| Kin selection theory predicts that resource competition is often more intense between phenotypically similar competitors in nature.Because siblings tend to be more similar in phenotype and genotype to each other than nonsiblings,this suggests that resource competition should be especially intense between siblings.However,kin selection theory predicts that mechanisms should evolve or minimizing the effects of kin competition between kin to get the max inclusive fitness.However,so far,the experimental results of these two theories have been confusing.In addition,there is no consensus on the universality of these two theories.Therefore,the important conditions for determining the impact of between kin may be complex,and human beings have not fully understood its essence with no consensus,which make it become a major problem to be solved in future research.Bufo gargarizans is widely distributed in China’s mainland,and its population is abundant.It is a typical explosive propagation.The characteristics of bulkiness and ease of capture of Bufo gargarizans make them an excellent model system studying the influence of kin and food composition on individual fitness.The main objectives of this study are two:(1)to clarify whether this species has kin-recognition ability,if it exists,whether it changes during the ontogeny;(2)when competing with close relatives,whether individuals could switch to use alternative resources and thus reduce exploitative competition with kin,which may enhance the growth and survival of related individuals.On February 13-17,2017,we captured 40 pairs mating bufo gargarizans from a deserted fish pond of industrial zoon in Pingqiao,which located in Xinyang,Henan(114°12′E,32°08′N,elevation 22-100m).And then we brought them back to the laboratories to lay eggs.Two weeks later,tadpole began to hatch after spawning.Then two experimental designs were implemented as originally planned,which lasted about three months.An important finding of the first experimental result was that the unfamiliar siblings’ growth and development conditions(such as body weight and body length at metamorphosis),which were isolated during early larval stages and then put together up to stage 23,were consistent with non-kin but not different from kin.This finding suggest that after stage of 23,test Bufo gargarizans tadpoles could not recognize their siblings by chemical cues.Therefore,it can be shown that the kinship recognition ability of the species can be changed during ontogeny.In addition,it has been found the kin have greater growth rates,faster growth rates,and can be metamorphosed early stage.However,the variability of developmental time and growth rate are significantly larger than those of non-kin and unfamiliar siblings losing kin-recognition ability.In addition,the proportion of metamorphosis between kin was the lowest.These findings indicate that the competition between siblings is not weakened but more intense.By contrast,the intense competition is also beneficial for them to growth and metamorphosis to land before pond drying up.Therefore,relatedness,which can promote larval development and metamorphosis,can also increase the general fitness of the species.An important finding of the second experiment was that when different groups tadpoles were fed for fish food,the kin showed a smaller body length and body weight than nonkin,however there was no such difference between them when fed for mixed food.In addition,the kin tadpoles fed for mixed food have significantly longer body length and body weight than those fed for fish food,by contrast,these index in non-kin were similar whether fed for fish food or mixed food.These results indicate that the competition is significantly fierce between kin when fed for fish food,which are unfavorable to their growth.This finding is consistent with the first experiment.While,individuals can switch to use alternative resources and thus reduce exploitative competition with kin when they are fed for mixed food.We suggest that mechanisms to lessen kin competition may be more likely to evolve in environments where alternative resources are available,and that selection to minimize exploitative competition between kin may promote the evolution of resource polyphenism. |
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