image: This is an inaccurate ant mimic, Micaria sociabilis, foraging on oak bark. view more
Credit: photograph by S. Pekar ©
When a bad mimic is good
Nature is full of mimics—creatures that have evolved to look or act like other more dangerous animals. However, some mimics imitate their models more convincingly than others, and new research helps explain why it sometimes pays to be a bad mimic. The research looked at three species of spider, all of which mimic, with varying degrees of accuracy, aggressive and bad-tasting ants. All of the mimics were good at avoiding being eaten by predators that target spiders, the research found. But the less accurate mimics also had a spider-like ability to evade predators that eat the model ants. "So by not looking like a spider, but also not quite looking like an ant, these inaccurate mimics have the best of both worlds, escaping both spider and ant predators," said Stano Pekár, a biologist at Masaryk University in the Czech Republic and one of the study's authors. The results show that the accuracy of mimics depends on the environment and the array of predators in the area.
Stano Pekár, Martin Jarab, Lutz Fromhage, and Marie E. Herberstein, "Is the Evolution of Inaccurate Mimicry a Result of Selection by a Suite of predators? A Case Study Using Myrmecomorphic Spiders."
You're not speaking my language: Sparrows don't respond to foreign dialects
Similar to regional dialects in human languages, bird songs often differ slightly between populations of the same species. A study led by Julie Danner of Virginia Tech shows that female rufous-collared sparrows have strong preferences for mating songs sung in a local dialect, and rarely respond sexually to foreign dialects. "The research indicates that picky females may inhibit breeding between close populations," Danner said. Such reproductive isolation could ultimately cause populations to diverge into different species. For their study, Danner and her team played recordings of several mating songs for captive females. One recording was a song from the female's local population. The other songs came from other sparrow populations, one from 15 miles away and the other from 2,500 miles away. A fourth song from a completely different bird species was also played. The research found that the females were much less likely to respond to the foreign songs. In fact, females were no more likely to respond to the song from 15 miles away than they were to the song from the other species. "Our study is the first to show tropical female mate preference for male song over a very short distance," Danner said.
Julie E. Danner, Raymond M. Danner, Frances Bonier, Paul R. Martin, Thomas W. Small, and Ignacio T. Moore, "Females, But Not Males, Respond More Strongly to the Local Song Dialect in a Tropical Sparrow: Implications for Population Divergence."
A Long-Distance Prediction for Pollinators
Is it possible to predict what kind of pollinator will visit a flower based on the flower's shape and chemistry? It is, according to a new study led by Scott Armbruster (University of Portsmouth (UK) and University of Alaska, Fairbanks). The study focused on Dalechampia, a genus of flowering vines that includes over 120 different species. After studying several Dalechampia species in South America and Africa, the researchers predicted that a previously unstudied Dalechampia species native to China would be pollinated by female resin-collecting bees around 12 to 20 millimeters in length. Armbruster and his team then conducted field observations in China to see if they were right. Sure enough, the Chinese species is pollinated by a female bee that fit the prediction. The study shows that pollination ecology can be predicted "from the pollination trends derived from studies conducted on the other side of the world," the researchers write. The finding validates the somewhat controversial idea that pollination ecology is sometimes predictable from the morphology of the flowers, Armbruster said.
W. Scott Armbruster, Yan-Bing Gong, and Shuang-Quan Huang, "Are Pollination Syndromes Predictive? Asian Dalechampia Fit Neotropical Models."
For the complete table of contents for the July issue, go to www.journals.uchicago.edu/an. For more information, contact Kevin Stacey at kstacey@press.uchicago.edu.
Since its inception in 1867, The American Naturalist has maintained its position as one of the world's most renowned, peer-reviewed publications in ecology, evolution, and population and integrative biology research.