Bats Evolved More Than One Way to Drink Nectar

ScienceDaily (Aug. 17, 2012) — A team of evolutionary biologists compared the anatomy and genes of bats to help solve a persistent question in evolution: Why do analyses of different features of an organism result in conflicting patterns of evolutionary relationships? Their findings, “Understanding phylogenetic incongruence: lessons from phyllostomid bats,” appear in the August 14 edition of Biological Reviews.

Two nectar-feeding bats in the Neotropical family Phyllostomidae; the glossophagine Pallas’s long-tongued bat, Glossophaga soricina, (left) and the lonchophylline orange nectar bat, Lonchophylla robusta, (right). In a new study Dávalos, Cirranello, et al., show that many anatomical features implying a common origin of nectar feeding for glossophagines and lonchophyllines — such as a long, extensible tongue — are related to their shared diet. Their evolutionary patterns are consistent with natural selection. (Credit: Felineora (left), Marco Tschapka (right).)


 

To answer this question, Liliana Dávalos, PhD, Assistant Professor in the Department of Ecology and Evolution, and member of the Consortium for Inter-Disciplinary Environmental Research (CIDER) at Stony Brook University, and Andrea Cirranello of the Division of Vertebrate Zoology at the American Museum of Natural History (AMNH), together with colleagues at the AMNH and the New York College of Osteopathic Medicine, examined the skin, skeleton, muscle, tongue, internal organs and a few genes of a family of New World bats, applying statistical models to uncover the genetic and anatomical features that produced the conflicts between evolutionary patterns. This work was funded in part by the National Science Foundation.

Specifically, the team examined why genes suggested that nectar feeding had evolved twice in Leaf-Nosed bats, while the anatomical features strongly pointed to a single origin of nectar feeding in this group. Most bats feed on insects, but New World Leaf-Nosed bats are exceptionally diverse in that they feed on nectar, fruit, frogs, lizards and even blood.

One hypothesis that the team tested is that traits linked to how bats feed have been shaped by natural selection for a nectar-based diet, resulting in the conflicting pattern. As Dávalos and Cirranello explain, connecting the conflicting pattern to the diet requires showing that the evolutionary pattern resulting from anatomical traits is wrong, and that the traits producing the conflict with the genetic data are linked to a shared dietary specialization.

“If a diet specializing in nectar helped shape the anatomy of the two groups of bats, then the traits that support the groups coming together should be related to feeding, and taking those traits out should break up the spurious group of nectar-feeding bats,” the researchers said. They found support for these predictions by analyzing evolutionary trees from two genomic data sets, alongside trees based on more than 200 anatomical traits; and applying a battery of statistical approaches to identify where in the evolutionary tree the conflicts arose and what genetic regions and traits supported the differences.

The team traced the conflict in evolutionary patterns among nectar-feeding bats to traits linked to feeding, such as the shape and number of teeth, gaining a “paintbrush” type tongue tip, and rearranging the tongue muscles to accommodate longer, extensible tongues. All of these traits are thought to be associated with specialized nectar feeding. The grouping of all nectar-feeding bats broke down into smaller groups when those traits were taken out of the analyses. Overall, the team found that anatomical traits and the studied genes tended to agree on many parts of the evolutionary tree, but that the anatomical traits associated with nectar feeding brought nectar-feeding bats together.

Natural selection has shaped the anatomy of organisms, but when specializations evolved long ago, it can be difficult for evolutionary biologists to demonstrate that traits bear its signature. By ruling out other biological processes that produce conflict among evolutionary trees, and tracing the conflict to specific traits that are known to enable drinking nectar, the team was able to narrow the options and discover patterns consistent with the signature of adaptation to diet. “We found that anatomical traits associated with nectar feeding have evolved and been lost several times, so they tend to bring bats from different branches of the evolutionary tree together, in direct conflict with genetic trees,” Dávalos and Cirranello said.


Story Source:

The above story is reprinted from materials provided by Stony Brook University.


Journal Reference:

  1. Liliana M. Dávalos, Andrea L. Cirranello, Jonathan H. Geisler, Nancy B. Simmons. Understanding phylogenetic incongruence: lessons from phyllostomid bats. Biological Reviews, 2012; DOI: 10.1111/j.1469-185X.2012.00240.x

Citation:

Stony Brook University (2012, August 17). Bats evolved more than one way to drink nectar. ScienceDaily. Retrieved August 23, 2012, from http://www.sciencedaily.com­ /releases/2012/08/120817151501.htm
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Iconic Darwin Finch Genome Sequenced

ScienceDaily (Aug. 17, 2012) — Scientists have sequenced the genome of one of the iconic Galapagos finches first described by Charles Darwin. The genome of the medium ground finch (Geospiza fortis) is among the first of a planned 100 genomes of vertebrate species to be sequenced and released by an international collaboration between the Genome 10K project and BGI.

Scientists have sequenced the genome of one of the iconic Galapagos finches first described by Charles Darwin, the medium ground finch (Geospiza fortis). (Credit: © jptenor / Fotol)

 

This finch genome, the first of the BGI-Genome 10K collaboration to be made available through the UCSC Genome Browser, represents both a scientific and a symbolic advancement, according to Duke University associate professor Erich Jarvis, who studies the neurobiology of vocal learning in songbirds.

“The scientific advancement,” Jarvis said, “is that it will allow us to investigate the genomes of a group of closely related species with a significant amount of diversity on an island population, allowing us to potentially better understand the genetics of trait evolution.”

Jarvis added, “It is symbolic because it was the diversity of phenotypes in these finches that contributed to Darwin’s theory of evolution.”

Endemic to the subtropical or tropical dry forests and shrublands of the Galapagos Islands, this species evolves rapidly in response to environmental changes.

The BGI’s associate director of research, Goujie Zhang, said, “These finches are of great historical significance, but when Darwin first studied these birds, he was unlikely to have envisioned how this species would become a perfect model to study evolution in action.”

Zhang said, “Having the reference genome of this species has opened the door for carrying out studies that can look at real-time evolutionary changes on a genomic level of all of these enigmatic species.”

Jarvis said this new genome will help us understand the evolution of vocal learning, “The availability of the Geospiza fortis will allow us to validate findings so far only found in the zebra finch genome.”

Jarvis said these include genes with positively selected mutations involved with the vocal learning trait in finches and also with behavior necessary for spoken language in humans.

Jarvis added that the medium ground finch has several song types, whereas the zebra finch “is a more stereotyped vocal learning species.” This difference is expected to be under genetic control.

Adding richness to the possibility of understanding the genomic components of vocal learning, researchers have been recording Geospiza songs over the last 40 years.

Jarvis said these recordings reveal dialectic patterns that can now be linked to the genome by sequencing the genomes of additional individuals from living and past populations. “Like human spoken language, Geospiza song dialects are stable over many generations, but can change with emigration.”

“Having the well assembled draft reference genome of one individual will now allow scientists to determine if this cultural evolution is partly affected by genetics or is all pure cultural transmission,” Jarvis added.

In addition to being useful for investigating speciation, the genomic data can help in conservation efforts, Zhang said. “They also serve as the base for population studies that will aid in the conservation of these renowned finches. BGI is looking forward to working with any collaborators interested in joining us to carry out this work.”

Zhang said the medium ground finch genome, which is nearly one-third the size of the human genome, was sequenced from an individual female, producing a high-quality draft using 115X coverage data from the Illumina HiSeq sequencing system, which is considered a “next-generation” technology. With the aid of transcriptome data, BGI was able to annotate 16,286 protein-coding genes in this genome.

Professor Jun Wang, Executive Director of BGI, indicated the groups acted to spur the most rapid access and use of these data and to enable and encourage pre-publication use.

For that reason, in addition to releasing the medium ground finch genome on the UCSC Genome Browser, BGI has openly released the genome in their GigaScience journal’s database, GigaDB, which makes data available in a citable format and hosts it under a CC0 license that provides the least restrictions possible for data use.

According to Genome 10K co-founder Stephen O’Brien, “The genome sequence empowerment of Darwin’s finches will initiate the solving of evolutionary riddles that have puzzled biologists for a century.” O’Brien is now chief scientific officer and director of the Dobzhansky Center for Genome Bioinformatics at St. Petersburg State University, Russia.

Oliver Ryder, director of genomics at the San Diego Zoo, placed the new genome in a larger context: “The availability of this high quality genome assembly produced by BGI will facilitate the stewardship of earth’s biodiversity — a cherished goal of Genome10K.”

 


Story Source:

The above story is reprinted from materials provided byBGI Shenzhen, via EurekAlert!, a service of AAAS.


Journal Reference:

  1. Zhang, G; Parker, P; Li, B; Li, H; Wang, J. The genome of Darwin’s Finch (Geospiza fortis)GigaScience, 2012 DOI: 10.5524/100040
Citation:

BGI Shenzhen (2012, August 17). Iconic Darwin finch genome sequenced.ScienceDaily. Retrieved August 23, 2012, from http://www.sciencedaily.com/releases/2012/08/120817093049.htm