Kinship alters the effects of forced cohabitation on body weight,mate choice and fitness in the rat-like hamster Tscheskia triton

It has been documented that social isolation imparts deleterious effects on gregarious rodents species, but caging in group imparts such effects on solitary rodents. This study was attempted at examining how kinship to affect body weight, behavioral interaction, mate choice and fitness when we caged male and female rat-like hamsters Tscheskia triton in pair, a solitary species. We found that females paired with nonsibling males became heavier than the females paired with sibling males, but both agonistic and amicable behavior between paired males and females did not differ between sibling and nonsibling groups. This indicated that kinship might reduce females＇ obesity in response to forced cohabitation, and dissociation might exist between physiological and behavioral responses. Furthermore, binary choice tests revealed that social familiarity between either siblings or nonsiblings decreased their investigating time spent in opposite sex conspeeifie of cage mates and/or their scents as compared with those of nonmates, suggesting effects of social association on mate and kin selection of the hamsters. On the other side, both females and males caged in pair with siblings show a preference between unfamiliar siblings or their scents and the counterparts of nonsiblings after two month separation, indicating that the kin recognition of the hamsters might also rely on phenotype matching. In addition, cohabitation （or permanent presence of fathers） elicited a lower survival of pups in nonsibling pairs than sibling pairs, but did not affect litter size, suggesting that kinship affects fitness when housing male and female ratlike hamsters together. Therefore, inbreeding might be adapted for rare and endangered animals.     

Plasticity in Metamorphic Traits of Rice Field Frog(Rana limnocharis) Tadpoles:The Interactive Effects of Rearing Temperature and Food Level

In organisms with complex life cycles, such as amphibians, morphological variation is strongly influenced by environmental factors(e.g. temperature) and maternal effects(e.g. diet). Although temperature and food level exert a strong influence on larval growth, little is known about the interacting effects of these factors on age and size at metamorphosis. In this study, plasticity in growth rates, survival, larval period, and size at metamorphosis were examined in Rice field Frog(Rana limnocharis) under different combinations of rearing temperature and food level. Rearing temperature did not affect age at metamorphosis, but a significant interaction between temperature and food level revealed that of tadpoles feeding at a high food level, those reared at 32°C had a shorter length of larval period than those reared at 29°C or 26°C. Similarly, our results also showed high food level produced a larger growth rate and mass at metamorphosis at 32°C, but not at 29 and 26°C. Therefore, our results revealed that the effects of food level on larval growth and metamorphosis were highly dependent on developmental temperature.     

Developmental and Liver Metabolite Changes Induced by TPhP Exposure in Brown Frog (Rana zhenhaiensis) Tadpoles

As an organophosphorus compound that frequently detected in water samples,triphenyl phosphate(TPhP)has been showed to have multiple toxicological effects on aquatic species.However,no attention has been paid to its potential impact on non-model amphibian species.Here,tadpoles of the Zhenhai brown frog(Rana zhenhaiensis)were exposed to different concentrations of TPh P(0,0.02 and 0.1 mg/L)throughout the developmental period to assess physiological and meta bolic impacts of TPh P exposure on amphibian larvae.After 30-day TPh P exposure,the developmental stage of tadpoles from the high-concentration treatment appeared to be more advanced than that from the other two treatments,but other measured traits(including body size,tail length and liver weight)did not differ among treatments.Metabolite profiles in tadpole livers based on liquid chromatographymass spectrometry(LC-MS)revealed a distinct metabolic disorder in exposed animals.Specifically,significant changes in various hepatic amino acids(such as glutamine,glutamate,valine and leucine)were observed.Overall,our results indicated that chronic TPhP exposure potentially caused developmental and hepatic physiological changes in R.zhenhaiensis tadpoles,although its impact on tadpole growth appeared to be minor.     

Effect of Incubation Temperature on the Somatic Development of the Snail-Eating Turtle Malayemys macrocephala

The rising average global temperature can lead to changes both in the physical and biological environments and affect the survival of organisms. Freshwater turtles are considered to be susceptible species since their development is dependent on incubation temperature. In Thailand, although several species of freshwater turtle are present, the extent of their susceptibility to temperature change is unknown due to the lack of information on their developmental patterns. This research, therefore, is aimed at examining the effects of temperature on somatic development in Malayemys macrocephala, a native species and the most common freshwater turtle in Thailand. Turtle eggs were collected from rice fields in the central part of Thailand during December 2011 to February 2012 inclusive. Eggs （237-238 per condition） were incubated in microprocessor-controlled incubators at three different temperatures （26 ℃, 29℃ and 32℃） with a relative humidity in excess of 80%. Each week, until the remaining eggs hatched, eggs were randomly selected, removed and dissected to reveal the developing embryo to screen for developmental stage and any abnormalities. The incubation period （lay to hatch） was not significantly different among the three temperatures （115 ±11.3 d, 115 ±20.3 d and 109±17.8 d, respectively）, but the growth patterns, as indicated by the stages of development and carapace lengths, were significantly different. At a high temperature （32℃）, turtle embryos showed a significantly faster growth rate than at the intermediate and low temperatures （29 ℃and 26 ℃）, but had a significantly （over 3.3-fold） higher incidence of developmental abnormalities （especially deformed bodies） than at the lower temperatures. Overall, the results indicate that incubation temperature is an important variable affecting the somatic development of this tropical freshwater turtle species, whilst abnormalities in the embryonic body may be a sensitive indicator of extreme thermal stress.     

Coinfection of the secondary symbionts,Hamiltonella defensa and Arsenophonus sp.contribute to the performance of the major aphid pest,Aphis gossypii(Hemiptera:Aphididae)

Bacterial endosymbionts play important roles in ecological traits of aphids.In this study,we characterize the bacterial endosymbionts of A.gossypii collected in Karaj,Iran and their role in the performance of the aphid.Our results indicated that beside Buchnera aphidicola,A.gossypii,also harbors both Hamiltonella defensa and Arsenophonus sp.Quantitative PCR(qPCR)results revealed that the populations of the endosymbionts increased throughout nymphal development up to adult emergence;thereafter,populations of Buchnera and Arsenophonus were diminished while the density of H.defensa constantly increased.Buchnera reduction caused prolonged development and no progeny production.Furthermore,secondary symbiont reduction led to reduction of the total life span and intrinsic rate of natural increase as well as appearance of the deformed dead offspring in comparison with the control insects.Reduction of the secondary symbionts did not affect parasitism rate of the aphid by the parasitic wasp Aphidius matricariae.Together these findings showed that H.defensa and Arsenophonus contributed to the fitness of A.gossypii by enhancing its performance,but not through parasitoid resistance.     

Social rank and cortisol among female rhesus macaques (Macaca mulatta)

In animal societies, some stressful events can lead to higher levels of physiological stress. Such stressors, like social rank, also predict an increased vulnerability to an array of diseases. However, the physiological relationship between social rank and stress varies between different species, as well as within groups of a single species. For example, dominant individuals are more socially stressed at times, while at other times it is the subordinate ones who experience this stress. Together, these variations make it difficult to assess disease vulnerability as connected to social interactions. In order to learn more about how physiological rank relationships vary between groups of a single species, cortisol measurements from hair samples were used to evaluate the effects of dominance rank on long-term stress levels in despotic and less stringent female rhesus macaque hierarchal groups. In despotic groups, cortisol levels were found not to be correlated with social rank, but a negative correlation was found between social rank and cortisol levels in less stringent hierarchies. Low ranking monkeys in less stringent groups secreted elevated levels of cortisol compared to higher ranking animals. These data suggest that variations in the strictness of the dominance hierarchy are determining factors in rank related stress physiology. The further consideration of nonhuman primate social system diversity and the linear degree of their hierarchies may allow for the development of valid rank-related stress models that will help increase our understanding and guide the development of new therapeutics for diseases related to human socioeconomic status.     

Boldness is related to the development of the cephalic crest in the male of the river blenny Salariafluviatilis （Asso, 1801）

Boldness is defined as the tendency of an individual to take risks when exposed to novel objects or situations. The main aim of this work was to dilucidate if boldness was related to the development of the secondary sexual traits （SSTs） in the male of the fiver blenny Salariafluviatilis, a freshwater fish which takes care of eggs. As a second objective SSTs effect on pa rental status adoption was also be explored. Wild young fish were caught in the Segre River （Ebro basin） in November 2010. Fish were kept in five aquaria in groups of eight males and eight females with artificial nests. Boldness （boldness score and hesitancy） of males （initially with little SSTs development） was tested as the time required to exit a refuge when exposed to a new environ ment. Fish were mantained in the same aquaria for several months, and males＇ SSTs development and reproductive behaviour were monitored. Boldness score was negatively associated to cephalic crest development. Hesitancy was negatively related to male length and was also influenced by the interaction between male length and cephalic crest. Parental status acquisition was positively related to the male＇s length, marginally related to anal gland development, and nonrelated to cephalic crest. These re sults suggest an intrasexual role of the crest as an informative trait of boldness （honest signal） which might not necessarily be chosen by the females. It is also discussed that correlational selection could be responsible for linking boldness and growth rate in this species. Sexual selection, in addition to having directed the evolution of secondary sexual traits, might have favored certain personality traits （e.g. boldness） associated with the achievement of a larger body length .     

Response of Polygonum viviparum species and community level to long-term livestock grazing in alpine shrub meadow in Qinghai-Tibet Plateau

Grazing by domestic herbivores is generally recognized as a major ecological factor and an important evolutionary force in grasslands. Grazing has both extensive and profound effects on individual plants and communities. We investigated the response patterns of Polygonum viviparum species and the species diversity of an alpine shrub meadow in response to long-term livestock grazing by a field manipulative experiment controlling livestock numbers on the Qinghai-Tibet Plateau in China. Here, we hypothesize that within a range of grazing pressure, grazing can alter relative allocation to different plant parts without changing total biomass for some plant species if there is life history trade-offs between plant traits. The same type of communities exposed to different grazing pressures may only alter relative species' abundances or species composition and not vary species diversity because plant species differ in resistant capability to herbivory. The results show that plant height and biomass of different organs differed among grazing treatments but total biomass remained constant. Biomass allocation and absolute investments to both reproduction and growth decreased and to belowground storage increased with increased grazing pressure, indicating the increasing in storage function was attained at a cost of reducing reproduction of bulbils and represented an optimal allocation and an adaptive response of the species to long-term aboveground damage. Moreover, our results showed multiform response types for either species groups or single species along the gradient of grazing Intensity. Heavy grazing caused a 13.2％ increase in species richness. There was difference in species composition of about 18％--20％ among grazing treatment. Shannon-Wiener (H') diversity index and species evenness (E) index did not differ among grazing treatments. These results support our hypothesis.     

Predatory Cues Influence the Behavioral Responses and Metamorphic Traits of Polypedates maculatus(Anura: Rhacophoridae)

Mechanisms of predator detection and the influence of the presence of nonlethal predators on antipredator defense behavior and metamorphic traits were studied in the Indian tree frog, Polypedates maculatus. Exposure of P. maculatus tadpoles to chemical cues of caged predator(crabs, Barytelphusa spp.) fed with either conspecific or heterogeneric tadpoles, or were starved elicited defense behavior(by avoiding predator zone) in them. Such a behavior was not evident when exposed to predators housed in a glass beaker(visual cues). Both early(Gosner stage 27–28) and later(Gosner stage 35–36) stage tadpoles when exposed to caged predators(fed with conspecific tadpoles), prey tadpoles spent less time swimming and remained motionless for longer periods. Yet, the time spent by prey in feeding was unaffected. Further, the predator avoidance behavior exhibited by them was of the same intensity regardless of whether the caged predators were fed or starved implying the influence of predator's kairomones. Tadpoles reared with caged predator reached the metamorphic climax stage(MC stage; Gosner stage 42) earlier than those reared without a predator. Size at emergence(Gosner stage 46) was comparable in both the groups. The findings suggest that P. maculatus tadpoles assess predation risk chiefly by sensing kairomones of the predator in eliciting antipredator defense behaviors. Accelerated development and early metamorphosis without any compromise of the size at emergence may be due to their unaltered feeding activity.     

Benefits of heterospecific aggregation on necromass: in fluence of temperature,group density,and compositi on on fitness-related traits

Necrophagous blowflies(Diptera:Calliphoridae)such as Calliphora vicina,a cold-tolerant species,and L ucilia serie ata,a warm-adapted species,are pioneer carrion?breeder.Although these two species have different temperature preferences,larvae aggregate actively and often feed simultaneously on carrion.The hypothesis to be tested was that L.sericata benefits from the association with C.vicina at lower temperatures(i.e.,15℃)and that C.vicina derives greater benefits from this association at higher temperatures(i.e.,28℃).Therefore,both species were raised at these two constant temperatures from first instars to adults under three different conditions:monospecific low-density,monospecific high-density,and heterospecific high-density.The time until larval migration,surface area of puparia,and survival rates were determined for each condition.Differences between these fitness-related traits were found between species,temperatures,group densities,and species compositions.At 28°C,C.vicina larvae bred in heterospecific groups migrated significantly earlier and in higher numbers than that under same density conspecific con?ditions,with a lower mortality rate.At 15°C,both species benefited from high-density heterospecific associations,expressed by faster development and larger puparia.In conclusion,necrophagous larvae benefited from heterospecific aggregations at suboptima 1 temperatures by adapting their migration time to that of the faster species.Since temperature changes throughout the day and over the year,the beneficiary of such a collective association also changes.The costs involved and deviations to the temperature-size rule highlight the complexity of the carrion ecosystem.     

Density-dependent growth and metamorphosis in the larval bronze frog<Emphasis Type="Italic">Rana temporalis</Emphasis> is influenced by genetic relatedness of the cohort

Effects of density and kinship on growth and metamorphosis in tadpoles ofRana temporalis were studied in a 2×4 factorial experiment. Fifteen egg masses were collected from streams in the Western Ghat region of south India. The tadpoles were raised as siblings or in groups of non-siblings at increasing density levels, viz. 15, 30, 60 and 120/5 l water. With an increase in density level from 15 to 120 tadpoles/5 l water, duration of the larval stage increased and fewer individuals metamorphosed irrespective of whether they belonged to sibling or non-sibling groups by day 100 when the experiments were terminated. The size of individuals at metamorphosis declined significantly with increase in the density of rearing. However, at higher densities (60 and 120 tadpoles/5 l water) sibling group tadpoles performed better compared to mixed groups and took significantly less time to metamorphose. Also, more individuals of sibling groups metamorphosed compared to non-sibling groups at a given density. Mixed rearing retarded growth rates, prolonged larval duration resulting in a wider spectrum of size classes, and lowered the number of individuals recruited to terrestrial life. The study shows that interference competition occurred more strongly in cohorts of mixed relatedness than in sibling groups.     

Kinship ecology of competition: size hierarchies in kin and nonkin laboratory cohorts of tadpoles

Summary This study provides an experimental test of the ecological significance of kinship in competitive interactions among individuals. Tadpoles of the fire-bellied toad, Bombina variegata (Anura, Discoglossidae) reared in the laboratory in a high density of siblings grew better and developed faster than when they were reared with similar densities of nonrelatives. Kinship-based genotypic uniformity may therefore be advantageous: it can lead to faster and more uniform growth. In nature it may well be kin recognition that permits such advantage to be realised. The largest tadpoles from pure-sibship cohorts accounted, on average, for the smaller fraction of the cohort total biomass than the largest tadpoles reared with cohorts of nonrelatives, although they attained the same absolute weight and developmental stage. The smallest individuals from pure-sibship cohorts had a much larger absolute body weight than the smallest tadpoles from mixed-sibship cohorts, and were also much more advanced developmentally. The results could be an effect of an altruistic restraint in growth rate on the part of the largest tadpoles in sibling cohorts and certainly not of the smallest ones. However, the results could also be due to the altruism-independent facilitation of living conditions in pure-sibship groups, resulting solely from potential advantages of homogeneous water conditioning.     

Effects of hydroperiod duration on developmental plasticity in tiger frog(Hoplobatrachus chinensis) tadpoles

While developmental plasticity can facilitate evolutionary diversification of organisms,the effects of water levels as an environmental pressure on tiger frogs remains unclear.This study clarifies the relationship by studying the responses of tiger frog(Hoplobatrachus chinensis)tadpoles to simulated hydroperiods(i.e.,constant low water levels,constant high water levels,increasing water levels,decreasing water levels,rapid changes in water levels and gradual fluctuations in water levels)in a laboratory setting.ANOVA analysis showed that none of the water level treatments had any significant effect on the total length,body mass,or developmental stages of H.chinensis tadpoles half way through development(11 days old).Tadpoles raised in rapidly fluctuating water levels had protracted metamorphosis,whereas tadpoles raised under low and gradually fluctuating water levels had shortened metamorphosis.None of the water level treatments had a significant effect on the snout-vent length(SVL)or body mass of H.chinensis tadpoles at Gosner stage 42,or on the body mass of tadpoles at Gosner stage 45.However,the tadpoles raised in high levels and rapidly fluctuating water levels,significantly larger SVL at Gosner stage 45,while ones under gradually fluctuating water levels had smaller SVL than the other groups.Time to metamorphosis was positively correlated with body size(SVL)at metamorphosis in H.chinensis tadpoles.H.chinensis tadpoles under constant low water level had the highest mortality rate among all the treatments(G-test).Moreover,ANOVA and ACNOVA(with body length as the covariate)indicated that water levels had no significant effect on either the morphology(i.e.head length,head width,forelimb length,hindlimb length and body width)or the jumping ability of juvenile H.chinensis.These results suggest that the observed accelerated metamorphosis and high mortality of H.chinensis tadpoles under decreasing water level treatment was driven by density-induced physical interactions among increasing conspecifics.     

Predator Avoidance and Alarm-response Behaviour in Kin-discriminating Tadpoles (Rana cascadae)

When captured by predators, the tadpoles of some species of frogs and toads may release an alarm substance that alters the behaviour of conspecifics. Such ‘alarm response’ behaviour has been proposed as a potential mechanism whereby related conspecifics may ‘warn’ relatives of a predator's presence and thus, improve their inclusive fitness. We examined predator avoidance and alarm response behaviour in tadpoles of the Cascades frog (Rana cascadae) and tested whether such behaviour is influenced by kinship factors. Tadpoles reduced activity when in the presence of a predatory newt (Taricha granulosa). Individuals in sibling groups were more active than both solitary tadpoles and individuals in mixed groups of siblings and nonsiblings. However, we found no evidence of an alarm response in R. cascadae. Behaviour of tadpoles in groups exposed only to predators was not different from that of tadpoles in groups exposed to predators plus crushed conspecifics. Tadpoles in groups exposed to crushed tadpoles were as active as tadpoles in groups exposed to water controls, and some test individuals fed upon the dead tadpoles. Thus, while R. cascadae tadpoles reduce activity in response to newt predators, crushed tadpoles appear to initiate a feeding response rather than an alarm response as has been previously proposed.     

Competing tadpoles: Australian native frogs affect invasive cane toads (Rhinella marina) in natural waterbodies

The cane toad (Rhinella marina) is one of the most successful invasive species worldwide, and has caused significant negative impacts on Australian fauna. Experimental work in the laboratory and in mesocosms has shown that tadpoles of native frogs can affect survival, size at metamorphosis and duration of larval period of cane toad tadpoles. To test if these effects occur in nature, we conducted a field experiment using two temporary ponds where we set up enclosures with tadpoles of native green tree frogs (Litoria caerulea) and cane toads in treatments with a range of densities and combinations. The presence of green tree frog tadpoles significantly decreased the growth rate of toad tadpoles and increased the duration of their larval period in both ponds; in one pond, frog tadpoles also significantly reduced the body length and mass of metamorph toads. Toad tadpoles did not have any significant negative effects on green tree frog tadpoles, but there was strong intraspecific competition within the latter species: increased frog tadpole density resulted in increased larval period and reduced survival, growth rate and size at metamorphosis for frogs at one or both ponds. Our results are encouraging for the possibility of using native frogs as one component of an integrated approach to the biological control of cane toads.     

The effects of kinship and density on growth and metamorphosis of the bronze frog (Rana temporalis) tadpoles

  Five clutches of Rana temporalis eggs collected along a stream were reared separately until formation of Gosner stage 25 tadpoles. The effect of kinship and density was then studied by rearing ten siblings in 1 (sib 1) or 5 (sib 5) l water, and mixed rearing of ten tadpoles (2 from each of the 5 clutches) in 1 (mix 1) or 5 (mix 5) l water; each group replicated five times. In all the groups tadpoles showed a sigmoid growth curve. Both kinship and density interacted to affect mean proportions of individuals reaching metamorphic climax (MC), mean body mass, and size frequency at MC (day 79). The proportion of tadpoles reaching MC was highest in sib 5 (82%) followed by mix 5 (77%), sib 1 (73%), and mix 1 (64%) groups. Crowding plus mixing significantly lowered the median developmental stage mean body mass and broadened the spectrum of developmental stages or size classes at MC. The size difference of individuals at MC was inversely related to density of rearing. Frequency of different developmental stages was comparable in sib 1, sib 5, and mix 5 groups. Interestingly, small individuals were significantly greater in number in the mix 1 group compared to sib 1. The above findings suggest that genotypic heterogeneity in conjunction with crowding retards growth rate of tadpoles in comparison with those reared in a genetically homogenous (sib) environment. Further, they suggest that the adverse effect of mixed rearing is context dependent. Received: 12 April 1999 / Received in revised form: 16 June 1999 / Accepted: 18 June 1999     

Influence of density and salinity on larval development of salt‐adapted and salt‐naïve frog populations

Environmental change and habitat fragmentation will affect population densities for many species. For those species that have locally adapted to persist in changed or stressful habitats, it is uncertain how density dependence will affect adaptive responses. Anurans (frogs and toads) are typically freshwater organisms, but some coastal populations of green treefrogs (Hyla cinerea) have adapted to brackish, coastal wetlands. Tadpoles from coastal populations metamorphose sooner and demonstrate faster growth rates than inland populations when reared solitarily. Although saltwater exposure has adaptively reduced the duration of the larval period for coastal populations, increases in densities during larval development typically increase time to metamorphosis and reduce rates of growth and survival. We test how combined stressors of density and salinity affect larval development between salt‐adapted (“coastal”) and nonsalt‐adapted (“inland”) populations by measuring various developmental and metamorphic phenotypes. We found that increased tadpole density strongly affected coastal and inland tadpole populations similarly. In high‐density treatments, both coastal and inland populations had reduced growth rates, greater exponential decay of growth, a smaller size at metamorphosis, took longer to reach metamorphosis, and had lower survivorship at metamorphosis. Salinity only exaggerated the effects of density on the time to reach metamorphosis and exponential decay of growth. Location of origin affected length at metamorphosis, with coastal tadpoles metamorphosing slightly longer than inland tadpoles across densities and salinities. These findings confirm that density has a strong and central influence on larval development even across divergent populations and habitat types and may mitigate the expression (and therefore detection) of locally adapted phenotypes.     

KIN-MEDIATED MORPHOGENESIS IN FACULTATIVELY CANNIBALISTIC TADPOLES

Inclusive fitness theory predicts that organisms can increase their fitness by helping or not harming relatives, and many animals modify their behavior toward kin in a manner consistent with this prediction. Morphogenesis also may be sensitive to kinship environment, particularly in species where certain individuals facultatively develop structures that can be used against conspecifics as weaponry. We tested this hypothesis by examining whether and how consanguinity affected the probability that a structurally distinctive carnivore phenotype, which is opportunistically cannibalistic, would be produced in plains spadefoot toad tadpoles (Spea bombifrons) and southern spadefoot toad tadpoles (S. multiplicata). For tadpoles of S. multiplicata, individuals were significantly more likely to express the carnivore phenotype in mixed sibship groups than in pure sibship groups. For tadpoles of S. bombifrons, individuals were significantly more likely to express the carnivore phenotype when reared alone than in pure sibship groups. Both outcomes were independent of food availability or sibship specific differences in size or growth rate, and waterborne chemical signals from nonkin were sufficient to trigger expression of the carnivore phenotype. Our results suggest that morphogenesis may be responsive to kinship environment in any species or population that occurs as multiple, environmentally induced forms (polyphenism) that differ in their ability to help or to harm others.     

Growth strategies of passerine birds are related to brood parasitism by the brown-headed cowbird (Molothrus ater)

Sibling competition was proposed as an important selective agent in the evolution of growth and development. Brood parasitism by the brown-headed cowbird (Molothrus ater) intensifies sibling competition in the nests of its hosts by increasing host chick mortality and exposing them to a genetically unrelated nestmate. Intranest sibling competition for resources supplied by parents is size dependent. Thus, it should select for high development rates and short nestling periods, which would alleviate negative impacts of brood parasitic chicks on host young. I tested these predictions on 134 North American passerines by comparative analyses. After controlling for covariates and phylogeny, I showed that high parasitism rate was associated with higher nestling growth rate, lower mass at fledging, and shorter nestling periods. These effects were most pronounced in species in which sibling competition is most intense (i.e., weighing over about 30 g). When species were categorized as nonhosts versus old hosts (parasitized for thousands of years) versus new hosts (parasitized the last 100-200 years), there was a clear effect of this parasitism category on growth strategies. Nestling growth rate was the most evolutionarily flexible trait, followed by mass at fledging and nestling period duration. Adjustments during incubation (incubation period length, egg volume) were less pronounced and generally disappeared after controlling for phylogeny. I show that sibling competition caused by brood parasites can have strong effects on the evolution of host growth strategies and that the evolution of developmental traits can take place very rapidly. Human alteration of habitats causing spread of brood parasites to new areas thus cascades into affecting the evolution of life-history traits in host species.     

Kinship alters the effects of forced cohabitation on body weight,mate choice and fitness in the rat-like hamster Tscheskia triton

It has been documented that social isolation imparts deleterious effects on gregarious rodents species,but caging in group imparts such effects on solitary rodents. This study was attempted at examining how kinship to affect body weight,behavioral interaction,mate choice and fitness when we caged male and female rat-like hamsters Tscheskia triton in pair,a solitary species. We found that females paired with nonsibling males became heavier than the females paired with sibling males,but both agonistic and amicable behavior between paired males and females did not differ between sibling and nonsibling groups. This indicated that kinship might reduce females' obesity in response to forced cohabitation,and dissociation might exist between physiological and behavioral responses. Furthermore,binary choice tests revealed that social familiarity between either siblings or nonsiblings decreased their investigating time spent in opposite sex conspecific of cage mates and/or their scents as compared with those of nonmates,suggesting effects of social association on mate and kin selection of the hamsters. On the other side,both females and males caged in pair with siblings show a preference between unfamiliar siblings or their scents and the counterparts of nonsiblings after two month separation,indicating that the kin recognition of the hamsters might also rely on phenotype matching. In addition,cohabitation (or permanent presence of fathers) elicited a lower survival of pups in nonsibling pairs than sibling pairs,but did not affect litter size,suggesting that kinship affects fitness when housing male and female ratlike hamsters together. Therefore,inbreeding might be adapted for rare and endangered animals.