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PubMed1998

Male and female behaviour and extra-pair paternity in the wheatear

Behavioural observations and DNA fingerprinting were used to determine the relationship between male and female behaviours and levels of extra-pair paternity in the wheatear, Oenanthe oenanthe. Behavioural observations were consistent with the hypothesis that males attempted to ensure paternity by mate guarding, while pursuing extra-pair copulations (EPCs) primarily outside the fertile period of their pair female. The intensity of guarding varied with time of season and was greater at late nests. However, although males on territories with late nests also experienced high intrusion rates, the intensity of guarding was influenced more by the operational sex ratio (which was female skewed at early nests) than by intrusion rates per se. We suggest that early breeding males adopted a strategy of territorial defence to ensure paternity, as opposed to guarding their female directly (which late breeding males did), to capitalize on the increased opportunities to pursue EPCs in neighbouring territories. Females were less conspicuous than males in their pursuit of EPCs, were never seen off territory or observed to solicit extra-pair males directly, and rejected the majority of EPCs. The frequency of extra-pair paternity was 11% of 73 offspring, in 29% of 17 broods, and was not correlated with the intensity of guarding. Female cooperation appeared to be important for successful copulation, and extra-pair paternity is therefore likely to be a consequence of solicited, or at least accepted, EPCs. We discuss why females might have participated in EPCs. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Male parental effort and paternity in a variable mating system

Recent theoretical models suggest that males may respond to changes in paternity by adjusting their parental effort. Male response will depend on the availability of reliable paternity cues and the relative costs and benefits of parental effort to the male (i.e. its effect on the survival of young and alternative mating opportunities). Males breeding in pairs may be constrained because reductions in male parental effort are unlikely to be compensated for by the female and thus the survival of both related and unrelated young may decrease. In contrast, males breeding in cooperative groups (i.e. with helpers or co-breeders) may not have this constraint if other individuals in the group compensate for reductions in male parental effort. White-browed scrubwrens, Sericornis frontalis, breed in pairs and cooperative groups, typically with one female and two males (alpha and beta). We found that male parental effort was related positively to paternity for beta males, but not for alpha or pair males. Alpha males had paternity in all broods and always fed young. In contrast, beta males often had no paternity and sometimes did not feed young. Time spent near the fertile female was not an accurate predictor of the percentage of young sired in a brood, but it was a good predictor of having sired young in a brood. Our results are consistent with the idea that male parental effort is allocated according to whether or not the male copulated with the female. We suggest that the relationship between male parental effort and paternity may vary among cooperatively breeding species depending on the type and availability of cues to a male's paternity. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Consistency of female choice in the túngara frog: a permissive preference for complex characters

Previous phonotaxis experiments in the túngara frog, Physalaemus pustulosus, indicated a permissiveness in female preference that allows sexually selected complex call characters to be replaced with various alternative characters. Although they prefer complex to simple calls, females as a group did not discriminate between several alternative complex characters appended to the simple conspecific call. However, these studies did not address the possibility that the apparent permissiveness in female preference occurred because of an averaging of population data. The observed patterns in female preference could result from all females finding a certain set of call variants equally attractive, or from a polymorphism in female call preference. To discriminate between these two alternatives, consistency of mate choice was determined for three pairs of calls that elicited no phonotactic bias in population studies. Individual females did not repeatedly choose one stimulus of a pair over the other, demonstrating that the patterns of permissiveness observed in the population are paralleled by similar patterns within females. A broad preference for complex calls in the P. pustulosus species group would permit the evolution of sexually selected call variation through sensory exploitation. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Spawning success in the damselfish Amblyglyphidodon leucogaster: the influence of eggs in the nest

Spawning success of males and its correlates were investigated in a natural colony of whitebelly damselfish, A. leucogaster (Pomacentridae), to explore the criteria that females use in choosing mates. The mating success of individual males was variable, with some males acquiring as few as 5000 eggs and others as many as 450 000 eggs during a breeding season. Male spawning success was not correlated with body size, territory size, nest site parameters or parental care behaviour. Egg hatching success was not related to either male size or egg clutch size, and all males were capable of rearing eggs to hatching. The temporal sequence of choices by females indicated non-independent choice by females, such that males chosen by females on the first spawn of the day were also chosen by females that spawned later in the day. Field observations indicated that, in the absence of male courtship, females preferentially visited males that had eggs in their nest site. Males that had recently mated were preferred by females over those males with either late-stage eggs or no eggs in the nest. This female preference did not appear to be related to increased paternal care or egg clutch survival. Given that the mating system is promiscuous and non-resource based, and that there appears to be little difference among males in body size, females may be mating non-independently by mimicking the choice of other females. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Pathogen transmission as a selective force against cannibalism.

Cannibalism is uncommon in most species despite being taxonomically widespread. This rarity is surprising, because cannibalism can confer important nutritional and competitive advantages to the cannibal. A general, but untested, explanation for why cannibalism is rare is that cannibals may be especially likely to acquire pathogens from conspecifics, owing to greater genetic similarity among conspecifics and selection for host specificity and resistance to host immune defences among pathogens. We tested this hypothesis by contrasting the fitness consequences of intra- versus interspecific predation of diseased and non-diseased prey. We fed cannibalistic tiger salamander (Ambystoma tigrinum) larvae diseased conspecifics, healthy conspecifics, diseased heterospecifics (a sympatric congener, small-mouthed salamanders, A. texanum), or healthy heterospecifics. Cannibals that ate diseased conspecifics were significantly less likely to survive to metamorphosis and grew significantly less than those that ate diseased heterospecifics, but none of the other groups differed. Tiger salamander larvae also preferentially preyed on heterospecifics when given a choice between healthy conspecifics and heterospecifics. These results suggest that pathogen transmission is an important cost of cannibalism and provide a general explanation for why cannibalism is infrequent in most species. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Interactions between cleaning gobies and territorial damselfish on coral reefs.

We studied the interactions between cleaning gobies, Elacatinus spp., at cleaning stations and territorial dusky damselfish, Stegastes fuscus, on a Barbadian fringing reef to enhance our understanding of the behavioural impact of cleaning stations on members of a coral reef community. Cleaning stations within damselfish territories were visited by significantly fewer species and fewer individuals than those outside damselfish territories. At cleaning stations within damselfish territories, the main client was the territory holder itself. Client behaviour did not differ between the two types of cleaning station; however, cleaning gobies at stations within damselfish territories spent less time cleaning clients, their cleaning bouts were shorter, and their feeding rate on clients was slower. These effects appear to be due to the repeated aggression of territorial damselfish towards fish intruding on to their territories to visit cleaning stations. The overlap between a territorial damselfish and a cleaning station therefore appears to have detrimental impacts on cleaning goby foraging. The presence of cleaning stations within damselfish territories exerted some effects on the territory owners. Although the rates of intrusions were similar on territories with and without cleaning stations, damselfish with cleaning stations tended to chase intruders more often, had a lower foraging rate, and were at higher risk of egg predation because of increased intrusions by egg predators. A potential benefit to territorial damselfish is regular access to a cleaning station; however, the magnitude of this benefit is unknown. This study reveals that damselfish, which are ubiquitous on coral reefs, can generate significant variation in levels of use of cleaning stations, which leads to new questions relating to the settlement behaviour of both cleaning gobies and damselfish. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Territorial defence in speckled wood butterflies: do the hottest males always win?

Males of the butterfly Pararge aegeria defend sun spot territories on the forest floor as a strategy to locate females: the defence involves a spiral flight between two competing males. The success of any particular fight has been interpreted as following the simple rule 'resident wins, intruder loses' as predicted by game theory models. Here we use field experiments to show that temperature has a marked effect on the territorial defence of these ectothermic insects. The spiral flights were true contests, not conventional signals, so the flight endurance of the butterflies was an important factor in determining the result of the contest. Butterflies that were warmer could fly for longer and were more likely to win a contest; therefore temperature was an important component of contest asymmetry, and resident butterflies that increased their body temperatures by basking in sun spots were more likely to win than the intruding males which might have cooled down during flight around the site. The rule that the resident always wins is not disputed; however, the causal factors underpinning the rule are questioned. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Adopting adoption.

The common occurrence of adoption among birds and mammals presents evolutionary biologists with an explanatory challenge. The benefits to adoptees are self-evident, but the benefits to the adopter(s), the origin of the set of behaviours that constitute 'adoptive' behaviour, and the conditions for its spread in populations are not always clear. Explanations in terms of direct and indirect benefits to adopters and adoptees, and in terms of conflict between them have been suggested to account for the current functions and the evolutionary origin of 'adoptive' behaviour. In this paper we emphasize one aspect of the parenting behaviour associated with adoption that has been neglected: we suggest that adoption in birds and mammals is a route for the transfer of learnt information through social learning of patterns of behaviour, including styles of parenting. By using simple models we show that learning parenting from non-parents may provide additional opportunities for the spread of the 'adoptive' behaviour itself, even when it has no selective advantage. We also offer an additional explanation for the adaptive significance of adoption for both adopters and adoptees. Our 'match-making' hypothesis suggests that in some cases, by adopting foreign young, parents provide their genetic young with future ecologically compatible, but genetically unrelated, mates. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Male parental care, differential parental investment by females and sexual selection.

Males play a variable parental role in reproduction, ranging from no male parental care to extensive male care. Females may acquire either direct or indirect fitness benefits from their mate choice, and direct fitness benefits include male parental care. Theoreticians have traditionally emphasized direct fitness benefits to females in species with extensive male parental care. We review the literature and show extensive variation in the patterns of male care, related to the attractiveness of males to females. At one extreme of this continuum, females invest differentially in parental care, investing more when paired with attractive males. The costs of female parental care and other aspects of parental investment may be balanced by benefits in terms of more attractive sons and/or more viable offspring. At the other extreme, in species with extensive direct fitness benefits, males with preferred sexual phenotypes provide the largest relative share of parental care. A comparative study of birds revealed that the extent of the differential female parental investment was directly related to the frequency of extra-pair paternity. Since extra-pair paternity may arise mainly as a consequence of female choice for indirect fitness benefits, this result supports our prediction that differential parental investment is prevalent in species where females benefit indirectly from their mate choice. The consequences for sexual selection theory of these patterns of male care in relation to male attractiveness are emphasized. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Male potential reproductive rate influences mate choice in a bushcricket.

Male bushcrickets, Requena verticalis, provide their mates with a proteinaceous nuptial gift, which functions both as paternal investment in offspring and to ensure sperm transfer. When nutrients are limited, males have a lower potential reproductive rate than females, so the operational sex ratio becomes female biased. Males are then expected to discriminate more in their choice of mate for two reasons: (1) the relatively higher female potential reproductive rate should reduce the costs of rejecting a female; (2) multiple mating by females should increase variance in female mate quality, because of first male sperm precedence. Males are known to discriminate against old females, which are more likely to have mated previously. Our objective in this study was to partition experimentally the influences of male potential reproductive rate (manipulated by diet) and variance in female quality (estimated by age) and to assess their relative influence on the level of mate choice of male bushcrickets. The potential reproductive rate of males had a great impact on their choosiness, whereas variance in female age had no effect. These results support recent theoretical models that predict costs, rather than benefits, will primarily influence the level of mate choice. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Singing and mating success in water pipits: one specific song element makes all the difference.

Positive correlations between male vocalization and reproductive success have been documented for many animal species. They are usually based on differences between males in vocalization rate, duration or repertoire size. Here, we present probably the first field study linking differences in territorial overlap and mating status to differences in a single, clearly definable song element, the 'Snarr'. Male water pipits, Anthus spinoletta, with high Snarr scores were mated more often than males with low scores, and their territories overlapped less with those of neighbours. Although correlating positively with male body condition, the frequency of the Snarr did not reflect male age, territory size, territory quality in terms of food and paternal performance. Therefore, it seems unlikely that the higher mating success of males with high Snarr scores results from active female choice of high-quality males; rather, high Snarr scores seem to signal dominance in males. Likely mechanisms that produce the link between vocalization and mating success, and potential costs that prevent some males from producing the Snarr at a higher rate, are discussed. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

How mixed-species foraging flocks develop in response to benefits from observational learning.

We created experimental situations where observers (great tit, Parus major and marsh tit, P. palustris) acquired one of five types of experience near conspecific and non-conspecific demonstrators: (1) neither demonstrator was feeding; (2) only the conspecific was feeding; (3) only the non-conspecific was feeding; (4) both were feeding and the observer received a reinforcement (food) near the conspecific; and (5) as (4), but the reinforcement was given near the non-conspecific. After each treatment, we recorded whether the observer approached a caged conspecific or a caged non-conspecific. There was a baseline preference for approaching conspecifics but this could be overcome by learnt associations so that the birds would then approach non-conspecifics. When there was an opportunity to distinguish between successful and unsuccessful foragers (demonstrators), and the successful forager was not conspecific, observers of the dominant species approached the successful subordinate non-conspecifics. Observers of the subordinate species approached the dominant species only if they had received a food reinforcement near them. Observers followed non-conspecific individuals more often at temperatures below than above 0 degreesC and chose a conspecific individual more often above than below 0 degreesC. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1998

Statistical models of transitive and intransitive dominance structures.

We present an approach based on generalized linear models for analysing dominance data. First, dominance is defined as a parameter characterizing the relationship between two individuals, determining the expected number of successes of the first individual in disputes with the other. Second, models known from the literature of two different forms of transitivity are defined in terms of these parameters, and examples of different tests of these models are given. Third, a new model is developed where the traits of individuals involved in the dominance interactions are included as covariates. Finally, we show how two forms of intransitive models of dominance structures can be constructed by including a certain interaction term between the trait variables, and terms taking into account the effect of relatedness between the individuals in the group. We reanalyse several data sets in the literature, and also discuss Appleby's method (1983, Anim. Behav., 31, 600-608), which is frequently used in analysis of dominance data. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

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PubMed1997

Synergistic enhancement of the postthaw growth of cryopreserved rice cells by oxygenated perfluorocarbon and pluronic F-68

The beneficial effects were assessed of supplementing culture medium with oxygenated perfluorocarbon, both alone and in combination with 0.01 (w/v) Pluronic F-68, on the postthaw viability, following cryopreservation, of suspension cultured cells of the Japonica rice, Oryza sativa cv. Taipei 309. The mean viability, as assessed by triphenyl tetrazolium chloride reduction, of cells at 4 days after thawing was increased 20% over control by oxygenated perfluorodecalin (P < 0.05) in 100-ml glass jars and similarly by 24% (P < 0.01) when recovered on a smaller scale in 24-well petri dishes. In a separate assessment, a 21% increase above control treatments (P < 0.05) in postthaw viability was also observed with oxygenated perfluorodecalin. A similar, 36% increase (P < 0.05) in postthaw viability occurred with cells exposed to 0.01% (w/v) Pluronic F-68 alone. A more pronounced, synergistic increase in viability, up to 57% over control (P < 0.05), occurred with cells recovered in the presence of both oxygenated perfluorodecalin and 0. 01% (w/v) Pluronic F-68. No significant difference was observed between Pluronic F-68 and oxygenated perfluorodecalin treatments. Both the perfluorodecalin and the Pluronic F-68 treatments alone and in combination also promoted an increase in biomass, measured as fresh weight gain 30 days after thawing, to a maximum of 38% above control (P < 0.05). These results demonstrate the marked cytoprotectant effects of oxygenated perfluorodecalin and Pluronic F-68, both alone and/or in combination, for plant cells recovered from cryostorage. Such options offer alternative postthaw handling strategies to cells of those plant species which, normally, respond poorly to conventional recovery procedures. Copyright 1997 Academic Press. Copyright 1997Academic Press

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PubMed1997

Aspects of the Cryobiology of the Intertidal Harpacticoid Copepod Tigriopus brevicornis (O. F. Muller)

Cold-resistance studies of marine invertebrates have concentrated on intertidal sedentary organisms, which are often subjected to subzero air temperatures in winter. Mobile rock pool inhabitants have been rarely studied because such habitats are thought to buffer environmental variation. However, it is not uncommon for small upper-shore rock pools ( approximately 2 by 1 cm) to become completely frozen. Such supralittoral habitats are subject to extreme physicochemical fluctuations especially in salinity (0 to 300 per thousand) and temperature (-1 to +32degreesC) due to evaporation and dilution. The dominant invertebrate in such habitats is the harpacticoid copepod Tigriopus brevicornis. Aspects of the cryobiology of T. brevicornis were investigated using differential scanning calorimetry (DSC). Thermograms obtained from DSC allowed determinations of freeze-onset (supercooling point, SCP), melt-onset, and melt-peak (melting point, MP) temperatures, together with estimation of the proportion of water freezing in the samples. The effects of acclimation salinity, temperature, starvation, and reproductive state on these cryobiological parameters were investigated. Acclimation to increasing salinity depressed the SCP, with the highest salinity (70 per thousand) producing the lowest SCP, melt-onset, and MP temperatures at -27.5, -15.2, and -9.5degreesC respectively. The highest acclimation temperature (20degreesC) produced the lowest SCP (-23.4degreesC). Starvation significantly increased the SCP, melt-onset, and MP temperatures in comparison to fed individuals acclimated to the same salinity. The presence of eggs or ovaries in individual copepods elevated the SCP compared to nongravid females and males. LT50 studies showed that acclimation to high salinity improved the ability of T. brevicornis to survive in frozen seawater. Seventy parts per thousand acclimated individuals had an LT50 of 64.9 h compared with just 1.4 h for 5 per thousand acclimated individuals in frozen seawater at -5degreesC. The study shows that the cold-resistance capabilities of T. brevicornis can be affected by several different factors, and the link between the osmoconforming nature of this species and its cold resistance is discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press

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PubMed1997

Overwintering status and cold hardiness of hypera punctata

We investigated overwintering status and various characteristics related to cold hardiness in the clover leaf weevil, Hypera punctata. The larvae continue to feed and grow in winter. The proportion of late instar larvae in a field population increased gradually between December and the following March, and fourth (last) instar larvae were found in mid-February onward. The lower thermal threshold of development was lower in the larval stage than in the other developmental stages. The supercooling point (SCP) varied with developmental stages. There was a close positive correlation between the SCP and larval body weight. Deprivation of food for 3 days increased the correlation and decrease their SCP by 5 to 8 degrees C in larvae at any instar. The SCP of overwintering larvae did not differ from that of fed larvae in the laboratory. The food-deprived early instar larvae in the laboratory died without being frozen, while the lower lethal temperature of fed larvae in the laboratory and overwintering larvae were almost equivalent to the respective SCPs at a temperature normally encountered in the field. These suggested that this weevil may not increase their cold hardiness during winter so far and the SCP may serve as an indicator of cold hardiness. Copyright 1997 Academic Press. Copyright 1997Academic Press

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PubMed1997

Purification and characterization of the NAD-dependent glutamate dehydrogenase in the ectomycorrhizal fungus laccaria bicolor (Maire) orton

The NAD-dependent glutamate dehydrogenase (GDH) (EC 1.4.1.2) from Laccaria bicolor was purified 410-fold to apparent electrophoretic homogeneity with a 40% recovery through a three-step procedure involving ammonium sulfate precipitation, anion-exchange chromatography on DEAE-Trisacryl, and gel filtration. The molecular weight of the native enzyme determined by gel filtration was 470 kDa, whereas sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave rise to a single band of 116 kDa, suggesting that the enzyme is composed of four identical subunits. The enzyme was specific for NAD(H). The pH optima were 7.4 and 8.8 for the amination and deamination reactions, respectively. The enzyme was found to be highly unstable, with virtually no activity after 20 days at -75 degrees C, 4 days at 4 degrees C, and 1 h at 50 degrees C. The addition of ammonium sulfate improved greatly the stability of the enzyme and full activity was still observed after several months at -75 degrees C. NAD-GDH activity was stimulated by Ca2+ and Mg2+ but strongly inhibited by Cu2+ and slightly by the nucleotides AMP, ADP, and ATP. The Michaelis constants for NAD, NADH, 2-oxoglutarate, and ammonium were 282 &mgr;M, 89 &mgr;M, 1.35 mM, and 37 mM, respectively. The enzyme had a negative cooperativity for glutamate (Hill number of 0.3), and its Km value increased from 0.24 to 3.6 mM when the glutamate concentration exceeded 1 mM. These affinity constants of the substrates, compared with those of the NADP-GDH of the fungus, suggest that the NAD-GDH is mainly involved in the catabolism of glutamate, while the NADP-GDH is involved in the catalysis of this amino acid. Copyright 1997 Academic Press. Copyright 1997 Academic Press

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PubMed1997

Direct evidence for Ca2+ regulation of hyphal branch induction

Grinberg, A., and Heath, I. B. 1997. Direct evidence for Ca2+ regulation of hyphal branch induction. 22, 127-139. Irradiation of growing hyphae of Saprolegnia ferax with microbeams of UV (300-380 and 385-450 nm) light induced an increase in cytoplasmic [Ca2+] followed by precocious formation of one or more branches within about 4 min. The distribution of branches was strongly skewed toward the subapical side of the irradiation site, but otherwise was apparantly random. Apical (10-&mgr;m) irradiations were more effective than subapical (50-&mgr;m) ones in that they induced branches at comparable frequencies but with lower doses, consistent with higher concentrations of putative target intracellular Ca2+ storage structures in this region. Once formed, induced adjacent branches seem to compete for "resources," with those closer than approximately 50 &mgr;m inhibiting each other. The results are most consistent with Ca2+-induced accumulation of branch initiating factors being the cause, not the consequence, of branch formation, thus supporting a primary role for Ca2+ in regulation of hyphal tip growth. Copyright 1997 Academic Press. Copyright 1997 Academic Press

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