Fri, 30 Jul 2010 12:32:55 +0100

NSF Awards Grant for Spider Research

It’s tough being a male wolf spider. As they court females, they don’t know if they are being evaluated as a potential mate or the main course for dinner.

The complexity of spider behavior — the longstanding research interest of Alma College biologist Dave Clark — is the subject of a research project that has been awarded a three-year $485,000 grant from the National Science Foundation. 

The project — which includes the development of animated spider images and the use of innovative digital video playback technology — is a collaboration between Alma College and the University of Cincinnati and a partnership with the Cincinnati Nature Center. Alma College students will spend a semester or summer session conducting research at the University of Cincinnati alongside graduate students and postdoctoral fellows.

Both laboratory and field components are included in the project, with a Spring Term opportunity at the Cincinnati Nature Center. Joining Clark as a co-principal investigator for the project is UC faculty researcher George Uetz.

“I’m very excited about this research and the opportunity for undergraduate students to conduct research in ways that will maximize their educational experience,” says Clark. “Our intent is to better understand how spiders communicate in complex environments.”

  Dave Clark

At Alma College, Clark has studied the different modes of communication used by a variety of animals, including lizards, fish and spiders.

For spiders, communication can take many forms, and some species use multiple modes, including visual communication, such as body posturing or leg waving. Spiders also can communicate by generating sounds, such as limb tapping, like a percussionist, or rubbing body parts. In addition, the spiders’ silk can communicate the presence of females or other males in the area.

For the current study, Clark and Uetz will investigate how the physical environment and the presence of the intended receivers, eavesdroppers and predators influence spider signals. High-definition computer animated versions of male spiders will be constructed at Alma College. Using digital video playback technology pioneered by the research team, animated spider images will be presented to wolf spiders and their predators on the handheld iPod Touch and iPad tablet computer.

“In our studies, we have found that male wolf spiders respond to the courtship of other males,” says Clark. “If they see courtship behavior by other males, that’s a signal to them that there may be a female in the area. As male density goes up, male courtship behavior increases. We want to continue to pursue how males use other males to find females.”

The problem for courting males, however, is that they are being evaluated for different purposes. Other males are using them to eavesdrop and find females. Females are evaluating them for their size and as a suitable mate — larger males translate into bigger and more eggs for the female.

“But females have a dual selective process,” says Clark. “Besides evaluating males as mates, females also are selecting males to eat. Females are choosy mates and not-so-choosy predators. Males, of course, are not interested in being the prey.”

And then there are other predators like toads and birds that will happily eat male spiders no matter what they look like.

“We want to look at both the influence of predators and how the physical environment affects detection and discrimination of male spider signals,” says Clark.

Clark and his students will use digital video playback technology to alter male signals and environmental backgrounds to test how spiders are detected and evaluated.

The faculty researchers will train and supervise teams of students in field data collection, video digitization and statistical analysis techniques. Students also will have the opportunity to conduct their own research projects to investigate related questions, search the literature using the Internet and make research presentations.

Same-sex behavior has been extensively documented in the non-human animal kingdom, concludes a new review of existing research.

Yep, homosexual behavior is common across species, from worms to frogs to birds - but there's a catch.   Same-sex 'behaviors' are not the same across species and researchers may be calling qualitatively different phenomena by the same name.

Published June 16 in the journal Trends in Ecology&Evolution, the review by Nathan Bailey and Marlene Zuk, a professor of biology at University of California-Riverside, also finds that although many studies are performed in the context of understanding the evolutionary origins of same-sex sexual behavior, almost none have considered its evolutionary consequences.

"It's clear that same-sex sexual behavior extends far beyond the well-known examples that dominate both the scientific and popular literature: for example, bonobos, dolphins, penguins and fruit flies," said Bailey, first author of the review paper and a postdoctoral researcher in the Department of Biology at UC Riverside.  "For example, male fruit flies may court other males because they are lacking a gene that enables them to discriminate between the sexes.   But that is very different from male bottlenose dolphins, who engage in same-sex interactions to facilitate group bonding, or female Laysan Albatross that can remain pair-bonded for life and cooperatively rear young.

"Same-sex behaviors—courtship, mounting or parenting—are traits that may have been shaped by natural selection, a basic mechanism of evolution that occurs over successive generations," Bailey said. "But our review of studies also suggests that these same-sex behaviors might act as selective forces in and of themselves."

A selective force, which is a sudden or gradual stress placed on a population, affects the reproductive success of individuals in the population.

"When we think of selective forces, we tend to think of things like weather, temperature, or geographic features, but we can think of the social circumstances in a population of animals as a selective force, too," Bailey said. "Same-sex behavior radically changes those social circumstances, for example, by removing some individuals from the pool of animals available for mating."

Bailey, who works in Zuk's lab, noted that researchers in the field have made significant strides in the past two and a half decades studying the genetic and neural mechanisms that produce same-sex behaviors in individuals, and the ultimate reasons for their existence in populations.

"But like any other behavior that doesn't lead directly to reproduction—such as aggression or altruism—same-sex behavior can have evolutionary consequences that are just now beginning to be considered," he said. "For example, male-male copulations in locusts can be costly for the mounted male, and this cost may in turn increase selection pressure for males' tendency to release a chemical called panacetylnitrile, which dissuades other males from mounting them."

The review paper:

• Examines work done to test hypotheses about the origins of same-sex behavior in animals.


• Provides a framework for categorizing same-sex behavior, for example, is it adaptive, not adaptive, occurs often, infrequently?


• Discusses what has been discovered about the genetics of same-sex behavior, especially in the model organism, the fruit fly Drosophila, and in human beings.


• Examines connections between human sexual orientation research, and research on non-human animals, and highlights promising avenues of research in non-human systems.

The reviewers expected the research papers they read for their article would give them a better understanding of the degree to which same-sex behaviors are heritable in animals.

"How important are genes to the expression of these behaviors, compared to environmental factors?" Bailey said. "This is still unknown. Knowing this information would help us better understand how the behaviors evolve, and how they affect the evolution of other traits. It could also help us understand whether they are something that all individuals of a species are capable of, but only some actually express."

Bailey recommends that fellow evolutionary biologists studying same-sex behavior in animals adopt some of the research approaches that have been successful in human studies.

"We have estimates, for example, of the heritability of sexual orientation in humans, but none that I know of in other animals," he said. "Scientists have also targeted locations on the human genome that may contribute to sexual orientation, but aside from the fruit fly, we have no such detailed knowledge of the genetic architecture of same-sex behavior in other animals."

Next in their research, Bailey and Zuk plan to begin experimentally addressing some of the many issues raised in their review.

Said Bailey, "We want to get at this question: what are the evolutionary consequences of these behaviors? Are they important in the evolution of mating behavior, or do they just add extra 'background noise'? We are pursuing work on the Laysan Albatross, in which females form same-sex pairs and rear young together. Same-sex behavior in this species may not be aberrant, but instead can arise as an alternative reproductive strategy."

The UCR Academic Senate funded the one-year study.

Article: Nathan W. Bailey, Marlene Zuk, 'Same-sex sexual behavior and evolution', Trends in Ecology&Evolution,  doi:10.1016/j.tree.2009.03.014 Available online 17 June 2009