The Largess of Motherhood

Anaconda ◽  
2020 ◽  
pp. 104-165
Author(s):  
Jesús A. Rivas
Keyword(s):  
Natural Selection ◽  
Young Adult ◽  
Reproductive Success ◽  
Reproductive Output ◽  
The Other ◽  
Reproductive Value ◽  
Lifetime Reproductive Success ◽  
Reproductive Decisions ◽  
Large Size ◽  
Breeding Resources

This chapter assesses the reasons and limitations for large size in female anacondas. Considering how large females are—nearly five times the size of males—it is obvious that the evolutionary pressures for large size act more strongly on females than males. One aspect in which natural selection definitely favors large size in females has to do with reproductive output. The larger a female is, the more babies can develop in her body and the larger the reproductive output. Reproductive value, or lifetime reproductive success, is the number of potential offspring that an individual can leave in the population over its lifetime. There are costs animals must face when they make reproductive decisions. Some of these costs are dependent on fecundity and some of them are not, such as the risk of being preyed upon during mating or pregnancy. A young adult female that has just reached maturity is under two opposite pressures: one is to breed right away and secure a few babies into the next generation, and the other is to skip reproduction, grow larger, and make more babies in a later year. A female that is going to breed faces another decision: how to invest her breeding resources. She can produce a large number of neonates of small size or a few offspring of large size.

Body mass influences maternal allocation more than parity status for a long-lived cervid mother

2019 ◽  
Vol 100 (5) ◽  
pp. 1459-1465 ◽  
Author(s):  
Eric S Michel ◽  
Stephen Demarais ◽  
Bronson K Strickland ◽  
Jerrold L Belant ◽  
Larry E Castle
Keyword(s):  
Reproductive Success ◽  
Body Mass ◽  
Litter Size ◽  
Reproductive Value ◽  
Lifetime Reproductive Success ◽  
Reproductive Tactics ◽  
High Quality ◽  
Maternal Body ◽  
Individual Offspring ◽  
Maternal Allocation

Abstract Mothers should balance the risk and reward of allocating resources to offspring to optimize the reproductive value of both offspring and mother while maximizing lifetime reproductive success by producing high-quality litters. The reproductive restraint hypothesis suggests maternal allocation should peak for prime-aged mothers and be less for younger mothers such that body condition is not diminished to a level that would jeopardize their survival or future reproductive events. We assessed if reproductive tactics varied by maternal body mass and parity status in captive female white-tailed deer (Odocoileus virginianus) to determine if prime-aged mothers allocate relatively more resources to reproduction than primiparous mothers. Maternal body mass, not parity status, positively affected maternal allocation, with heavier mothers producing both heavy litters and heavy individual offspring. Conversely, maternal body mass alone did not affect litter size, rather the interaction between maternal body mass and parity status positively affected litter size such that maternal body mass displayed a greater effect on litter size for primiparous than multiparous mothers. Our results suggest that heavy white-tailed deer mothers allocate additional resources to current year reproduction, which may be an adaptation allowing mothers to produce high-quality litters and increase their annual reproductive success because survival to the next reproductive attempt is not certain.

The relationship between immunocompetence during winter and subsequent reproductive decisions and survival in the Great Tit

2008 ◽  
Vol 58 (2) ◽  
pp. 199-209 ◽  
Author(s):  
Rianne Pinxten ◽  
Marcel Eens ◽  
Frank Adriaensen ◽  
Erik Matthysen ◽  
Tinne Snoeijs
Keyword(s):  
Immune Response ◽  
Breeding Season ◽  
Parus Major ◽  
Reproductive Value ◽  
Laying Date ◽  
Lifetime Reproductive Success ◽  
Winter Period ◽  
Reproductive Decisions ◽  
Term Survival ◽  
Male And Female

AbstractThe typical costs associated with parasitism have led to the suggestion that immunosuppression in the host may be an important mechanism mediating the life history cost of reproduction, defined as a decrease in residual reproductive value as a consequence of parental effort. More immunocompetent individuals have therefore been predicted to reveal higher fitness through more optimal reproductive decisions and increased survival. In this study, we simulated a challenge to the immune system of male and female great tits (Parus major) by injecting a novel but harmless antigen, sheep red blood cells (SRBC), and related the elicited immune response to (long-term) survival and reproductive traits, relevant to the determination of lifetime reproductive success in this species. In females, we could not detect any relationships between humoral immunocompetence and laying date, clutch size, or mean fledging mass during the breeding season following the winter period during which we assessed the immune response. Furthermore, immune response to SRBC did not predict survival of male and female great tits until the following breeding season as well as until the breeding season the year after. Overall, humoral immunological quality measured during winter did not predict important fitness components in great tits.

Growth, mortality, and longevity of the Egyptian tortoise Testudo kleinmanni Lortet, 1883

2009 ◽  
Vol 55 (2) ◽  
pp. 133-147 ◽  
Author(s):  
Daniele Macale ◽  
Massimiliano Scalici ◽  
Alberto Venchi
Keyword(s):  
Reproductive Success ◽  
Growth Model ◽  
Reproductive Output ◽  
Growth Patterns ◽  
Male Reproductive Success ◽  
Population Status ◽  
Female Reproductive Success ◽  
Large Size ◽  
Threatened Taxa

Both demography and population regulation play an important role in the theory of sustainable exploitation and conservation of threatened taxa, such as terrestrial Chelonia. Here, we show and discuss some dynamic aspects of Testudo kleinmanni using modal progression analysis of length compositions. Although the Testudinata physiology is very different from that of fish, their growth model conforms to the Von Bertalanffy growth model. We observed a maximum of three age classes for both juveniles and females, and four classes for males. No appreciable between-sex differences were found in growth patterns, except for the diverse asymptotic length. Females should be subject to a strong sexual selection to quickly reach a large size in order to optimize lifetime reproductive output. The T. kleinmanni male size could be driven by predation escape and by easy accessibility to females, rather than by fighting for them. Thus, male reproductive success increases with the ability to fertilize females and female reproductive success increases with the ability to produce eggs, creating a large divergence in the context of selection between sexes. Different selective (synergetic or antagonistic) forces would appear to favor divergence in size between sexes. Additional properties found in the study regard the elevated mortality rate, probably also due to the human impact (poaching), and the relatively high longevity (26 and 22 years for females and males, respectively). Dynamics studies are useful for planning in situ activities of monitoring the population status, and could have a role in introducting programs and in control of reintroduced individuals during a restocking project.

scholarly journals Variation in annual and lifetime reproductive success of lance-tailed manakins: alpha experience mitigates effects of senescence on siring success

2011 ◽  
Vol 279 (1733) ◽  
pp. 1551-1559 ◽  
Author(s):  
Emily H. DuVal
Keyword(s):  
Reproductive Success ◽  
Reproductive Output ◽  
Early Adulthood ◽  
Male Reproduction ◽  
Lifetime Reproductive Success ◽  
Negative Effects ◽  
Factors Influencing ◽  
Display Area ◽  
Relationship Of ◽  
Siring Success

The causes of variation in individual reproductive success over a lifetime are not well understood. In long-lived vertebrates, reproductive output usually increases during early adulthood, but it is difficult to disentangle the roles of development and learning on this gain of reproductive success. Lekking lance-tailed manakins provide an opportunity to separate these processes, as the vast majority of male reproduction occurs after a bird obtains alpha status and maintains a display area in the lek, but the age at which males achieve alpha status varies widely. Using 11 years of longitudinal data on age, social status and genetic siring success, I assessed the factors influencing variation in siring success by individuals over their lifetimes. The data show increases in annual reproductive success with both age and alpha experience. At advanced ages, these gains were offset by senescence in fecundity. Individual ontogeny, rather than compositional change of the population, generated a nonlinear relationship of breeding tenure with lifetime success; age of assuming alpha status was unrelated to tenure as a breeder, or success in the alpha role. Importantly, these findings suggest that social experience can mitigate the negative effects of senescence in older breeders.

Mating Strategy and Reproductive Success in the Teiid Lizard, Ameiva Plei

Behaviour ◽  
1995 ◽  
Vol 132 (7-8) ◽  
pp. 529-557 ◽  
Author(s):  
Ellen J. Censky
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Success ◽  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Large Size ◽  
Trade Offs ◽  
Males And Females ◽  
Current Selection ◽  
Growth And Reproduction

AbstractCurrent selection on sexual size dimorphism was studied in a widely foraging non-territorial lizard, Ameiva plei. Males were significantly larger than females. Large males won intrasexual agonistic encounters and guarded females during their entire receptive period (1-4 days). Guarding males spent significantly less time foraging than males who were alone. Only males that guarded females were observed to mate. Mating success was highly skewed with only six of 21 mature males in the study site observed mating. All six males who mated were 141 mm SVL (males mature at 62 mm SVL). The four largest males obtained 84% of all observed matings and were estimated to have fertilized 88% of the eggs. Sexual selection appears to favor large size in males due to competition among males to guard females. Large females on Anguilla also had higher reproductive success bccause SVL was positively correlated with clutch size and number of clutches in a season. It appears that natural selection has favored different trade-offs between growth and reproduction in males and females.

scholarly journals Natural selection increases female fitness by reversing the exaggeration of a male sexually selected trait

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kensuke Okada ◽  
Masako Katsuki ◽  
Manmohan D. Sharma ◽  
Katsuya Kiyose ◽  
Tomokazu Seko ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Experimental Evolution ◽  
Genetic Correlations ◽  
Lifetime Reproductive Success ◽  
Fundamental Theory ◽  
Female Fitness ◽  
Male Trait ◽  
Flour Beetles ◽  
Male Specific

AbstractTheory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to our knowledge, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we use experimental evolution of replicate populations of broad-horned flour beetles to test for effects of sex-specific predation on an exaggerated sexually selected male trait (the mandibles), while also testing for effects on female lifetime reproductive success. We find that populations subjected to male-specific predation evolve smaller sexually selected mandibles and this indirectly increases female fitness, seemingly through intersexual genetic correlations we document. Predation solely on females has no effects. Our findings support fundamental theory, but also reveal unforseen outcomes—the indirect effect on females—when natural selection targets sex-limited sexually selected characters.

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