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Sullivan, IL, United States

Krimmel B.,University of California at Davis | Pearse I.S.,Illinois Natural History Survey
Ecology | Year: 2016

Avoidance and tolerance of herbivory are important components of plant interactions with herbivores. Their relationship to each other and to plant defense is important in understanding how plants maximize fitness in the face of herbivore pressure. Various tarweed species have populations comprised of both early-season and late-season flowering individuals. Late-season flowering individuals employ a recently described indirect defense against herbivores in which the accumulation of dead insects on their sticky surfaces attracts predatory insects that eat herbivores. In two tarweed species (Hemizonia congesta and Madia elegans), we observed that key herbivores rarely interact with early-season individuals in the field, and early-season individuals did not invest in dense glandular trichomes that cause indirect defense. We conducted field and greenhouse bud-removal experiments to assess tolerance of M. elegans to herbivore damage. We found that lateseason individuals were more tolerant of simulated herbivory than early-season individuals in both the field and the greenhouse. Late-season individuals that were forced into an earlier phenology with a 24-h light cue lost their tolerance to simulated herbivory. One possible mechanism linking phenological avoidance of herbivores with decreased tolerance is that early-season individuals invested less in below-ground biomass than late-season individuals, which may accumulate belowground resources for regrowth at the expense of early flowering. © 2016 by the Ecological Society of America. Source

Retzer M.E.,Illinois Natural History Survey
Zootaxa | Year: 2010

Teugels et al. (1991) considered the genus Auchenoglanis to be comprised of two valid species: A. biscutatus and A. occidentalis. A new analysis of all the nominal species and subspecies of the genus supports the recognition of all nominal taxa as species. Each species is diagnosed primarily on mensural characters, size and shape of the premaxillary tooth patches, and pigmentation patterns. In addition, a new species, Auchenoglanis senegali, is described from Senegal. © 2010. Magnolia Press. Source

Pearse I.S.,Illinois Natural History Survey | Hipp A.L.,University of Illinois at Chicago
Proceedings. Biological sciences / The Royal Society | Year: 2014

There is often an inverse relationship between the diversity of a plant community and the invasibility of that community by non-native plants. Native herbivores that colonize novel plants may contribute to diversity-invasibility relationships by limiting the relative success of non-native plants. Here, we show that, in large collections of non-native oak trees at sites across the USA, non-native oaks introduced to regions with greater oak species richness accumulated greater leaf damage than in regions with low oak richness. Underlying this trend was the ability of herbivores to exploit non-native plants that were close relatives to their native host. In diverse oak communities, non-native trees were on average more closely related to native trees and received greater leaf damage than those in depauperate oak communities. Because insect herbivores colonize non-native plants that are similar to their native hosts, in communities with greater native plant diversity, non-natives experience greater herbivory. © 2014 The Author(s) Published by the Royal Society. All rights reserved. Source

News Article
Site: http://phys.org/biology-news/

The study, published in Animal Behaviour, reveals that cowbird juveniles leave the host parents at dusk and spend their nights in nearby fields, returning just after daybreak. This behavior likely plays a role in the cowbirds' ability to avoid imprinting on their host parents. "If I took a chickadee and I put it in a titmouse nest, the chickadee would start learning the song of the titmouse and it would actually learn the titmouse behaviors," said Matthew Louder, who conducted the study as a Ph.D. student with Illinois Natural History Survey avian ecologist Jeff Hoover and INHS biological surveys coordinator Wendy Schelsky. "And then, when it was old enough, the chickadee would prefer to mate with the titmouse, which would be an evolutionary dead end," he said. Louder is now a postdoctoral researcher with East Carolina University in North Carolina and Hunter College in New York. The imprinting process is widespread among birds and other animals, but brood parasites like the cowbird appear to be resistant to imprinting. They will imprint on a different species if confined with that species for an extended period of time in a cage, but the birds don't appear to do so in the wild. Cowbird hosts, such as the prothonotary warblers in this study, have their own habits and habitats, and seldom choose to live where the cowbirds live or eat what they eat. Prothonotary warblers, for example, live in forests and dine on insects and caterpillars. Cowbirds spend most of their adult lives in open fields and prairies, and while they do eat insects, about three-quarters of their diet consists of seeds. "Among other things, cowbirds have got to learn to eat like cowbirds or they're not going to survive very long," Hoover said. The researchers wanted to test the hypothesis that cowbird moms are the ones that lead their offspring out of the forest. There was some support for this idea. A recent study from the same team found that cowbird females don't simply abandon their eggs in another species' nest. They pay attention to whether the young birds survive, sometimes wrecking the nests of birds that kick the cowbird eggs out of their nests. The cowbird females also return to nests where young cowbirds survived to fledging age. Cowbird females are often spotted in the vicinity of cowbird nestlings, Schelsky said, and sometimes respond (with vocalizations, not food) to the nestlings' begging calls. To track the birds in the forest and prairie, the researchers put radio telemetry transmitters on the cowbird nestlings and on adult female cowbirds in the forest where the host parents made their nests. The team took blood from the birds and conducted genetic analyses to match the juveniles (and their radio signals) to their biological mothers. But tracking the birds, even with the radio transmitters, was next to impossible, Louder said. He tried for a year, but was unable to get meaningful data. Then study co-author Michael Ward, a professor of natural resources and environmental sciences at the University of Illinois, came up with a new approach. "He helped construct an automated telemetry system," Louder said. "We put up three radio towers, each with six antennas on it, so you have 360-degree directional coverage. All three towers track one individual cowbird at a time and then move to the next individual." With this system, Louder could track the location of each study bird every one-to-two minutes. "We were able to watch the juveniles and see if they left the forest at the same time as a female and, if so, whether that female was their mom," he said. "Strangely enough, the juveniles did not follow the females out of the forest," Louder said. Instead, they left on their own, after dark, returning only the following morning, he said. "I started seeing this in the data and I thought it was wrong," Louder said. So he went to the forest and followed a single juvenile cowbird for one night. The bird left the forest in the evening, moving to a rosebush on the adjacent prairie. It was out there all night, alone. "As soon as the sun came up, the juvenile flew back into the forest and to the warbler's territory," Louder said. "Without the automated radio telemetry, I would have assumed that it had stayed in the forest all night." The discovery doesn't explain how cowbirds find their way into a cowbird flock, where they learn most of their social and survival skills and eventually find a mate. But it does offer some insight into the processes that allow young cowbirds to avoid imprinting on their hosts, the researchers said. "Clearly, there's a lot more to these birds than people would have thought," Hoover said. "We still have more layers to peel away from this onion that is the cowbird." More information: Matthew I.M. Louder et al. Out on their own: a test of adult-assisted dispersal in fledgling brood parasites reveals solitary departures from hosts, Animal Behaviour (2015). DOI: 10.1016/j.anbehav.2015.09.009

News Article
Site: http://phys.org/biology-news/

The results are published in the journal PLOS ONE. The western rattlesnake (Crotalus viridis) is found across a significant portion of the United States, from Mexico to Canada and from the Missouri River to the West Coast. Most work classifying rattlesnake species and subspecies was conducted in the mid-20th century. Since then, scientific methods have advanced to allow for a more comprehensive understanding of the path of rattlesnake evolution. Mark Davis, a research scientist at the Illinois Natural History Survey, part of the Prairie Research Institute at the University of Illinois, collected data from nearly 3,000 western rattlesnakes for this study. He gathered data from preserved samples of this group available at natural history museums across the western United States. "We are able to see that these different subspecies, which have different habits, live in different areas and have other different characteristics, have heads that have been shaped differently over evolutionary time," Davis said. For western rattlesnakes, the head is the primary organ for conducting daily life. It is especially important for feeding and reproductive rituals. Head shape has evolved to better accommodate these critical behaviors, Davis said. The shape can vary drastically between different species of snakes. Given the importance of this feature, Davis and his colleagues used geometric morphometrics, a relatively novel method that allows researchers to quantify head shape without any influence of head size. To complement the shape analyses, Davis and his team analyzed genetic data from the snakes. Combining head shape and genetic information created a comprehensive perspective, Davis said. Together, these data confirm that several groups of snakes previously labeled as subspecies have substantial enough differences to qualify for a separate species designation. One of the greatest challenges to ecological conservation is identifying what species actually exist. For legal protections - including the Endangered Species Act - to be effective, scientists must specifically identify the units of biodiversity that may be in need of protection. "It's important to me to try to work with conservation practitioners to develop strategies for preserving biodiversity," Davis said. With this study, Davis and his colleagues recommend officially elevating to the level of full species several groups of snakes previously believed to be subspecies. Davis expects that the national and international organizations responsible for naming various species will adopt the recommendations proposed in the study. More information: Deconstructing a Species-Complex: Geometric Morphometric and Molecular Analyses Define Species in the Western Rattlesnake (Crotalus viridis), dx.doi.org/10.1371/journal.pone.0146166

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