October 4, 2013
Researchers Find Two Subspecies Of Bryde’s Whales
April Flowers for redOrbit.com - Your Universe Online
Researchers attempting to define populations of a medium-sized and poorly understood baleen whale say that saving the whales often means knowing - sometimes on a genetic level - one group of whales from another. A group of scientists from Wildlife Conservation Society, the American Museum of Natural History, Columbia University, NOAA, and other groups are working to define separate groups and subspecies of the Bryde's whale, which are sometimes targeted by Japan's scientific whaling program, found in the Indian and western Pacific Oceans.
The team was able to discriminate among different Bryde's whales (pronounced BREW-dus) by generating genetic information that was akin to a bar code. The research team was able to confirm the existence of two subspecies: one is larger in size and lives in offshore waters, the other is smaller and frequents more coastal marine habitats. The results of this study are published in the Journal of Heredity.
"Very little is known about Bryde's whales in terms of where populations are distributed, the extent of their range, or even relationships among them at the population, sub-species and species levels," said Columbia University researcher Francine Kershaw. "Our genetic research will help define these groups and identify populations in need of additional protection."
"The ability to delineate different populations and subspecies of Bryde's whales—particularly ones threatened by low numbers and genetic diversity—will help management authorities prevent the loss of unique and distinct genetic lineages and distinct populations," said Dr. Howard Rosenbaum, director of the Wildlife Conservation Society's Ocean Giants Program.
The Bryde's whale grows to about 50 foot in length and inhabits tropical, subtropical, and warm temperate waters of the Atlantic, Pacific, and Indian Oceans. The species, named after Norwegian whaler and entrepreneur Johan Bryde, encounters such threats as scientific whaling, ship strikes, fisheries bycatch, hydrocarbon exploration, and development in coastal waters.
Marine managers face a conservation dilemma because of a lack of knowledge about the Bryde's whale, specifically how many species and populations there are. The International Union for Conservation of Nature (IUCN) considers the species "Data Deficient." In addition, the International Whaling Commission grants Japan an annual take of Bryde's whales in the northwest Pacific Ocean through the provisions of special scientific permit. Japan was allowed 34 Bryde's whales in the 2012/2013 season.
The research team conducted an analysis of Bryde's whale populations in the Indian and Pacific Oceans to fill in these knowledge gaps by examining new genetic samples from 56 individual whales from the waters of Oman, Maldives, and Bangladesh. Published data sets from Java, the coast of Japan, and the northwest Pacific were also used in the study.
Using mitochondrial DNA material, the researchers examined nine diagnostic characters from each of the samples. The majority of samples were harmlessly collected skin samples obtained from living whales using small biopsy darts launched from crossbows. A small percentage of samples were collected from beached whales and individuals killed in ship strikes.
The material gathered from skin samples were examined with a technique called polymerase chain reaction (PCR) to amplify specific regions of mitochondrial DNA, which is passed on through maternal lines of a population. The team performed a statistical analysis on the data to measure how genetically different individuals were.
The genetic analysis confirmed the existence of two subspecies or types of Bryde's whales. One type is coastal and one is offshore, which underlines the need to designate both subspecies as separate conservation units, with specific management needs for each type.
In addition, the findings revealed significant population structure for each subspecies between regions. The analysis revealed that the larger offshore Bryde's whale populations in Maldives, Java, and the Northwest Pacific were genetically distinct from one another. According to the researchers, each population should be considered a separate conservation unit.
An extremely low genetic diversity was observed in the smaller coastal form of Bryde's whale, the lowest ever measured in a baleen whale population. In the 45 whales sampled in Bangladesh and Oman, only a single maternal line or haplotype was detected, leading the researchers to insist that this population must be considered a conservation unit independent from coastal Bryde's whales found off Japan.