The Proceedings of the Eighth International Conference on Creationism (2018)

conditions is broad and includes temperature, sunlight, moisture, chemicals, nutrition, population density, etc. Polyphenism is a type of plasticity where discrete, all-or-nothing expressions of traits happens upon exposure—usually to a threshold level. The change in color of an artic fox’s fur from grey-brown to white in the fall is an example of seasonal polyphenism. The significance of phenotypic plasticity to diversification and adaptation is described by West and Packer (2002) who say that the “environmental effects on trait morphology can be substantial, outweighing both genetic effects and reproductive advantages” (p. 1339). A few illustrations highlight the importance of external- condition detectors to initiate developmental, physiological, phenotypic, or behavioral changes, and the extent to which these changes could lead to speciation and diversification. Observable phenotypic differences that distinguish species, and certainly genera, are assumed to be the result of genetic polymorphisms. But this assumption may not be accurate. Susoy et al. (2016) report experiments which indicate that some genera-level morphotypes of afig-associatednematode Pristionchus are the result of polyphenism and not genetic polymorphism. Upon colonizing the island-like microecosystem of individual figs, symbiotic nematodes of the genus Pristionchus expressed a polyphenismwith up to five discrete adult morphotypes per species. The principle target condition in this study was found to be both fig type and fig maturation. Since juvenile development cannot be cultured outside of figs, any environmental cues detected during development associated with differing morphs cannot be identified. Yet, the five major morphotypes identified were associated with fig type, fig phase (early and late interfloral), and transit on, versus through, their specific wasp vector ( Ceratosolen spp.). Genetic sequencing demonstrated that from a single genotype, developmental plasticity had led to discontinuous novelties whose variation exceeded level of genera in the same family. They concluded that this was a case of “macroevolutionary-scale” diversification, with some structures having no analogs in other nematodes, without genetic divergence. Tadpoles of the tree frog Hyla chrysoscelis demonstrate developmental phenotypic adjustment when exposed only to aquarium tank water that had harbored dragonfly larvae of the tadpole predators Aeshna or Anax . McCollum and Leimberger (1997) document that tadpoles have exquisite capability to, “detect waterborne chemical” substances “produced by predators” (p. 616). Post-exposure, tadpoles developed a thick, muscular, bright red tail which increased their probability to escape future predation better than tadpoles isolated from predator exposure during development. Relyea (2005) followed up on the tadpole-predator study to determine whether a plastic trait expressed in one generation could be passed on to offspring which themselves experienced variable levels of the exposure during their development. He concluded that “predator-induced traits can frequently be heritable, although the magnitude of heritability can be wide ranging across environments. Moreover, the plasticity of these defenses also can be heritable” (p.864). Multiple studies identify an exquisite detection-response linkage in some organisms. They detect the presence of predators, respond with phenotypic adjustments either during development or as adult forms, and then pass a tendency for the adjusted form on to offspring. Stabell and Lwin (1997) conducted experiments to determine elements of an underlying mechanism that might explain why the body depth and muscle mass of crucian carp, Carassius carassius , increases in the presence of the predator northern pike, Esox lucius . They demonstrated that crucian carp did not respond with growth changes after exposure to either the pike itself, nor to pike-fed Arctic char, Salvelinus alpinus. Morphological changes occurred only after carp were exposed to pike which had been feeding on other crucian carp, or when exposed to water containing skin tissue (prepared and homogenized) of conspecifics. They conclude that chemical substances from the skin of conspecific fish are a stimulus for induction of the phenotypical changes. Another review paper indicates that the role of phenotypic plasticity for diversification and speciation may be going unnoticed. Pfennig et al. (2010) document cases of speciation resulting fromphenotypic plasticity and conclude that “generally, phenotypic plasticity can play a largely underappreciated role in driving diversification and speciation” (p. 459). They point out that an organism’s abilities to rapidly respond to changes facilitate diversification since “… alternative resource-use morphs might be particularly effective at facilitating speciation because the same conditions that promote resource polyphenism simultaneously foster speciation’s three components: genetic isolation, divergence and reproductive isolation” (p. 462). 2. Adult Response to Environmental Dynamics A. Phenotypic response Patterson (2007) discusses how the thickness, length, and color of a male lion’s mane, which may vary over the course of a single year, depends on its ability to detect at least two conditions: temperature and rainfall. West and Packer (2002) also note how the presence of these conditions, available nutrition, and a non-environmental exposure (age), play a more prominent role than genetics in determining the characteristics of mane. The speed of adult phenotypic alteration is demonstrated in desert locusts which can change reversibly between solitarious and gregarious phases. These are so dissimilar in physiology, morphology and behavior, that they were recognized as different species until 1921. Rogers et al. (2014) shows that, when a previously discovered sensor on the hind femora is subjected to increased tactile stimulation due to forced crowding, solitarious locusts begin within one hour to exhibit the behaviors of the long- term gregarious locusts. Then by the next molt (within 4-7 hours) they completely morph into the gregarious phenotype. Miller et al. (2008) establishes how “depending on their rearing density, female desert locusts Schistocerca gregaria epigenetically endow their offspring with differing phenotypes…[which] affords organisms robustness against environmental fluctuation…[and is] persistent for some duration in the absence of inducing stimuli” (p. 300). Adult forms that maintain sexual plasticity demonstrate the potential of adult phenotypic modification. In a large resident female Blue-headed Wrasse, Thalassoma bifasciatum , ovaries regress and testes grow within a single day if a territorial male is lost (Warner and Swearer 1991). Even though Godwin et al. (2008) assert that the environment is sending information to a female Guliuzza and Gaskill ◀ How organisms continuously track environmental changes ▶ 2018 ICC 163