Effects of Natural Variation in Sex Ratio and Habitat Structure On Mate-Guarding Decisions in Amphipods (Crustacea)

Behaviour ◽  
1996 ◽  
Vol 133 (13-14) ◽  
pp. 985-996 ◽  
Author(s):  
Jaimie T.A. Dick ◽  
Robert W. Elwood
Keyword(s):  
Natural Populations ◽  
Mate Guarding ◽  
Reproductive Behaviour ◽  
Male Competition ◽  
Female Body Size ◽  
The Social ◽  
Size Assortment ◽  
Assortative Pairing ◽  
Study Species

AbstractWe employed field-based studies, with complementary laboratory-based studies, to investigate social and environmental influences on tactical mate-guarding decisions in amphipods (Crustacea). Firstly, we investigated variation in precopulatory mate-guarding duration in Cammarus duebeni celticus in relation to the social structure of natural populations. Variation in population density of up to two orders of magnitude had no effect on precopula duration, whereas guarding durations increased as the sex ratios of the populations became more male biased. That is, males have some ability to assess the probability of other males taking females into precopula and are prepared to guard for longer as this threat of male: male competition increases. A field demonstration of tactical shifts in reproductive behaviour in response to pertinent social conditions is thus provided. Secondly, the 'habitat segregation' hypothesis, which proposes that positive size-assortative pairing in amphipod populations arises due to variation in the use of micro-habitats, was tested in natural field populations and under laboratory conditions in Echinogammarus marinus. This was necessary in order to distinguish any purely environmental determinants of size-assortment from the role of active decisions by males concerning mate choice and male: male competition. The hypothesis was rejected on the grounds that size-assortative pairing arises under both heterogeneous and homogeneous environmental conditions. Further, in both study species, male and female body size were positively correlated with precopula duration. Thus, indirect competition for access to large, fecund females, based on the timing of male entry into precopula, together with direct aggression, provides the explanation for size-assortative pairing in amphipods.

Sexual competition in an acanthocephalan parasite of fish

Parasitology ◽  
2000 ◽  
Vol 120 (1) ◽  
pp. 65-69 ◽  
Author(s):  
P. SASAL ◽  
E. JOBET ◽  
E. FALIEX ◽  
S. MORAND
Keyword(s):  
Sperm Competition ◽  
Reproductive Behaviour ◽  
Male Competition ◽  
Testicular Volume ◽  
Testis Size ◽  
Sexual Competition ◽  
Gobiid Fish ◽  
Female Body Size ◽  
Body Sizes ◽  
Acanthocephalan Parasite

Acanthocephalans are polygamous parasites of vertebrates and some species are known to aggregate in sexual congress to mate. Such a reproductive behaviour could lead to male–male competition for access to females and could have consequences for sexual selection. We dissected 87 gobiid fish, Gobius bucchichii, harbouring 891 acanthocephalans, Acanthocephaloides propinquus. The parasites were sexed and their body sizes were measured. Testicular volume was also evaluated in 82 males in order to establish their phenotypic sexual investment in relation to the estimated sex ratio. We found that parasite intensity (i.e. the number of individuals/fish) was not correlated with fish size, but that parasite size was significantly related to host size. Our results showed that there was a significant relationship between the mean female body size and their number within one host. We found that when the percentage of male parasites in a host increased, presumably increasing male–male competition for access to females, males had a larger testicular volume. We discuss these results in terms of energy allocation, sexual and sperm competition. We conclude that competition for space should be less important for males than competition for access to females. Moreover, increasing testis size should confer advantages to males especially for their reproductive success when sperm competition occurs.

scholarly journals No evidence that relatedness or familiarity modulate male harm in wild Drosophila melanogaster

2021 ◽  
Author(s):  
Ana Marquez-Rosado ◽  
Clara García-Có ◽  
Claudia Londoño-Nieto ◽  
Pau Carazo
Keyword(s):  
Drosophila Melanogaster ◽  
Sexual Conflict ◽  
Kin Selection ◽  
Kin Recognition ◽  
Natural Populations ◽  
Male Competition ◽  
Natural Conditions ◽  
Population Average ◽  
In The Wild

Sexual selection frequently promotes the evolution of aggressive behaviours that help males compete against their rivals, but which may harm females and hamper their fitness. Kin selection theory predicts that optimal male-male competition levels can be reduced when competitors are more genetically related to each other than to the population average, contributing to resolve this sexual conflict. Work in Drosophila melanogaster has spearheaded empirical tests of this idea, but studies so far have been conducted in lab-adapted populations in homogeneous rearing environments that may hamper kin recognition, and used highly skewed sex ratios that may fail to reflect average natural conditions. Here, we performed a fully factorial design with the aim of exploring how rearing environment (i.e. familiarity) and relatedness affect male-male aggression, male harassment, and overall male harm levels in a natural population of Drosophila melanogaster, under more natural conditions. Namely, we: a) manipulated relatedness and familiarity so that larvae reared apart were raised in different environments, as is common in the wild, and b) studied the effects of relatedness and familiarity under average levels of male-male competition in the field. We show that, contrary to previous findings, groups of unrelated-unfamiliar males were as likely to fight with each other and harass females than related-familiar males, and that overall levels of male harm to females were similar across treatments. Our results suggest that the role of kin selection in modulating sexual conflict is yet unclear in Drosophila melanogaster, and call for further studies that focus on natural populations and realistic socio-sexual and ecological environments.

scholarly journals The complexities of inferring symbiont function: Paraburkholderia symbiont dynamics in social amoeba populations and its impact on the amoeba microbiome

2021 ◽  
Author(s):  
James G DuBose ◽  
Michael S Robeson ◽  
Mackenzie Hoogshagen ◽  
Hunter Olsen ◽  
Tamara S Haselkorn
Keyword(s):  
Natural Populations ◽  
Multiple Roles ◽  
Social Amoeba ◽  
Symbiotic Relationships ◽  
Endosymbiotic Bacteria ◽  
The Social ◽  
Toxin Degradation ◽  
The Relationship ◽  
Food Bacteria

The relationship between the social amoeba Dictyostelium discoideum and its endosymbiotic bacteria Paraburkholderia provides a model system for studying the development of symbiotic relationships. Laboratory experiments have shown that any of three species of Paraburkholderia symbiont allow D. discoideum food bacteria to persist through the amoeba lifecycle and survive in amoeba spores, rather than being fully digested. This phenomenon is termed "farming", as it potentially allows spores dispersed to food poor locations to grow their own. The occurrence and impact of farming in natural populations, however, has been a challenge to measure. Here, we surveyed natural D. discoideum populations and found that only one of the three symbiont species, P. agricolaris, remained prevalent. We then explored the effect of Paraburkholdia on the amoeba microbiome, expecting that by facilitating bacterial food carriage it would diversify the microbiome. Contrary to our expectations, Paraburkholderia tended to infectiously dominate the D. discoideum microbiome, in some cases decreasing diversity. Similarly, we found little evidence for Paraburkholderia facilitating the carriage of particular food bacteria. These findings change our understanding of farming and suggest the possibility that Paraburkholderia could be playing multiple roles for its host, as inferred metagenomic analysis indicates a potential role of P. agricolaris in toxin degradation.

Social Representations and Commitment

2018 ◽  
Vol 23 (3) ◽  
pp. 233-249 ◽  
Author(s):  
Eric Bonetto ◽  
Fabien Girandola ◽  
Grégory Lo Monaco
Keyword(s):  
Social Representations ◽  
Social Representation ◽  
Second Line ◽  
Review Of The Literature ◽  
First Line ◽  
Research Perspectives ◽  
The Social ◽  
Bibliographic Search ◽  
English Articles

Abstract. This contribution consists of a critical review of the literature about the articulation of two traditionally separated theoretical fields: social representations and commitment. Besides consulting various works and communications, a bibliographic search was carried out (between February and December, 2016) on various databases using the keywords “commitment” and “social representation,” in the singular and in the plural, in French and in English. Articles published in English or in French, that explicitly made reference to both terms, were included. The relations between commitment and social representations are approached according to two approaches or complementary lines. The first line follows the role of commitment in the representational dynamics: how can commitment transform the representations? This articulation gathers most of the work on the topic. The second line envisages the social representations as determinants of commitment procedures: how can these representations influence the effects of commitment procedures? This literature review will identify unexploited tracks, as well as research perspectives for both areas of research.

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