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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Holy Bat Detector! Ecologists Develop First Europe-Wide Bat ID Tool

ScienceDaily (Aug. 3, 2012) — Just as differences in song can be used to distinguish one bird species from another, the pips and squeaks bats use to find prey can be used to identify different species of bat. Now, for the first time, ecologists have developed a Europe-wide tool capable of identifying bats from their echolocation calls.

Grey Long-Eared bat. (Credit: copyright Hugh Clark / Bat Conservation Trust)


The new free online tool — iBatsID — will be a major boost to conserving bats, whose numbers have declined significantly across Europe over the past 50 years. Details are published August 7 in the British Ecological Society’s Journal of Applied Ecology.

Working with an international team of ecologists, lead author and PhD student Charlotte Walters from the Zoological Society of London (ZSL) selected 1,350 calls of 34 different European bat species from EchoBank, a global echolocation library of more than 200,000 bat calls.

The calls were then analysed to find out which characteristics were most useful in distinguishing different bat species. According to Walters: “Lots of different measurements can be taken from an echolocation call, such as its maximum and minimum frequency, how quickly the frequency changes during the call, and how long the call lasts, but we didn’t know which of these measurements are most useful for telling different species’ calls apart.”

The 12 most useful call parameters were then used to train artificial neural networks to produce the new identification tool, iBatsID, which can identify 34 different bat species across the whole of Europe. Most species can be identified correctly more than 80% of the time, although accuracy varies because some species are much harder to identify than others.

“iBatsID can identify 83-98% of calls from pipistrelle species correctly, but some species such as those in the Myotis genus are really hard to tell apart and even with iBatsID we can still only identify 49-81% of Myotis calls correctly,” she explains.

iBatsID should have a major impact on European bat conservation, which until now has been hampered by the absence of a standardised, objective and continent-scale identification tool.

According to Professor Kate Jones, another of the paper’s authors and chair of the Bat Conservation Trust: “Acoustic methods are really useful for surveying and monitoring bats, but without using the same identification methods everywhere, we can’t form reliable conclusions about how bat populations are doing and whether their distributions are changing. Because many bats migrate between different European countries, we need to monitor bats at a European, as well as at country, scale. In iBatsID, we now have a free, online tool that works anywhere in Europe.”

Bat populations have declined significantly across Europe since the middle of the 20th century. As a result, all bats are now protected through the EU Habitats Directive. Bats face many pressures, including loss of roosting sites in trees and buildings; loss of feeding habitats in woodlands, meadows, parks and gardens; falling insect numbers; and habitat fragmentation resulting in the loss of green corridors such as hedges that provide connectivity in the landscape.

As well as providing vital ecosystem services, such as pollinating plants and controlling insect pests, bats are important indicators of biodiversity. “Bats are very sensitive to changes in their environment, so if bat populations are declining, we know that something bad is going on in their environment. Monitoring bats can therefore give us a good idea of what is going on with biodiversity in general,” Walters adds.

 

Link:

http://www.alphagalileo.org/ViewItem.aspx?ItemId=122962&CultureCode=en

Journal Reference:

  1. Charlotte L Walters et al. A continental-scale tool for acoustic identification of European bats. Journal of Applied Ecology, 7 August 2012 DOI: 10.1111/j.1365-2664.2012.02182.x

Citation:

British Ecological Society (BES) (2012, August 3). Holy bat detector! Ecologists develop first Europe-wide bat ID tool. ScienceDaily. Retrieved August 9, 2012, from http://www.sciencedaily.com­ /releases/2012/08/120807101243.htm