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Rui Diogo’s Followers (4)
Rui Diogo
More books by Rui Diogo…
“One interesting aspect of his book is that it argued that the more specialized a species is, the less likely it is to continue to recognize appropriate habitats as
conditions change. Species displaying a less plastic/diverse inventory of behavioral choices, such as those focusing on a single type of food, are the most susceptible. For instance, parasites often have a single host species, which does not present any
problems for them as long as the host species does not become extinct. That is why, according to Eldredge, ecologically specialized species become extinct at much higher rates than do ecologically generalized species in the fossil record. The concept that specialization often leads to an evolutionary dead end was first proposed by Cope as the “law of the unspecialized” and has continued to be key for evolutionary biology since then. In Eldredge’s view, the balance of life will tend to produce ecologically specialized organisms because they often flourish
more than generalists in the short run, but extinction then normally affects more the ranks of the specialists. In the long run, the generalists thus hang on—‘living fossils’ often being generalists—whereas the ranks of specialists are quickly refilled by the continuous evolution of new taxa. For him, taxa that descend from species that are already somewhat specialized tend to have a greater chance of focusing on a specific portion of the resources not completely exploited by the parental taxa. He designated this as a “ratchet-like mechanism” of the quick accumulation of evolutionary change as lineages keep splitting and new taxa are formed from old ones within specialized lineages. Thus, he directly connects behavioral/ecological specializations to cladogenesis and the rapid evolutionary events predicted in punctuated equilibrium. In turn, he argues that stasis is often related to generalist lineages because without a comparable degree of successful speciation, these lineages tend to have far fewer extant species at any one time than their specialized counterparts. That is, generalists are not really evolving at slower morphological rates: they are simply not generating so many new species. As a result, the gradual fluctuation of form among the members of the generalized taxa is not being fixed by cladogenesis, thus leading to new species.”
― Evolution Driven by Organismal Behavior: A Unifying View of Life, Function, Form, Mismatches and Trends
conditions change. Species displaying a less plastic/diverse inventory of behavioral choices, such as those focusing on a single type of food, are the most susceptible. For instance, parasites often have a single host species, which does not present any
problems for them as long as the host species does not become extinct. That is why, according to Eldredge, ecologically specialized species become extinct at much higher rates than do ecologically generalized species in the fossil record. The concept that specialization often leads to an evolutionary dead end was first proposed by Cope as the “law of the unspecialized” and has continued to be key for evolutionary biology since then. In Eldredge’s view, the balance of life will tend to produce ecologically specialized organisms because they often flourish
more than generalists in the short run, but extinction then normally affects more the ranks of the specialists. In the long run, the generalists thus hang on—‘living fossils’ often being generalists—whereas the ranks of specialists are quickly refilled by the continuous evolution of new taxa. For him, taxa that descend from species that are already somewhat specialized tend to have a greater chance of focusing on a specific portion of the resources not completely exploited by the parental taxa. He designated this as a “ratchet-like mechanism” of the quick accumulation of evolutionary change as lineages keep splitting and new taxa are formed from old ones within specialized lineages. Thus, he directly connects behavioral/ecological specializations to cladogenesis and the rapid evolutionary events predicted in punctuated equilibrium. In turn, he argues that stasis is often related to generalist lineages because without a comparable degree of successful speciation, these lineages tend to have far fewer extant species at any one time than their specialized counterparts. That is, generalists are not really evolving at slower morphological rates: they are simply not generating so many new species. As a result, the gradual fluctuation of form among the members of the generalized taxa is not being fixed by cladogenesis, thus leading to new species.”
― Evolution Driven by Organismal Behavior: A Unifying View of Life, Function, Form, Mismatches and Trends
“As also noted by Morris, empirical data from various lineages of fish and amphibians have shown, for instance, that more plastic clades tend to be more
speciose than sister taxa of similar age but with less plasticity, due to a combination of greater opportunities to diversify and augmented evolvability of plastic features and thus of decreased risk of extinction. In addition, empirical studies show that
even populations that derive from ancestors that were particularly overspecialized for a certain, very specific way of life, including parasitism, have successfully
changed their behavior by becoming non-parasitic and displaying a morphology that is substantially different from that of their ancestors as seen for example in
lamprey evolution. Morris argued that random variations arising in a population may decrease plasticity and that the plastically changed phenotype
linked with the behavioral shift may be negatively affected. Therefore, these variants will be likely eliminated by selection, whereas variants that decrease plasticity in the direction of the plastic change will tend to be selected and spread through the population. This may lead to a situation in which the phenotype might appear similar across generations, but its plasticity is actually increasingly reduced until an environmental shift will no longer provoke phenotypic changes. As noted by Morris, Baldwin allowed for other non-mutually exclusive scenarios to occur, such as the rise of variants that increase plasticity in general, thus increasing the ‘fit’
between organisms and their environment and the degree to which evolution could be directed, thus leading to evolutionary trends.”
― Evolution Driven by Organismal Behavior: A Unifying View of Life, Function, Form, Mismatches and Trends
speciose than sister taxa of similar age but with less plasticity, due to a combination of greater opportunities to diversify and augmented evolvability of plastic features and thus of decreased risk of extinction. In addition, empirical studies show that
even populations that derive from ancestors that were particularly overspecialized for a certain, very specific way of life, including parasitism, have successfully
changed their behavior by becoming non-parasitic and displaying a morphology that is substantially different from that of their ancestors as seen for example in
lamprey evolution. Morris argued that random variations arising in a population may decrease plasticity and that the plastically changed phenotype
linked with the behavioral shift may be negatively affected. Therefore, these variants will be likely eliminated by selection, whereas variants that decrease plasticity in the direction of the plastic change will tend to be selected and spread through the population. This may lead to a situation in which the phenotype might appear similar across generations, but its plasticity is actually increasingly reduced until an environmental shift will no longer provoke phenotypic changes. As noted by Morris, Baldwin allowed for other non-mutually exclusive scenarios to occur, such as the rise of variants that increase plasticity in general, thus increasing the ‘fit’
between organisms and their environment and the degree to which evolution could be directed, thus leading to evolutionary trends.”
― Evolution Driven by Organismal Behavior: A Unifying View of Life, Function, Form, Mismatches and Trends
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