Life Sciences Commons^™

G00-1778 Field Windbreaks, James Brandle, Laurie Hodges

Laurie Hodges

gricultural producers face many challenges as they try to balance efficient production systems with increasing environmental demands. For these systems to be successful, they must optimize the balance between inputs and final production. Field windbreaks are one way to increase yields while at the same time reducing inputs and improving both environmental quality and production efficiency. Windbreaks reduce wind speed and alter the microclimate in sheltered areas. Field windbreaks reduce wind erosion and the damage to crops caused by wind-blown soil. They improve water use efficiency, reduce risks associated with drought, and manage blowing snow.

Field windbreaks provide positive economic …

Nf91-43 Blossom End Rot In Tomatoes, Laurie Hodges, Don Steinegger

Laurie Hodges

This NebFact discusses the causes, prevention and treatment of blossom end rot in tomatoes.

Nf97-353 What Is Quality. . . .In A Tomato?, Laurie Hodges

Laurie Hodges

This NebFact examines the many factors affecting tomato quality.

Nf96-274 Seed Sources For Commercial Vegetable Production, Laurie Hodges

Laurie Hodges

This NebFact has addresses of distributors of seeds for commercial vegetable production.

Genetic Admixture In Multidimensional Niche Space: Asymmetrical Niche Similarity Promotes Gene Flow In Armadillos (Dasypus Novemcinctus), Maria Arteaga, John Mccormack, Luis Eguiarte, Rodrigo Medellín

John E. McCormack

We unite genetic data with a robust test of niche divergence to test the hypothesis that patterns of gene flow between two lineages of the nine-banded armadillo are influenced by their climatic niches. We collected Geographical Information System (GIS) data on climate using locality information from 111 individuals from two lineages that had associated genetic material. We tested whether niches of these lineages were more conserved or divergent than the background environments of their geographic ranges and found evidence for niche conservatism on two axes and no evidence for divergence on any axis. To address the role of niche similarity …

New Phylogenetic Information Suggests Both An Increase And At Least One Loss Of Cooperative Breeding During The Evolutionary History Of Aphelocoma Jays, Elena Berg, Robert Aldredge, A. Peterson, John Mccormack

John E. McCormack

Efforts to identify ecological and life history factors associated with cooperative breeding have been largely unsuccessful, and interest is growing in the role of phylogenetic history in determining the distribution of this social system among lineages. In birds, cooperative breeding is distributed non-randomly among lineages, suggesting that phylogenetic inertia may play an important role in determining its distribution. The bird genus Aphelocoma has been particularly well studied because, although it is a relatively small genus, it shows broad among-lineage variation in level of cooperation. Previous analyses described an unusual unidirectional pattern of evolutionary loss of cooperation in Aphelocoma. Here, historical …

Calibrating Divergence Times On Species Tree Versus Gene Trees: Implications For Speciation History Of Aphelocoma Jays, John Mccormack, Joseph Heled, Kathleen Delaney, A. Peterson, L. Knowles

John E. McCormack

Estimates of the timing of divergence are central to testing the underlying causes of speciation. Relaxed molecular clocks and fossil calibration have improved these estimates; however, these advances are implemented in the context of gene trees, which can overestimate divergence times. Here we couple recent innovations for dating speciation events with the analytical power of species trees, where multilocus data are considered in a coalescent context. Divergence times are estimated in the bird genus Aphelocoma to test whether speciation in these jays coincided with mountain uplift or glacial cycles. Gene trees and species trees show general agreement that diversification began …

Potential For Kochia Prostrata And Perennial Grasses For Rangeland Rehabilitation Efforts In Jordan, Raed Al-Tabini, D. Bailey, B. Waldron, J. Libbin, M. Al-Oun, K. Al-Khlidi

Raed Al-Tabini

Six varieties of forage kochia [Kochia prostrata (L.) Shad.], two Atriplex shrubs native to cold deserts in the western United States, and four drought-tolerant perennial grass varieties were seeded and evaluated under arid rangeland conditions in Jordan. Varieties were seeded in December 2007 and evaluated in August 2008 and June 2009 for frequency and height at two sites in arid rangeland areas of southern and northern Jordan. Conditions were very dry with the southern site (Qurain) receiving 110 mm and 73 mm of annual precipitation, and the northern site (Tal Rimah) receiving 58 and 43 mm during the winters of …

Does Niche Divergence Accompany Allopatric Divergence In Aphelocoma Jays As Predicted Under Ecological Speciation?: Insights From Tests With Niche Models, John Mccormack, Amanda Zellmer, L. Knowles

John E. McCormack

The role of ecology in the origin of species has been the subject of long-standing interest to evolutionary biologists. New sources of spatially explicit ecological data allow for large-scale tests of whether speciation is associated with niche divergence or whether closely related species tend to be similar ecologically (niche conservatism). Because of the confounding effects of spatial autocorrelation of environmental variables, we generate null expectations for niche divergence for both an ecological-niche modeling and a multivariate approach to address the question: do allopatrically distributed taxa occupy similar niches? In a classic system for the study of niche evolution—the Aphelocoma jays—we …

Small-Scale Divergence In Egg Color Along An Elevation Gradient In The Mexican Jay (Aphelocoma Ultramarina): A Condition-Dependent Response?, John Mccormack, Elena Berg

John E. McCormack

The functional significance of bird egg color and patterning is a continuing subject of interest and debate. Extreme polymorphism in eggshell appearance is often thought to be maintained by frequency-dependent selection operating within populations. However, variation could also be explained by small-scale differentiation combined with limited migration. Here, we report the existence of extreme variation in egg color in a population of Mexican Jays (Aphelocoma ultramarina) inhabiting a steep elevation and habitat gradient within a single mountain range, the Sierra del Carmen of Coahuila, Mexico. We quantified egg color of 143 eggs from 54 nests throughout the mountain range, using …

Maximum Likelihood Estimates Of Species Trees: How Accuracy Of Phylogenetic Inference Depends Upon The Divergence History And Sampling Design, John Mccormack, Huateng Huang, L. Knowles

John E. McCormack

The understanding that gene trees are often in discord with each other and with the species trees that contain them has led researchers to methods that incorporate the inherent stochasticity of genetic processes in the phylogenetic estimation procedure. Recently developed methods for species-tree estimation that not only consider the retention and sorting of ancestral polymorphism but also quantify the actual probabilities of incomplete lineage sorting are expected to provide an improvement over earlier summary-statistic based approaches that discard much of the information content of gene trees. However, these new methods have yet to be tested on truly challenging evolutionary histories …

Landscape Genetics Of California Mule Deer (Odocoileus Hemionus): The Roles Of Ecological And Historical Factors In Generating Differentiation, Katherine Pease, Adam Freedman, John Pollinger, John Mccormack, Wolfgang Buermann, Jeff Rodzen, Jim Banks, Erin Meredith, Vernon Bleich, Robert Schaefer, Ken Jones, Robert Wayne

John E. McCormack

Landscape genetics is an emerging discipline that utilizes environmental and historical data to understand geographic patterns of genetic diversity. Niche modelling has added a new dimension to such efforts by allowing species–environmental associations to be projected into the past so that hypotheses about historical vicariance can be generated and tested independently with genetic data. However, previous approaches have primarily utilized DNA sequence data to test inferences about historical isolation and may have missed very recent episodes of environmentally mediated divergence. We type 15 microsatellite loci in California mule deer and identify five genetic groupings through a Structure analysis that are …

Mexican Jay (Aphelocoma Ultramarina), John Mccormack, L. Brown

John E. McCormack

No abstract provided.

Niche Expansion Leads To Small-Scale Adaptive Divergence Along An Elevation Gradient In A Medium-Sized Passerine Bird, John Mccormack, Thomas Smith

John E. McCormack

Niche expansion can lead to adaptive differentiation and speciation, but there are few examples from contemporary niche expansions about how this process is initiated. We assess the consequences of a niche expansion by Mexican jays (Aphelocoma ultramarina) along an elevation gradient. We predicted that jays at high elevation would have straighter bills adapted to feeding on pine cones, whereas jays at low elevation would have hooked bills adapted to feeding on acorns. We measured morphological and genetic variation of 95 adult jays and found significant differences in hook length between elevations in accordance with predictions, a pattern corroborated by analysis …

Integrating Paleoecology And Genetics Of Bird Populations In Two Sky Island Archipelagos, John Mccormack, Bonnie Bowen, Thomas Smith

John E. McCormack

Background: Genetic tests of paleoecological hypotheses have been rare, partly because recent genetic divergence is difficult to detect and time. According to fossil plant data, continuous woodland in the southwestern USA and northern Mexico became fragmented during the last 10,000 years, as warming caused cool-adapted species to retreat to high elevations. Most genetic studies of resulting 'sky islands' have either failed to detect recent divergence or have found discordant evidence for ancient divergence. We test this paleoecological hypothesis for the region with intraspecific mitochondrial DNA and microsatellite data from sky-island populations of a sedentary bird, the Mexican jay (Aphelocoma ultramarina). …

Speciation In The Highlands Of Mexico: Genetic And Phenotypic Divergence In The Mexican Jay (Aphelocoma Ultramarina), John Mccormack, A. Peterson, E. Bonaccorso, Thomas Smith

John E. McCormack

The pine-oak woodlands of the Mexican highlands harbour significant biological diversity, yet little is known about the evolutionary history of organisms inhabiting this region. We assessed genetic and phenotypic differentiation in 482 individuals representing 27 populations of the Mexican jay (Aphelocoma ultramarina) — a widespread bird species of the Mexican highlands — to test whether populations in the central and northern Mexican sierras display discrete breaks between groups, which would be consistent with a role for the different mountain chains in divergence and speciation. We found abrupt breaks in mitochondrial DNA (mtDNA; ND2 and control region) delineating four major genetic …

Producer-Scrounger Roles And Joining Based On Dominance In A Free-Living Group Of Mexican Jays (Aphelocoma Ultramarina), John Mccormack, Piotr Jablonski, Jerram Brown

John E. McCormack

While foraging, animals often exploit group members to obtain food. One way to describe this behaviour is with the producer-scrounger (PS) model, where scroungers use social interaction to obtain food discovered by producers. Mexican jays (Aphelocoma ultramarina) are a groupforaging species with a linear dominance hierarchy. We studied interactions in a free-living foraging group to determine (1) if foraging interactions can be explained with the PS model, (2) if these roles are consistent and (3) if dominance or relatedness affects joining frequency. We recorded board-flipping, eating, and joining events during sets of feeding trials. We show that Mexican jays use …

Recent Postglacial Range Expansion Drives The Rapid Diversification Of A Songbird Lineage In The Genus Junco, Borja Milá, John Mccormack, Gabriela Castañeda, Robert Wayne, Thomas Smith

John E. McCormack

Pleistocene glacial cycles are thought to have played a major role in the diversification of temperate and boreal species of North American birds. Given that coalescence times between sister taxa typically range from 0.1 to 2.0 Myr, it has been assumed that diversification occurred as populations were isolated in refugia over long periods of time, probably spanning one to several full glacial cycles. In contrast, the rapid postglacial range expansions and recolonization of northern latitudes following glacial maxima have received less attention as potential promoters of speciation. Here we report a case of extremely rapid diversification in the songbird genus …

Slate-Throated Redstarts (Myioborus Miniatus) Breeding In Maderas Del Carmen, Coahuila, Mexico, John Mccormack

John E. McCormack

The breeding range of the slate-throated redstart (Myioborus miniatus) stretches from South America to Mexico, where it extends northward along the Sierra Madre Oriental to southeastern Coahuila and along the Sierra Madre Occidental to southern Chihuahua and Sonora. We report the discovery of slate-throated redstarts breeding in the Maderas del Carmen mountains in Coahuila. This represents a range extension of approximately 400 km and is, to our knowledge, the northernmost breeding record for this species.

Precise, Highly Female-Biased Sex Ratios In A Social Spider, Leticia Avilés, John Mccormack, Asher Cutter, Todd Bukowski

John E. McCormack

It has been recognized for some time that the risk of producing maleless clutches should select for a lower than binomial variance in the sex ratio of organisms with female–biased sex ratios, small clutches and breeding groups containing the clutch of a single female. However, to date, precise sex ratios have only been reported for organisms with haplodiploid sex determination, a system which allows direct control of the sex of individual offspring. In contrast, under heterogametic sex determination chance is expected to play a crucial role in determining the sex composition of any one family, in particular when males are …