Wednesday, April 25, 2007

Whiting et al. 2004 / Trueman et al. 2004

Whiting, M.F., S. Bradler and T. Maxwell. 2004. Loss and recovery of wings in stick insects. Nature. 421: 264-267.

This paper has been commented upon in three different reading/discussion groups that I have attended so I thought I should post some of my comments of the paper here. I will also add notes on some of the rebuttals that have been published.

Whiting et al. used phylogeny to demonstrate that the first Phasmatodea was wingless and that wings evolved secondarily and on numerous occasions in this group. They suggest that wing developmental pathways are conserved in wingless stick bugs.

Data used: 1) 18S rDNA; 2) 28S rDNA; 3) portion of Histone 3.
-sequenced 22 outgroup specimens (representing all Polyneoptera)
-sequenced 37 ingroup taxa (representing 14 out of 19 subfamily groups)

Analyses: -used bootstrap and bremer support
-used POY for optimization alignment analysis and compared this to MP, ML and bayesian methods

[Notes: Acctran = Accelerated transformation -changes are assigned as close to the root of the cladogram (where the outgroups and ingroups diverge) as possible. Favours reversals.
Deltran = Delayed transformation -puts the character change as far from the root as possible. Favours parallelisms.]

Some of the problems that I had with this paper are:

1) what about fossil phasmids that have wings?
2) why did they use POY? This seems to be very rarely used and unfortunately I have never used it so I can't really comment on this program. Why didn't they publish their ML or Bayesian trees?

Another point that seems to be important and that is a direct quote from this paper is: "re-evolution of wings in insects is thought to be impossible because functional wings require complex interactions among multiple structures, and the associated genes would be free to accumulate mutations in wingless lineages, effectively blocking the path for any future wing reacquisition."

Trueman, J.W.H., B.E. Pfeil, S.A. Kelchener and D.K. Yeates. 2004. Did stick insects really regain their wings? Systematic Entomology. 29: 138-139.

Points that the authors make in this paper are:

1) two lines of evidence are necessary for the Whiting et al. hypothesis to hold true:
1) topology of phylogenetic tree
2) distribution of wing/wingless transformations on tree

2) Whiting et al. have overstated significantly the probability of wing re-evolution in stick

3) reconstruction of the phasmid ancestor is not the relevant issue

4) support for each hypothesis needs to be compared when alternative ancestral states are
assumed to be true

The authors then do some easy math to show how the ratio of lost wings to gained wings is a mere 2.5:1.

Whiting, M.F. and A.S. Whiting. 2004. Systematic Entomology. 29: 140-141.

Whiting and Whiting then published a reply to Trueman et al. I found the tone very whiny. We did this and you didn't. We had super computers and you didn't, so there. It's really not even worth commenting on.

Wednesday, April 18, 2007

Hanski and Niemela 1990

Hanski I, Niemelä J. 1990. Elevational distributions of dung and carrion beetles in northern Sulawesi. In: Knight WJ, Holloway JD, editors. Insects and the Rain Forests of South East Asia (Wallacea). p 145-152.

This paper is really interesting to me because I work on carrion beetles in Asia and this paper is specific to my work. In this paper, the authors attempt to document the elevational distributions for all dung and carrion beetles in northern Sulawesi (Indonesia). It was hoped that this would give insight into the processes which are important in structuring dung and carrion beetle communities in tropical forests. They state that carrion beetles are a good animal to use for transect studies because their numbers can be accurately estimated in a short period of time. They compared their transect study in Sulawesi to one previously conducted in Borneo.

Hankski and Niemila found:

1) beetle diversity was higher in Sulawesi than Borneo (apparently because of higher availability of resources-I would have to question this).

2) species richness (# of species) was the same in the two localities -but more montane species were found in Sulawesi (they state that this is probably because Sulawesi has more montane forests than Borneo).

3) no distinct elevational species assemblages were found in Sulawesi

Interestingly, they state, "detailed observations however indicated mutually exclusive ranges in Nicrophorus (two species)...". However, they then contradict themselves by stating further in the paper that, "two species [N. charon and N. distinctus] were found together at one site at 1450 m on Gn. Muajat and therefore their distributions are touching or slightly overlapping". I have also found this evidence where N. distinctus and N. charon occured at the same place at one of my sites. Unfortunately, I was not able to study the elevational ranges of these two species due to the 'problems' I encountered in Dongi Dongi and Rano Rano. In Dongi Dongi, the problem was local people conducting illegal logging and making sure no one (especially white foreigners who look like they could tell the government) was snooping around in the area. The problem in Rano Rano was that it was a 6 hour hike to get to the top and we didn't bring enough food to stay longer than 1 day.

Another interesting quip is "most dung and carrion beetles in SE Asia are attracted, to a varying degree, to both dung and carrion" (Hanski 1988). I wonder if the nepalensis group (Nicrophorus) is attracted to dung as well?

"In SE Asia, only one species occurs in one region: podagricus: Borneo; insularis: Java [also occurs on Sumatra and Bali]; nepalensis: northern Philippines [and mainland Asia], apo: Mindanao; heurni: New Guinea; insignis: Flores."

"As a rule Nicrophorus in SE Asia are restricted to montane forests, but in Solomon Islands and Sulawesi, one species occurs only in the lowlands while the other one is restricted to montane forests". I found that this is not entirely true for species on Sulawesi. Although N. charon is restricted to the highlands, N. distinctus is not restricted to the lowlands.

"Sumatra has two allopatric montane Nicrophorus species". This would be N. insularis and N. hersheli. Nicrophorus hersheli is one of the two species for which I desperately need fresh tissue sample from. It is interesting that the authors state that the two species are allopatric. What barriers on the large island of Sumatra could have caused this allopatry, if it is not one of elevational distribution (and looking at locality data I don't believe it is). I know Sumatra has had a history of partial and full submergence due to sea levels rising and falling in glacial periods, perhaps this had something to due with their ranges?

Thursday, April 5, 2007

Johnson and Black 2006.

Johnson, M.S. and R. Black. 2006. Islands increase genetic subdivision and disrupt patterns of connectivity of intertidal snails in a complex archipelago. Evolution. 60(12): 2498-2506.

Because my work involves the biogeography of the malay archipelago, my supervisor thought this paper may be important for me to read. Unfortunately it really does not relate to my work at all because Johnson and Black's research is based on marine patterns, whereas my work deals with terrestrial patterns. Nonetheless, I read the paper and these are the important bits:

1) the authors wanted to find out what local conditions might favour the isolation of populations of marine species with planktonic dispersal.

2) allozyme variation among 35 populations of the intertidal snail, Austrocochlea constricta indicated highly localized populations in the Houtman Abrolhos Islands, Australia.

3) islands are important for retention of locally produced larvae and disruption of patterns of connectivity.

4) models of gene flow in marine larval populations need to take islands into account.

This paper rated 8 out of 10 on the boring scale (but this may be because it does not relate to my work at all).