Coral Genes May Help Solve Species Mystery

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True corals reside in tropical reefs south of the equator, yet about 30 species of soft corals found in the Pēnghú archipelago west of Taiwan bear a strong resemblance to their southern neighbors, leading scientists to question if they are the same species.

Students in the lab of Harvey Mudd College biology Professor Cathy McFadden are helping find the answer.

Rising sophomores Prudence Hong, Sara Shi (POM) and Samuel Du (POM) have extracted DNA from more than 200 coral tissue samples and targeted specific genes identified as helpful in telling species apart. Once those genes are sequenced, the students will begin the arduous task of comparing sequences from different samples to see whether or not they find matches between the northern soft corals and those found on reefs south of Taiwan.

Should species from the two areas prove a genetic match, it may offer hope for the future of corals threatened by rising sea temperatures.

“We’re concerned about global climate change and coral reefs have taken a hit with changing temperatures, including mass mortalities around the world during warm water events,” said McFadden. “So there is concern about whether coral reefs will be able to adapt and, should the organisms move further north as water temperatures increase, whether they can adapt quickly enough.”

If the northern corals are the same species as those found on the southern reefs, it is likely they can and will adapt.

Genetic research may also solve a second, much-debated coral mystery explored in the McFadden lab: Can two different coral species give rise to hybrids?

An earlier study has suggested that two soft coral species living side by side off the coast of Great Britain might be producing hybrids. It revealed that a protein, which always expressed an AA genotype in one parent species and a BB genotype in the other, existed as an AB genotype in the suspected hybrids. Unfortunately, this finding did not rule out the possibility of a naturally occurring, genetic variant.

To tackle the hybrid question, McFadden plans to move beyond a single protein to sequencing the whole genomes of both parent species and the suspected hybrids. “We hope to find genes where we always see an AA vs. BB difference between the two parents. So, if we find 400 genes that are always AA or BB, and then screen whole genomes for the hybrids and see those same 400 genes are always AB, then that’s going to be much more convincing evidence,” McFadden said.

A project that size requires the processing of large amounts of data and the creation of software programs to sift through and extract the specific, desired information.

Mathematical and computational biology major Kennedy Agwamba ’16 is working with sample data to outline the steps necessary to retrieve and analyze the required genetic information. He is also reviewing the lab’s current software programs to determine which tools are available and what more may need to be developed once the genome data arrives.

The genetic projects are part of HMC’s Summer Research Program, which engages students in 10 weeks of full-time research. More than 175 HMC students are pursuing research projects this summer alongside 45 faculty members in biology, chemistry, computer science, engineering, mathematics and physics.