Why Are Juveniles Smaller Than Their Parents?

Ellstrand, Norman C.

doi:10.1111/j.1558-5646.1983.tb05637.x

Cited by 13 publications

(7 citation statements)

References 39 publications

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“…Although we measured only adults, we found that FA decreased with body size regardless of context. Because body size tends to be correlated with age (Ellstrand, 1983), this suggests that older individuals exhibit lower levels of asymmetry than younger individuals. An intriguing alternative hypothesis is that FA may be reduced with age because of compensatory growth.…”

Section: Discussionmentioning

confidence: 99%

The perils of city life: patterns of injury and fluctuating asymmetry in urban lizards

Winchell

Briggs

Revell

2019

Biological Journal of the Linnean Society

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Animals that live in cities face a number of challenges particular to the urban environment that may impact on overall health and survival. Nevertheless, relatively few studies have investigated injury and health in urban species. We measured body condition, injury rate and fluctuating asymmetry in urban and forest populations of the tropical lizard Anolis cristatellus. We found that although there were strong differences in body condition between urban and forest populations, the direction of this difference varied between municipalities. We also found that injury rates (amputated digits and bone fractures) were slightly, but significantly, more common in urban populations; this phenomenon may be due to changes in intraspecific interactions or predation pressure in urban sites. Contrary to our expectations, we found that fluctuating asymmetry was greater in forest compared to urban populations. Because our data were collected from adults, this may be a sign of stronger natural selection on the symmetry of functional traits in urban than in forest environments. Finally, we found no persuasive evidence that city living is inherently detrimental to individuals of this species despite a slightly higher rate of injury. Being able to overcome the challenges of city life may be integral to urban persistence and a step along the path to urban adaptation.

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Section: Discussionmentioning

confidence: 99%

The perils of city life: patterns of injury and fluctuating asymmetry in urban lizards

Winchell

Briggs

Revell

2019

Biological Journal of the Linnean Society

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“…Evolution is fundamentally the product of more than a single factor. Beyond the four classic “forces”, evolution also depends on various constraints such as history, demography, development, organismal structure, genomic structure, and environment (e.g., Antonovics, 1976; Ellstrand, 1983; Gould and Lewontin, 1979). The point here is that none of these should be stereotyped without good reason.…”

Section: Discussionmentioning

confidence: 99%

Is gene flow the most important evolutionary force in plants?

Ellstrand

2014

American J of Botany

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243

203

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Although theory has demonstrated rather low levels of gene flow are sufficient to counteract opposing mutation, drift, and selection, widespread recognition of the evolutionary importance of gene flow has come slowly. The perceived role of gene flow as an evolutionary force has vacillated over the last century. In the last few decades, new methods and analyses have demonstrated that plant gene flow rates vary tremendously-from nil to very high-depending on the species and specific populations involved, and sometimes over time for individual populations. In many cases, the measured gene flow rates are evolutionarily significant at distances of hundreds and sometimes thousands of meters, occurring at levels sufficient to counteract drift, spread advantageous alleles, or thwart moderate levels of opposing local selection. Gene flow in plants is likely to often act as a cohesive force, uniting individual plant species into real evolutionary units. Also, gene flow can evolve under natural selection, decreasing or increasing. The fact of frequent, but variable, plant gene flow has important consequences for applied issues in which the presence or absence of gene flow might influence the outcome of a policy, regulatory, or management decision. Examples include the unintended spread of engineered genes, the evolution of invasiveness, and conservation. New data-rich genomic techniques allow closer scrutiny of the role of gene flow in plant evolution. Most plant evolutionists now recognize the importance of gene flow, and it is receiving increased recognition from other areas of plant biology as well.

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“…The next principle-which follows from sexual reproduction-is that offspring are always born smaller than their mothers, as highlighted satirically by Ellstrand. [3] He named this the juvenile small size (JSS) principle and offered six supposedly serious reasons why it should hold. These included plausible considerations of population dispersal, predation, and parent-offspring competition.…”

Section: Introductionmentioning

confidence: 99%

Big Baby, Little Mother: Tsetse Flies Are Exceptions to the Juvenile Small Size Principle

et al. 2020

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While across the animal kingdom offspring are born smaller than their parents, notable exceptions exist. Several dipteran species belonging to the Hippoboscoidea superfamily can produce offspring larger than themselves. In this essay, the blood-feeding tsetse is focused on. It is suggested that the extreme reproductive strategy of this fly is enabled by feeding solely on highly nutritious blood, and producing larval offspring that are soft and malleable. This immense reproductive expenditure may have evolved to avoid competition with other biting flies. Tsetse also transmit blood-borne parasites that cause the fatal diseases called African trypanosomiases. It is discussed how tsetse life history and reproductive strategy profoundly influence the type of vector control interventions used to reduce fly populations. In closing, it is argued that the unusual life history of tsetse warrants their preservation in the areas where human and animal health is not threatened.

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Why Are Juveniles Smaller Than Their Parents?

Cited by 13 publications

References 39 publications

The perils of city life: patterns of injury and fluctuating asymmetry in urban lizards

The perils of city life: patterns of injury and fluctuating asymmetry in urban lizards

Is gene flow the most important evolutionary force in plants?

Big Baby, Little Mother: Tsetse Flies Are Exceptions to the Juvenile Small Size Principle

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