The Advantages of Obscurity: Charles Darwin's Negative Inference from the Histories of Domestic Breeds

In The Origin of Species, Charles Darwin famously accounted for the lack of fossil evidence in support of species evolution on the grounds that the fossil record is naturally incomplete. This essay examines a similar argument that Darwin applied to his analogy between natural and artificial selection: the scarcity of data about the historical backgrounds of domestic breeds was the natural by-product of an extremely gradual change process. The point was to enhance the ability of the artificial selection analogy to suggest that nature's species had undergone a similar transformation. Darwin did not depend on this negative inference alone, however, for in his writings he included whatever information he could find about the actual histories of particular breeds. A comparison with Darwin's treatment of the fossil record suggests the reasonableness of this combined use of opposite kinds of evidence to establish a single point. The comparison also suggests the unique qualities of negative inference as applied to the breeding analogy.     

The unique features of follicular T cell subsets

The germinal center (GC) reaction is critical for humoral immunity, but also contributes adversely to a variety of autoimmune diseases. While the major protective function of GCs is mediated by plasma cells and memory B cells, follicular helper T (TFH) cells represent a specialized T cell subset that provides essential help to the antigen-specific B cells in the form of membrane-bound ligands and secreted factors such as IL-21. Recent studies have revealed that TFH cells are capable of considerable functional diversity as well as possessing the ability to form memory cells. The molecular basis of this plasticity and heterogeneity is only now emerging. It has also become apparent that several other populations of follicular T cells exist, including natural killer T cells and regulatory T cells. In this review we will discuss the function of follicular T cells and interaction of these populations within the GC response.     

Assortative mating in insects: sexual selection vs. sampling artifact

In this report we analyze patterns of size-assortative mating in an insect genus by (1) describing the consistency and strength of assortative mating among populations of a species and among species of a genus, and (2) determining the role of sampling artifacts in generating this nonrandom pattern of mating. Our data consist of 18 samples of soldier beetles (8 species of the genus Chauliognathus ) from 17 sites within the southwestern United States. Of the 18 samples, just 6 exhibited significant correlations between elytron lengths of mating pairs. We show how these and other significant correlations are generated by 3 kinds of sampling artifacts: mixed-species samples, mixed-population samples, and mixed-microsite samples.     

Pilfering of stored seeds and the relative costs of scatter-hoarding versus larder-hoarding in yellow pine chipmunks

Yellow pine chipmunks ( Tamias amoenus ) scatter-hoard food during summer and autumn but must form a larder as a winter food source before winter begins. Yellow pine chipmunks do not larder-hoard large quantities of food during the summer, apparently because a summer larder could not be defended from pilferers. We tested the assumption that the rate of pilferage from an unguarded larder would be significantly greater than the rate of pilferage from surface caches (which are also unguarded by yellow pine chipmunks) during the summer and autumn. Buried plastic buckets were used as artificial nests containing larders of 1000 sunflower seeds or 200 Jeffrey pine ( Pinus jeffreyi ) seeds. The pilferage of larder contents was monitored daily and compared to pilferage of surface caches. Animals (yellow pine chipmunks and deer mice, Peromyscus maniculatus ) removed sunflower seeds from caches much faster than from larders, but caches of Jeffrey pine seeds disappeared much more slowly than pine seeds in larders. Further, animals removed pine seeds from larders more quickly than they did sunflower seeds from larders. The difference between seed species was probably because sunflower seeds have much stronger odors, which rodents readily detect, and because chipmunks prefer pine seeds over sunflower seeds. Yellow pine chipmunks must spend a considerable portion of their time foraging for seeds and may not be able to defend a large larder during summer.     

Relict occurrence of three "American" Scolytidae (Coleoptera) in Asia

The first non-American representatives of the bark beetle genus Pseudopityophthorus , of the subtribe Corthylina (Corthylini), and of the Ips concinnus species group are named. All are apparently relicts of an early faunal exchange with North America. The new taxa include: Gnatharus , new genus, and its type-species Gnatharus tibetensis , new species (Tibet); Xenophthorus , new subgenus, and its type-species Pseudopityophthorus (Xenophthorus) peregrinus , new species (Tibet), and Ips orientalis , new species (Tibet, China). The intercontinental exchange of other taxa in Scolytidae are also mentioned.     

Cicuta bulbifera L. (Umbelliferae) in Alaska

Cited are distribution records for Alaska of Cicuta bulbifera L. It was discovered growing in the Nowitna National Wildlife Refuge in north central Alaska in 1984 and again in 1987. An earlier record is also known from near Fairbanks.     

New synonymy and new species of American bark beetles (Coleoptera: Scolytidae)

New replacement names for junior homonyms are presented as follows; Acanthotomicus tuberculifer for A. (Mimips) tuberculatus Schedl 1967, Chactoptelius versicolor for C. (Acrantus) tricolor Schedl 1958, Hylesinopsis angolanus for H. (Aridiamerus) angolensis Schedl 1982, Hylurgops tuberculifer for H. tuberculatus Schedl 1947, Pseudothysanoes spinatifer for P. spinatus Wood 1956, Scolytodes aterrimus for S. ater (Hylocurosoma atrum Eggers) 1941, Scolytodes boliviensis for S. (Prionosceles) bolivianus Eggers 1928, Scolytodes brasiliensis for S. (Hexacolus) brasiliensis Schedl 1935, Scolytodes discriminatus for S. discedens Eggers 1943, Scolytodes elongatissimus for S. elongatus (Hylocurosoma elongatum Eggers) 1943, Scolytodes gennaens for S. genialis Wood 1978, Scolytodes laevigatulus for S. (Hexacolus) laevigatus Schedl 1962, Scolytodes laevicorpus for S. laevis (Hylocurosoma laeve Eggers) 1943, Scolytodes majus for S. major Eggers 1943, Scolytodes medialis for S. medius Eggers 1943. New synonymy is reported for Dactylipalpus niger Schedl (= D. unctus Wood), Dendroctonus armandi Tsai & Li (= D. prosorovi Kurenzov & Kononov), Sinophloeus porter Brèthes (= S. destructor Eggers). Species new to science include: Acacicis bicornis (New Guinea), Acacicis zeylanicus (Sri Lanka), Sphaerotrypes bengalensis (India), Sphaerotrypes costatus (North Andaman Island), Sphaerotrypes cristatus (Sri Lanka), Sphaerotrypes pentacme (Burma), Sphaerotrypes ranasinghei (Sri Lanka), Xylechinus ougeiniac (India), Xylechinus padus (India).     

Aquatic birds of the White River, Uintah County, Utah

Abundance, seasonal use, and species composition of waterfowl and other aquatic birds are described along a 32.8 km stretch of the White River, Uintah County, Utah, at the site of the proposed White River Dam. Fourteen species of waterfowl and eight other species of aquatic birds were recorded. Waterfowl populations along the river were highest in April, but densities were much lower than on lakes and reservoirs at nearby Ouray National Wildlife Refuge.         

Soil properties associated with vegetation patches in a Pinus ponderosa —bunchgrass mosaic

Since Euro-American settlement, fire exclusion and other factors have dramatically altered interior western coniferous forests. Once open and parklike, present-day structure in many southwestern Pinus ponderosa forests consists of dense stands of young, small-diameter trees, with small patches of larger, old trees, and relict open bunchgrass areas. Our objectives were to assess differences in soil properties associated with these different vegetation patches. We examined soil morphological characteristics, pH, organic C concentration, total N concentration, C:N ratio, and phytolith concentration from profiles within 6 transects (18 soil pedons) crossing patches of dense stands of small diameter trees, patches of old-growth trees, and open grassy areas. Results indicate that old-growth plots had significantly lower A horizon pH and thicker O horizons than grass plots. In general, we found vegetation patches had statistically similar C and N concentrations and C:N ratios for A and B horizons; however, C in the A horizon was positively correlated with O horizon accumulation ( r 2 = 0.79). Greater accumulation of organic C in the A horizon of forested areas contrasts with commonly reported results from mesic, mid-continental prairie-forest ecosystems but is typical for many arid, semiarid, and humid savanna ecosystems. Phytolith concentration was similar among old-growth pine, dense younger pine, and open grassy plots; the lack of a spatial pattern in phytolith distribution could indicate that grass cover was more spatially continuous in the past. Additionally, this interpretation is consistent with current theories regarding historical vegetation change in these forests.