genus Oceanodroma Reichenbach 1853 is
paraphyletic. The citation for Oceanodroma Reichenbach 1853 is:
Oceanodroma Reichenbach, 1853["1852"], Avium systema naturale: das natürliche System der Vogel
mit hundert Tafeln grosstentheils Original-Abbildungen der bis jetzt entdecken
fast zw_lfhundert typischen Formen, p.iv. Type, by original
designation, Procellaria
furcata J. F. Gmelin, 1789.
Oceanodroma furcata (J. F. Gmelin 1789) Fork-tailed Storm-Petrel
aligns with Hydrobates pelagicus (Linnaeus 1758) European Storm-Petrel. That
node has 1.00 posterior probability support.
Since Hydrobates Boie 1822 predates Oceanodroma Reichenbach 1853, Oceanodroma must become a junior synonym of Hydrobates.
Recommendation
That Oceanodroma Reichenbach 1853 become a junior synonym of Hydrobates Boie 1822.
Note: a further proposal considers
the application of generic names within the Hydrobatini.
John
Penhallurick, November 2005
________________________________________________________________________________________
Comments from Stiles:
"[190 and 191] are linked, such that a YES vote on 190 implies a YES on
191 as well. So far as it goes, the genetic evidence appears to favor the
proposals, so a tentative YES to both. My main caveat is that only one gene was
sequenced: is this sufficient?"
Comments from Remsen: "NO.
I strongly suspect that the Penhallurick-Wink data reveal the true phylogeny of
the Hydrobatidae. Nonetheless, my personal policy on changes in classification
is ... or tries to be ... based on congruence of two or more "data
sets", e.g., two genes show same signal within the same paper, or two
separate papers show same genetic results using different genes, or two sets of
independent phenotypic characters shows the same thing, or any partial combination
of the above. The guiding principal is that congruence among independent data
sets gives me confidence that the results reveal true phylogeny, whereas I
treat a single character as a phylogenetic hypothesis that should spawn
additional testing. I doubt that I've been consistent in the application of
this "policy", but I think when I've voted for a change based on 1
character, other characters that may not have been formerly analyzed are
nonetheless consistent with the change. In this case, we're dealing with
placing in synonymy the largest and most familiar genus name in the family, and
so before making such a 'drastic' change to the classification, I eagerly await
a second data set that supports this change."
Comments solicited by Remsen from
Dr. Chris Witt, MVZ, UC Berkeley: "In a
cytochrome b phylogeny, Oceanodroma is paraphyletic with respect to Hydrobates
pelagicus. The generic name Hydrobates has priority. If the cytochrome b phylogeny
reflects the true species relationships, a generic revision is warranted.
Penhallurick is proposing that O.
furcata and H. pelagicus should be in the same genus, although
he doesn't state that explicitly. It seems like a reasonable idea given the
close mtDNA relationship of these two species.... but shouldn't morphology,
behavior, life-history, or biogeography also enter into this decision? Making
the argument based on molecular data alone might be acceptable if there were
data from multiple loci, but this case involves only cytochrome b sequence
data. Available effort should be spent on generating more data or examining
patterns of phenotypic divergence with respect to the cytochrome b phylogeny.
After all, O. furcata and H.
pelagicus look totally
different!!!
"Certainly, if furcata and pelagicus are to be considered congeneric, they
should both be in Hydrobates....
but I think the best course of action would be to hold off on any changes until
nuclear loci corroborate the phylogeny and/or a reasoned argument based on
levels of phenotypic divergence is made for the splitting or lumping of
storm-petrel genera within the Hydrobates/Oceanodroma cytochrome b clade."
Comments sent to Remsen from
someone who wished to remain anonymous: "It is my understanding that
the SACC bases its decisions entirely on published material, is that right? If
so, I'm not sure if you guys have realized that the results on which
Penhallurick is partly basing his arguments for these new proposals have not
been published, as the Bayesian analyses he refers to were not included in the
paper he co-authored with Wink.
"In that paper they only
presented a distance tree, a parsimony tree, and a maximum-likelihood tree, and
they only presented bootstrap values for the distance tree, which in general
means that the support for particular clades on their other phylogenies cannot
be assessed. With regards to proposal 190, yes, all analyses put Hydrobates in a clade with Oceanodroma but relationships within the clade relevant
to the position of Hydrobates are not well-supported in the only tree
that has bootstrap values on it, which implies that based on the results
presented in the paper one cannot reject the possibility that Hydrobates and Oceanodroma are sister genera in favor of his
proposal that Hydrobates is nested within Oceanodroma.
"To me, it seems that
Penhallurick may have a good case here (at least based only on cyt-b and I see
the jury is still out on whether that's enough), but only if one accepts that Hydrobates is sister to one of the species of Oceanodroma with a high posterior probability. However,
that piece of information (i.e. the strong support for that sister relationship
in a Bayesian analysis) has not been published. This may be only a minor
technical issue, but I thought I'd bring it up just in case you think it may
matter... "
Comments from Robbins: "NO.
Given that the published data for support of this proposal are based on only a
single gene coupled with comments by Witt and an anonymous reviewer I vote
"NO". I note during the past two years that the vast majority of
molecular derived avian phylogenies are based on at least two genes and
depending on the level of the question usually at least a mtDNA and a nuclear
gene are used. Today, one would have a difficult time getting a phylogeny
published (at least in most journals) based on only a single gene."
Comments from Silva: "NO.
I would prefer to see the paper published as well as evidence from at least one
more gene."
Comments from Stiles: "I
originally voted YES on this, but with the caveat that I was not sure that a
single gene (cyt-b) was enough to justify such a change. The cogent arguments
of Witt and the anonymous reviewer (and I hate anonymous reviewers!!..) have
convinced me that one gene is NOT enough; more evidence is required, and
pending that evidence I will change my vote to NO."
Comments from Pacheco: "NO.
Diante dos argumentos bastante
convincentes empilhados acima, sou de opinião que os resultados de Penhallurick
and Wink (2004) precisam ser corroborados por evidências extraídas de um
conjunto diferente de genes."
Comments from Zimmer: "NO,
for all of the reasons cited by others, particularly as summed up in the last
paragraph by Chris Witt."
Comments from Jaramillo: "NO
- Being one of the last to vote on this, well, most of the good stuff has been
said. I think that when results from a single gene analysis are so surprising,
well if I was the researcher I would want to back this up with more data to
feel comfortable about it myself. Even a good summary of vocal, behavioral, or
other data that may bear on this result would be good to have. I don't doubt
that it could very well be the "truth" in this case, but for the
reasons noted by others I am hesitant to accept this to be the case.