Glacial cycles promote greater dispersal, which can help explain larger clutch sizes, in north temperate birds

Earth’s glacial history and patterns in the life history traits of the planet’s avifauna suggest the following interpretations of how recent geological history has affected these key characteristics of the biota: 1) Increased colonizing ability has been an important advantage of increased dispersal, and life history strategies are better categorized by dispersive colonizing ability than by their intrinsic growth rates; 2) Birds of the North Temperate Zone show a greater tendency to disperse, and they disperse farther, than tropical or south temperate birds; 3) Habitat changes associated with glacial advance and retreat selected for high dispersal ability, particularly in the North; and 4) Selection for greater dispersal throughout the unstable Pleistocene has also resulted in other well-recognized life history contrasts, especially larger clutch sizes in birds of North Temperate areas

Agroforests as Model Systems for Tropical Ecology1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117179/1/ecy2008894913.pd

Common Garden Experiment Reveals Genetic Control of Phenotypic Divergence between Swamp Sparrow Subspecies That Lack Divergence in Neutral Genotypes

Adaptive divergence between populations in the face of strong selection on key traits can lead to morphological divergence between populations without concomitant divergence in neutral DNA. Thus, the practice of identifying genetically distinct populations based on divergence in neutral DNA may lead to a taxonomy that ignores evolutionarily important, rapidly evolving, locally-adapted populations. Providing evidence for a genetic basis of morphological divergence between rapidly evolving populations that lack divergence in selectively neutral DNA will not only inform conservation efforts but also provide insight into the mechanisms of the early processes of speciation. The coastal plain swamp sparrow, a recent colonist of tidal marsh habitat, differs from conspecific populations in a variety of phenotypic traits yet remains undifferentiated in neutral DNA.Here we use an experimental approach to demonstrate that phenotypic divergence between ecologically separated populations of swamp sparrows is the result of local adaptation despite the lack of divergence in neutral DNA. We find that morphological (bill size and plumage coloration) and life history (reproductive effort) differences observed between wild populations were maintained in laboratory raised individuals suggesting genetic divergence of fitness related traits.Our results support the hypothesis that phenotypic divergence in swamps sparrows is the result of genetic differentiation, and demonstrate that adaptive traits have evolved more rapidly than neutral DNA in these ecologically divergent populations that may be in the early stages of speciation. Thus, identifying evolutionarily important populations based on divergence in selectively neutral DNA could miss an important level of biodiversity and mislead conservation efforts

Avian Foraging Behavior in Two Different Types of Coffee Agroecosystem in Chiapas, Mexico

This study describes the foraging ecology of birds during summer and winter in two different types of coffee agroecosystems in Chiapas, Mexico. Avian foraging behavior is documented in two agroecosystems of differing management intensity, structurally similar but with different levels of floristic diversity, during summer and winter seasons. The distribution of tree species used by birds was more even, and birds used a greater diversity of tree species, in the more diverse coffee shade system. Much of the variation in resource use derived from shifts in the use of flowers and fruit, highlighting the importance in resource phenology for birds. Insectivory was more frequent in winter than summer for the coffee layer, and in summer for the shade layer. Given the vegetative structural similarity of the two coffee agroecosystems included in this study, floristic differences probably accounted for much of the difference in the bird communities between the management systems, especially given the strong seasonal response to flowering and fruiting. This work suggests that plentiful and diverse food resources associated with the high diversity of plant species may facilitate coexistence of the high number of bird species found in shade-grown coffee agroecosystems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72797/1/j.1744-7429.2006.00248.x.pd

Avian Conservation Practices Strengthen Ecosystem Services in California Vineyards

Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services

Comet 17P/Holmes in Outburst: The Near Infrared Spectrum

Jupiter family comet 17P/Holmes underwent a remarkable outburst on UT 2007 Oct. 24, in which the integrated brightness abruptly increased by about a factor of a million.We obtained near infrared (0.8 - 4.2 micron) spectra of 17P/Holmes on UT 2007 Oct. 27, 28 and 31, using the 3.0-m NASA Infrared Telescope Facility (IRTF) atop Mauna Kea. Two broad absorption bands were found in the reflectance spectra with centers (at 2 micron and 3 micron, respectively) and overall shapes consistent with the presence of water ice grains in the coma. Synthetic mixing models of these bands suggest an origin in cold ice grains of micron size. Curiously, though, the expected 1.5 micron band of water ice was not detected in our data, an observation for which we have no explanation. Simultaneously, excess thermal emission in the spectra at wavelengths beyond 3.2 micron has a color temperature of 360 +/- 40 K (corresponding to a superheat factor of ~ 2.0 +/- 0.2 at 2.45 AU). This is too hot for these grains to be icy. The detection of both water ice spectral features and short-wavelength thermal emission suggests that the coma of 17P/Holmes has two components (hot, refractory dust and cold ice grains) which are not in thermal contact. A similarity to grains ejected into the coma of 9P/Tempel 1 by the Deep Impact spacecraft is noted.Comment: 27 pages, 11 figures, accepted for publication in A

Impacts of major predators on tropical agroforest arthropods: comparisons within and across taxa

In food web studies, taxonomically unrelated predators are often grouped into trophic levels regardless of their relative importance on prey assemblages, multiple predator effects, or interactions such as omnivory. Ants and birds are important predators likely to differentially shape arthropod assemblages, but no studies have compared their effects on a shared prey base. In two separate studies, we excluded birds and ants from branches of a canopy tree ( Inga micheliana ) in a coffee farm in Mexico for 2 months in the dry and wet seasons of 2002. We investigated changes in arthropod densities with and without predation pressure from (1) birds and (2) ant assemblages dominated by one of two ant species ( Azteca instabilis and Camponotus senex ). We first analyzed individual effects of each predator (birds, Azteca instabilis , and C. senex ) then used a per day effect metric to compare differences in effects across (birds vs ants) and within predator taxa (the two ant species). Individually, birds reduced densities of total and large arthropods and some arthropod orders (e. g., spiders, beetles, roaches) in both seasons. Azteca instabilis did not significantly affect arthropods (total, small, large or specific orders). Camponotus senex , however, tended to remove arthropods (total, small), especially in the dry season, and affected arthropod densities of some orders both positively and negatively. Predators greatly differed in their effects on Inga arthropods (for all, small, large, and individual orders of arthropods) both in sign (±) and magnitudes of effects. Birds had stronger negative effects on arthropods than ants and the two dominant ant species had stronger effects on arthropods in different seasons. Our results show that aggregating taxonomically related and unrelated predators into trophic levels without prior experimental data quantifying the sign and strengths of effects may lead to a misrepresentation of food web interactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47705/1/442_2004_Article_1561.pd

Classical kinematics for Lorentz violation

Classical point-particle relativistic lagrangians are constructed that generate the momentum-velocity and dispersion relations for quantum wave packets in Lorentz-violating effective field theory.Comment: 6 pages, accepted for publication in Physics Letters