Sexual Selection: Big-brain vs. Small-brain

Gianna Amatucci, Nick Mulvey, Caitlin Welsh, & Cayleigh Shufelt (Stonehill College, BIO 323 Evolution, Fall 2019)

Predominantly residing in the tropics of South America, guppies are small and colorful freshwater fish. They are omnivorous animals, primarily consuming algae and brine shrimp. Unfortunately, guppies are preyed upon by a number of larger creatures, including birds, larger fish and mammals. While constantly having to avoid such predators, guppies are always in search of a suitable mate to spread their gene pools to future offspring. Alberto Corral-López and colleagues studied how predation pressure, in addition to cognitive ability and brain size, affected sexual behavior and sexual selection in guppies. The actions of both large-brained and small-brained female and male guppies were observed by Corral-López in order to study this phenomenon.

Domestic male guppy in an S-curve mating display. Image credit: “older guy 22feb08” by Alice Chaos is licensed under CC BY-NC-SA 2.0
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Why do birds get divorced?

Divorce in Savannah Sparrows of Kent Island

by: Michael Calcagno, Meghan Ghazal, Lizzie Poyant & Zarir Sidhwa (Stonehill College Evolution Fall 2017)

In Savannah sparrows (Passerculus sandwichensis) that reside on Kent Island, New Brunswick, Canada an understanding of divorce rates within the species was analyzed to determine the molecular basis of the phenotypic trait. As well as, to determine if divorce is an adaptive strategy for greater fitness for females. In this species, approximately 47% of pairs in which both partners survived to the following breeding season ended in divorce. Neither the lifetime number of divorces nor whether an individual had ever divorced affected the fitness of either sex, thus suggesting little to no sexual selection for the trait. Divorce in the Savannah sparrows appeared to be an inheritable behavior in which expression depending primarily upon an individual’s age, mating status, sex, and size.

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