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Adaptation to contrasting environments across a heterogeneous landscape favors the formation of ecotypes by promoting ecological divergence. Patterns of fitness variation in the field can show whether natural selection drives loca...
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Adaptation to contrasting environments across a heterogeneous landscape favors the formation of ecotypes by promoting ecological divergence. Patterns of fitness variation in the field can show whether natural selection drives local adaptation and ecotype formation. However, to demonstrate a link between ecological divergence and speciation, local adaptation must have consequences for reproductive isolation. Using contrasting ecotypes of an Australian wildflower, Senecio lautus in common garden experiments, hybridization experiments, and reciprocal transplants, we assessed how the environment shapes patterns of adaptation and the consequences of adaptive divergence for reproductive isolation. Local adaptation was strong between ecotypes, but weaker between populations of the same ecotype. F1 hybrids exhibited heterosis, but crosses involving one native parent performed better than those with two foreign parents. In a common garden experiment, F2 hybrids exhibited reduced fitness compared to parentals and F1 hybrids, suggesting that few genetic incompatibilities have accumulated between populations adapted to contrasting environments. Our results show how ecological differences across the landscape have created complex patterns of local adaptation and reproductive isolation, suggesting that divergent natural selection has played a fundamental role in the early stages of species diversification.
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The lack of a stomach is not uncommon amongst teleost fishes, yet our understanding of this reductive specialisation is lacking. The absence of a stomach does not restrict trophic preference, resulting in fishes with very similar ...
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The lack of a stomach is not uncommon amongst teleost fishes, yet our understanding of this reductive specialisation is lacking. The absence of a stomach does not restrict trophic preference, resulting in fishes with very similar alimentary morphology capable of digesting differing diets. We examined the digestive biochemistry of four beloniform fishes: two herbivorous halfbeaks (Hemiramphidae) and two carnivorous needlefish (Belonidae) to determine how these fishes digest their respective diets with their simple, short gut. We found that although the halfbeaks showed significantly greater alpha-amylase activity than that of the needlefish (P < 0.01), trypsin, lipase, aminopeptidase and maltase activity were not substantially different between the two families. We also found that habitat (freshwater vs. marine) appears to play a significant role in digestive capability, as the two freshwater taxa and the two marine taxa were significantly different (ANOSIM; dietary Gobal R = 0.544, P = 0.001, habitat Global R = 0.437, P = 0.001), despite their phyletic and dietary similarities. Our findings offer partial support for the adaptive modulation hypothesis, support the Plug-Flow Reactor model of digestion in herbivorous halfbeaks and also support the compartmental model of digestion but suggest that another model is required to describe stomachless carnivorous needlefish.
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P>1. The sublethal impact of parasites on host behaviour and the mechanism linking them to population level effects remain largely unquantified. On the Great Barrier Reef, juvenile gnathiid isopods (mobile ectoparasites) are one o...
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P>1. The sublethal impact of parasites on host behaviour and the mechanism linking them to population level effects remain largely unquantified. On the Great Barrier Reef, juvenile gnathiid isopods (mobile ectoparasites) are one of the most common ectoparasites of fishes. Previous laboratory studies on damselfishes suggest that a single gnathiid can kill settlement-stage larvae and very young juveniles, while repeated attacks affect the growth of a juvenile damselfish. Nothing, however, is known of how gnathiids affect the performance, and the survival of settlement stage fishes in the wild.2. We sampled juveniles of the damselfish Pomacentrus amboinensis for gnathiids and tested the effect of a single gnathiid (Gnathia auresmaculosa) on juvenile survival in the laboratory. We also tested the effect of this gnathiid on the swimming performance, oxygen consumption, and successful establishment in the wild of settlement-stage larvae.3. Of the juvenile fish sampled at dawn, 3 center dot 5% had a gnathiid attached; at other times of the day, fish had no gnathiids. In the laboratory, most gnathiids (79%) remained attached to juvenile fish for up to 6 h and all fish survived exposure to one gnathiid.4. When tested in pairs in a double-lane swim chamber, fish that had previously been fed on by one gnathiid ceased swimming first in 77% of the trials and had a lower critical swimming speed compared to fish not exposed to a gnathiid. Previously parasitized fish had a 35% higher oxygen consumption rate than did unexposed fish. When tagged fish were placed in pairs on dead coral patches in the wild and monitored, the previously parasitized fish disappeared from the reef first in 67% of the trials.5. Our analysis indicates that a single ectoparasitic gnathiid isopod significantly decreases the performance of young P. amboinensis and their persistence on the reef. Gnathiids, by affecting fish performance, may therefore indirectly affect the successful establishment of fishes on the reef at settlement, a critical transitional stage for most coral reef fishes. Unsuccessful establishment on the reef most likely increases the interactions of settling fish with predators and thus gnathiids may contribute to the high mortality observed at this time.
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<abstract_text><p>The most commonly assumed cost for exaggerated male ornamentation is increased predation pressure owing to decreased locomotor performance or increased conspicuousness to predators. Despite its intuitive basis, t...
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<abstract_text><p>The most commonly assumed cost for exaggerated male ornamentation is increased predation pressure owing to decreased locomotor performance or increased conspicuousness to predators. Despite its intuitive basis, the locomotor costs of male ornamentation are not well established. We tested the hypothesis that multiple male signals that are used independently during female choice and male competition could lead to varied locomotor costs. Multiple signals with varied costs could provide a more detailed indicator of overall male quality, as only the highest-quality individuals could support all costs. To test this idea, we investigated the burst locomotor consequences of multiple ornaments for males of the pacific blue-eye (Pseudomugil signifer). We evaluated five competing models relating body size, ornament size and performance traits to field measures of dominance and attractiveness. Non-propulsive male fin ornaments used during male competition were different from those used in female choice. First dorsal fin length was the most important predictor of male attractiveness, while dominance was only associated with anal fin length. Furthermore, first dorsal fin length was positively correlated with swim speed, while anal fin length was negatively associated with speed. Our study shows that multiple male signals that are used independently during male competition and female choice also differ in their associated costs. This provides a mechanism for understanding why locomotor costs for exaggerated male ornamentation are not often empirically demonstrated.</p></abstract_text>
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Many new questions on the regulation of shoot branching have been raised in recent years, prompting a review and reassessment of the role of each signal involved. Sugars and their signaling networks have been attributed a major ro...
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Many new questions on the regulation of shoot branching have been raised in recent years, prompting a review and reassessment of the role of each signal involved. Sugars and their signaling networks have been attributed a major role in the early events of axillary bud outgrowth, whereas cytokinin appears to play a critical role in the modulation of this process in response to the environment. Perception of the recently discovered hormone strigolactone is now quite well understood, while the downstream targets remain largely unknown. Recent literature has highlighted that auxin export from a bud is important for its subsequent growth.
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A general observation emerging from estimates of additive genetic variance in sets of functionally or developmentally related traits is that much of the genetic variance is restricted to few trait combinations as a consequence of ...
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A general observation emerging from estimates of additive genetic variance in sets of functionally or developmentally related traits is that much of the genetic variance is restricted to few trait combinations as a consequence of genetic covariance among traits. While this biased distribution of genetic variance among functionally related traits is now well documented, how it translates to the broader phenome and therefore any trait combination under selection in a given environment is unknown. We show that 8,750 gene expression traits measured in adult male Drosophila serrata exhibit widespread genetic covariance among random sets of five traits, implying that pleiotropy is common. Ultimately, to understand the phenome-wide distribution of genetic variance, very large additive genetic variance-covariance matrices (G) are required to be estimated. We draw upon recent advances in matrix theory for completing high-dimensional matrices to estimate the 8,750-trait G and show that large numbers of gene expression traits genetically covary as a consequence of a single genetic factor. Using gene ontology term enrichment analysis, we show that the major axis of genetic variance among expression traits successfully identified genetic covariance among genes involved in multiple modes of transcriptional regulation. Our approach provides a practical empirical framework for the genetic analysis of high-dimensional phenome-wide trait sets and for the investigation of the extent of high-dimensional genetic constraint.
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The outgrowth of axillary buds into branches is regulated systemically via plant hormones and the demand of growing shoot tips for sugars. The plant hormone auxin is thought to act via two mechanisms. One mechanism involves auxin ...
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The outgrowth of axillary buds into branches is regulated systemically via plant hormones and the demand of growing shoot tips for sugars. The plant hormone auxin is thought to act via two mechanisms. One mechanism involves auxin regulation of systemic signals, cytokinins and strigolactones, which can move into axillary buds. The other involves suppression of auxin transport/canalization from axillary buds into the main stem and is enhanced by a low sink for auxin in the stem. In this theory, the relative ability of the buds and stem to transport auxin controls bud outgrowth. Here, we evaluate whether auxin transport is required or regulated during bud outgrowth in pea (Pisum sativum). The profound, systemic, and long-term effects of the auxin transport inhibitor N-1-naphthylphthalamic acid had very little inhibitory effect on bud outgrowth in strigolactone-deficient mutants. Strigolactones can also inhibit bud outgrowth in N-1-naphthylphthalamic acid-treated shoots that have greatly diminished auxin transport. Moreover, strigolactones can inhibit bud outgrowth despite a much diminished auxin supply in in vitro or decapitated plants. These findings demonstrate that auxin sink strength in the stem is not important for bud outgrowth in pea. Consistent with alternative mechanisms of auxin regulation of systemic signals, enhanced auxin biosynthesis in Arabidopsis (Arabidopsis thaliana) can suppress branching in yucca1D plants compared with wild-type plants, but has no effect on bud outgrowth in a strigolactone-deficient mutant background.
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In accordance with the consensus that sexual selection is responsible for the rapid evolution of display traits on macroevolutionary scales, microevolutionary studies suggest sexual selection is a widespread and often strong form ...
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In accordance with the consensus that sexual selection is responsible for the rapid evolution of display traits on macroevolutionary scales, microevolutionary studies suggest sexual selection is a widespread and often strong form of directional selection in nature. However, empirical evidence for the contemporary evolution of sexually selected traits via sexual rather than natural selection remains weak. In this study, we used a novel application of quantitative genetic breeding designs to test for a genetic response to sexual selection on eight chemical display traits from a field population of the fly, Drosophila serrata. Using our quantitative genetic approach, we were able to detect a genetically based difference in means between groups of males descended from fathers who had either successfully sired offspring or were randomly collected from the same wild population for one of these display traits, the diene (Z,Z)-5,9-C-27 : 2. Our experimental results, in combination with previous laboratory studies on this system, suggest that both natural and sexual selection may be influencing the evolutionary trajectories of these traits in nature, limiting the capacity for a contemporary evolutionary response.
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Sexing wild marine mammals that show little to no sexual dimorphism is challenging. For sirenians that are difficult to catch or approach closely, molecular sexing from tissue biopsies offers an alternative method to visual discri...
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Sexing wild marine mammals that show little to no sexual dimorphism is challenging. For sirenians that are difficult to catch or approach closely, molecular sexing from tissue biopsies offers an alternative method to visual discrimination. This paper reports the results of a field study to validate the use of two sexing methods: (1) visual discrimination of sex vs (2) molecular sexing based on a multiplex PCR assay which amplifies the male-specific SRY gene and differentiates ZFX and ZFY gametologues. Skin samples from 628 dugongs (Dugong dugon) and 100 Florida manatees (Trichechus manatus latirostris) were analysed and assigned as male or female based on molecular sex. These individuals were also assigned a sex based on either direct observation of the genitalia and/or the association of the individual with a calf. Individuals of both species showed 93 to 96% congruence between visual and molecular sexing. For the remaining 4 to 7%, the discrepancies could be explained by human error. To mitigate this error rate, we recommend using both of these robust techniques, with routine inclusion of sex primers into microsatellite panels employed for identity, along with trained field observers and stringent sample handling.
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Sexing wild marine mammals that show little to no sexual dimorphism is challenging. For sirenians that are difficult to catch or approach closely, molecular sexing from tissue biopsies offers an alternative method to visual discri...
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Sexing wild marine mammals that show little to no sexual dimorphism is challenging. For sirenians that are difficult to catch or approach closely, molecular sexing from tissue biopsies offers an alternative method to visual discrimination. This paper reports the results of a field study to validate the use of two sexing methods: (1) visual discrimination of sex vs (2) molecular sexing based on a multiplex PCR assay which amplifies the male-specific SRY gene and differentiates ZFX and ZFY gametologues. Skin samples from 628 dugongs (Dugong dugon) and 100 Florida manatees (Trichechus manatus latirostris) were analysed and assigned as male or female based on molecular sex. These individuals were also assigned a sex based on either direct observation of the genitalia and/or the association of the individual with a calf. Individuals of both species showed 93 to 96% congruence between visual and molecular sexing. For the remaining 4 to 7%, the discrepancies could be explained by human error. To mitigate this error rate, we recommend using both of these robust techniques, with routine inclusion of sex primers into microsatellite panels employed for identity, along with trained field observers and stringent sample handling.
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