Keeping up with the Railses: New Zealand's flightless rails

In a previous post I touched briefly on two species of New Zealand rail in the genus Porphyrio. As mentioned, the pūkeko is one subspecies (Porphyrio porphyrio melanotus) that belongs to a cosmopolitan species complex. The takahē (Porphyrio hochsetterii), on the other hand, is endemic to New Zealand.  In addition to these two extant species there is an extinct member of the genus, the mōho (Porphyrio mantelli), also known as the North Island takahē. The pūkeko and takahē are morphologically similar as would the mōho have been, which is what you expect given that they are congeneric (i.e. in the same genus). From fossil evidence we know that the mōho and the takehe were more similar to each other than to the pūkeko: the main difference being that the mōho had longer legs, was larger and was more slender than the takahē. The strong morphological similarity between the mōho and takahē led early taxonomists to classify them as two subspecies, Porphyrio mantelli mantelli  and Porphyrio mantelli hochsetterii respectively. Because all three species are in the same genus, we know that they share a common ancestor. Therefore, pragmatically we might expect that they all evolved from this common ancestor in New Zealand.

However, this expectation is not supported by both fossil and molecular (DNA) evidence. In the mid-nineties, Steven Trewick (note the link to his personal page is broken but this takes you to his lab website) undertook a study of New Zealand rails to determine their origins, evolutionary history and the relationships among them. What he found was somewhat surprising in regard to the mōho and takahē. Rather than sharing a common ancestor with an in-situ divergence event, the mōho and takahē were the result of two separate colonisations by similar volant ancestorsprobably a species similar to the pūkeko. This evidence resulted in a revision of the two subspecies into two separate species as indicated above. It also raised some interesting questions regarding the evolution of flightlessness among New Zealand rails.

New Zealand has (including recently extinct species) a relatively high diversity of rails (18), about half of which are flightless. An interesting question that Steve Trewick and his research group are asking is why seemingly mobile, volant species evolve into flightless range-restricted species. This comes partially from the fact that the likely ancestors of the mōho and the takahē came from the same lineage as the pūkeko. Because birds are highly mobile - the pūkeko being a perfect example in this case the - gene flow tends to be high reducing the probability of speciation. In fact, there is little evidence for speciation among birds on islands. In other words, it takes a substantial barrier to stop gene flow in birds which reduces the probability of speciation. Yet there have been several independent rail colonisations in NZ with many resulting in a flightless species. To me this indicates that there is strong selection for rails to fly when necessary (i.e. in the presence of predators) but it is easily relaxed without predators. But the question of even rates of gene flow remains.

A quote about us all

"The chief obstacle to the progress of the human race is the human race." - Don Marquis

This statement is often quite true. I have just started reading The Moral Landscape by Sam Harris (on my new kindle-get one). Early on, and I am sure later (actually I know later because I can word search with my kindle-see I told you to get one), Harris talks about stem-cell research and the opposition it faces in the US. Sadly, this opposition has significant negative impact on our ability to develop medical treatments that would save countless lives.

Note: sorry no photo this time.

Part 2: do you believe in evidence?


The second part of my analysis of the statement on creation/evolution published by Ponahui Christian School picks up where part one left off: it might get better.
Indeed, it seemed like it might with a promising title. The title of the second part of the statement “[c]ommonly accepted science we believe in.” It is better because at least they accept some science, but inserting the world ‘believe’ in reference to science is cringe worthy. Science is not based on beliefs, science is based on evidence. Accept would have been better but it would hardly change their intent. The second part of the statement is as follows:

We believe in all the experimentally verifiable laws of science. We also teach that the laws of physics and chemistry are purposely designed by the Creator to support life. If the known physical constants of the universe are slightly different, or the angle in a water molecule was slightly different, or the chemical laws of equilibria, etc, are any different then life would be impossible. (Imagine a universe without gravity for example.) Even something as simple as burning wood in a controlled campfire requires several laws of physics and chemistry to be just right, and several conditions on planet Earth to be just right also. This paradox is a puzzle to evolutionists who base everything on chance, but not to the creationist who believe that even something as simple as controlled fire, and something more complex such as life, is God’s design. The unproven and unprovable theory of the existence of millions of universes is based solely on trying to explain this paradox. If there are millions of universes is has to be just right somewhere! (We don’t subscribe to this.)
This means that we believe in the overwhelming majority of science in the NZ curriculum and teach it accordingly, and we feel privileged to be part of the NZ education system. Our students have consistently scored above the national average in all external science exams, including biology.
In the area of biology we believe in natural selection, genetic drift, speciation, and adaptive radiation. We believe that God has designed these processes to enable living things to change slightly, within their kind, to enhance population health in new or changing environments. These processes are all re-arrangements, frequency shifts, and net losses of genetic information which is already present.

Following on from using ‘believe’ in the title, the word is inserted here again, although in reference to “experimentally verifiable laws of science.” If something is an experimentally verifiable law belief is entirely redundant. A scientific law is a phenomenon of nature that has been proven to invariably occur whenever certain conditions exist or are met. Therefore, it is ironic, that people who believe in the unverifiable nature of the supernatural require something to be verified experimentally. Also, there are very few laws in science yet they suggest that “[they] believe in the overwhelming majority of science in NZ curriculum” which cannot be true if they only ‘believe’ in laws. Science is built upon laws, theories, principles and hypotheses and the NZ science curriculum is built on all of these, not just laws.

It is true that the physical constants on Earth are just right for the way the world is now. However, while we can speculate that life as we know it would not exist if the earth and universe were not exactly as it is now, we cannot be sure that life in any other form would not. Things would be different, but that is what they would be. I would most likely not exist and neither would you. The suggestion of a paradox is quite difficult to understand. I see no paradox. The conditions on Earth are just right for the life that exists on it is in no way paradoxical, it just is. The claim that the multiverse concept was proposed is an attempt to account for the ‘paradox’ is patently incorrect. These ideas arose independently of evolutionary biology given that it comes from the field of theoretical physics and have been around for a long time. Recent empirical observations of the universe appear to support the concept of a multiverse. See here for a paper on a concept called Eternal Inflation. Warning! It is not straight forward. Also note that authors do not talk about resolving any paradox. Further note that I am not a physicist and cannot verify the work I am simply putting trust in those who do know about physics in the same way that I, and most other people, trust bridge builders and car manufacturers.

I have purposely left the final paragraph about biology because I think it is best addressed along with the next few sections that cover biology and evolution in more ‘detail’. What I will do is congratulate Ponatahi for their “consistently. . . above the national average in all external science exams, including biology.” However, I will add that it seems odd that their students achieve above results in biology exams based on a curriculum that explicitly covers evolution. It is fishy and reeks of dishonesty somewhere down the line. I have no evidence so I am just speculating.