Influence of black spot disease on shoaling behaviour in female western mosquitofish, Gambusia affinis (Poeciliidae, Teleostei)

Parasites can fundamentally alter the cost-benefit ratio of living in a group, e.g. if infected individuals increase the predation risk of shoal mates. Here, the effect of an infection with a trematode, Uvulifer sp. (Diplostomatidae) on the shoaling behaviour of female western mosquitofish, Gambusia affinis, was investigated. The parasite examined causes a direct phenotypical change of the host by forming black spots on its body surface. When given a choice between a stimulus shoal and no shoal, we found shoaling tendencies to be significantly reduced in infected focal fish. In another experiment, we tested for association preferences relative to the infection status of the stimulus fish. Given the choice between an infected and a healthy stimulus fish, both infected and healthy focal fish preferred to associate with non-infected stimulus fish. Our results suggest that (1) the cost-benefit ratio of shoaling might be different for infected and non-infected individuals. Infected fish may be more affected by competition for food within a shoal. (2) Associating with infected conspecifics appears to be costly for female mosquitofish, maybe due to increased predation ris

Differential susceptibility to food stress in neonates of sexual and asexual mollies ( Poecilia , Poeciliidae)

The maintenance of sex is still an evolutionary puzzle given its immediate costs. Stably coexisting complexes of asexually and sexually reproducing forms allow to study mechanisms that balance the costs and benefits of both asexual and sexual reproduction. Here, we tested whether coexisting asexual and sexual fish of the genus Poecilia differed in neonate mortality when exposed to environmental stress in the form of fluctuating temperatures and food deprivation. We find that asexual Amazon mollies, Poecilia formosa, are significantly more sensitive to food stress than their sexual relative Poecilia latipinna, but both are equally unaffected by variable temperatures. Differences in the susceptibility to environmental stress may contribute to diminishing the asexuals' benefits of a higher intrinsic population growth rate and thus mediate stable coexistence of the two reproductive form

Patterns of trophic resource use and individual specialization in two species of darters (Etheostoma: Percidae)

Citation: Hopper, G. W., & Tobler, M. (2016). Patterns of trophic resource use and individual specialization in two species of darters (Etheostoma: Percidae). Evolutionary Ecology Research, 17(1), 53-73. Retrieved from ://WOS:000384803400004Background: Species are often grouped into distinct trophic guilds based on their average diets. But the diets of populations may be highly variable through space and time. Even populations that are described as foraging on a wide variety of dietary resources are often comprised of individuals with very narrow dietary preferences, and such individual specialization may vary among populations as a function of local conditions. River gradients provide subtle variation in environmental conditions, so that stream fishes that occur along such gradients may be studied to reveal how environmental conditions shape trophic resource use and individual specialization. Questions: How does trophic resource use vary among species and populations? Does it correlate with local resource availability? What variability exists in individual dietary widths among populations and species? May we attribute variation in individual dietary widths among sites to any environmental variation? Organisms: Two sympatric stream fishes (Etheostoma flabellare and E. spectabile, Percidae) from nine locations in Oklahoma, USA. Methods: We analysed gut contents of the fish. We measured individual dietary width in each of the populations. We also measured resource diversity and densities as well as the number of competitor species. Results: We found significant variation in the diets between species and among populations of the same species. Furthermore, most populations consisted of individuals with narrow dietary width (i.e. high individual dietary specialization). Variation in individual dietary widths in populations of E. flabellare was correlated with invertebrate density and the number of competitor species, and in E. spectabile with the number of invertebrate species and invertebrate density

Patterns of trophic resource use and individual specialization in two species of darters (Etheostoma: Percidae)

Citation: Hopper, G. W., & Tobler, M. (2016). Patterns of trophic resource use and individual specialization in two species of darters (Etheostoma: Percidae). Evolutionary Ecology Research, 17(1), 53-73. Retrieved from ://WOS:000384803400004Background: Species are often grouped into distinct trophic guilds based on their average diets. But the diets of populations may be highly variable through space and time. Even populations that are described as foraging on a wide variety of dietary resources are often comprised of individuals with very narrow dietary preferences, and such individual specialization may vary among populations as a function of local conditions. River gradients provide subtle variation in environmental conditions, so that stream fishes that occur along such gradients may be studied to reveal how environmental conditions shape trophic resource use and individual specialization. Questions: How does trophic resource use vary among species and populations? Does it correlate with local resource availability? What variability exists in individual dietary widths among populations and species? May we attribute variation in individual dietary widths among sites to any environmental variation? Organisms: Two sympatric stream fishes (Etheostoma flabellare and E. spectabile, Percidae) from nine locations in Oklahoma, USA. Methods: We analysed gut contents of the fish. We measured individual dietary width in each of the populations. We also measured resource diversity and densities as well as the number of competitor species. Results: We found significant variation in the diets between species and among populations of the same species. Furthermore, most populations consisted of individuals with narrow dietary width (i.e. high individual dietary specialization). Variation in individual dietary widths in populations of E. flabellare was correlated with invertebrate density and the number of competitor species, and in E. spectabile with the number of invertebrate species and invertebrate density

Consumers' knowledge about climate change

Several studies have unveiled various misconceptions about climate change that the public holds, for instance, confusion about climate change and ozone depletion. However, so far, there has been no uniform and standardized way to measure climate-related knowledge, which complicates comparisons between different countries or samples. To develop an extensive knowledge scale, we therefore examined the Swiss public's understanding of climate change in a mail survey and related this scale to attitudes toward climate change. We thereby aimed to consider a broad range of climate-related knowledge, namely physical knowledge about CO2 and the greenhouse effect, knowledge about climate change and its causes, knowledge about the expected consequences of climate change, and action-related knowledge. The questionnaire included items of different degrees of difficulty, ranging from knowledge that is covered by newspapers to experts' knowledge. Our findings indicate that people still hold several misconceptions, although people's knowledge related to CO2 seems to have increased compared to previous studies. Of all knowledge subscales, knowledge about climate change and causes was most strongly related to attitudes toward climate chang

Late Glacial and Holocene temperature changes at Egelsee, Switzerland, reconstructed using subfossil chironomids

A temperature reconstruction using chironomids was attempted at Egelsee, Switzerland, a site where pollen and macrofossil records showed a correspondence between vegetation and climatic changes inferred by other proxies in Europe. The general pattern of temperature changes inferred from chironomids during the Late Glacial [i.e. cold temperatures between ca. 16,500 and 14,800cal BP, close to present-day temperature between 15,000 and 13,000cal BP and colder temperatures during the Younger Dryas (YD)], and the major temperature changes of the Holocene (i.e. the Younger Dryas-Holocene transition and the Late Holocene cooling trend) at Egelsee, were mirrored in other European climate reconstructions using various proxies. However, the amplitude of temperature changes during the YD was smaller than reconstructed by other proxies at various sites, and the 8,200years BP event was not apparent. These differences between records were probably due to the dominance of Corynocera ambigua, with percentages reaching 60% in parts of the Egelsee sequence. This taxon was not present in any of the 103 lakes used for the transfer function and its absence may have yielded less accurate inferences. Its presence in samples only associated with cold inferences at Egelsee suggests that this taxon is a cold indicator. However, it was also found in warm Danish lakes and the factors that determine the presence of C. ambigua remain unexplained. Most samples had a poor fit to temperature and instead, dissolved organic carbon seemed to be a factor influencing the chironomid assemblages during the Holocene. These results illustrate the need to better understand the ecology of chironomids and to disentangle the various factors that affect chironomid communities through time. Ultimately, such information will lead to more accurate temperature reconstruction

Consumers' knowledge about climate change

ISSN:0165-0009ISSN:1573-148

Black spots and female association preferences in a sexual/asexual mating complex ( Poecilia , Poeciliidae, Teleostei)

We investigated whether female association preferences for males are influenced by black spot disease (BSD), a parasite induced change of the host phenotype. We compared three different species of fish: a gynogenetic hybrid species, Poecilia formosa (amazon molly) and two sexual species (Poecilia latipinna and Poecilia mexicana), which were involved in the natural hybridisation leading to the amazon molly. Contrary to their sexual relatives, asexual amazon mollies significantly avoided images of males infected with black spot disease. We propose that amazon molly females have direct fitness benefits from choosing healthy males. The adaptive significance of the preference for BSD-uninfected males in the asexual amazon molly is yet unclear but may involve avoidance of predation or parasite infection as well as increased sperm availabilit

Sexual harassment in live-bearing fishes (Poeciliidae): comparing courting and noncourting species

Sexual harassment by males has been reported from several live-bearing fishes (Poeciliidae) and has been shown to inflict costs on females. For example, poeciliid females have reduced feeding opportunities when accompanied by a male because females dedicate attention to avoiding male copulation attempts. Poeciliid species differ considerably in male mating behavior, such as the presence or absence of courtship. Courting males display in front of the females, but males attempting to sneak-copulate approach females from behind, that is, in the blind portion of their visual field, and force copulations, which can be viewed as a male persistence trait. We predicted that poeciliid females need to be more vigilant in the presence of noncourting males, and costs of harassment by noncourting males might be stronger. In a comparative approach we examined the costs of male sexual harassment for females as reduced feeding time in 9 species of live-bearing fishes, including courting (Poecilia latipinna, Poecilia reticulata, Xiphophorus cortezi, Xiphophorus variatus) and noncourting species (Poecilia mexicana [surface- and cave-dwelling form], Poecilia orri, Gambusia affinis, Gambusia geiseri, Heterandria formosa). In all species examined except for the cave form of P. mexicana, focal females spent significantly less time feeding in the presence of a male than when together with another female. The time females spent feeding was found to significantly decline with increasing male mating activity (sum of all sexual behaviors), but there was no support for the idea that females would spend more time feeding in the presence of courting males compared with noncourting one