Lake Malawi boasts the highest diversity of freshwater fishes in the world. Nearshore sites are c... more Lake Malawi boasts the highest diversity of freshwater fishes in the world. Nearshore sites are categorized according to their bottom substrate, rock or sand, and these habitats host divergent assemblages of cichlid fishes. Sexual selection driven by mate choice in cichlids led to spectacular diversification in male nuptial coloration. This suggests that the spectral radiance contrast of fish, the main determinant of visibility under water, plays a crucial role in cichlid visual communication. This study provides the first detailed description of underwater irradiance, radiance and beam attenuation at selected sites representing two major habitats in Lake Malawi. These quantities are essential for estimating radiance contrast and, thus, the constraints imposed on fish body coloration. Irradiance spectra in the sand habitat were shifted to longer wavelengths compared with those in the rock habitat. Beam attenuation in the sand habitat was higher than in the rock habitat. The effects ...
Here, we review the recently burgeoning literature on color polymorphisms, seeking to integrate s... more Here, we review the recently burgeoning literature on color polymorphisms, seeking to integrate studies of the maintenance of genetic variation and the evolution of reproductive isolation. Our survey reveals that several mechanisms, some operating between populations and others within them, can contribute to both color polymorphism persistence and speciation. As expected, divergent selection clearly can couple with gene flow to maintain color polymorphism and mediate speciation. More surprisingly, recent evidence suggests that diverse forms of within-population sexual selection can generate negative frequency dependence and initiate reproductive isolation. These findings deserve additional study, particularly concerning the roles of heterogeneous visual environments and correlational selection. Finally, comparative studies and more comprehensive approaches are required to elucidate when color polymorphism evolves, persists, or leads to speciation.
Perceived certainty of paternity is expected to influence a male's behavior towar... more Perceived certainty of paternity is expected to influence a male's behavior toward his offspring: if he is uncertain of his reproductive success with a current brood due to the presence of cuckolders, it may benefit him to invest instead in future reproduction. A decrease in perceived certainty of paternity incites filial cannibalism (the eating of one's own offspring) in some teleost fishes that provide parental care; however, no work has demonstrated that cannibalism increases proportionately with increased levels of cuckoldry. Here we show for the first time in a fish with no parental care that as the number of cuckolders at a spawning event increases, so does the probability that a male will cannibalize eggs. In field observations of Telmatherina sarasinorum, a small fish endemic to Sulawesi, Indonesia, males increased filial cannibalism behavior threefold in the presence of one cuckolder and nearly sixfold in the presence of two or more cuckolders. This suggests that males may use detection of cuckolders as an indication that the paternity of current offspring has been compromised.
ABSTRACT Turbidity, and associated sedimentation, is increasing in aquatic ecosystems globally an... more ABSTRACT Turbidity, and associated sedimentation, is increasing in aquatic ecosystems globally and is thought to be a major driver of aquatic biodiversity loss. In this study, hatching success of Spotted Gar (Lepisosteus oculatus), a Threatened species in Canada, is reported for eggs held under clear and turbid conditions. Spotted Gar embryos were held in either clear or mildly turbid water (∼5 NTU). Fertilized eggs held in turbid water exhibited a final 24 % reduction in hatching success by the end of the hatching period. Turbidity is identified as a potential threat for this species in Canada. The decrease in hatching success found here indicates that this early life history stage is particularly vulnerable to disturbance by turbidity and sedimentation.
Aquatic Conservation: Marine and Freshwater Ecosystems, 2014
ABSTRACT The use of non-lethal experiments to elucidate behavioural and physiological thresholds ... more ABSTRACT The use of non-lethal experiments to elucidate behavioural and physiological thresholds to environmental stressors can provide valuable data for identifying threats to, and critical habitat of, imperilled species. Increased turbidity contributes to population declines and loss of fish diversity globally, but the complex direct and indirect effects of this stressor on imperilled species are not well understood.Response to turbidity was examined in a group of closely related North American fishes (Notropis spp.), including four imperilled shiners: pugnose shiner (N. anogenus), bridle shiner (N. bifrenatus), blacknose shiner (N. heterolepis), blackchin shiner (N. heterodon), and the more common mimic shiner (N. volucellus). Two experiments quantified (i) the behavioural response of each species to progressively increasing turbidity, and (ii) critical swimming speed of fishes acclimated in turbid- and clear-water treatments to provide insights into effects of low turbidity on aerobic performance.Very low levels of turbidity (
Lake Malawi boasts the highest diversity of freshwater fishes in the world. Nearshore sites are c... more Lake Malawi boasts the highest diversity of freshwater fishes in the world. Nearshore sites are categorized according to their bottom substrate, rock or sand, and these habitats host divergent assemblages of cichlid fishes. Sexual selection driven by mate choice in cichlids led to spectacular diversification in male nuptial coloration. This suggests that the spectral radiance contrast of fish, the main determinant of visibility under water, plays a crucial role in cichlid visual communication. This study provides the first detailed description of underwater irradiance, radiance and beam attenuation at selected sites representing two major habitats in Lake Malawi. These quantities are essential for estimating radiance contrast and, thus, the constraints imposed on fish body coloration. Irradiance spectra in the sand habitat were shifted to longer wavelengths compared with those in the rock habitat. Beam attenuation in the sand habitat was higher than in the rock habitat. The effects ...
Here, we review the recently burgeoning literature on color polymorphisms, seeking to integrate s... more Here, we review the recently burgeoning literature on color polymorphisms, seeking to integrate studies of the maintenance of genetic variation and the evolution of reproductive isolation. Our survey reveals that several mechanisms, some operating between populations and others within them, can contribute to both color polymorphism persistence and speciation. As expected, divergent selection clearly can couple with gene flow to maintain color polymorphism and mediate speciation. More surprisingly, recent evidence suggests that diverse forms of within-population sexual selection can generate negative frequency dependence and initiate reproductive isolation. These findings deserve additional study, particularly concerning the roles of heterogeneous visual environments and correlational selection. Finally, comparative studies and more comprehensive approaches are required to elucidate when color polymorphism evolves, persists, or leads to speciation.
Perceived certainty of paternity is expected to influence a male's behavior towar... more Perceived certainty of paternity is expected to influence a male's behavior toward his offspring: if he is uncertain of his reproductive success with a current brood due to the presence of cuckolders, it may benefit him to invest instead in future reproduction. A decrease in perceived certainty of paternity incites filial cannibalism (the eating of one's own offspring) in some teleost fishes that provide parental care; however, no work has demonstrated that cannibalism increases proportionately with increased levels of cuckoldry. Here we show for the first time in a fish with no parental care that as the number of cuckolders at a spawning event increases, so does the probability that a male will cannibalize eggs. In field observations of Telmatherina sarasinorum, a small fish endemic to Sulawesi, Indonesia, males increased filial cannibalism behavior threefold in the presence of one cuckolder and nearly sixfold in the presence of two or more cuckolders. This suggests that males may use detection of cuckolders as an indication that the paternity of current offspring has been compromised.
ABSTRACT Turbidity, and associated sedimentation, is increasing in aquatic ecosystems globally an... more ABSTRACT Turbidity, and associated sedimentation, is increasing in aquatic ecosystems globally and is thought to be a major driver of aquatic biodiversity loss. In this study, hatching success of Spotted Gar (Lepisosteus oculatus), a Threatened species in Canada, is reported for eggs held under clear and turbid conditions. Spotted Gar embryos were held in either clear or mildly turbid water (∼5 NTU). Fertilized eggs held in turbid water exhibited a final 24 % reduction in hatching success by the end of the hatching period. Turbidity is identified as a potential threat for this species in Canada. The decrease in hatching success found here indicates that this early life history stage is particularly vulnerable to disturbance by turbidity and sedimentation.
Aquatic Conservation: Marine and Freshwater Ecosystems, 2014
ABSTRACT The use of non-lethal experiments to elucidate behavioural and physiological thresholds ... more ABSTRACT The use of non-lethal experiments to elucidate behavioural and physiological thresholds to environmental stressors can provide valuable data for identifying threats to, and critical habitat of, imperilled species. Increased turbidity contributes to population declines and loss of fish diversity globally, but the complex direct and indirect effects of this stressor on imperilled species are not well understood.Response to turbidity was examined in a group of closely related North American fishes (Notropis spp.), including four imperilled shiners: pugnose shiner (N. anogenus), bridle shiner (N. bifrenatus), blacknose shiner (N. heterolepis), blackchin shiner (N. heterodon), and the more common mimic shiner (N. volucellus). Two experiments quantified (i) the behavioural response of each species to progressively increasing turbidity, and (ii) critical swimming speed of fishes acclimated in turbid- and clear-water treatments to provide insights into effects of low turbidity on aerobic performance.Very low levels of turbidity (
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Papers by Suzanne Gray