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  • From birth to death – the evolution of guppies under the threat of predation-Monthly Meeting

From birth to death – the evolution of guppies under the threat of predation

Thu, Feb 02, 2023   7:00 pm

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Monthly Meeting


Guppies are popular aquarium fish because they are easy to raise, beautifully colored and have exuberant behavior.  What may be news to you is that guppies are also model research organisms, often for reasons similar to those that make them popular pets. They are easy to work with, have short generation times, and their reproductive biology makes them ideal subjects for studies of behavior, ecology, evolution or as models for addressing basic biological questions.  I will introduce you to some of the ways guppies have proven to be ideal subjects for research.

I work on natural populations of guppies from the island of Trinidad, which is in the heart of their native range.  Guppies range from the brackish water estuaries of the largest rivers up into the small mountain tributaries.  In the estuaries and larger downstream rivers they lead a fugitive existence, surrounded by a diversity of predators.  In the tributaries, they are one of only two fish species present, have low risk of mortality and are found at high population densities.  wild guppies.667 The differences in mortality risk and life expectancy among these different types of habitat make them ideal for testing predictions from evolutionary theory that models how traits like size at birth, age at maturity, numbers of babies per brood and life expectancy/aging will evolve.  In the end, they were also ideal for studying how the process of evolution happens in real time and for estimating how fast evolution can be.  One answer was that we could see evolution happening many thousands of times faster than had been inferred from the fossil record, which is where scientists had traditionally looked for making inferences about the nature of evolution.

I will summarize some of this work, plus show you the beauty of the tropical rainforest home of natural populations of guppies and how what began as a childhood hobby became a lifelong career in science.

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guppy habitat reznick.360Bio for David Reznick, UC Riverside professor: 

I received academic degrees from Washington University (BA – 1974) and the University of Pennsylvania (PhD – 1980). I was a research associate at the Academy of Natural Sciences in Philadelphia then the Department of Zoology at the University of Maryland from 1980 to 1984 and describe myself has being incipiently unemployed since I was supporting myself with competitive grants from the US National Science Foundation. I then moved to the Department of Biology at the University of California, Riverside, where I am now a Distinguished Professor of Biology. My guppy work has been featured in general biology and evolution textbooks and is represented by many scientific publications in leading science journals, including Nature and Science. It has also been continuously supported with competitive grants from the National Science Foundation.

I have received some career achievement awards (Faculty Research Lectureship, UCR; Fellow of the American Association for the Advancement of Science and the American Academy of Arts and Sciences; Guggenheim Fellow; Humboldt Fellow).

In addition to my work on guppies, I have also worked on the evolution of life histories in the guppy family - the Poeciliidae – which now has over 250 recognized species. I was following the advice of a mentor who said that we should all, as part of our careers as scientists, expand our knowledge about some large group of organisms. All of these species, save one, bear live young. What I discovered is that they have also evolved the functional equivalent of a mammalian placenta at least 9 times and that the evolution of how mothers provision their young before birth is linked to how males evolve and whether or not males will evolve the attributes that have made some of them popular in the aquarium hobby (e.g, the swords of swordtails, sailfins of mollies or bright colors of guppies). This work has also given me a good excuse to travel and see the world since it has meant going to eight different countries in Central and South America.

In addition to my science writing, I have also written a book entitled “The Origin Then and Now – an interpretive guide to the Origin of Species” (Princeton University Press) with the goal of making Darwin’s book more accessible to a general audience.