How Female Fish Shape Evolution

By: Aisling Finnegan, Gracie Knudsen, & Angela Peri (Stonehill College, BIO323: Evolution, Spring 2026)

Even small choices in nature can have big effects over time. In Bahamas mosquitofish, the way females respond to males can influence who mates, and over time, can lead to the formation of new species. When talking about species in the context of this article, it is a group of organisms that can successfully mate and produce offspring. Speciation happens when populations of the same species become so different that they no long mate. This process often begins with behavioral isolation, which is when groups stop choosing each other as mates.

In the study we highlight here published in BMC Ecology and Evolution, Varpu Pärssinen and others examine if living in different environments could cause these kinds of behavioral changes. The researchers studied Bahamas mosquitofish, which are small freshwater fish that live in streams and ponds in the Bahamas. They observed populations that live in areas filled with predators and others that live in environments with a lack of predators. They notice that these differences in predation levels influence how the fish behave and live.

A short podcast summarizing the article. Image of Bahamas mosquitofish by Araújo et al. (2014): https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.1140

November 27, 2023

The Benefits of Commitment in Black-headed Gulls

By: Karina Rodrigues, Joanna Soliman, Yenifer Oseguera, and Giana Youssef (Stonehill College, BIO323: Evolution, Spring 2023)

Overview

Loyalty, a quality some lack and some do not. Have you ever thought about the positive effects loyalty has on people, better yet species? In terms of evolution, loyalty translates to how committed a species is to its breeding partner. Originating from the Netherlands, black-headed gulls (Chroicocephalus ridibundus) were used to study the benefits of long-term relationships and if it plays a role in how parents invest more with their partners as well as their pair bond with one another. These seabirds were studied in a model environment that fits the birds natural needs in order to exhibit their natural behaviors. After testing different mechanisms, selection for mate retention reduces parental care conflicts between a pair and also sheds light to selecting traits that increase individuals fitness throughout evolution.

A short podcast summarizing the article.

December 22, 2019

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.

https://soundcloud.com/user-669960307/sexual-selection-big-brain-vs-small-brain/s-vmGa5

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

November 16, 2017December 5, 2017

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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