The estimation of phylogenetic divergence times from sequence data is an important component of many molecular evolutionary studies. There is now a general appreciation that the procedure of divergence dating is considerably more complex than that initially described in the 1960s by Zuckerkandl and Pauling (1962, 1965). In particular, there has been much critical attention toward the assumption of a global molecular clock, resulting in the development of increasingly sophisticated techniques for inferring divergence times from sequence data. In response to the documentation of widespread departures from clocklike behavior, a variety of local- and relaxed-clock methods have been proposed and implemented. Local-clock methods permit different molecular clocks in different parts of the phylogenetic tree, thereby retaining the advantages of the classical molecular clock while casting off the restrictive assumption of a single, global rate of substitution (Rambaut and Bromham 1998; Yoder and Yang 2000).

Accounting for calibration uncertainty in phylogenetic estimation of evolutionary divergence times

The traditional trophic cascades model is based on consumer-resource interactions at each link in a food chain. However, trophic-level interactions, such as mesocarnivore release resulting from intraguild predation, may also be important mediators of cascades. From September 2001 to August 2004, we used spatial and seasonal heterogeneity in wolf distribution and abundance in the southern Greater Yellowstone Ecosystem to evaluate whether mesopredator release of coyotes (Canis latrans), resulting from the extirpation of wolves (Canis lupus), accounts for high rates of coyote predation on pronghorn (Antilocapra americana) fawns observed in some areas. Results of this ecological perturbation in wolf densities, coyote densities, and pronghorn neonatal survival at wolf-free and wolf-abundant sites support the existence of a species-level trophic cascade. That wolves precipitated a trophic cascade was evidenced by fawn survival rates that were four-fold higher at sites used by wolves. A negative correlation between coyote and wolf densities supports the hypothesis that interspecific interactions between the two species facilitated the difference in fawn survival. Whereas densities of resident coyotes were similar between wolf-free and wolf-abundant sites, the abundance of transient coyotes was significantly lower in areas used by wolves. Thus, differential effects of wolves on solitary coyotes may be an important mechanism by which wolves limit coyote densities. Our results support the hypothesis that mesopredator release of coyotes contributes to high rates of coyote predation on pronghorn fawns, and demonstrate the importance of alternative food web pathways in structuring the dynamics of terrestrial systems.

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Indirect effects and traditional trophic cascades: a test involving wolves, coyotes, and pronghorn

Evaporative light scattering detector (ELSD) is a quasi-universal detector for liquid, countercurrent and supercritical fluid chromatography, since it can detect any analyte less volatile than the mobile phase. Operation principle mainly consists of three successive processes: nebulization of the chromatographic effluent; evaporation of the mobile phase; measurement of the scattered light. After 20 years of development, its usage appears significant advantages and potentialities as well as several limitations. In this paper, operation principles, technological innovations, methodological approaches, chemometrics, application areas (pharmaceuticals, foods and beverages, natural products, biological samples and polymers), potentialities and limitations of ELSD are thoroughly reviewed. A bibliography of 83 representative references is given.

Twenty Years of Evaporative Light Scattering Detection

Large mammals are thought to evolve to be smaller on islands, whereas small mammals grow larger. A negative correlation between relative size of island individuals and body mass is termed the “island rule.” Several mechanisms—mainly competitive release, resource limitation, dispersal ability, and lighter predation pressure on islands, as well as a general physiological advantage of modal size—have been advanced to explain this pattern. We measured skulls and teeth of terrestrial members of the order Carnivora in order to analyze patterns of body size evolution between insular populations and their near mainland conspecifics. No correlations were found between the size ratios of insular/mainland carnivore species and body mass. Only little support for the island rule is found when individual populations rather than species are considered. Our data are at odds with those advanced in support of theories of optimal body size. Carnivore size is subjected to a host of selective pressures that do not v...

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Body size of insular carnivores: little support for the island rule.

Neospora caninum in wildlife.

We studied effects of recolonizing wolves (Canis lupus) in the North Fork of the Flathead area of northwestern Montana on the diets of coyotes (C. latrans) from 1994 to 1997. Wolf and coyote diets differed in frequency of occurrence of prey species during 3 of the 4 summers and winters (P 45 kg) prey species and coyotes, small (<2 kg) prey (P < 0.001). Wolves selected a larger proportion of adults (P < 0.001), whereas coyotes selected a larger proportion of juveniles (P < 0.001) during summer. We believe that differential use of food resources facilitates coexistence of wolves and coyotes in the North Fork of the Flathe...

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Dietary overlap between wolves and coyotes in northwestern montana

Successful coexistence of sympatric canid species often relies on the subdominant species' ability to reduce competition through the differential selection of niche space. Information regarding the process of niche selection and its effect on the structure of canid communities in the Great Basin Desert is unavailable. From Dec. 1999 to Aug. 2001, we quantified the spatial, dietary and temporal resource overlap of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) on the U.S. Army Dugway Proving Ground, Utah. Kit foxes and coyotes demonstrated substantial levels of spatial, temporal and dietary overlap. However, where the two species had overlapping home ranges, space use within the home range differed between the two species, with kit foxes using vegetative and landscape ruggedness characteristics not regularly used by coyotes. Although there was little evidence of seasonal change in either canid's use of habitat, in some areas kit foxes made nightly movements to more productive habitats with moderate ruggedness. Regardless of spatial partitioning, incidents of interference competition were high; 56% of known kit fox deaths were attributed to coyotes. In our study, high levels of temporal and dietary overlap, kit fox movement from extreme to moderate topography during foraging and selection for abundant cover demonstrated competitive pressures exerted on the kit fox population by the sympatric coyote population.

https://www.jstor.org/stable/info/20491376

Niche Overlap and Resource Partitioning Between Sympatric Kit Foxes and Coyotes in the Great Basin Desert of Western Utah

Variation in kit fox (Vulpes macrotis) population parameters can be influenced by vegetative cover and the distribution and abundance of other predator and prey species. Dramatic changes to Great Basin Desert habitats, which can potentially impact mammalian species, have occurred in some areas in Utah. We examined kit fox demographics and prey populations from 1999 to 2001 on Dugway Proving Ground (DPG), a U.S. Army facility in Utah, and compared some parameters to historical levels (1956–1958–1966–1969). Adult survival rates were fairly consistent between 1999 and 2000 and between 1999 and 2001; however, survival was greater in 2001 than in 2000. Reproductive rates ranged from 1.0 to 3.8 pups per female in 1999–2000 and were similar to historical numbers (1.0–4.2 pups per female). We found a decrease in pre-whelping kit fox density from the 1960s (0.12 foxes · km−2) to 1999–2001 (0.04 foxes · km−2); however, densities were similar between the current study and the 1950s (0.08 foxes · km−2). Usin...

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Changes in kit fox–coyote–prey relationships in the great basin desert, utah

We examined the ecological and physical characteristics of den sites for 13 adult kit fox (Vulpes macrotis) in western Utah from December 1998 to February 2001 We also compared current and historical den distribution among habitat types The number of den sites used was not influenced by home-range size (P = 011) or season (P = 040), but was influenced by geographical area Home-range size was smallest (P = 0007) and the number of dens used was greatest (P = 0009) in mountainous areas Ecological and physical characteristics of single-use dens (n = 30) were compared with those of multiple-use (n = 53) and natal dens (n = 8) Characteristics that differed between den types included number of entrances (P = 00001), diameter of entrances (P = 0003), and height of vegetation along transects (P = 00001) Natal den entrance azimuths were weighted towards a northwesterly aspect (P = 00022); however, single- and multiple-use den exits appeared to be randomly distributed Historical changes in kit fox den

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Characteristics of current and historical kit fox (Vulpes macrotis) dens in the Great Basin Desert

Many studies determine which habitat components are important to animals and the extent their use may overlap with competitive species. However, such studies are often undertaken after populations are in decline or under interspecific stress. Since habitat selection is not independent of interspecific stress, quantifying an animal's current landscape use could be misleading if the species distribution is suboptimal. We present an alternative approach by modeling the predicted distributions of two sympatric species on the landscape using dietary preferences and prey distribution. We compared the observed habitat use of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) against their predicted distribution. Data included locations of kit foxes and coyotes, carnivore scat transects, and seasonal prey surveys. Although habitats demonstrated heterogeneity with respect to prey resources, only coyotes showed habitat use designed to maximize access to prey. In contrast, kit foxes used habitats which did not align closely with prey resources. Instead, habitat use by kit foxes represented spatial and behavioral strategies designed to minimize spatial overlap with coyotes while maximizing access to resources. Data on the distribution of prey, their dietary importance, and the species-specific disparities between predicted and observed habitat distributions supports a mechanism by which kit fox distribution is derived from intense competitive interactions with coyotes.

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Wendy M. Arjo

Papers

Dietary overlap between wolves and coyotes in northwestern montana

Niche Overlap and Resource Partitioning Between Sympatric Kit Foxes and Coyotes in the Great Basin Desert of Western Utah

Changes in kit fox–coyote–prey relationships in the great basin desert, utah

Characteristics of current and historical kit fox (Vulpes macrotis) dens in the Great Basin Desert

Effects of Intraguild Predation: Evaluating Resource Competition between Two Canid Species with Apparent Niche Separation