Mutualisms are cooperative interactions between members of different species. We focus on obligate mutualism, where each species cannot survive without the other. From a theoretical aspect, obligate mutualism is simil...Mutualisms are cooperative interactions between members of different species. We focus on obligate mutualism, where each species cannot survive without the other. From a theoretical aspect, obligate mutualism is similar to the relationship between male and female. Empirical data indicate a sex-ratio selection: male and female have a specific ratio in their population sizes. In the present paper, we apply lattice model to obligate mutualism between two species, and present a theory of “ratio selection” which is a generalization of sex-ratio selection. Computer simulations are carried out by two methods: local and global interactions. In the former, interactions occur between neighbouring cells, while in the latter they occur between any pair of cells. Simulations in both interactions show the so-called Allee effect: both species can survive, when both densities are large in some extent. However, we find a large difference between local and global simulations. In the case of local interaction, restriction for survival is found to be extremely severe compared to global interaction. Both species require a proper ratio for their sustainability. This result leads to the theory of ratio selection: when interaction occurs locally, the ratio of both species is uniquely determined. We discuss that the ratio selection explains not only the evolution of endosymbionts from free-living ancestors but also the evolution from endosymbionts to organelles.展开更多
Mater nal effects occur whe n the phe no type of the mother in flue nces that of the young to the detriment of her survival, growth or fitn ess. The in vestment of the mother can be affected by mater nal body conditio...Mater nal effects occur whe n the phe no type of the mother in flue nces that of the young to the detriment of her survival, growth or fitn ess. The in vestment of the mother can be affected by mater nal body condition and/or experience. Trivers-Willard Hypothesis (TWH) and Local Resource Competition Hypothesis (LRCH) are the main hypotheses used to explain bias in birth sex-ratios in mammals, as well as for sex-biased maternal investment. Both hypotheses suggest that a different amount of investment must be expected according to the sex of the young. However, recent studies suggest that these differences are not in quantity but in the strategies: mechanisms and objectives may differ for each sex. We studied how maternal characteristics (age, body mass, body condition, and domi nance status) influence re leva nt aspects of the birth and early growth of the calf (birth date, birth body mass, body mass at weaning, and body condition at weaning) separately for each sex;and how that investment is mediated by milk production and composition (lactose, fat, and protein). One hundred eighty-eight newborns from 75 captive red deer hinds aged from 2 to 19 years were analyzed. The main differential investment observed was related to birth date: when producing a female, hinds give birth earlier in the season only if they have a good body condition;however, when gestating a male it is the older hinds those which deliver earlier. Subsequently, milk production and composition are correlated with birth body mass in female calves, but to weaning body mass in males. Thus, only hind body mass affects the weaning body mass of female calves, compared with age and hind body mass in males. These results suggest that while TWH fits the maternal investment strategy found for male calves, it is LRCH which correlates with the maternal investment patterns observed for females.展开更多
We report the current status of Taimen (Hucho taimen) population in Wusuli River of China. The amount of catch per year was only 1 800 - 5 400 individuals ranging from 2-15 years old during 1998-2002. Of all the captu...We report the current status of Taimen (Hucho taimen) population in Wusuli River of China. The amount of catch per year was only 1 800 - 5 400 individuals ranging from 2-15 years old during 1998-2002. Of all the captured, individuals with sexual maturity were up to 30%-70% (female maturity at 5 years old and male 6 years old). Sex ratio varied greatly among different localities. Its breeding population mainly consisted of males aged 5-10 years and females aged 8-13 years’old, which spawned in May each year.Females breed once with about 4 000 - 23 000 eggs produced every 2-3 years. Taimen grows fast and average growth rate is about 10 cm per year prior to 10 years’s old, which corresponded with von Bertelanffy’s equation calculated as L t=246 41[1-e -0 0407(t-0 4625) ] and W t= 174 075 72 [1-e -0 0407(t-0 4622) ] 2 9537 , and the relationship between body length and weight was W=0 015018L u 2020 .展开更多
文摘Mutualisms are cooperative interactions between members of different species. We focus on obligate mutualism, where each species cannot survive without the other. From a theoretical aspect, obligate mutualism is similar to the relationship between male and female. Empirical data indicate a sex-ratio selection: male and female have a specific ratio in their population sizes. In the present paper, we apply lattice model to obligate mutualism between two species, and present a theory of “ratio selection” which is a generalization of sex-ratio selection. Computer simulations are carried out by two methods: local and global interactions. In the former, interactions occur between neighbouring cells, while in the latter they occur between any pair of cells. Simulations in both interactions show the so-called Allee effect: both species can survive, when both densities are large in some extent. However, we find a large difference between local and global simulations. In the case of local interaction, restriction for survival is found to be extremely severe compared to global interaction. Both species require a proper ratio for their sustainability. This result leads to the theory of ratio selection: when interaction occurs locally, the ratio of both species is uniquely determined. We discuss that the ratio selection explains not only the evolution of endosymbionts from free-living ancestors but also the evolution from endosymbionts to organelles.
文摘Mater nal effects occur whe n the phe no type of the mother in flue nces that of the young to the detriment of her survival, growth or fitn ess. The in vestment of the mother can be affected by mater nal body condition and/or experience. Trivers-Willard Hypothesis (TWH) and Local Resource Competition Hypothesis (LRCH) are the main hypotheses used to explain bias in birth sex-ratios in mammals, as well as for sex-biased maternal investment. Both hypotheses suggest that a different amount of investment must be expected according to the sex of the young. However, recent studies suggest that these differences are not in quantity but in the strategies: mechanisms and objectives may differ for each sex. We studied how maternal characteristics (age, body mass, body condition, and domi nance status) influence re leva nt aspects of the birth and early growth of the calf (birth date, birth body mass, body mass at weaning, and body condition at weaning) separately for each sex;and how that investment is mediated by milk production and composition (lactose, fat, and protein). One hundred eighty-eight newborns from 75 captive red deer hinds aged from 2 to 19 years were analyzed. The main differential investment observed was related to birth date: when producing a female, hinds give birth earlier in the season only if they have a good body condition;however, when gestating a male it is the older hinds those which deliver earlier. Subsequently, milk production and composition are correlated with birth body mass in female calves, but to weaning body mass in males. Thus, only hind body mass affects the weaning body mass of female calves, compared with age and hind body mass in males. These results suggest that while TWH fits the maternal investment strategy found for male calves, it is LRCH which correlates with the maternal investment patterns observed for females.
文摘We report the current status of Taimen (Hucho taimen) population in Wusuli River of China. The amount of catch per year was only 1 800 - 5 400 individuals ranging from 2-15 years old during 1998-2002. Of all the captured, individuals with sexual maturity were up to 30%-70% (female maturity at 5 years old and male 6 years old). Sex ratio varied greatly among different localities. Its breeding population mainly consisted of males aged 5-10 years and females aged 8-13 years’old, which spawned in May each year.Females breed once with about 4 000 - 23 000 eggs produced every 2-3 years. Taimen grows fast and average growth rate is about 10 cm per year prior to 10 years’s old, which corresponded with von Bertelanffy’s equation calculated as L t=246 41[1-e -0 0407(t-0 4625) ] and W t= 174 075 72 [1-e -0 0407(t-0 4622) ] 2 9537 , and the relationship between body length and weight was W=0 015018L u 2020 .
