scholarly journals Decoupled maternal and zygotic genetic effects shape the evolution of development

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Christina Zakas ◽  
Jennifer M Deutscher ◽  
Alex D Kay ◽  
Matthew V Rockman
Keyword(s):  
Population Genetic ◽  
Genetic Factors ◽  
Forward Genetics ◽  
Larval Size ◽  
Evolutionary Transitions ◽  
Major Transition ◽  
Larval Evolution ◽  
Streblospio Benedicti ◽  
Positive Frequency Dependence ◽  
Positive Frequency

Evolutionary transitions from indirect to direct development involve changes in both maternal and zygotic genetic factors, with distinctive population-genetic implications, but empirical data on the genetics of such transitions are lacking. The polychaete Streblospio benedicti provides an opportunity to dissect a major transition in developmental mode using forward genetics. Females in this species produce either small eggs that develop into planktonic larvae or large eggs that develop into benthic juveniles. We identify large-effect loci that act maternally to influence larval size and independent, unlinked large-effect loci that act zygotically to affect discrete aspects of larval morphology. The likely fitness of zygotic alleles depends on their maternal background, creating a positive frequency-dependence that may homogenize local populations. Developmental and population genetics interact to shape larval evolution.

scholarly journals Decoupled Maternal and Zygotic Genetic Effects Shape the Evolution of Development

2017 ◽  
Author(s):  
Christina Zakas ◽  
Jennifer M. Deutscher ◽  
Alex D. Kay ◽  
Matthew V. Rockman
Keyword(s):  
Larval Feeding ◽  
Heritable Variation ◽  
Larval Size ◽  
Adult Form ◽  
Planktonic Food ◽  
Large Numbers ◽  
Indirect Development ◽  
Larval Evolution ◽  
Size And Morphology ◽  
Positive Frequency Dependence

AbstractMany animals develop indirectly via a larval stage that is morphologically and ecologically distinct from its adult form. Hundreds of lineages across animal phylogeny have secondarily lost larval forms, instead producing offspring that directly develop into adult form without a distinct larval ecological niche1–7. Indirect development in the sea is typically planktotrophic: females produce large numbers of small offspring that require exogenous planktonic food to develop before metamorphosing into benthic juveniles. Direct development is typically lecithotrophic: females produce a smaller number of larger eggs, each developing into a juvenile without the need for larval feeding, provisioned by yolk. Evolutionary theory suggests that these alternative developmental strategies represent stable alternative fitness peaks, while intermediate states are disfavored4,8–11. Transitions from planktotrophy to lecithotrophy thus require crossing a fitness valley and represent radical and coordinated transformations of life-history, fecundity, ecology, dispersal, and development7,12–16. Here we dissect this transition in Streblospio benedicti, the sole genetically tractable species that harbors both states as heritable variation17–19. We identify large-effect loci that act maternally to influence larval size and independent, unlinked large-effect loci that act zygotically to affect discrete aspects of larval morphology. Because lecithotrophs and planktotrophs differ in both size and morphology, the genetic basis of larval form exhibits strong maternal-by-zygotic epistasis for fitness20. The fitness of zygotic alleles depends on their maternal background, creating a positive frequency-dependence that may homogenize local populations. Developmental and population genetics interact to shape larval evolution.

Upper airway walls impedance measured with head plethysmograph

1984 ◽  
Vol 57 (2) ◽  
pp. 596-600 ◽  
Author(s):  
R. Peslin ◽  
C. Duvivier ◽  
P. Jardin
Keyword(s):  
Upper Airway ◽  
Normal Subjects ◽  
Forced Oscillations ◽  
Respiratory Impedance ◽  
Respiratory Compliance ◽  
Airway Opening ◽  
Positive Frequency Dependence ◽  
Airway Walls ◽  
Extrathoracic Airway ◽  
Positive Frequency

Respiratory input impedance (Zrs) measured by forced oscillations needs to be corrected for the motion of extrathoracic airway walls. Two methods of obtaining the impedance of this shunt pathway [upper airway impedance (Zuaw)] were compared in six normal subjects. In the first, flow was measured at the airway opening during Valsalva maneuvers, as described by Michaelson et al. (10). In the second, motions of upper airway walls were directly assessed during respiratory impedance measurements by use of a head plethysmograph. Larger upper airway impedance values were found during Valsalva maneuvers, corresponding to a larger upper airway resistance (Ruaw) (at 20 Hz, Ruaw = 9.1 +/- 4.7 compared with 7.0 +/- 2.1 cmH2O X 1–1 X s with the second method) and inertance (Iuaw) (Iuaw = 0.053 +/- 0.036 vs. 0.025 +/- 0.008 cmH2O X 1–1 X s2, P less than 0.05) and a lower upper airway compliance (Cuaw) (Cuaw = 0.78 +/- 0.33 vs. 1.15 +/- 0.15 ml X cmH2O–1, P less than 0.05). Active contraction of facial muscles during Valsalva maneuvers may be responsible for this finding. As a consequence, respiratory impedance values are undercorrected when using the Valsalva method, leading in normal subjects to an overestimation of respiratory compliance by 30% and an underestimation of inertance by 16% (P less than 0.05) and promoting positive frequency dependence of respiratory resistance. Substantial errors may be avoided by using a head plethysmograph, which permits measuring Zrs and Zuaw simultaneously.

scholarly journals Shrinking dinosaurs and the evolution of endothermy in birds

2020 ◽  
Vol 6 (1) ◽  
pp. eaaw4486 ◽  
Author(s):  
Enrico L. Rezende ◽  
Leonardo D. Bacigalupe ◽  
Roberto F. Nespolo ◽  
Francisco Bozinovic
Keyword(s):  
Heat Transfer ◽  
Body Size ◽  
Energy Requirements ◽  
Transfer Model ◽  
Metabolic Rates ◽  
Evolutionary Transitions ◽  
Thermal Niche ◽  
Stem Lineage ◽  
Major Transition ◽  
Size Data

The evolution of endothermy represents a major transition in vertebrate history, yet how and why endothermy evolved in birds and mammals remains controversial. Here, we combine a heat transfer model with theropod body size data to reconstruct the evolution of metabolic rates along the bird stem lineage. Results suggest that a reduction in size constitutes the path of least resistance for endothermy to evolve, maximizing thermal niche expansion while obviating the costs of elevated energy requirements. In this scenario, metabolism would have increased with the miniaturization observed in the Early-Middle Jurassic (~180 to 170 million years ago), resulting in a gradient of metabolic levels in the theropod phylogeny. Whereas basal theropods would exhibit lower metabolic rates, more recent nonavian lineages were likely decent thermoregulators with elevated metabolism. These analyses provide a tentative temporal sequence of the key evolutionary transitions that resulted in the emergence of small, endothermic, feathered flying dinosaurs.

scholarly journals Dimorphic development inStreblospio benedicti: genetic analysis of morphological differences between larval types

2014 ◽  
Author(s):  
Christina Zakas ◽  
Matthew V Rockman
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Morphological Traits ◽  
Natural Populations ◽  
Larval Size ◽  
Developmental Evolution ◽  
Marine Polychaete ◽  
Streblospio Benedicti ◽  
Planktotrophic Larvae ◽  
Morphological Differences

The marine polychaeteStreblospio benedictiexhibits two distinct larval types, making it a model for the study of developmental evolution. Females produce either large eggs or small ones, which develop into distinct lecithotrophic or planktotrophic larvae with concomitant morphological and life-history differences. Here, we investigate the inheritance of key morphological traits that distinguish the larval types. We use genetic crosses to establish the influence of maternal and zygotic differences on larval phenotypes. We find a large maternal effect on larval size and the number of larval chaetae, while the number and length of these chaetae are also strongly influenced by zygotic genotype. Interestingly, the distribution of larval phenotypes produced by these crosses suggests traits intermediate to the two parental types should not be uncommon. Yet, despite gene flow between the types in natural populations, such intermediates are rarely found in nature, suggesting that selection may be maintaining distinct larval modes.

scholarly journals Rapid dissolution of dioecy by experimental evolution

2019 ◽  
Author(s):  
G. G. Cossard ◽  
J. F. Gerchen ◽  
X. Li ◽  
Y. Cuenot ◽  
J. R. Pannell
Keyword(s):  
Experimental Evolution ◽  
Male Flower ◽  
Fold Increase ◽  
Sex Expression ◽  
Recent Analysis ◽  
Evolutionary Transitions ◽  
Sexual Systems ◽  
Major Transition ◽  
Rapid Dissolution ◽  
Male Flowers

AbstractEvolutionary transitions from hermaphroditism to dioecy have been frequent in flowering plants, but recent analysis indicates that reversions from dioecy to hermaphroditism have also been common. Here, we use experimental evolution to expose a mechanism for such reversions. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that varied in their propensity for the occasional production of male flowers; such ‘leaky’ sex expression is common in both males and females of dioecious plants. Over only four generations, females evolved a 23-fold increase in average male-flower production. The phenotypic masculinization of females was also sufficient to render them effective at siring progeny in the presence of males. Our study illustrates the rapid dissolution of dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion. It thereby experimentally validates a mechanism for a major transition in plant sexual systems..

scholarly journals Coexistence theory and the frequency-dependence of priority effects

2018 ◽  
Author(s):  
Po-Ju Ke ◽  
Andrew D. Letten
Keyword(s):  
Frequency Dependence ◽  
Priority Effects ◽  
Coexistence Theory ◽  
Positive Frequency Dependence ◽  
Positive Frequency

AbstractPriority effects encompass a broad suite of ecological phenomena. Several studies have suggested reframing priority effects around the stabilizing and equalizing concepts of coexistence theory. We show that the only compatible priority effects are those characterized by positive frequency dependence.

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