Butterfly color diversity due to female preferences

Butterfly color diversity due to female preferences
Dorsal wing color by sex of European butterflies. Credit: Kalle Tunström

Butterflies have long captured our attention due to their amazing color diversity. But why are they so colorful? A new publication led by researchers from Sweden and Germany suggests that female influence butterfly color diversity by mating with colorful males.

In many species, especially birds and butterflies, males are typically more colorful than females, a phenomenon known as dichromatism. In many dichromatic species, the more conspicuous sex is more vulnerable to predation. Certainly, the male peacock is a much easier target than the more camouflaged hen. Explaining why one member of a species would place itself in more danger was a challenge to Charles Darwin’s early views on evolution by natural selection, as Darwin envisioned natural selection acting to reduce such risks.

Examples of dichromatism in fact were one of the issues that lead him to develop his theory of sexual selection, where elaborate male traits could evolve through female preference for conspicuous males, even in the face of the increased dangers such males would encounter.

Today, many naturalists and biologists alike generally ascribe the exaggerated coloration of males as being due to sexual selection. However, when we see a species in which males are more colorful than females, sexual selection is not necessarily the only answer. An alternative route to dichromatism might begin with males and females both being very colorful, followed by natural selection acting upon females to make them less conspicuous, perhaps due to the cost of being easier prey. Stated another way, perhaps females become less colorful so they are better camouflaged and therefore preyed upon less. The argument that natural selection could give rise to dichromatism was posited by Darwin’s contemporary, Alfred Russel Wallace. Darwin and Wallace in fact argued for decades about the origins of dichromatism in birds and butterflies.

The reason for this long debate between Darwin and Wallace arises because, without knowing how males and females looked in evolutionary past, either sexual selection or natural selection could give rise to dichromatism. Since they had no way of formally assessing what species used to look like, their argument had few routes for resolution.

This is where researchers from Sweden (Stockholm University and Lund University) and Germany (University of Marburg) have recently made progress, by developing statistical means for inferring the ancestral color states of males and females over evolutionary time.

To do this, they first reconstructed the evolutionary relationships among European butterflies and put this into a time calibrated framework. Then they scanned scientific drawings of all these male and female butterfly species, and used that color information in its evolutionary context to estimate the direction of butterfly color evolution for each sex, and in relation to the amounts of dichromatism per species. “Tracking evolutionary color vectors through time made it possible to quantify both the male and female contribution to dichromatism”, says Dr. Dirk Zeuss from the University of Marburg, who is coauthor of the new study.

“We find that the

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Bowdoin College student athletes of color demand action, equity from athletic department

BRUNSWICK — For months, Lester Jackson felt like he had a weight on his chest. Walking around the Bowdoin College campus, his home for the past three years, felt different, less enjoyable. The “imaginary bubble around Bowdoin” had popped and the mood among his football teammates had soured, he said, following an incident last fall when an assistant coach, who is white, used a racial slur in the locker room — something Jackson, co-president of the school’s Athletes of Color Coalition, said left him and his teammates “shook to the core.” 

While there was no malice behind it (the coach was reportedly asking players to turn off a song he said used the n-word too many times), that he “felt the need to comment on how inappropriate a song was but did not recognize how wrong it was for him to say that word,” was inexcusable, Jackson said in a letter to the editor in the Bowdoin Orient, the student newspaper.

The coach apologized and the team and coaches discussed what happened and why it was wrong, but “nothing could truly make this incident and its impact go away,” he said. 

This incident is one of several actions — racial slurs or demeaning terms, athletes of color being mistaken for other teammates or feeling “othered” as the only person of color on the team — that had ripple effects across the athletic community, according to a series of op-eds penned by the Athletes of Color Coalition and published in the Orient early last month. 

As social and political attention turned to issues of race and bias this summer following the national outcry and surge of protests after the deaths of Ahmaud Arbery, Breonna Taylor, George Floyd and Jacob Blake, the Athletes of Color Coalition seized the opportunity to turn the lens on Bowdoin. 

Led by Jackson and co-president Kendall Rogers, the group drafted a list of demands they felt would improve the experience for athletes of color at Bowdoin. There are 45 to 50 members of the group, and roughly 650 student-athletes at Bowdoin. 

The demands include a list of expected changes within the department, including annual facilitated discussions around race and training on racial bias prevention and allyship tailored to athletics, more transparency, diversity and access within the athletic hiring and recruiting process, a bias-specific reporting process, and team-wide discussions and action plans followed with an annual report on the changes. An expected timeline was also included.

“We have recognized that racial bias incidents are a consistent occurrence in the Bowdoin Athletic department and they have involved players, coaches and those in our community,” the students wrote. “These incidents often go unreported, because many athletes of color feel uncomfortable speaking up and that no action will be taken as a result of a complaint. … Black athletes have continued to be called the N-word, are being mistaken for each other, and do not truly feel welcome on their respective teams.” 

“Though some of the most decorated athletes on campus

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