On the island of Trinidad off the coast of Venezuela, guppy fish populations liv

Question

On the island of Trinidad off the coast of Venezuela, guppy fish populations live in high altitude, mountain streams and low altitude streams near the coast. In the mountain streams, the fish predator is a killifish. This predator prefers juvenile guppies so mortality is much higher on juvenile guppies than adult guppies. In low altitude streams near the cost, the main predator is a cichlid, and this predator prefers adult guppies. Please fill in the life history traits (in a relative sense) in these 2 environments where age-specific mortality varies. For each life history, briefly explain why natural selection would favor these life history traits.

Age at First Reproduction

Investment in Reproduction versus Metabolism/Repair

Size and Number of Offspring (Fewer/Larger or More/Smaller

High Altitude Environment (Higher Juvenile Mortality)

Low Altitude Environment (Higher Adult Mortality)

Age at First Reproduction

Investment in Reproduction versus Metabolism/Repair

Size and Number of Offspring (Fewer/Larger or More/Smaller

High Altitude Environment (Higher Juvenile Mortality)

Low Altitude Environment (Higher Adult Mortality)

Explanation / Answer

Life history theory predicts that high adult mortality rates select for earlier maturity and increased reproduction.High mortality selects for earlier maturity at a smaller size, as observed in commercial fisheries and as predicted by theory. Furthermore, the nature and magnitude of predator-induced mortality are comparable to those caused by commercial fishing. The rate of evolution in guppies predicts similar evolution in commercial fisheries on a time scale of decades. These attributes support arguments that humans, like predators, have acted as an agent of selection when exploiting populations of fish.

resource availability and density matter in regulation of guppy populations. Guppies reduce their fecundity and reproductive allocation in response to scarce food. When food is abundant, they increase brood size.Differential reproductive allocation can be the cause of seasonality of life-history characteristics in some guppy populations.Population density also matters in simpler environments because higher intraspecific competition causes a decrease in reproductive rate and somatic growth rate, and a corresponding increase in juvenile mortality rate due to cannibalism.It was confirmed that in low-predation habitats, guppy populations are in part regulated by density.

One major factor that affects wild guppies' senescence patterns is the mortality rate caused by predation. Guppies from high-predation environments suffer high extrinsic mortality rate because they are more likely to be killed by predators. Female guppies from high-predation habitats experience a significant increase in mortality at 6 months of age, while those from low-predation habitats do not suffer increased mortality until 16 months. However, guppies from high-predation environments were found to have longer lifespans because their reproductive lifespans are longer. No significant difference is seen in postreproductive lifespans

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