Losers in the ‘Rock-Paper-Scissors’ game: The role of non-hierarchical competition and chaos as biodiversity sustaining agents in aquatic systems

Processes occurring within small areas (patch-scale) that influence species richness and spatial heterogeneity of larger areas (landscape-scale) have long been an interest of ecologists. This research focused on the role of patch-scale deterministic chaos arising in phytoplankton assemblages characteristic of “Rock-Paper-Scissors” population dynamics (i.e., competitively non-hierarchical). We employed a simple 2-patch model configuration with lateral mixing and through-flow, and tested the robustness of species richness at the scale of the landscape and spatial heterogeneity. Three different assemblages were used that in a dimensionless box model configuration exhibited chaotic behavior. Our results showed that when a spatial dimension was added to the model configuration, and when all species were shared between patches (i.e., no invading populations), chaos-induced species richness and spatial heterogeneity were quickly reduced with the onset of mixing. While assemblages in each patch were comprised of exactly the same species, they differed in their proportional population densities due to differing stages of succession and the incidence of alternative assemblage structures. Even at very low mixing rates (0.001 d⁻¹), which produced low passive migration rates (0.1% of the total biomass per day), the incidence of high richness and heterogeneity decreased by ∼80%. Interestingly, this sensitivity was not the same for the three assemblages tested. Declines in species richness and spatial heterogeneity associated with mixing were greater in assemblages comprised of competitively dissimilar species (based on the area occupied in the resource-tradeoff space defined by the R* model). The underlying mechanisms may involve the degree to which nutrient dynamics are altered with the arrival of immigrants. Our findings suggest that in partially to well-mixed aquatic systems, the roles of patch-scale non-hierarchical competition and chaos as factors maintaining species richness and spatial heterogeneity may be limited. However, in aquatic systems that experience periods of very low mixing, or even disconnection, non-hierarchical competition and chaos might indeed contribute significantly to biodiversity.     

A dynamic programming implemented resource competition game theoretic model

Resource competition is commonly occurred in animal populations and studied intensively by researchers. Previous studies have applied game theoretic model by finding Nash equilibrium to investigate this phenomenon. However computation of the Nash equilibrium requires an understanding of the payoff matrix that allocates the rewards received by players when they adopt each of the strategies in the game. In our study we present a dynamic programming implemented framework to compute 2 × 2 intraspecific finite resource allocation game's payoff matrix explicitly. We assume that two distinct types of individuals, aggressive and non-aggressive, are in the population. Then we divide the entire animal development period into three different stages: initialization, quasilinear growth and termination. Each stage for each type of players is specified with their own development coefficient, which determines how resource consumption could convert into strength as reward. Each player has equal and finite resource at the beginning of their development and fights against other players in the population to maximize its own potential reward. Based on these assumptions it is reasonable to use backward induction dynamic programming to compute payoff matrix. We present numerical examples for three different types of aggressive individuals and compute the payoff matrices correspondingly. Then we use the derived payoff matrices to determine the Nash equilibrium and Evolutionary Stable Strategy. Our research provide a framework for future quantitative studies on animal resource competition problems and could be expanded to n-players interspecific stochastic asymmetric resource allocation problem by changing some settings of dynamic programming formulation.     

溶藻放线菌对铜绿微囊藻和小球藻竞争生长的影响

从土壤中分离获得l株对铜绿微囊藻有明显抑制作用的橄榄网状链霉菌SG-001（Streptomyces olivoreticuli SG-001）,研究其对铜绿微囊藻（Microcystis aeruginosa）和小球藻（Chlorefla pyrenoidosa）竞争生长的影响。结果表明：SG-001菌株的活性物质主要存在于无菌滤液中,能够强烈抑制铜绿微囊藻的生长,但对小球藻的生长具有明显的促进作用。当混藻中两种藻细胞初始接种浓度均为4.0×106 mL-1时,在BG11纯培养条件下,添加SG-001无菌滤液有利于小球藻生长,但对铜绿微囊藻抑制作用不明显;而SG-001无菌滤液对天然加富水样中的铜绿微囊藻具有明显抑制作用,在同时接种有铜绿微囊藻和小球藻的混合藻液中,添加SG-001无菌滤液能够明显提高小球藻的生长竞争能力,且水体中氨氮和可溶性总磷的去除率可分别达到85%和93.33%,而铜绿微囊藻在第8天时生长基本被小球藻抑制。     

Is female promiscuity constrained by the presence of her social mate? An experiment with bluethroats <Emphasis Type="Italic">Luscinia svecica</Emphasis>

Extra-pair paternity is common in birds and much research has focussed on the selective advantage of extra-pair matings for both sexes. In contrast, little attention has been given to the fact that in most species the majority of offspring are sired by the social male. We investigated whether extra-pair matings of female bluethroats (Luscinia svecica) are constrained by the presence of the pair male, by detaining males in cages on their territories for one morning during the peak of female fertility. The proportion of offspring sired by extra-pair males was higher in broods where males had been detained (35%) than in control broods (16%), while the proportion of broods that had at least one extra-pair offspring did not differ significantly between experimental (65%) and control broods (44%). Within the experimental group, levels of extra-pair paternity were not related to the day of experiment in relation to start of egg laying, but males caught early in the morning lost more paternity than males caught later on. Our results show that pair males exert constraints on the frequency of extra-pair paternity by being present during the period of peak fertility, which could be a direct effect of their mate guarding effort and/or due to an advantage in sperm competition for pair males.     

Factors predicting male fertilization success in an external fertilizer

In postcopulatory sexual selection both sperm competition and cryptic female choice are considered to be important selective agents, but their relative importance for male fertilization success has received little attention. We tested whether sperm quality, male spawning coloration, male heterozygosity, and genetic overlap with the female explained a male’s fertilization success in controlled in vitro fertilization competition trials between equal numbers of sperm from pairs of male Arctic charr (Salvelinus alpinus), an external fertilizer. Offspring were genotyped to determine each males’ share of paternity. The velocity of a male’s sperm relative to the velocity of the competing male’s sperm was the best predictor of male fertilization success. Yet, sperm velocity was not related to spawning coloration or male heterozygosity. In fact, the most brightly colored male in a pair had the lowest fertilization probability. This could result from cryptic female choice for pale males, but might rather be a result of paler males producing more competitive sperm than more colored males. Furthermore, the more microsatellite alleles a male shared with the female relative to the competing male, the higher fertilization success he had. We argue that this latter may be an effect of assortative cryptic female choice, which might prevent hybridization with sympatric Arctic charr morphs or one form of kin selection.     

Sex-specific costs of hatching last: an experimental study on herring gulls (<Emphasis Type="Italic">Larus argentatus</Emphasis>)

An organism’s pattern of development can have important long-term fitness effects. In species where the sexes differ in size or other phenotypic traits, they may also have different optimal developmental rates. This influences both parental sex allocation strategies and susceptibility of the sexes to early developmental conditions. However, sex differences in developmental rate and vulnerability to environment during the embryonic period are not well understood. In birds, sibling competition and hatching asynchrony may select for accelerated embryonic development of the last offspring in order to reduce their competitive disadvantage after hatching. They may advance their hatching in response to vocal stimuli by the older siblings. It is, however, unclear whether this flexibility in developmental rates is sex specific. In this study, we experimentally manipulated between-embryo contact and tested whether this affected the pre-natal developmental rate and post-hatching performance of male and female offspring from last-laid eggs in the herring gull. Post-hatching performance was measured both in competitive and non-competitive situations. Among young incubated in isolation, males hatched faster than females, but both sexes fledged in similar, relatively good condition. Among young incubated with normal between-embryo contact, hatching time did not differ between sexes, but males fledged in poorer condition than females, regardless of whether they were reared singly or in a brood. These results suggest that male and female offspring differ in their ability to mitigate the costs of hatching asynchrony.     

Sex-related asymmetry in competitive ability of sexually monomorphic barn swallow nestlings

In diverse taxa, offspring solicit parental care using complex displays, which may evolve as reliable signals of condition or as mechanisms to manipulate parental investment. Differential sex allocation may therefore result from adaptive parental decisions or sex-related variation in competitive ability or because of sex-related asymmetries in kin selection. Under normal food provisioning, female barn swallow (Hirundo rustica) nestlings begged more loudly but did not receive more food than male nestlings. After food deprivation, begging call loudness of males but not females increased. Begging loudness positively predicted the number of feedings received by the nestlings, and males gained more mass than females after food deprivation. Male nestlings are more severely affected by chronic food reduction and may therefore accrue a larger benefit compared to females by increasing their food intake under short-term conditions of food scarcity. These results suggest that either females do not increase begging intensity to favour male broodmates which are more vulnerable to prolonged food stress, or that males prevail in scramble competition despite being similar in size to females.     

Infant handling and mortality in yellow baboons (<Emphasis Type="Italic">Papio cynocephalus</Emphasis>): evidence for female reproductive competition?

This study examines negative and positive infant handling behavior in 24 free-ranging yellow baboon infants (Papio cynocephalus) studied over a 5-year period in Mikumi National Park, Tanzania. We test predictions of the female reproductive competition hypothesis to explain patterns of infant handling behavior by adult females (excluding the infants mother) in relation to observed cases of infant mortality by age 3 months (25% of infants in this study). Results show that: (1) low-ranking infants received more negative infant handling than high-ranking infants; conversely high-ranking infants received more positive infant handling; (2) female kin engaged in higher levels of positive infant handling than did non-kin, whereas non-kin showed higher levels of negative infant handling; (3) rates of negative infant handling varied by season, with high levels at the onset of the rainy season; and (4) high level of negative infant handling was a significant predictor of infant mortality by age 3 months (infant rank and sex did not predict survival). We discuss how the occurrence and interpretation of infant handling behavior in the literature has likely been confused by different definitions of this behavior, as well as differences in the socio-ecological context in which this behavior occurs.Communicated by C. Nunn     

以模仿为主要手段的旅游地开发

引入博弈论中的豪泰林(Hottelling)价格竞争模型与“偏离-份额分析法”,讨论了无直接竞争状态、价格竞争状态、产品组合竞争状态下的旅游产品模仿问题。通过分析,试图为旅游产品开发提供一种新视角,为旅游产品生产者服务。     

我国公路交通伤亡现状分析

本文对统计、上报、公布交通伤亡数据业务的不足作了简要分析,分别对城市交通伤亡、收费道路交通伤亡、乡村和山区非收费道路交通伤亡提出了相应的数学描述模型,并提出了收费路伤亡高发期和稳定期的观点和数学模型。提出了交通伤亡责任追究制的思想,行政管理的效果非常有限,应该根据不同情况进行技术型专业管理。