Delayed Selfing as an Optimal Mating Strategy in Preferentially Outcrossing Species: Theoretical Analysis of the Optimal Age at First Reproduction in Relation to Mate Availability

2003 ◽  
Vol 162 (3) ◽  
pp. 318-331 ◽  
Author(s):  
Anne Tsitrone ◽  
Sébastien Duperron ◽  
Patrice David
Keyword(s):  
Theoretical Analysis ◽  
Mating Strategy ◽  
Mate Availability ◽  
Age At First Reproduction ◽  
Delayed Selfing ◽  
First Reproduction ◽  
Outcrossing Species

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.

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.

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.

scholarly journals Effects of non-toxic filamentous cyanobacteria isolated from tri an reservoir on Daphnia

2020 ◽  
Vol 42 (3) ◽  
Author(s):  
Pham Thanh Luu ◽  
Tran Thi Hoang Yen ◽  
Tran Thanh Thai ◽  
Ngo Xuan Quang ◽  
Hoang Nghia Son
Keyword(s):  
High Performance Liquid Chromatography ◽  
Life History ◽  
Liquid Chromatography ◽  
Secondary Metabolites ◽  
High Performance ◽  
Toxic Effects ◽  
Filamentous Cyanobacteria ◽  
Age At First Reproduction ◽  
Bioactive Secondary Metabolites ◽  
First Reproduction

This study is aimed to examine whether the presence of non-toxic filamentous cyanobacteria can cause toxic effects on Daphnia magna. Six strains of Oscillatoria perornata were isolated from the Tri An Reservoir and cultured in our laboratory for investigation. The results revealed that all strains were negative with the mcyA moleculer marker. The high performance liquid chromatography (HPLC) results showed that toxin was not detected in their culture products, indicating that these strains corresponded to non-toxin producing strains. However, the results of chronic assay indicated that these non-toxin producing O. perornata conferred toxic effects on the tested animals. The age at first reproduction of D. magna was delayed and the survival of D. manga decreased in proportional with the increase of the density of cells of O. perornata exposed. Significant differences in the life history responses were observed for D. mangna exposed to O. perornata. These results suggested that bioactive secondary metabolites other than microcystins produced by the filamentous cyanobacteria O. perornata may contribute to the toxic effects on Daphnia. Besides cyanotoxins, other secondary metabolites must be taken into account when investigating the toxic effects of cyanobacteria.   

scholarly journals Age at first reproduction in male fallow deer: age-specific versus dominance-specific behaviors

1997 ◽  
Vol 8 (4) ◽  
pp. 456-462 ◽  
Author(s):  
Petr E. Komers ◽  
Christophe Pélabon ◽  
David Stenström
Keyword(s):  
Fallow Deer ◽  
Age At First Reproduction ◽  
First Reproduction
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