Guppy

Abstract: 1 Preview 2 Ecology of the guppy in Trinidad 3 Evading predators 4 Reproduction 5 Life history 6 Reproductive isolation 7 Conservation of diversity 8 Postscript and prospects References

Abstract: The theory of r- and K-selection was one of the first predictive models for life-history evolution. It helped to galvanize the empirical field of comparative life-history and dominated thinking on the subject from the late 1960s through the 1970s. Large quan- tities of field data were collected that claimed to test predictions of the theory. By the early 1980s, sentiment about the theory had changed so completely that a proposal to test it or the use of it to interpret empirical results would likely be viewed as archaic and naive. The theory was displaced by demographic models that concentrated on mortality patterns as the cause of life-history evolution. Although demographic models are known for their density-independent approach and focus on extrinsic mortality, these models can incorporate many ecological features captured by r- and K-selection, such as density-dependent pop- ulation regulation, resource availability, and environmental fluctuations. We highlight the incorporation of these factors in recent theory, then show how they are manifest in our research on life-history evolution in Trinidadian guppies (Poecilia reticulata). Explanations of the repeatable suites of life-history differences across populations of guppies originate from demographic models of predator-driven age-specific mortality. Recently, careful ex- amination of guppy demography and habitat has revealed that density-dependent regulation and resource availability may have influenced the evolution of guppy life histories. In the field, these factors covary with predation risk; however, they can be uncoupled experi- mentally, providing insight into how they may have synergistically driven guppy life-history evolution. Although life-history theory has shifted away from a focus on r- and K-selection, the themes of density-dependent regulation, resource availability, and environmental fluc- tuations are integral to current demographic theory and are potentially important in any natural system.

Abstract: Prior research has demonstrated a strong association between the species of predators that co‐occur with guppies and the evolution of guppy life histories. The evolution of these differences in life histories has been attributed to the higher mortality rates experienced by guppies in high‐predation environments. Here, we evaluate whether there might be indirect effects of predation on the evolution of life‐history patterns and whether there are environmental differences that are correlated with predation. To do so, we quantified features of the physical and chemical environment and the population biology of guppies from seven high‐ and low‐predation localities. We found that high‐predation environments tend to be larger streams with higher light levels and higher primary productivity, which should enhance food availability for guppies. We also found that guppy populations from high‐predation environments have many more small individuals and fewer large individuals than those from low‐predation e...