The Effects of Body Mass, Phylogeny, Habitat, and Trophic Level on Mammalian Age at First Reproduction

Evolution ◽  
1987 ◽  
Vol 41 (4) ◽  
pp. 732 ◽  
Author(s):  
J. Timothy Wootton
Keyword(s):  
Body Mass ◽  
Trophic Level ◽  
Age At First Reproduction ◽  
First Reproduction

scholarly journals Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Meike Köhler ◽  
Victoria Herridge ◽  
Carmen Nacarino-Meneses ◽  
Josep Fortuny ◽  
Blanca Moncunill-Solé ◽  
...  
Keyword(s):  
Life History ◽  
Body Mass ◽  
Growth Period ◽  
Extended Period ◽  
Island Rule ◽  
Rule Based ◽  
Age At First Reproduction ◽  
Slow Pace ◽  
First Reproduction ◽  
Adaptive Shifts

AbstractThe 1-m-tall dwarf elephant Palaeoloxodon falconeri from the Pleistocene of Sicily (Italy) is an extreme example of insular dwarfism and epitomizes the Island Rule. Based on scaling of life-history (LH) traits with body mass, P. falconeri is widely considered to be ‘r-selected’ by truncation of the growth period, associated with an early onset of reproduction and an abbreviated lifespan. These conjectures are, however, at odds with predictions from LH models for adaptive shifts in body size on islands. To settle the LH strategy of P. falconeri, we used bone, molar, and tusk histology to infer growth rates, age at first reproduction, and longevity. Our results from all approaches are congruent and provide evidence that the insular dwarf elephant grew at very slow rates over an extended period; attained maturity at the age of 15 years; and had a minimum lifespan of 68 years. This surpasses not only the values predicted from body mass but even those of both its giant sister taxon (P. antiquus) and its large mainland cousin (L. africana). The suite of LH traits of P. falconeri is consistent with the LH data hitherto inferred for other dwarfed insular mammals. P. falconeri, thus, not only epitomizes the Island Rule but it can also be viewed as a paradigm of evolutionary change towards a slow LH that accompanies the process of dwarfing in insular mammals.

scholarly journals How do invasion syndromes evolve? An experimental evolution approach using the ladybird Harmonia axyridis

2019 ◽  
Author(s):  
Julien Foucaud ◽  
Ruth A. Hufbauer ◽  
Virginie Ravigné ◽  
Laure Olazcuaga ◽  
Anne Loiseau ◽  
...  
Keyword(s):  
Body Mass ◽  
Artificial Selection ◽  
Female Body ◽  
Harmonia Axyridis ◽  
Direct Selection ◽  
Age At First Reproduction ◽  
Introduced Populations ◽  
First Reproduction ◽  
Selection Experiments ◽  
Female Body Mass

ABSTRACTExperiments comparing native to introduced populations or distinct introduced populations to each other show that phenotypic evolution is common and often involves a suit of interacting phenotypic traits. We define such sets of traits that evolve in concert and contribute to the success of invasive populations as an ‘invasion syndrome’. The invasive Harlequin ladybird Harmonia axyridis displays such an invasion syndrome with, for instance, females from invasive populations being larger and heavier than individuals from native populations, allocating more resources to reproduction, and spreading reproduction over a longer lifespan. Invasion syndromes could emerge due to selection acting jointly and directly on a multitude of traits, or due to selection on one or a few key traits that drive correlated indirect responses in other traits. Here, we investigated the degree to which the H. axyridis invasion syndrome would emerge in response to artificial selection on either female body mass or on age at first reproduction, two traits involved in their invasion syndrome. To further explore the interaction between environmental context and evolutionary change in molding the phenotypic response, we phenotyped the individuals from the selection experiments in two environments, one with abundant food resources and one with limited resources. The two artificial selection experiments show that the number of traits showing a correlated response depends upon the trait undergoing direct selection. Artificial selection on female body mass resulted in few correlated responses and hence poorly reproduced the invasion syndrome. In contrast, artificial selection on age at first reproduction resulted in more widespread phenotypic changes, which nevertheless corresponded only partly to the invasion syndrome. The artificial selection experiments also revealed a large impact of diet on the traits, with effects dependent on the trait considered and the selection regime. Overall, our results indicate that direct selection on multiple traits was likely necessary in the evolution of the H. axyridis invasion syndrome. Furthermore, they show the strength of using artificial selection to identify the traits that are correlated in different selective contexts, which represents a crucial first step in understanding the evolution of complex phenotypic patterns, including invasion syndromes.

Effects of body size, population density, and maternal characteristics on age at first reproduction in bighorn ewes

1993 ◽  
Vol 71 (12) ◽  
pp. 2509-2517 ◽  
Author(s):  
Jon T. Jorgenson ◽  
Marco Festa-Bianchet ◽  
Mauro Lucherini ◽  
William D. Wishart
Keyword(s):  
Population Density ◽  
Body Mass ◽  
Age Distribution ◽  
Ovis Canadensis ◽  
The Body ◽  
The Other ◽  
Significant Interaction Effect ◽  
Age At First Reproduction ◽  
Maternal Characteristics ◽  
First Reproduction

The factors affecting variation in age at first reproduction of bighorn ewes (Ovis canadensis) were investigated in two marked populations in Alberta. One population was studied for 20 years, the other for 11 years. As yearlings, females that lactated at 2 years of age were on average heavier and larger, and had longer horns than females that did not lactate at 2 years. However, there was wide overlap in body mass between early and late producers, and increases in body mass over the threshold for reproduction had little effect on the probability of early lambing. The body mass of females at 4 months of age explained less than half of the variance in female body mass at 1 year or at 15 months. In one population, the proportion of 2-year-old ewes lactating was not correlated with density and declined after a pneumonia epizootic. In the other population, the proportion of 2-year-old ewes lactating was higher during an experimental reduction of density, and dropped to near zero as density increased. There was a significant interaction effect of body mass and population density upon the probability that a ewe would lactate at 2 years of age. Independently of body mass, yearlings were less likely to lactate at 2 years of age at high population density than at low density. The number and age distribution of rams did not affect the proportion of 2-year-old ewes lactating. The mothers of lactating 2-year-olds were not older or heavier than the mothers of ewes that did not lactate at 2 years. Although some of the variation in age at first reproduction was due to differences in mass and population density, much of it remained unexplained and could be due to genetic factors.

scholarly journals Group-foraging is not associated with longevity in North American birds

2009 ◽  
Vol 6 (1) ◽  
pp. 42-44 ◽  
Author(s):  
Guy Beauchamp
Keyword(s):  
Body Mass ◽  
Group Size ◽  
North American ◽  
Life History Theory ◽  
Foraging Efficiency ◽  
Passerine Birds ◽  
Group Foraging ◽  
Evolutionary Transitions ◽  
Age At First Reproduction ◽  
First Reproduction

Group-foraging is common in many animal taxa and is thought to offer protection against predators and greater foraging efficiency. Such benefits may have driven evolutionary transitions from solitary to group-foraging. Greater protection against predators and greater access to resources should reduce extrinsic sources of mortality and thus select for higher longevity according to life-history theory. I assessed the association between group-foraging and longevity in a sample of 421 North American birds. Taking into account known correlates of longevity, such as age at first reproduction and body mass, foraging group size was not correlated with maximum longevity, with and without phylogenetic correction. However, longevity increased with body mass in non-passerine birds. The results suggest that the hypothesized changes in predation risk with group size may not correlate with mortality rate in foraging birds.

Long-term reproductive patterns and sighting bias in Weddell seals (Leptonychotes weddelli)

1987 ◽  
Vol 65 (5) ◽  
pp. 1091-1099 ◽  
Author(s):  
J. Ward Testa
Keyword(s):  
Reproductive Performance ◽  
Age At First Reproduction ◽  
Reproductive Patterns ◽  
Weddell Seals ◽  
Signy Island ◽  
First Reproduction ◽  
Reproductive Rates ◽  
The Cost ◽  
The Impact

The reproductive performance of tagged Weddell seals (Leptonychotes weddelli) was monitored at McMurdo Sound, Antarctica, from 1970 to 1984. An age-specific reproductive schedule revealed the major onset of pupping at age 6 years, and a mean age of first birth of 7.1 years. The average asymptotic pupping rate of 0.61 is reached by age 10. The cost of pupping in a given year is reflected in a 0.05 drop in the probability of pupping the following year. This cost is not evident in females over 7 years old, suggesting that postweaning condition affects newly mature females more than those that are fully mature. Annual adult reproductive rates ranged from 0.46 to 0.79, with a possible periodicity of 5 to 6 years. Simulations were conducted to determine the impact on reproductive estimates of sighting biases associated with seals having had at least one pup (Parous) or having pupped that season (With-Pup). Age at first reproduction as deduced from an age-specific pupping schedule is strongly affected by both forms of sighting bias, but bias in sighting Parous females was the more important. Estimates of adult reproduction were affected minimally. Comparisons of reproductive estimates with those of Weddell seals at Signy Island are discussed with regard to the effects of sighting biases.

scholarly journals Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

2014 ◽  
Vol 281 (1797) ◽  
pp. 20142103 ◽  
Author(s):  
Marlee A. Tucker ◽  
Tracey L. Rogers
Keyword(s):  
Community Structure ◽  
Body Size ◽  
Body Mass ◽  
Marine Environment ◽  
Trophic Level ◽  
Marine Mammals ◽  
Trophic Position ◽  
Trophic Levels ◽  
Predator Prey ◽  
Terrestrial Mammals

Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial ( n = 51) and marine ( n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities.

scholarly journals Trophic cascades alter eco-evolutionary dynamics and body size evolution

2020 ◽  
Vol 287 (1938) ◽  
pp. 20200526
Author(s):  
Thomas M. Luhring ◽  
John P. DeLong
Keyword(s):  
Body Mass ◽  
Trophic Level ◽  
Evolutionary Dynamics ◽  
Trophic Cascades ◽  
Trophic Levels ◽  
Chain Model ◽  
Top Predator ◽  
Predator Prey ◽  
Top Predators ◽  
Time Changes

Trait evolution in predator–prey systems can feed back to the dynamics of interacting species as well as cascade to impact the dynamics of indirectly linked species (eco-evolutionary trophic cascades; EETCs). A key mediator of trophic cascades is body mass, as it both strongly influences and evolves in response to predator–prey interactions. Here, we use Gillespie eco-evolutionary models to explore EETCs resulting from top predator loss and mediated by body mass evolution. Our four-trophic-level food chain model uses allometric scaling to link body mass to different functions (ecological pleiotropy) and is realistically parameterized from the FORAGE database to mimic the parameter space of a typical freshwater system. To track real-time changes in selective pressures, we also calculated fitness gradients for each trophic level. As predicted, top predator loss generated alternating shifts in abundance across trophic levels, and, depending on the nature and strength in changes to fitness gradients, also altered trajectories of body mass evolution. Although more distantly linked, changes in the abundance of top predators still affected the eco-evolutionary dynamics of the basal producers, in part because of their relatively short generation times. Overall, our results suggest that impacts on top predators can set off transient EETCs with the potential for widespread indirect impacts on food webs.

The Evolution of Life History Parameters in Teleosts

1984 ◽  
Vol 41 (6) ◽  
pp. 989-1000 ◽  
Author(s):  
Derek A. Roff
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Life History Theory ◽  
Larval Survival ◽  
Reasonable Assumption ◽  
Natural Mortality ◽  
Age At First Reproduction ◽  
Life History Parameters ◽  
First Case ◽  
First Reproduction

Empirical studies have shown that in teleosts there is a significant correlation between the life history parameters, age at first reproduction, natural mortality, and growth rate. In this paper 1 hypothesize that these correlations are the result of evolutionary adjustments due to the trade-off between reproduction, growth, and survival. A simple and reasonable assumption is that the costs of reproduction are sufficient to cause the ltmt function to decrease. A simple expression relating the age at first reproduction is derived from this assumption. This formula accounts for a statistically significant portion (60.6%) of the variation in age at first reproduction in 30 stocks of fish. To extend the model to predict the distribution of life history parameters across all teleosts, an explicit cost function is incorporated. The model is analyzed with respect to two fitness measures, the expected lifetime fecundity and malthusian parameter, r. In the first case it is shown that the optimal age at maturity, T, depends only on the natural mortality rate (M) and the growth rate (k). In the second case, T is a function of k and the logarithm of a parameter, In C; the latter is a product of egg and larval survival, maximum body length (Lx), and the proportionality coefficient of the fecundity/length function. Difficulties of measuring egg and larval survival make the testing of the latter case difficult for particular species. However, this method provides a simple formula for the computation of r; this is shown generally to be approximately zero, thereby adding strength to the assumptions of the first analysis. The distribution patterns of T on k and M on k are predicted and compared with the observed pattern. In general, the predictions are validated: however, certain combinations of k and ln C are shown to occur very infrequently. The prediction of such "empty" regions of the parameter space remains a challenge for future development of life history theory.

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