Loss of amphibian population

Hey Brandon,

Neither the fish in the Royal Society article nor the development of bacterial resistance support Darwinian evolution—they’re both examples of adaptation to environmental conditions.  For example, some bacteria carry latent genes that code for antibiotic resistance; these genes become active in the presence of certain antibiotics.  In other bacteria, mutations lead to resistance to certain types of antibiotic, but the resistance comes with a cost, such as slower growth rate or decreased resistance to other antibiotics—when these bacteria are in natural conditions (with no antibiotics), they aren’t able to compete with the faster growing non-mutated bacteria.   

Here are several related articles...  

The agents of divergent selection are extrinsic and can include abiotic and biotic factors such as food resources, climate, habitat, and interspecies interactions such as disease, competition, and behavioral interference.

This comes from Evidence for Ecological Speciation and Its Alternative, Dolph Schluter, in Science Magazine ( http://www.sciencemag.org/cgi/content/full/323/5915/737?ijkey=57JzKGxEe.F.Q&keytype=ref&siteid=sci ).  This sounds good when you’re promoting Darwinian evolution.

Potential causes [of worldwide decrease in amphibian population] include habitat degradation, pollution, acid rain, ultraviolet irradiation, pesticides, predators, competition from introduced species, climate changes, and disease.

From Holt, W. V. et al, eds. 2003. Reproductive Science and Integrated Conservation. Cambridge, UK: Cambridge University Press, 360.  (You can look this page up online at amazon.com.)  This sounds good when you’re talking about protecting the environment.

So, what we have here are scientists with very different perspectives based on different fields of study.   One says that climate, habitat, and so on, drive evolutionary change and development of new species and classes of organisms, and Dawkins would agree with this.  The other suggests that these same factors lead to population degradation and loss of many  species.  Apparently the factors that are said to have driven Darwinian evolution (with its development of increasingly complex species) in the past, and supposedly continue to do so now, also lead to species degeneration and loss.  How do the same factors manage to lead to both increase and decrease of species (and concomitant  genetic information)?

According to the second reference, a decrease in amphibian population over time has been observed by scientists—that part is something we can know for sure.  What isn’t known for sure is the cause for the decrease in population.  It doesn’t make sense that the same factors would drive both the increase of complexity/genetic information and the decrease of complexity/genetic information.  If climate, habitat, and so on do drive Darwinian evolution, why are amphibians not evolving into something else rather than disappearing?  

As previously reported from allozyme analyses, A. japonicus exhibits little genetic differentiation, in strong contrast to salamanders of the genus Hynobius with which their distributions overlap. This reduced genetic variability in A. japonicus is attributable to a unique mating system of polygyny, delayed sexual maturity, notable longevity, life in a stable aquatic environment, and gigantism, as well as bottleneck effects following habitat fragmentation and extinction of local populations during Quaternary glaciations. The species is thus susceptible to extinction by potential environmental fluctuations, and requires extensive conservation measures. Matsui, M., et al. 2008. Reduced genetic variation in the Japanese giant salamander, Andrias japonicas (Amphibia: Caudata). Molecular Phylogenetics and Evolution. 49 (1): 318-326. linkinghub.elsevier.com/retrieve/pii/S1055790308003795

According to this study, A. japonicus (the Japanese giant salamander) has reduced genetic variability (genetic differentiation).  Organisms that have insufficient genetic variability are less able to adapt to environmental changes.  Because of this, the giant salamander is susceptible to extinction due to environmental fluctuations. This reduced genetic differentiation would be expected with genetic entropy.  If Darwinian evolution were taking place, one would expect environmental fluctuations to be driving further evolutionary development of new genetic information in order to help the amphibians adapt—but this doesn’t seem to be taking place.  Overall, we readily observe extinctions, but no one has ever observed the development of life from non-life or of a new class of organism with greater complexity from one with lesser complexity, such as a eukaryote from bacteria.  We readily observe adaptations within a kind, such as the above bacteria and fish, but we don’t observe one kind developing into another, more complex kind.  

Susan