Small tree finch Camarhynchus parvulus with naris damage caused by larvae of the avian vampire fly, Philornis downsi.
Photo: Dr Katharina Peters, Flinders University.
It's always fun when Creationist frauds are exposed and their credulous dupes shown to be... well... credulous dupes (to be kind). It's even more delicious when the scientists unwittingly doing it are using those iconic birds, Darwin's finches, or more correctly, Galápagos finches of the genus Camarhynchus.
The story begins back in the 1960s when the parasitic avian vampire fly (Philornis downsi) was accidentally introduced onto one island in the Galápagos group. Females of this species lay their eggs in the nests of certain species of bird and the larvae feed on the blood and tissues of the young. They are especially attracted to the ears and nostrils of the chicks and cause distortions and deformities in those which survive to adulthood. 50-100% of a brood can be lost to an attack. After spending 10 days eating the chicks, the fly larvae then pupate in the base of the nest and emerge as adult 16 days later to begin the cycle again.
As a result of this newly-introduced predation, 10 species of Darwin's finches are now under sever threat of extinction so there is intense selection pressure on the birds to evolve strategies for resisting or avoiding this predation. There is similar selection pressure on the flies to continue their predation by selecting hosts with the lowest ability to avoid predation.
In other words, the introduction of these parasites has created a new host-parasite dynamic and the conditions for evolution to operate under selection pressure, so creating a 'natural' laboratory for studying how evolution works in practice. It also makes it possible to test out predictions made by the TOE. This has been closely monitored and investigated by teams of scientists from Flinders University.
From a Flinders University news release:
In summary, the researchers found evidence of adaptation on the part of the parasite in that it selects the easier target, the medium tree finch C. pauper, which lives only on Floreana Island and, as a result of this predation, is critically endangered. They also found that this species is responding by hybridizing with the small tree finch, C. parvulus much more readily than before the introduction of the parasite. What is happening here is that the selection pressures that would normally lead to barriers to hybridization have tilted toward hybridization because the parasites don't select the hybrid's nests so readily, possibly related to the height from the ground at which the different species nest, with C. Pauper the highest and C. parvulus the lowest. The parasite appears to favour higher nests.This tells us a story from both sides; on one hand, it demonstrates that natural selection would favour those flies that target this threatened species, but it also shows us how the finches are fighting back.Now, two new studies have explored how the various species of finches across the islands, whose discovery by Charles Darwin was pivotal to his research into natural selection and evolution, have been dealing with the fly, potentially providing further insight into the evolutionary pathways of introduced parasites.
We found that nests belonging to these hybrid finches played host to fewer flies and had the lowest parasite survival rate, suggesting that hybridisation between the small and medium tree finches may be their defence strategy against this invasive parasite.
Laura K Common, lead author, first paper
PhD candidate
College of Science and Engineering, Flinders University
Adelaide, South Australia, Australia
In one study, published in the Nature journal Scientific Reports and led by Lauren Common, PhD Candidate in the Flinders University BirdLab, the researchers investigated which species of finch proved to be the most successful hosts for the flies.
The team found the fly’s larvae were most abundant and had the best survival rates inside the nests of the critically endangered medium tree finch, which lives only on Floreana Island, but had less success in the nests of hybrid tree finches.
“This tells us a story from both sides; on one hand, it demonstrates that natural selection would favour those flies that target this threatened species, but it also shows us how the finches are fighting back,” says Miss Common.
Since the arrival of the avian vampire fly, medium tree finches have started interbreeding with small tree finches to form a hybrid population.
We found that nestlings that struggled more during handling also tended to have more deformed nostrils due to vampire fly parasitism.“We found that nests belonging to these hybrid finches played host to fewer flies and had the lowest parasite survival rate, suggesting that hybridisation between the small and medium tree finches may be their defence strategy against this invasive parasite,” says Miss Common.
While we don’t yet know why this is the case, one possibility is that more vigorous nestlings are unwittingly attracting parasitic larvae to them by moving around inside the nest.
Over time, we may expect to see more docile nestlings surviving to adulthood at greater rates, which could potentially change the behavioural traits of Darwin’s finches at a population level.
Dr Andrew C Katsis, Lead author, second paper
College of Science and Engineering
Flinders University
Adelaide, South Australia, Australia
In the second project, led by Dr Andrew Katsis from the Flinders University BirdLab, the team looked at how the birds cope with being infested by the parasites.
The study, published in the journal Biological Journal of the Linnean Society, measured each nestling’s ‘behavioural type’ by recording how much it struggled during human handling and then compared this with how much damage the baby birds sustained from the flies.
“We found that nestlings that struggled more during handling also tended to have more deformed nostrils due to vampire fly parasitism,” says Dr Katsis.
“While we don’t yet know why this is the case, one possibility is that more vigorous nestlings are unwittingly attracting parasitic larvae to them by moving around inside the nest.
“Over time, we may expect to see more docile nestlings surviving to adulthood at greater rates, which could potentially change the behavioural traits of Darwin’s finches at a population level.”
Most hybridization is the result of mating between female C. pauper and male C. parvulus and in both species, it is the male which builds the nest, so choosing the height at which to build it. The result is that most hybrids come from lower nests built by C. parvulus males.
There is a concept in evolutionary theory known as the 'Red Queen Hypothesis' or 'Red Queen Strategy', which was explained in a paper by Flinders scientist dealing with the same Galápagos finch/avian vampire fly dynamic, in the introduction to their April, 2019 paper:
1. IntroductionThe observation appears to be confirming this 'Red Queen Hypothesis' - an example of a confirmed prediction of the TOE. The increased genetic diversity due to this introgression enables the hybrids to evolve more rapidly in response to the parasite's evolution and this improved survivability outweighs any disadvantage due to hybridization and consequent loss of specialisation which normally drives the evolution of barriers to hybridization and eventual full speciation. The dynamic evolution of a parasite-host complex has turned the normal pattern of evolution on its head.
Introduced parasites can wreak havoc on native hosts, especially in island systems where naive hosts lack defensive anti-parasite mechanisms [1]. The Red Queen Hypothesis proposes that hosts are selected to constantly adapt to rapidly evolving parasites, and hence novel genetic recombinations that facilitate adaptation in the host can present a fitness advantage under conditions of parasitism. One mechanism to increase genetic diversity in a host is genetic introgression via hybridization [2]. Adaptation to an introduced parasite through hybrid vigour presents a hypothesis for the occurrence of hybridization, hence recognizing hybrid vigour in systems with introduced parasites is a crucial step towards understanding the extensive occurrence of hybridization worldwide and its evolutionary role in host–parasite systems [3].
Peters, Katharina J.; Evans, Christine; Aguirre, J. David; Kleindorfer, Sonia (2019)
Genetic admixture predicts parasite intensity: evidence for increased hybrid performance in Darwin's tree finches;
Royal Society Open Science 6(4):181616; DOI:10.1098/rsos.181616
Copyright: © 2018 The authors. Published by The Royal Society
Open access.
Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0)
The second paper also makes a prediction derived from the TOE - those chicks that are less active in the nest and so less likely to be parasitised by the avian vampire fly larvae, will come to predominate in the population. A simple prediction from the observable fact that those traits being actively selected for will increase in the species gene pool. If the link between activity and susceptibility to parasitism is real, this prediction should be confirmed. If not, it suggests this link may not really exist.
The first team, led by Laura Commons, published their findings, open access, in the Nature journal, Scientific Reports:
AbstractThe second team, led by Dr Andrew Katsis, published their findings in the Biological Journal of the Linnean Society, sadly behind an exclusive and expensive paywall. However, their abstract can be read here.
In invasive parasites, generalism is considered advantageous during the initial phase of introduction. Thereafter, fitness costs to parasites, such as host-specific mortality, can drive parasites towards specialism to avoid costly hosts. It is important to determine changes in host specificity of invasive populations to understand host-parasite dynamics and their effects on vulnerable host populations. We examined changes in mortality in the introduced avian vampire fly (Philornis downsi) (Diptera: Muscidae), a generalist myasis-causing ectoparasite, between 2004 and 2020 on Floreana Island (Galápagos). Mortality was measured as the proportion of immature larvae found upon host nest termination. Over the time period, the avian vampire fly was most abundant and had low mortality in nests of the critically endangered medium tree finch (Camarhynchus pauper) and had the highest mortality in nests of hybrid tree finches (Camarhynchus spp.). Low larval mortality was also found in small tree (Camarhynchus parvulus) and small ground finch (Geospiza fuliginosa) nests. Selection could favour avian vampire flies that select medium tree finch nests and/or avoid hybrid nests. Overall, the finding of differences in avian vampire fly survival across host species is parsimonious with the idea that the introduced fly may be evolving towards host specialisation.
Common, Lauren K.; Sumasgutner, Petra; Dudaniec, Rachael Y.; Colombelli-Négrel, Diane; Kleindorfer, Sonia
Avian vampire fly (Philornis downsi) mortality differs across Darwin’s finch host species
Scientific Reports 11, 15832 (2021). DOI:10.1038/s41598-021-94996-7
Open access. Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
Reference:So, why do these papers and this situation with Darwin's finches make a fool of Creationists?
Firstly there is the ludicrous arms race as exemplified by the 'Red Queen Strategy', where both host and parasite are obliged to continue to adapt in response to the other in order to continue to exist. For a designer to design such a system, it would need to be exceptionally stupid, yet it has supposedly created and designed innumerable such arms races in nature. What on earth is intelligent in competing against yourself and for what end? Simply to stand still? And yet, in the mind of a Creationist, this magic super-intelligent [sic] designer has designed the avian vampire fly to parasitize nesting birds (with all the attendant sadistic malevolence that implies) and then when they start to do what they were designed to do, this allegedly intelligent [sic] designer redesigns the birds, so they resist the parasitic flies' attention! Then, it redesigns the parasitic flies so they get around the defences of the birds, and so on in an endless pursuit of its own tail! Creationists hold that this is a better explanation of reality than the entirely natural, amoral and unintelligent one that science has evidence for - evolution by natural selection, that Creationists are conditioned to reject, no matter how strong the evidence for it is and no matter that they are portraying their beloved malevolence in such a poor light by claiming it is responsible for these horrors and glaring examples of inept stupidity.
Secondly, there is the evidence of testable predictions being confirmed whilst Creationists have been programmed to try to dismiss the TOE by claimign it isn't a real science since it can't make testable predictions! Holding onto a dogma in the face of contrary evidence is a very effective way to make a fool of yourself.
Thirdly, we have the glorious spectacle of Creationists still insisting that the TOE is a theory in crisis, about to be overthrown by the childish notion of intelligent design! Yet, as these papers show, not only is the TOE alive and well, but it is the only way to explain what we can observe, and there is absolutely no hint anywhere in these papers that the scientist have any doubt about the TOE. Again, Creationists are making fools of themselves by insisting on something that is manifestly untrue and about which they have so obviously been lied to.
Lastly, but not leastly, we have the way evolutionary theory makes testable, and in this case, accurate predictions based on the prediction of what will happen naturally, and yet Creationisst continue to insist that nothing evolves naturally and all diversity is the result of intelligent [sic] design by a magic, omniscient, omnipotent god (which thusly appears to be bound by the natural laws that scientists believe govern evolution).
And the delicious irony is that Darwin's Finches are instrumental in exposing Creationists to riducule, again.
To be fair to Darwin's finches and the scientists from Fliners University who have made this evidence available to us, it is not they who are making fools of Creationists, so much as Creationists who are makign fools of themselves, or more precisely perhaps, the professional Creationist frauds who fool them with disinformation and demonstrable lies who are responsible for it.
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