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The ecological consequences of biological range extensions reflect the interplay between the functional characteristics of the newly arrived species and their recipient ecosystems. Teasing apart the relative contribution of each component is difficult because most colonization events are studied retrospectively, i.e., after a species became established and its consequences apparent. We conducted a prospective experiment to study the ecosystem consequences of a consumer introduction, using whole-stream metabolism as our integrator of ecosystem activity. In four Trinidadian streams, we extended the range of a native fish, the guppy (Poecilia reticulata), by introducing it over barrier waterfalls that historically excluded it from these upper reaches. To assess the context dependence of these range extensions, we thinned the riparian forest canopy on two of these streams to increase benthic algal biomass and productivity. Guppy's range extension into upper stream reaches significantly impacted stream metabolism but the effects depended upon the specific stream into which they had been introduced. Generally, increases in guppy biomass caused an increase in gross primary production (GPP) and community respiration (CR). The effects guppies had on GPP were similar to those induced by increased light level and were larger in strength than the effects stream stage had on CR. These results, combined with results from prior experiments, contribute to our growing understanding of how consumers impact stream ecosystem function when they expand their range into novel habitats. Further study will reveal whether local adaptation, known to occur rapidly in these guppy populations, modifies the ecological consequences of this species introduction. [ABSTRACT FROM AUTHOR]

Metabolic rates and life history strategies are both thought to set the "pace of life", but whether they evolve in tandem is not well understood. Here, using a common garden experiment that compares replicate paired populations, we show that Trinidadian guppy (Poecilia reticulata) populations that evolved a fast-paced life history in high-predation environments have consistently higher metabolic rates than guppies that evolved a slowpaced life history in low-predation environments. Furthermore, by transplanting guppies from high- to low-predation environments, we show that metabolic rate evolves in parallel with the pace of life history, at a rapid rate, and in the same direction as found for naturally occurring populations. Together, these multiple lines of inference provide evidence for a tight evolutionary coupling between metabolism and the pace of life history. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is the capacity for an individual genotype to produce different phenotypes in response to environmental variation. Most traits are plastic, but the degree to which plasticity is adaptive or non-adaptive depends on whether environmentally induced phenotypes are closer or further away from the local optimum. Existing theories make conflicting predictions about whether plasticity constrains or facilitates adaptive evolution. Debate persists because few empirical studies have tested the relationship between initial plasticity and subsequent adaptive evolution in natural populations. Here we show that the direction of plasticity in gene expression is generally opposite to the direction of adaptive evolution. We experimentally transplanted Trinidadian guppies (Poecilia reticulata) adapted to living with cichlid predators to cichlid-free streams, and tested for evolutionary divergence in brain gene expression patterns after three to four generations. We find 135 transcripts that evolved parallel changes in expression within the replicated introduction populations. These changes are in the same direction exhibited in a native cichlid-free population, suggesting rapid adaptive evolution. We find 89% of these transcripts exhibited non-adaptive plastic changes in expression when the source population was reared in the absence of predators, as they are in the opposite direction to the evolved changes. By contrast, the remaining transcripts exhibiting adaptive plasticity show reduced population divergence. Furthermore, the most plastic transcripts in the source population evolved reduced plasticity in the introduction populations, suggesting strong selection against non-adaptive plasticity. These results support models predicting that adaptive plasticity constrains evolution, whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection. The role of non-adaptive plasticity in evolution has received relatively little attention; however, our results suggest that it may be an important mechanism that predicts evolutionary responses to new environments. [ABSTRACT FROM AUTHOR]

Evolutionary biologists have long sought to understand the relationship between microevolution (adaptation), which can be observed both in nature and in the laboratory, and macroevolution (speciation and the origin of the divisions of the taxonomic hierarchy above the species level, and the development of complex organs), which cannot be witnessed because it occurs over intervals that far exceed the human lifespan. The connection between these processes is also a major source of conflict between science and religious belief. Biologists often forget that Charles Darwin offered a way of resolving this issue, and his proposal is ripe for re-evaluation in the light of recent research. [ABSTRACT FROM AUTHOR]

The maintenance of genetic variation in traits under natural selection is a long-standing paradox in evolutionary biology. Of the processes capable of maintaining variation, negative frequency-dependent selection (where rare types are favoured by selection) is the most powerful, at least in theory; however, few experimental studies have confirmed that this process operates in nature. One of the most extreme, unexplained genetic polymorphisms is seen in the colour patterns of male guppies (Poecilia reticulata). Here we manipulated the frequencies of males with different colour patterns in three natural populations to estimate survival rates, and found that rare phenotypes had a highly significant survival advantage compared to common phenotypes. Evidence from humans and other species implicates frequency-dependent survival in the maintenance of molecular, morphological and health-related polymorphisms. As a controlled manipulation in nature, this study provides unequivocal support for frequency-dependent survival—an evolutionary process capable of maintaining extreme polymorphism. [ABSTRACT FROM AUTHOR]

Classical theories for the evolution of senescence predict that organisms that experience low mortality rates attributable to external factors, such as disease or predation, will evolve a later onset of senescence. Here we use patterns of senescence in guppies derived from natural populations that differ in mortality risk to evaluate the generality of these predictions. We have previously found that populations experiencing higher mortality rates evolve earlier maturity and invest more in reproduction, as predicted by evolutionary theory. We report here that these same populations do not have an earlier onset of senescence with respect to either mortality or reproduction but do with respect to swimming performance, which assesses neuromuscular function. This mosaic pattern of senescence challenges the generality of the association between decreased extrinsic mortality and delayed senescence and invites consideration of more derived theories for the evolution of senescence. [ABSTRACT FROM AUTHOR]

In live-bearing animal lineages, the evolution of the placenta is predicted to create an arena for genomic conflict during pregnancy, drive patterns of male sexual selection, and increase the rate of speciation. Here we test these predictions of the viviparity driven conflict hypothesis (VDCH) in live-bearing poecilid fishes, a group showing multiple independent origins of placentation and extreme variation in male sexually selected traits. As predicted, male sexually selected traits are only gained in lineages that lack placentas; while there is little or no influence of male traits on the evolution of placentas. Both results are consistent with the mode of female provisioning governing the evolution of male attributes. Moreover, it is the presence of male sexually selected traits (pre-copulatory), rather than placentation (post-copulatory), that are associated with higher rates of speciation. These results highlight a causal interaction between female reproductive mode, male sexual selection and the rate of speciation, suggesting a role for conflict in shaping diverse aspects of organismal biology. The viviparity driven conflict hypothesis predicts the evolution of the placenta will suppress the evolution of traits associated with pre-copulatory mate choice and accelerate speciation rate. Furness et al. support the former and disprove the latter predictions with comparative analyses of the poecilid fishes. [ABSTRACT FROM AUTHOR]

This corrects the article DOI: 10.1038/nature15256 [ABSTRACT FROM AUTHOR]