Variation in risk-taking versus risk-averse behaviour can become a target of natural and/or sexual selection. However, the link between animal personality and mate choice—as a major component of ...sexual selection—remains understudied. We asked (1) whether females and males of the livebearing fish
Poecilia mexicana
prefer risk-taking mating partners (directional mating preference), (2) or if their preferences are dependent on the choosing individual’s own personality type (assortative mating). We characterized each individual for its risk-taking behaviour, assessed as time to emerge from shelter and enter an unknown area. In dichotomous association preference tests, we offered two potential mating partners that differed in risk-taking behaviour but were matched for other phenotypic traits (body size, shape, and colouration). Females, but not males, exhibited a strong directional preference for risk-taking over risk-averse mating partners. At the same time, the strength of females’ preferences correlated positively with their own risk-taking scores. Our study is the first to demonstrate that an overall preference for risk-taking mating partners does not preclude effects of choosing individuals’ own personality type on (subtle) individual variation in mating preferences. More generally, two different preferences functions appear to interact to determine the outcome of individual mate choice decisions.
Consistent individual differences in behavioral tendencies (animal personality) can affect individual mate choice decisions. We asked whether personality traits affect male and female mate choice ...decisions similarly and whether potential personality effects are consistent across different mate choice situations. Using western mosquitofish (Gambusia affinis) as our study organism, we characterized focal individuals (males and females) twice for boldness, activity, and sociability/shoaling and found high and significant behavioral repeatability. Additionally, each focal individual was tested in two different dichotomous mate choice tests in which it could choose between computer-animated stimulus fish of the opposite sex that differed in body size and activity levels, respectively. Personality had different effects on female and male mate choice: females that were larger than average showed stronger preferences for large-bodied males with increasing levels of boldness/activity (i.e., towards more proactive personality types). Males that were larger than average and had higher shoaling tendencies showed stronger preferences for actively swimming females. Size-dependent effects of personality on the strength of preferences for distinct phenotypes of potential mating partners may reflect effects of age/experience (especially in females) and social dominance (especially in males). Previous studies found evidence for assortative mate choice based on personality types or hypothesized the existence of behavioral syndromes of individuals' choosiness across mate choice criteria, possibly including other personality traits. Our present study exemplifies that far more complex patterns of personality-dependent mate choice can emerge in natural systems.
Understanding whether and how ambient ecological conditions affect the distribution of personality types within and among populations lies at the heart of research on animal personality. Several ...studies have focussed on only one agent of divergent selection (or driver of plastic changes in behavior), considering either predation risk or a single abiotic ecological factor. Here, we investigated how an array of abiotic and biotic environmental factors simultaneously shape population differences in boldness, activity in an open‐field test, and sociability/shoaling in the livebearing fish Poecilia vivipara from six ecologically different lagoons in southeastern Brazil. We evaluated the relative contributions of variation in predation risk, water transparency/visibility, salinity (ranging from oligo‐ to hypersaline), and dissolved oxygen. We also investigated the role played by environmental factors for the emergence, strength, and direction of behavioral correlations. Water transparency explained most of the behavioral variation, whereby fish from lagoons with low water transparency were significantly shyer, less active, and shoaled less than fish living under clear water conditions. When we tested additional wild‐caught fish from the same lagoons after acclimating them to homogeneous laboratory conditions, population differences were largely absent, pointing toward behavioral plasticity as a mechanism underlying the observed behavioral differences. Furthermore, we found correlations between personality traits (behavioral syndromes) to vary substantially in strength and direction among populations, with no obvious associations with ecological factors (including predation risk). Altogether, our results suggest that various habitat parameters simultaneously shape the distribution of personality types, with abiotic factors playing a vital (as yet underestimated) role. Furthermore, while predation is often thought to lead to the emergence of behavioral syndromes, our data do not support this assumption.
We investigated how an array of abiotic and biotic environmental factors simultaneously shape population differences in three personality traits in the livebearing fish Poecilia vivipara from six ecologically different lagoons. We found that (1) turbidity was the most important factor to shape population differences in all three personality traits, followed by the factors predation risk and dissolved oxygen and that (2) population differences largely disappeared after maintaining test fish under homogeneous laboratory conditions, pointing toward behavioural plasticity as a mechanism underlying the observed behavioural differences. Furthermore, we found correlations between individual behavioural tendencies (behavioural syndromes) to vary substantially and unpredictably in strength and direction among populations, with no obvious associations with environmental factors.
Millions of people across the world have been exposed to the wildlife documentaries of David Attenborough and Bernhard Grzimek, who have thus greatly influenced the public’s views on nature and ...biodiversity. We investigated the way organisms’ biology is portrayed in these documentaries, quantifying different types of animal interactions shown. We evaluated 1498 (Attenborough) and 391 (Grzimek) interactions within- and between-species from documentaries covering a wide range of environments and animal taxa, first aired between 1956 and 2019. We tested whether the relative frequencies of different interactions were influenced by temporal trends as well as by the presenters and their production teams who likely reflect the given Zeitgeist in the UK compared to the European mainland. For our categorisation of animal interactions, we contrasted interspecific versus intraspecific interactions and antagonistic versus cooperative behaviour. While Grzimek’s documentaries put a stronger emphasis on cooperation and Attenborough’s on antagonistic behaviour, the trends were not statistically significant. Furthermore, these patterns show no significant change over time, contrasting with the changing view among biologists that cooperation is more predominant than considered in the traditional understanding of nature as ‘red in tooth and claw’.
One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable ...individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system.
We characterized focal females for their personality and found behavioral measures of 'novel object exploration', 'boldness' and 'activity in an unknown area' to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females' strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small.
Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively.
Recent studies on consistent individual differences in behavioural tendencies (animal personality) raised the question of whether individual differences in cognitive abilities can be linked to ...certain personality types. We tested female Atlantic mollies (
Poecilia mexicana
) in two different classical conditioning experiments. For the first time, we provide evidence for highly consistent individual differences in associative learning speed in fish. We characterized the same individuals for boldness in two experimental situations (latency to emerge from shelter and freezing time after a simulated predator attack) and found high behavioural repeatability. When we tested for a potential correlation between associative learning speed and boldness, however, there was no evidence for a link between them. Our study design included several steps to avoid typical pitfalls of disadvantaging shy individuals during learning tests. We caution that other experimental studies may have suffered from erroneous interpretations due to a more cautious coping style of shy individuals in the respective setup used to assess learning.
The existence of individual variation in males' motivation to mate remains a conundrum as directional selection should favour high mating frequencies. Balancing selection resulting from ...(context-dependent) female mate choice could contribute to the maintenance of this behavioural polymorphism. In dichotomous choice tests, mosquitofish (Gambusia holbrooki) females preferred virtual males showing intermediate mating frequencies, reflecting females' tendencies to avoid harassment by highly sexually active males. When tested in the presence of a female shoal—which protects females from male harassment—focal females showed significantly stronger preferences for high sexual activity. A trade-off between (indirect) benefits and (direct) costs of mating with sexually active males probably explains context-dependent female mate choice, as costs depend on the social environment in which females choose their mates. No preference was observed when we tested virgin females, suggesting that the behavioural pattern described here is part of the learned behavioural repertoire of G. holbrooki females.
Abstract
The extent to which males exert mate choice (mate choosiness) depends on various environmental factors associated with the costs of mate acquisition and mate quality assessment, and the risk ...of remaining unmated. When low population densities translate into low mate encounter rates, this should result in reduced mate choosiness. In a system with overall high mating costs for males (due to precopulatory mate guarding, called amplexus), we investigated amplexus re-establishment after separating mating pairs and presenting focal males with a novel, size-matched female. Male Gammarus roeselii from a low-density (LD) population spent significantly less time until amplexus re-establishment than males from a high-density (HD) site, suggesting reduced choosiness in LD males. We experimentally ruled out alternative explanations such as differences in locomotor activity or mate finding abilities. To further demonstrate independent evolutionary trajectories of our study populations, we examined divergence in morphology and found males to differ in several traits involved in mate assessment and mate guarding. Together, we report phenotypic divergence in behavioural and morphological traits that is probably driven by contrasting selective regimes arising from different population densities. Our study exemplifies how population parameters contribute to phenotypic diversification of sexually selected traits during local adaptation along ecological gradients.
Behavior is critical for animal survival and reproduction, and possibly for diversification and evolutionary radiation. However, the genetics behind adaptive variation in behavior are poorly ...understood. In this work, we examined a fundamental and widespread behavioral trait, exploratory behavior, in one of the largest adaptive radiations on Earth, the cichlid fishes of Lake Tanganyika. By integrating quantitative behavioral data from 57 cichlid species (702 wild-caught individuals) with high-resolution ecomorphological and genomic information, we show that exploratory behavior is linked to macrohabitat niche adaptations in Tanganyikan cichlids. Furthermore, we uncovered a correlation between the genotypes at a single-nucleotide polymorphism upstream of the AMPA glutamate-receptor regulatory gene
and variation in exploratory tendency. We validated this association using behavioral predictions with a neural network approach and CRISPR-Cas9 genome editing.
Lay Summary We found that in a freshwater fish, only risk-taking males mislead rivals during mate choice through approaching non-desired females. Such "audience effects" prevent other males from ...copying their choices but also bear the risk of losing the preferred female-she may just swim away. As only the bold, risk-taking males accept this risk, a male's personality influences which mate choice strategy to choose.Males in various species adjust their mate choice to sperm competition risk and intensity arising when females potentially mate with several competing males. If males use social information and copy other males' choices, this leads to an increased likelihood of sperm competition for both, the copying and the copied male. In livebearing fishes (Poeciliidae), males appear to avoid the risk of being copied by temporarily moving away from preferred females and approaching nonpreferred ones ("audience effect"), thereby exploiting the rival's propensity to copy. Responding to rival presence with an audience effect bears the risk of losing the initially preferred female, which may swim away, but may help to reduce sperm competition intensity. Males may rate this risk-benefit ratio differentially depending on their personality, for example, more risk-taking (bolder) males might be more likely to respond to an audience. Using Atlantic mollies (Poecilia mexicana) as our study organism, we characterized focal and audience males along the boldness-activity behavioral axis. As overall competition levels are known to affect male mate choice, we subjected half of the males to a low competition (single-male housing) and the other half to a high-competition treatment (group housing) before they were tested in binary mate choice tests. Only males from the high competition treatment responded to rival presence with an audience effect. In congruence with our prediction, bolder males within this cohort showed a stronger audience effect. Our study exemplifies that (depending on the social context) bolder, not shyer, individuals can be more responsive to their social environment.
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