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Dominant frequency is an important feature of cricket song, as it can be used for species recognition and mate choice. The dominant frequency usually ranges from 2 to 8 kHz and corresponds to the fundamental frequency of the song. In preliminary studies we documented high-frequency songs in the subfamily Eneopterinae. To analyse this phenomenon further, we investigate the spectral properties of these cricket songs. Based on the analysis of the frequency spectra in reference to phylogeny, we show that a shift of dominant frequency from the fundamental toward the second or the third harmonic of the song occurred in the Lebinthini tribe. In this clade the upper harmonics (second or third) become the most powerful frequencies of the song. From an evolutionary point of view, we document a case of convergence toward high-frequency calling between species of Eneoptera Burmeister, 1838, which emit alternatively low and high fundamental frequencies, and the Lebinthini, which emit high frequencies using upper harmonics. Functional hypotheses are discussed to explain how these high frequencies could be produced. [ABSTRACT FROM AUTHOR]

Many species of gekkotan lizards possess adhesive subdigital pads that allow them to adhere to, and move easily on, a wide variety of surfaces. However, although the mechanism of adhesion and the potential adhesive capacity of this system have been extensively studied, the adaptive value of these structures and their deployment in natural situations have rarely been examined. The maximal adhesive capacity of gekkotan setal fields has been shown to greatly exceed the force needed to support the body. This high adhesive potential is likely an adaptation for movement on the natural surfaces that these lizards encounter in their environment. Natural surfaces may be rough, undulant, and unpredictable, and provide only limited, patchy areas with which adhesive structures can make contact. Here we examine the microtopography of rock surfaces used by a southern African species of gecko of the genus Rhoptropus Peters, 1869, and compare this to the form, configuration, compliance, and functional morphology of the setal fields of this species. Our results demonstrate that the structure and topology of natural surfaces are important factors in understanding the design of subdigital pads, and provide insight into the evolution of the adhesive system of gekkonid lizards and its adaptive value on topographically unpredictable surfaces. [ABSTRACT FROM AUTHOR]

Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic (Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic (Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increased over lactation, and A. gazella pups approached adult body shape faster than did A. tropicalis pups. Our results indicate that preweaning growth is associated with significant changes in body shape, involving the acquisition of a longer, more slender body with larger foreflippers in A. gazella. These differences suggest that A. gazella pups are physically more mature at approximately 100 d of age (close to weaning age) than A. tropicalis pups of the same age. [ABSTRACT FROM AUTHOR]

According to the hypothesis of parasite-mediated sexual selection, for a communication system to work reliably, parasites should reduce the showiness of sexual signals of their host. In this study, we examined whether the expression of breeding coloration in free-ranging adult European Green Lizards (Lacerta viridis (Laurenti, 1768)) is linked with infestation by their common ectoparasite Ixodes ricinus (L., 1758) (Acari: Ixodidae). We found that tick infestation was higher in males than in females. Males showing relatively heavier body for their tail length (predominantly males with regenerated tails) and relatively thinner tail base experienced higher infestation rates. In turn, relatively heavier females for their snout–vent length were less tick infested. Although some components of throat and chest coloration varied significantly with relative tail length, tail-base thickness, body mass, and head size, a measure of male throat and female chest color saturation seemed independent of lizard morphology. After correcting for the effects of morphology on skin coloration and tick load, the saturation of blue throat color in male lizards decreased with increasing level of tick infestation. In contrast, yellow chest color saturation increased with residual tick numbers in females. Considering presumably different signaling functions of male and female lizard coloration, our work suggests that tick infestation might represent a handicap for Green Lizards. [ABSTRACT FROM AUTHOR]

We monitored foraging effort of radio-tagged Surf Scoters (Melanitta perspicillata (L., 1758)) in three different habitats: (1) shellfish farm structures with high densities of mussels and strong seasonal prey depletion, (2) soft-bottom clam beds with more stable but less available prey, and (3) rocky intertidal beds with moderate mussel densities and depletion rates. We predicted that foraging effort would vary uniquely by habitat, with effort increasing more where depletion was strongest. However, variation in both hourly and daily foraging efforts was best explained by date only. Effort per hour was lowest in early December (presumably owing to very high prey abundance), increased until mid-February as prey declined, and then decreased again in March (probably owing to increased daylight time for foraging). Foraging effort estimated over a full day increased steadily from December to March as prey were depleted. Temporal patterns of effort did not vary by habitat after accounting for seasonal effects. Instead of increasing foraging effort in habitats with strong depletion, Surf Scoters redistributed to habitats with lower degrees of prey reduction as the season progressed. We suggest that Surf Scoters respond to variation in prey by adjusting both foraging effort and habitat selection as the prey landscape changes. [ABSTRACT FROM AUTHOR]

The distribution of freshwater mussels Pyganodon Crosse and P. Fischer, 1894 traditionally inferred from morphological characters was validated by a genetic characterization of the genus within the Quebec peninsula. Individuals were identified by comparing the sequences from the female mitochondrial genome (COI and 16S) with those of reference individuals, while hybridization was assessed with male mitochondrial (COI and COII) and nuclear genomes (ITS1 and ITS2). The results confirmed most of the previous morphological identifications but revealed unexpected results. Both male and female mitochondrial genomes support the distinction between Pyganodon fragilis (Lamarck, 1819) and Pyganodon cataracta (Say, 1817). However, only one lineage of Pyganodon grandis (Say, 1829), instead of the two expected, was detected in the sampled area. The genetic survey also revealed the presence of two unidentified Pyganodon lineages, previously unreported within the Quebec peninsula. These extremely rare lineages harbour the signature of ancestral hybridizations. Finally, recent divergence and hybridizations make shell characters only partially efficient in discriminating Pyganodon lineages. [ABSTRACT FROM AUTHOR]

Stable isotopes measured in keratinized tissues like hair or hoof have proven to be a useful tool for reconstructing the dietary history of animals with a weekly to daily resolution. Quantitative reconstruction of dietary preferences requires a precise estimate of tissue turnover by means of controlled feeding experiments. We determined the turnover rates of carbon in hoof and tail hair of growing steers (Bos taurus L., 1758) fed a C3-based diet, followed by a C4-based diet, for 168 d. As with horses, turnover in steer hair was successfully described by a three-pool modelling approach, with apparent half-lives of 1.7, 7.7, and 69.1 d for each of the pools, each contributing 53%, 20%, and 28% of the total signal, respectively. Two pools only were identified in bovine hoof, which recorded the diet switch more slowly than hair with a reduction in the amplitude of short-term isotope changes. We interpreted this result as a sampling artefact and found that the hooves reflected the same pools as the hair if growth geometry is taken into account. The model parameters defined in this study allowed us to quantitatively reconstruct previous diets of steers of different breeds and individual history with a precision of ±1‰. [ABSTRACT FROM AUTHOR]

River otters (Lontra canadensis (Schreber, 1777)) and beavers (Castor canadensis Kuhl, 1820) are semi-aquatic mammals that can occur sympatrically in freshwater ecosystems of North America, including beaver ponds. Although little research has been done on the relationship between these species, it has been described as commensal. Relatively little is known about what pond characteristics potentially influence otter use. During the summer of 2004, we documented otter activity signs (i.e., feces) at 56 beaver ponds located in Kouchibouguac National Park of Canada, along the east coast of New Brunswick. We sought to identify which of 16 variables describing pond attributes were related to otter use. Otter activity at beaver ponds was positively associated with beaver presence, pond size, and vegetation cover. We discuss how these pond characteristics can benefit otters in terms of two key habitat needs, availability of prey and shelter. Our results are a first indication that the source–sink dynamic of beavers, whereby ponds are created, expanded, and abandoned, will create a mosaic of ponds that ultimately influences the river otter’s own pattern of habitat use and distribution. [ABSTRACT FROM AUTHOR]

White-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) are now common in many urban environments throughout their geographic range. Yet, how male and female deer in the urban environment associate, behave socially, and the evolutionary implications of that behavior remains unstudied. We examined predictions of the predation risk and the social factor hypotheses to explain intersexual grouping patterns and social behavior observed in white-tailed deer inhabiting the small city of San Marcos (population size ~45 000) in central Texas. Two routes were surveyed weekly from a vehicle at dawn and dusk for 1 year. Group size, composition, distance to vehicle, and alarm state of deer to the vehicle were recorded. Focal animal sampling was used to measure the time males and females spent and number of aggressions within one body length of each other when in groups. Female-only groups were most prevalent year round followed by mixed-sex groups, which increased in prevalence in summer and during the mating season. Alarm state was weakly related to group size but not to group composition. Males were farther apart and more aggressive than females in groups. Proportion of males in mixed-sex groups declined with increased group size. Intersexual patterns of grouping and social behavior of urban deer supported the social factor hypothesis but not the predation risk hypothesis. [ABSTRACT FROM AUTHOR]

Animal-unit equivalences needed for joint-stocking calculations of ungulates are rarely studied because of difficulties deriving accurate estimates of forage intake. We used indigestible internal and external markers (double n-alkane ratio) to determine animal-unit equivalence of bison (Bison bison (L., 1758)), wapiti (Cervus elaphus canadensis L., 1758), and mule deer (Odocoileus hemionus (Rafinesque, 1817)) in the aspen parkland of east-central Alberta. We hypothesized that dry matter intake would differ among species in absolute terms (kg·day–1) but not when expressed as percent body mass (%BM) or when related to metabolic mass (g·kg–1·day–1 BM0.75). We administered slow-release n-alkane capsules to 12 bison, 3 wapiti, and 11 mule deer and released them into separate 3–7 ha paddocks during summer and fall. Intake of dry matter by bison, wapiti, and mule deer differed significantly among species when expressed as total intake (p = 0.009) and %BM (p = 0.014) but not when related to metabolic mass (p = 0.237). Dry matter intake related to metabolic mass did not differ between bison and mule deer in any comparison despite a 6.8-fold difference in body size, suggesting that intake scales to metabolic mass, and is the preferred expression of animal-unit equivalents. [ABSTRACT FROM AUTHOR]

False killer whales (Pseudorca crassidens (Owen, 1846)) are incidentally taken in the North Pacific pelagic long-line fishery, but little is known about their population structure to assess the impact of these takes. Using mitochondrial DNA (mtDNA) control region sequence data, we quantified genetic variation for the species and tested for genetic differentiation among geographic strata. Our data set of 124 samples included 115 skin-biopsy samples collected from false killer whales inhabiting the eastern North Pacific Ocean (ENP), and nine samples collected from animals sampled at sea or on the beach in the western North Pacific, Indian, and Atlantic oceans. Twenty-four (24) haplotypes were identified, and nucleotide diversity was low (π = 0.37%) but comparable with that of closely related species. Phylogeographic concordance in the distribution of haplotypes was revealed and a demographically isolated population of false killer whales associated with the main Hawaiian islands was identified (ΦST = 0.47, p < 0.0001). This result supports recognition of the existing management unit, which has geo-political boundaries corresponding to the USA’s exclusive economic zone (EEZ) of Hawai‘i. However, a small number of animals sampled within the EEZ but away from the near-shore island area, which is defined as <25 nautical miles (1 nautical mile = 1.852 km) from shore, had haplotypes that were the same or closely related to those found elsewhere in the ENP, which suggests that there may be a second management unit within the Hawaiian EEZ. Biologically meaningful boundaries for the population(s) cannot be identified until we better understand the distribution and ecology of false killer whales. [ABSTRACT FROM AUTHOR]

Echolocation calls of most bats are emitted at high intensities and subject to eavesdropping by nearby conspecifics. Bats may be especially attentive to “feeding buzz” calls, which are emitted immediately before attack on airborne insects and indicate the potential presence of prey in the nearby area. Although previous work has shown that some species are attracted to feeding buzzes, these studies did not provide a well-controlled test of eavesdropping, as comparisons were made between responses to natural and altered signals (e.g., forward versus backward broadcasts of calls). In this study, I assessed the importance of feeding buzzes by conducting playbacks of controlled echolocation stimuli. I presented free-flying Brazilian free-tailed bats, Tadarida brasiliensis (I. Geoffroy, 1824), with echolocation call sequences in which feeding buzz calls were either present or absent, as well as a silence control. I determined levels of bat activity by counting the number of echolocation calls and bat passes recorded in the presence of each stimulus, and found significantly greater bat activity in response to broadcasts that contained feeding buzzes than to broadcasts without feeding buzzes or to the silence control. These results indicate that bats are especially attentive to conspecific feeding buzz calls and that eavesdropping may allow a bat to more readily locate rich patches of insect prey. [ABSTRACT FROM AUTHOR]

We developed an innovative method for estimating human impacts on animal species by measuring changes in feeding behaviour. We illustrate our approach with a study of the effect of vegetation control in a power-line right-of-way (ROW) passing through essential winter habitat of white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) at the northern limit of their range. We used giving-up densitiy (GUD; i.e., the amount of food left behind when an animal stops foraging in a patch) to evaluate, in one deer yard, if the loss of forest shelter caused by the power-line installation had a greater effect on deer than the gain of food regenerated in the cleared area. We used GUDs to compare deer estimate of habitat quality in the ROW and in the forest. Our results suggest that the ROW had a negative impact on deer. GUDs were lower in the forest compared with the ROW. Either increased metabolic costs or increased predation risk in the ROW, apparently the latter, lead deer to abandon more food in the ROW than elsewhere. Higher GUDs were strongly correlated with greater snow depth in the ROW. Deer preferred habitats at the edge of the ROW where food and cover were both available. [ABSTRACT FROM AUTHOR]

Autotomy (self-amputation) of appendages and subsequent regeneration is common to many taxa. These processes are known to affect foraging abilities, growth, and development time in many taxa. However, little is known about their effects in arachnids. We addressed the effects of autotomy and regeneration on body condition, growth (size and mass), and development time (molt interval) for the wolf spider Schizocosa ocreata (Hentz, 1844) in the field and laboratory. Frequency of autotomy in the field was high (11%–19%). Field-caught individuals with missing or regenerating legs had significantly lower body size, mass, and condition. To test the effects of regeneration on size, mass, and molt interval in the laboratory, we induced autotomy of one or both forelegs. Spiders regenerating two legs had reduced molt intervals, were smaller, and weighed less than spiders that were intact or regenerating one leg. Field-caught spiders that had undergone autotomy and regeneration in the laboratory exhibited reduced size, mass, and molt interval. In contrast, laboratory-reared spiders exhibited increased molt intervals but no difference in mass after regeneration. These results reveal that limb loss via autotomy is common (but potentially costly) in S. ocreata, and that environmentally mediated trade-offs between growth and development time may occur during regeneration. [ABSTRACT FROM AUTHOR]

Geographic variation indicating local adaptation, as well as its quantitative genetic basis, is commonly investigated in common garden experiments in the laboratory. However, the applicability of laboratory results to the complex conditions experienced by populations in the wild may be limited. Our previous laboratory experiments showed maternally determined local adaptation in embryonic acid-stress tolerance (viz. survival) of the moor frog, Rana arvalis Nilsson, 1842. Here we tested whether this laboratory finding holds even when embryos are exposed to acid stress in the wild. We conducted reciprocal crosses between an acid-origin population and a neutral-origin population of R. arvalis and transplanted the embryos to an acid site (pH ~4) in the field. Embryonic survival was much lower in the field experiment than in previous laboratory experiments, but, consistent with laboratory work, embryos from acid-origin females had threefold higher survival than embryos from neutral-origin females. These results suggest that laboratory tests can provide appropriate estimates of among population variation, as well as the quantitative genetic basis of acid-stress tolerance in amphibians. [ABSTRACT FROM AUTHOR]

Wildfire, ubiquitous and recurring over thousands of years, is the most important natural disturbance in northern coniferous forest. Accordingly, forest fires may exert a strong influence on the structure and functioning of small-mammal communities. We compared the composition of rodent and shrew communities in burned and unburned patches of a Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) – western larch (Larix occidentalis Nutt.) forest in western Montana, USA. Trapping was conducted during two consecutive summers after a wildfire. Four trapping sites were sampled in areas that burned at high severity and two in unburned forest. Small-mammal communities in burned sites were characterized by strong numerical dominance of deer mice (Peromyscus maniculatus (Wagner, 1845)) and greatly reduced proportion of southern red-backed voles (Clethrionomys gapperi (Vigors, 1830)) and red-toothed shrews (genus Sorex L., 1758). Relatively rare species such as northern flying squirrels (Glaucomys sabrinus (Shaw, 1801)) and bushy-tailed woodrats (Neotoma cinerea (Ord, 1815)) were largely restricted to unburned areas. The numbers of chipmunks (genus Tamias Illiger, 1811) were similar in burned and unburned areas. Rodent diversity was higher in unburned forest, but only during the 1st year after fire. Overall, the fire shifted small-mammal communities away from more specialized red-backed voles and shrews and towards greater abundance of generalist deer mice. [ABSTRACT FROM AUTHOR]

Organisms may become adapted to disturbances when these disturbances occur periodically and at intermediate intensity. To investigate the effects of flood suppression, this study compared diet and competition of semi-aquatic snakes during flood (2000–2001) and no flood (2003–2005) years. Three natricine species, Nerodia erythrogaster (Forster in Bossu, 1771), Nerodia fasciata (L., 1766), and Thamnophis proximus (Say in James, 1823), were palpated for prey items in an east Texas floodplain under both conditions. Prey items were classified as crayfish, salamanders, anurans, or fish. Simpson’s diversity index of prey, frequency of consumed prey type, and prey importance values were compared between flood and no flood years. Pianka’s index of niche overlap was used to compare changes in diet overlap between species in the years with floods and those without. In the absence of floods, the number of prey types consumed by N. erythrogaster and T. proximus decreased. The frequency of prey types consumed during flood years was significantly different from the period of flood suppression for all three species. The order of prey importance also changed in the absence of floods for all three snake species. Without floods, diet overlap decreased between N. erythrogaster and the other two species; however, overlap between N. fasciata and T. proximus doubled. [ABSTRACT FROM AUTHOR]

Host individuals who are infected with a pathogen may alter their behaviour in ways that influence transmission. We observed a marked population of house finches (Carpodacus mexicanus (Muller, 1776)) in Ithaca, New York, to test whether individuals change their behaviour at feeding stations when infected with a prevalent bacterial pathogen, Mycoplasma gallisepticum (MG). We found that house finches with conjunctival lesions consistent with MG infection fed for longer bouts of time than individuals without conjunctivitis. Furthermore, the same individuals that were observed both with and without conjunctivitis during 3 years of study were more likely to feed alone and associated in significantly smaller flocks when conjunctivitis signs were present. These results suggest house finches alter their foraging and social behaviour at feeding stations when visibly infected with MG. Since MG transmission is thought to primarily occur at feeders, these changes in host behaviour likely have important consequences for MG transmission dynamics. [ABSTRACT FROM AUTHOR]

Reproduction is a key life-history process often constrained by abiotic conditions, which affect resource availability and influence reproductive output, including the number of females in a population that reproduce within a given year. We investigated whether population-level fluctuations in reproductive effort (i.e., the number of nesting females) result in fluctuations in the number of offspring produced under environmentally stochastic conditions. Here we show that timing and frequency of tropical storms constrain reproductive success in green sea turtles (Chelonia mydas (L., 1758)); in years when storms arrive early or when multiple storms occur most green sea turtle nests are inundated by seawater and fail to hatch. Although equal proportions of the nests were destroyed by tropical storms in peak and non-peak nesting years, significantly more hatchlings emerged from nests during peak nesting years. Thus, the cyclic patterns of green sea turtle reproduction result in cyclic patterns of hatchling emergence under high levels of nest failure owing to seawater inundation. Ultimately, green sea turtle reproductive success is constrained by the timing of tropical storms in relation to the nesting season. Continuing increases in the severity of tropical storms from changing global climates could contribute to a higher proportion of nesting seasons with low reproductive success, such that population growth rates are slowed, which may have long-term negative effects on the ability of this species to recover to historical levels. [ABSTRACT FROM AUTHOR]

The torch tail rat, Trinomys yonenagae Rocha, 1995 (family Echimyidae), is the morphologically most divergent of the spiny rats. In this study, we evaluate the hypothesis that gaits preferentially used by this species evolved as an adaptation to the desert-like dunes where they live. We filmed spontaneous locomotion of T. yonenagae, Trinomys albispinus minor Reis and Pessôa, 1995, and Proechimys cayennensis (Desmarest, 1817) with a high-speed camera. We detected, for each of the 323 cycles of the reference forelimb recorded, the kind of gait developed, the time lags between the touchdown of each pair of limbs, and the relative velocity. Trinomys yonenagae walked twice as fast as P. cayennensis and T. a. minor using mainly the asymmetrical transverse gallop, half-bounds, and bounds, while the other two species used mainly the lateral sequence walk. Gaits changed from symmetrical to asymmetrical with increasing velocity for T. yonenagae but not for the other species. We argue that the gait pattern found in T. yonenagae is autapomorphic, that its origin coincides with the shift to a desert-like habitat, and that this type of gait confers higher adaptive value to explore resources in open areas than the plesiomorphic pattern. Therefore, we conclude that it can be considered adaptive to life in the dunes. [ABSTRACT FROM AUTHOR]

In vitro experiments were performed on melanophores bourne on scale slips sampled from three major areas (general background, dark band, and white spot) of the integumentary pattern of winter flounder, Pseudopleuronectes americanus (Walbaum, 1792). The effects of the respective β1- and β2-adrenoceptor agonists dobutamine and terbutaline and antagonists atenolol and ICI 118551 on pattern-related melanosome aggregation in response to exogenously applied L-noradrenaline were determined, as well as their effects on melanosome dispersion in balanced salt solution. The results demonstrate β1-adrenoceptor mediation in flatfish melanosome dispersion, with pattern-related variation, and also provide further evidence for β2-subtype involvement. Based on mammalian physiology, two β-subtypes will facilitate melanophore responsiveness to both neural and circulatory catecholamines. The in vivo role of these β-subtypes is discussed in relation to previously described attributes of the patterning behaviour of this species, which incorporates balances between α- and β-adrenoceptors. Dark band melanophores display a β-adrenoceptor bias, in contrast with other areas of the pattern, which would be consistent with their capacity for pigment dispersion in stressed flounders and with the slow paling of these bands during background-related responses. [ABSTRACT FROM AUTHOR]

Field-based food supplementation experiments can determine whether populations are limited by natural food availability. However, they may yield spurious results if added food is hoarded by dominants, exploited by immigrants, or delivered ineffectively. Surprisingly, population-level approaches accounting for these potential sources of bias have not been established. We explored responses of free-ranging snowshoe hares (Lepus americanus Erxleben, 1777) to food supplementation by contrasting per capita browsing rates on three study sites with added food with those on three control sites during two winters. Food augmentation reduced foraging pressure by hares; this reduction was significant when browse species of high dietary importance were considered. By implication, hares on manipulated sites switched from favored natural foods to supplemental food, meaning that the extra food found its mark and was not heavily exploited by immigrants or hoarded by dominants. Demographic responses to food addition were not detected on the manipulated sites, indicating that the study population was not food limited. Given the success with which we detected the signal of supplementation and eliminated potential confounding factors, we suggest that future studies using food addition in the context of herbivore population dynamics would benefit from a more mechanistic approach; this may involve measurement of browsing rates on manipulated and control sites. [ABSTRACT FROM AUTHOR]

A review of studies on nestling bird food requirements indicates that degree of sexual size dimorphism reliably predicts disparity in sex-specific food requirements, but that parents often fail to meet the excess requirement of the larger sex. We studied a population of Nazca boobies (Sula granti Rothschild, 1902), a sexually dimorphic pelagic seabird, to determine whether parents provide more care to daughters, the larger sex. Daughters grew to a larger size than did sons during the nestling period, but did not reach the mean size of adult females, while sons exceeded the size of adult males. Estimates of parental effort exerted for sons versus daughters indicated similar levels of effort, and that females fledged in poorer condition than males did in the study year, one of intermediate breeding conditions. Results from another study conducted during better breeding conditions indicated little limitation on growth of either sex. Together, these studies are consistent with a ceiling on parental effort in a long-lived species that allows consistent self-maintenance for parents, but causes poor performance in the costlier sex under poor breeding conditions. Complementary studies of short-lived species are needed to evaluate our suggested linkage between parental effort, self-maintenance, and sexual size dimorphism. [ABSTRACT FROM AUTHOR]

We compared body size and mass of the whole body, organs, adipose tissue, and muscles of adult Pacific Black Brant (Branta bernicla nigricans (Lawrence, 1846)) collected concurrently in Alaska and Baja California during the fall, winter, and spring of 2002–2003. Head and tarsal lengths of males were similar between sites and slightly larger for females in Alaska than in Baja California. Brant appear to operate under similar physiological bounds, but patterns of nutrient allocation differ between sites. Birds wintering in Alaska lost similar amounts of adipose tissue during early winter as birds in Baja California gained during late winter before migration. Masses of the body, adipose tissue, and flight muscles during mid-winter were similar between sites. Seasonal adipose tissue deposition may, therefore, equally favor winter residency or long-distance migration. Gonad and liver masses increased in late winter for birds in Alaska but not for those in Baja California, suggesting birds wintering in Baja may delay reproductive development in favor of allocating reserves needed for migration. Phenotypic flexibility allows Brant to use widely divergent wintering sites. The wintering location of Brant likely depends more upon changes in environmental conditions and food availability, than upon physiological differences between the two wintering populations. [ABSTRACT FROM AUTHOR]

Stable isotope measurements are being used increasingly to track migratory wildlife, especially birds. This approach relies on the assumption that tissue isotopic values represent a known period of dietary integration and that such a period is long enough to provide information on previous geographic origin. To date, such measurements have been obtained by switching isotopic composition of diets of sedentary captive individuals. The assumption has been that such measurements of elemental turnover likely represent minimal estimates, since wild migratory birds undergo increased metabolism and exercise during migratory flights. We tested this assumption using isotopic manipulation of diet on captive Rosy Starling (Sturnus roseus (L., 1758)) conditioned for flight in a wind tunnel. We used four control (no exercise) and four experimental (exercised) birds. For both groups, diet was switched from primarily a C-3 content to a C-4 content and blood samples were taken throughout our experiment until day 53. Contrary to expectation, δ13C values in blood did not follow an exponential model of growth to a plateau under the new diet. Instead, the best fit was a linear increase in δ13C value of the blood cellular fraction following the switch (day 15) until day 50, after which no further isotopic change was noted. We found no difference between experimental and control groups in the rate of carbon turnover. Our results support the contention that metabolic costs of migratory flight in conditioned birds may not result in increases in carbon elemental turnover in tissues and that previous estimates of tissue isotopic turnover based on captive, nonexercised birds may be applied to wild birds. [ABSTRACT FROM AUTHOR]

Deforestation may increase predation risk for prey because it may make prey more conspicuous and limit the number of refuges suitable to avoid predators. Therefore, prey may need to increase the magnitude of escape responses. However, excessive antipredatory effort might lead to a loss of body mass and a decrease in defense against parasites, with important consequences for short- and long-term fitness. We analyzed whether Psammodromus algirus (L., 1758) lizards that inhabit patches with different levels of deterioration of the vegetation within the same oak forest differed in relative abundance numbers, microhabitat use, antipredatory strategies, and health state. Results showed lizards selected similar microhabitats regardless of the level of deterioration of the vegetation and relative abundance of lizards was similar in both areas. However, habitat deterioration seemed to increase predation risk, at least for females, because they were detected at longer distances in deteriorated areas. Females seemed to adjust their antipredatory behavior accordingly to high risk of predation by increasing approach distances allowed to predators. The costs associated with frequent antipredatory displays might explain why females in deteriorated habitats had lower body condition and greater blood parasite loads than females in natural areas. This loss of body condition and increased parasitemia might have deleterious consequences for female fitness and therefore affect the maintenance of lizard populations in the long-term. [ABSTRACT FROM AUTHOR]

The physiological state of an animal may have a significant impact on its reproductive success because individuals in good body condition are generally considered to be competitively superior to individuals in poor body condition. In this study, we tested if body condition at weaning affected survival and reproduction of prairie voles (Microtus ochrogaster (Wagner, 1842)) living under ecologically relevant conditions at two different initial population densities. We detected no evidence that better body condition at weaning was associated with either enhanced survival or reproduction. Moreover, genetic analysis of parentage found that mating between males and females was random with respect to body condition. Results of this study indicate body condition at weaning was not a reliable predictor of future survival or reproduction in prairie voles. This may be because body condition at weaning does not accurately forecast the energetic state of prairie voles at later ages, or because other factors have a greater effect on an individual’s survival and reproductive success at the densities observed in this study. [ABSTRACT FROM AUTHOR]

Understanding the contribution of ecological interactions to the origin and maintenance of diversity is a fundamental challenge for ecologists and evolutionary biologists, and one that is currently receiving a great deal of attention. Natural enemies (e.g., predators, parasites, and herbivores) are ubiquitous in food webs and are predicted to have significant impacts on phenotypic diversity and on speciation, and extinction rates of their prey. Spurred by the development of a theoretical framework beginning in the late 1970s, there is now a growing body of literature that addresses the effects of enemy–prey interactions on the evolution of prey. A number of theoretical models predict that enemies can produce phenotypic divergence between closely related species, even in the absence of interspecific competition for resources. Effects on diversification of prey are more variable, and enemies may either enhance or depress speciation and extinction rates of their prey. Empirical evidences from a number of study systems, notably those involving predators and prey in aquatic environments and interactions between insects and flowering plants, confirm both predictions. There is now considerable evidence for the role of enemies, especially those that are size-selective or use visual cues when identifying suitable prey, on phenotypic divergence of sympatric and allopatric taxa. Enemies may spur diversification rates in certain groups under some circumstances, and hinder diversification rates in other cases. I suggest that further research should focus on the role of enemies in diversification of prey, with significant insights likely to be the product of applying traditional experimental approaches and emerging comparative phylogenetic methods. [ABSTRACT FROM AUTHOR]

Habitat selection can directly affect the fitness of an individual and the evolutionary dynamics of the population to which that organism belongs. We studied habitat use of the Puerto Rican yellow-chinned anole (Anolis gundlachi Peters, 1876) to examine whether this arboreal lizard uses its environment in a nonrandom manner. Males and females preferred woody vegetation substrates over nonwoody plants and sierra palms (Prestoea acuminata var. montana (Graham) A. Henderson and G. Galeano) as perching sites, and they also selected wider vegetation than what was randomly available. Selection for minimizing conspicuousness to potential predators and for increased locomotion capacity may help explain the preference for woody substrates and broader surfaces, respectively. Anolisgundlachi relies almost exclusively on visual cues for foraging and social interactions, and using wider perches also increases an individual's ability to scan a larger proportion of its territory. Our findings thus indicate that the nonrandom habitat use of free-ranging A. gundlachi leads to the selection of perching substrates that may increase performance of ecologically relevant capabilities. [ABSTRACT FROM AUTHOR]

In a seasonal environment, immune function in bird nestlings has been reported to decline with hatching date. Two groups of factors are expected to contribute to this decline: (1) seasonal deterioration of environmental conditions, e.g., food availability, and (2) differences in individual quality between parents breeding early and late in the season. To distinguish between these effects, an experimental manipulation of hatching date in great tits (Parus major L., 1758) was conducted. Whole clutches were swapped between pairs of nests with a 6-day difference in expected hatching date, while some nests remained nonmanipulated, constituting a control group. Nestling T-cell-mediated immune response to phytohaemagglutinin was negatively related to hatching date both within nonmanipulated control broods and all broods pulled together. Experimental change in hatching date produced changes in nestling immune response, as predicted from the seasonal trend observed in the control nests. Male and female nestlings did not differ in the level of immune response and the seasonal decline in immune response did not differ between sexes. Our results indicate that the seasonal decline in nestling immune function may be driven by date-dependent environmental conditions rather than differences in parental quality. [ABSTRACT FROM AUTHOR]

The costs of mating with multiple partners include expenditure of energy and time and a reduction in lifespan, but females of many taxa mate with several different partners shortly after their first copulation. Often it is not clear what females gain from this behaviour. In this study, we used the red flour beetle (Tribolium castaneum Herbst, 1797) to test the hypothesis that females mate with multiple males for fertility assurance because the first copulation often does not lead to offspring production. We found that the probability of producing offspring, as measured by the proportion of females that produced offspring, was not affected by multiple mating when females were mated to virgin partners. However, when females were mated to nonvirgin partners, multiple mating led to an increased probability of producing offspring. To establish the mechanism through which multiple mating enhanced the probability of producing offspring, we further investigated whether this result was observed because multiple mating provided genetically compatible sperm or because it provided sufficient sperm. Viability of larvae from multiply mated females was higher than that of larvae from singly mated females, but the total number of adult offspring produced was not significantly different between the two groups. The capacity of males to inseminate females decreased in successive matings after the initial copulation, suggesting that ineffective copulations between virgin females and nonvirgin males are likely due to male sperm depletion. Therefore, mating with multiple males increased the probability that females would produce offspring and served as fertility assurance. [ABSTRACT FROM AUTHOR]

The genetic compatibility hypothesis proposes that females should mate with genetically dissimilar males whose alleles best complement their own, resulting in greater offspring heterozygosity. It predicts that genetic similarity between social pairs will be positively related to the proportion of extra-pair young within broods and negatively related to hatching success. We tested these two predictions in tree swallow (Tachycineta bicolor (Vieillot, 1808)) pairs (n = 72). Tree swallows have one of the highest rates of extra-pair paternity among socially monogamous passerines. Contrary to expectation, genetic similarity of a social pair, as measured by the band-sharing coefficient (estimated from multilocus DNA fingerprints), tended to be negatively related to the proportion of extra-pair young within broods, but failed to predict hatching success. When including only the subset of nests for which we had complete genotyping data (n = 37), we again found a significant negative relationship between genetic similarity and the proportion of extra-pair young within broods. Genetic similarity did not differ significantly between nests with and without extra-pair young, nor did it differ between nests with total versus partial hatching success. Overall, our data do not support the genetic compatibility hypothesis in tree swallows, and in fact show some evidence against it. [ABSTRACT FROM AUTHOR]

Stable-isotope ratios are increasingly being used to examine ecological questions pertaining to dietary choices, physiological status, and animal migration. It has been shown that animal tissues reflect the isotopic signature present in food, altered by a small reproducible fractionation value. The average diet–tissue discrimination for δ13C and δ15N is approximately 1‰and 3‰, respectively, although the degree of diet–tissue discrimination may be affected by a range of factors and vary between organisms and tissue types. Although the average δ34S is approximately zero, the sulfur diet–tissue discrimination values have only been determined for a few organisms. It is necessary to determine accurate diet–tissue discrimination values between tissue and dietary components to have confidence in any food-web study or determination of diet quality. In this paper, we determine carbon, nitrogen, and sulfur diet–tissue discrimination values for whole blood, liver, skeletal muscle, heart, brain, and fat (carbon only) from adult mice (Mus musculus L., 1758) equilibrated on three diets with unique isotopic signatures for carbohydrate carbon and for protein carbon, nitrogen, and sulfur. These data will aid researchers in choosing tissues to be used to examine food-web changes over time. [ABSTRACT FROM AUTHOR]

Environmental conditions frequently affect the reproduction of many mammal and bird species by modulating maternal body condition. In our long-term study of European rabbits, Oryctolagus cuniculus (L., 1758), we investigated the effects of winter weather conditions and body mass on reproductive performance and reproductive timing. Specifically, we tested whether winter temperature affects both reproductive timing and reproductive performance of female rabbits or whether females compensate for low body mass after winter by a shift in the timing of the onset of breeding. Winter body mass loss was higher in years with lower winter temperatures, and the onset of breeding was delayed after these conditions. However, mean size and mass of the first litter of each season and seasonal fecundity were not reduced after harsh winters. At the individual level, females with lower winter body mass started to reproduce later, but we did not find any effects on litter size and mass. In contrast, breeding body mass was a strong predictor of the females' reproductive performance. We also found high between-year variation in mean body mass in late winter but not in mean breeding body mass. In conclusion, our results suggest that the negative effects of winter weather on the body mass of females, which should potentially affect their reproductive performance, were compensated for by delaying the onset of breeding. [ABSTRACT FROM AUTHOR]

Time spent in the water and diving behaviour of subantarctic fur seals (Arctocephalus tropicalis (Gray, 1872)) at Amsterdam Island in the southern Indian Ocean were investigated using time–depth recorders throughout the pup-rearing period. The main finding of this study, contrary to the findings of previous studies conducted on other fur seal species, was the decrease in the mean daily amount of time spent in the water throughout the pup-rearing period. The decrease in the amount of time spent in the water by older individuals compared with younger ones is likely to be related to the reduction of the pups' energy expenditure with a decreasing provisioning rate by their mothers. No change in the number of dives or the amount of time dedicated to diving relative to the time spent in the water could be detected throughout the pup-rearing period. The mean maximum dive depth increased with pup age and decreased with pup mass, and maximum dive duration was also found to increase with pup age. The positive effect of pup size on dive rates was the only relationship suggesting that pups' growth performance may act positively on the ontogeny of their diving capabilities. The large interindividual variation in the amount of time spent in the water and in dive rates, and the absence of any clear relationship with pup mass and pup growth performance, suggest the existence of alternative strategies: either pups invest more energy in developing their swimming and diving abilities, to the detriment of the body fat stores, or reduce their activity level to enhance body fat stores to increase their postweaning survival rate. [ABSTRACT FROM AUTHOR]

Blue-eyed shags are known to be capable of the deepest dives in the cormorant family. Yet, the way these birds balance their energy and time budgets remains enigmatic. Using ventrally attached time–depth recorders on chick-rearing Crozet shags (Phalacrocorax melanogenis Blyth, 1860), we simultaneously described their time budget and diving behaviour. Crozet shags are diurnal, benthic foragers (mean foraging range 1.7 km) that spend 37% of the daytime at sea. While at sea, they spend 49% of their time on the water, 44% diving, and 7% flying, and consume mainly benthic nototheniid fish. Larger fish (>20 g) were caught at shallower depths during shorter trips. They made, on average, 4.4 trips/day, each including 2.5 diving periods of 14 dives. On average, Crozet shags dove to 28 m (max. 145 m) for 2 min 2 s (max. 6 min 11 s). Descent and ascent rates became less variable at a depth of 40 m, possibly owing to a change in bird relative buoyancy at that depth. Ten percent of dives exceeded the estimated behavioural aerobic dive limit (4 min) and diving depths showed a bimodal distribution at <5 and ~18 m for dives lasting ~1 min. This dive duration corresponded to dives with higher dive duration/postdive interval ratios. The Crozet shags managed their dive cycle to fully exploit their breathing capacities, thus optimizing foraging performance. [ABSTRACT FROM AUTHOR]

The genus Cyphoderris, or hump-winged grigs, is represented by three species of cold-adapted, acoustic Ensifera with a geographic distribution that is generally restricted to the high-elevation coniferous forests of western North America. A phylogenetic analysis based on 29 morphological and 3 behavioural characters produced one tree, (C. buckelli (C. strepitans, C. monstrosa)) with a consistency index of 1.0. We discuss possible explanations for the observation that almost all of the autapomorphic change was concentrated in C. monstrosa. [ABSTRACT FROM AUTHOR]

Prey species that occur across a range of habitats may be exposed to variable communities of multiple predator species across habitats. Predicting the combined effects of multiple predators can be complex. Many experiments evaluating the effects of multiple predators on prey confound either variation in predator density with predator identity or variation in relative predator frequency with overall predation rates. We develop a new experimental design of factorial predator combinations that maintains a constant expected predation rate, under the null hypothesis of additive predator effects. We implement this design to evaluate the combined effects of three predator species (bass, aeshnid and libellulid odonate naiads) on mortality rate of a prey species, Hyla cinerea (Schneider, 1799) tadpoles, that occurs across a range of aquatic habitats. Two predator treatments (libellulid and aeshnid + libellulid) resulted in lower tadpole mortality than any of the other predator treatments. Variation in tadpole mortality across treatments was not related to coarse variation in microhabitat use, but was likely due to intraguild predation, which occurred in all predator treatments. Hyla cinerea tadpoles have constant, low survival values when exposed to many different combinations of predator species, and predation rate probably increases linearly with predator density. [ABSTRACT FROM AUTHOR]

This study identified daily variations in oxygen consumption, antioxidant-defense system, and lipoperoxidation in the gills and hepatopancreas of the crab Chasmagnathus granulata (Dana, 1851) (Decapoda, Brachyura). In gills, oxygen consumption was higher in the early afternoon and in the middle of the night (p < 0.05). Lipoperoxidation level and non-proteic sulfhydryl content were higher in the middle of the night (p < 0.05). The enzyme glutathione-S-transferase showed lower activity at the end of photophase and higher values during the night (p < 0.05). The enzyme catalase did not show daily variation in activity (p > 0.05). Oxygen consumption in the hepato pancreas showed a similar profile to that in gills, i.e., higher values in the early afternoon and the middle of the night. Glutathione-S-transferase activity and lipoperoxidation levels showed significant variation, with lower values during the afternoon and peaks in the middle of the night (p < 0.05). Catalase activity was significantly higher (p < 0.05) in the middle of the night. The non-proteic sulfhydryl content remained fairly constant (p > 0.05). The results showed daily variations in aerobic metabolism of the gills and hepatopancreas of C. granulata, with concomitant oxidative damage (lipoperoxidation), but with differences between tissues. Whereas in the gills the defense system focused on catalase and non-proteic sulfhydryl, in the hepatopancreas other non-enzymatic components and other antioxidant enzymes besides catalase and glutathione-S-transferase might be involved. [ABSTRACT FROM AUTHOR]

On the basis of its external morphology, Myotis tricolor (Temminck, 1832) should be able to both aerial-feed and glean. Furthermore, this bat is known to use broadband calls of short duration, reinforcing the prediction that it gleans. However, results from this study indicate that M. tricolor does not commonly glean. This conclusion was reached after studying the foraging behaviour of M. tricolor in a flight room. We presented M. tricolor with mealworms, moths, mole crickets, beetles, and cicadas in a variety of ways that required either gleaning and (or) aerial feeding. Although M. tricolor readily took tethered prey, it did not take any of the variety of insects presented to it in a manner that required gleaning. We therefore compared its wing morphology and echolocation calls with those of several known gleaners, Nycteris thebaica E. Geoffroy, 1818, Myotis lucifugus (Le Conte, 1831), and Myotis septentrionalis (Trouessart, 1897), and an aerial forager, Neoromicia capensis (A. Smith, 1829). In a discriminant analysis wing-tip shape was the only variable to provide some degree of discrimination between species, with M. tricolor having more pointed wing tips than the known gleaners. Discriminant analysis of echolocation-call parameters grouped M. tricolor with the other Myotis species and separated it from N. capensis and N. thebaica. However, M. tricolor did not use harmonics as did the other Myotis species. The apparent failure of M. tricolor to glean might therefore be due to its relatively pointed wings and narrow-bandwidth echolocation calls, owing to the absence of harmonics in its calls. [ABSTRACT FROM AUTHOR]

This study investigated the aggressive behavior of female Japanese macaques (Macaca fuscata (Blyth, 1875)) during lactation. Following parturition, the frequency of aggression showed an initial decline during weeks 1–2 of infant life, then increased to peak during weeks 7–8 post partum, and finally declined again to prepartum levels. Neither the initial decline nor the subsequent increase in aggression rate post partum was related to sociodemographic characteristics of the mother–infant dyad or to measures of maternal style. These results suggest that variation in postpartum aggression may be influenced less by the quality of the mother–infant relationship than by the mother's relationships the mother has with group mates. [ABSTRACT FROM AUTHOR]

During 1960–2002, the arrival times of all spawning male and female Atlantic salmon (Salmo salar L., 1758) and brown trout (Salmo trutta L., 1758) entering Dalälven River were recorded. To study the role of environmental variation in spawning migration timing, we used long-term temperature (river and sea) and river discharge data. For salmon, the spawning migration peak was strongly correlated with mean monthly sea and river temperatures during spring: salmon arrived earlier when temperatures were higher and later when temperatures were lower. River discharge explained little of the variation in migration timing. Female salmon migration showed a stronger correlation with temperature than male salmon migration, and female salmon arrived ≈18 days earlier than males. Trout showed a larger variation in their spawning migration, but river and sea temperatures and river discharge explained little of the variation. Trout females arrived ≈7 days earlier than males. The sea and river temperatures were highly correlated during the spawning migration, indicating that large climate processes determine the temperature regimes in the Baltic Sea and its tributaries. Time of arrival at the river was not correlated with ovulation date; a female salmon or brown trout arriving late could ovulate almost immediately, whereas a female arriving early could wait to ovulate. [ABSTRACT FROM AUTHOR]

Several crayfish species behave as biological invaders. Their establishment in an area has frequently been accompanied by the reduction or elimination of indigenous species. A laboratory study was designed to investigate whether the invasive crayfish Procambarus clarkii (Girard, 1852) is dominant over the indigenous (to Delaware) crayfish Procambarus acutus acutus (Girard, 1852) in either the absence or the presence of a shelter as a limited resource. As expected, we found that P. clarkii is more aggressive than the similarly sized P. a. acutus, thus confirming previous studies that demonstrated an inherent dominance of the invasive over the indigenous crayfish. We then hypothesized that species showing a lower preference for an offered shelter (P. clarkii) should be less motivated to defend it. To the contrary, in a competitive context P. clarkii excluded P. a. acutus from the shelter but did not use the resource. Caution must be used in extrapolating these laboratory studies to the field, and future studies should analyze multiple factors, including the autoecology of the two species and their reproductive potential and recruitment patterns. However, our results might help in highlighting the risks for freshwater biodiversity created by the uncontrolled translocations of P. clarkii and other similar invasive species. ..LAN-FR Plusieurs espèces d'écrevisses se comportent comme des envahisseurs biologiques. Leur établissement dans une région s'accompagne souvent de la réduction ou de l'élimination des espèces indigènes. Nous avons mis au point une étude de laboratoire pour voir si l'écrevisse envahissante Procamburus clarkii (Girard, 1852) est dominante par rapport à l'écrevisse indigène (au Delaware) Procamburus acutus acutus (Girard, 1852) en présence ou en absence d'abris comme ressource limitée. Comme prévu, P. clarkii est plus agressif que P. a. acutus, un animal de même taille, ce qui confirme les études antérieures qui ont démontré l'existence d'une dominance inhérente de l'écrevisse envahissante par rapport à l'indigène. Nous avons alors posé l'hypothèse selon laquelle l'espèce qui montre le moins de préférence pour l'abri offert (P. clarkii) devrait être moins motivée pour le défendre. Au contraire, dans une situation de compétition, P. clarkii élimine P. a. acutus de l'abri, sans pour autant s'en servir lui-même. Il faut être prudent en extrapolant ces résultats de laboratoire aux situations de terrain; les études futures devront analyser plusieurs facteurs, dont l'autécologie des deux espèces, leur potentiel reproductif et leurs patterns de recrutement. Néanmoins, nos résultats peuvent servir à souligner les risques pour la biodiversité créés par les transferts incontrôlés de P. clarkii et d'autres espèces envahissantes semblables.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

In anadromous salmonid fishes, a fraction of the males ("jacks") spend fewer years at sea than females and most males in the population. It has been hypothesized that the higher survival rates of jacks at sea are balanced by their reduced reproductive success. One component of reproductive success is in-stream longevity, and jacks were reported to have a shorter reproductive life-span than older males. To test this hypothesis, we examined the interactions between arrival date, mode of death (senescent, bear-killed, gull-killed, stranded), and reproductive life-span of male sockeye salmon, Oncorhynchus nerka (Walbaum in Artedi, 1792), in a small Alaskan creek. Of the senescent males, early-arriving fish lived longer than later arrivals, and jacks and older males had similar reproductive life-spans (p = 0.932). Jacks were less susceptible to premature mortality (mostly from bears and gulls) than older males. The life-span of fish that died prematurely was greater for jacks than non-jacks (p < 0.001). Considering all sources of mortality (both premature and senescent), jacks had a greater mean life-span than older males (5.84 vs. 3.12 days; p < 0.001). Despite this fact, jacks are scarce (1.7% in this population), suggesting that they suffer in other components of fitness such as proportion of eggs fertilized. [ABSTRACT FROM AUTHOR]

The Central European water frog Rana esculenta L., 1758 is a natural hybrid between Rana lessonae Camerano, 1882 (LL) and Rana ridibunda Pallas, 1771 (RR). Hybrids are usually diploid (RL) or triploid (LLR or RRL). Distinguishing LL from RL, RR from RL, and LLR from RRL according to external morphology is ambiguous. In this study we checked whether the DNA content in erythrocyte nuclei measured by image cytometry is useful in determination of the taxonomic status of diploids (LL, RR, and RL) and the genome composition of triploids (LLR and RRL). For exact and direct identification of parental species, as well as for determination of genome composition in hybrids, we applied actinomycin D – 4',6-diamidino-2-phenylindole chromosome staining to metaphase plates. We analyzed 43 LL, 12 RR, and 32 RL diploids, and 37 LLR and 19 RRL triploids. All diploid hybrids had 2n = 26 chromosomes, and all triploid hybrids had 3n = 39 chromosomes. Neither aneuploid nor mosaic hybrids were detected. The expected numbers of 13 R. lessonae (L) and 13 R. ridibunda (R) chromosomes in RL hybrids were recorded in about 31% of individuals. In the rest of the sample the composition was variable, ranging from 9 to 14 R chromosomes and the corresponding number of L chromosomes. The expected composition of 26 L and 13 R chromosomes was detected in about 32% of LLR triploids, whereas in the rest of the sample the composition of chromosomes ranged from 8 to 15 R chromosomes and the corresponding number of L chromosomes. The expected numbers of 26 R and 13 L chromosomes were detected in about 26% of RRL triploids, whereas in the rest of the sample the composition of chromosomes ranged from 19 to 28 R chromosomes and the corresponding number of L chromosomes. The DNA content densitometry showed that RR and RL diploids had 9.5% and 3.8% more DNA, respectively, than LL diploids. These differences, although statistically significant, were not sufficient to unequivocally discriminate LL from RL and RR from RL. Triploids had about 50% more DNA than LL diploids (49% in LLR and 51% in RRL), but these differences were too small for unequivocal determination of their genome composition. [ABSTRACT FROM AUTHOR]

The Ponto-Caspian amphipod Echinogammarus ischnus (Stebbing, 1899) is reportedly replacing the North American amphipod Gammarus fasciatus Say, 1818, in the lower Great Lakes, but the two species appear to coexist in the upper St. Lawrence River several years after invasion by E. ischnus. A multi-site survey in the river between Lake Ontario and Montreal (Quebec) found that E. ischnus and G. fasciatus respond differently to substrate characteristics, water chemistry variables, and current velocity. Both species increase in abundance in the presence of dreissenid mussels. However, E. ischnus density is positively correlated with current velocity and an increasing proportion of gravel-sized sediment, while G. fasciatus density is positively correlated with benthic filamentous algal (Cladophora spp.) biomass, macrophyte biomass, and pH. Habitat heterogeneity within the river may be promoting the coexistence of native and exotic amphipods by allowing them to segregate along physicochemical gradients. [ABSTRACT FROM AUTHOR]

Few studies have systematically examined edge effects on nest predators, although many invoke these processes as potential mechanisms for decreased nesting success of songbirds. Species richness and relative abundance of avian and mammalian nest predators were compared between forest edge and interior in two landscapes, Allegan State Game Area and Fort Custer Training Center (FCTC), in southwest Michigan. One avian predator, the American crow (Corvus brachyrhynchos Brehm, 1822), was more abundant at edges than forest interior at FCTC; however, other predators did not demonstrate an edge response. Abundance of the brood parasite (Molothrus ater (Boddaert, 1783)) was greater at edges in FCTC. Overall abundance was higher at FCTC in both years; however, this could not be attributed to a greater extent of fragmentation. Total species richness for both landscapes did not differ between edge and interior. Remote-camera systems captured three predation events, two involving red squirrels (Tamiasciurus hudsonicus (Erxleben, 1777)) and one involving a blue jay (Cyanocitta cristata (L., 1758)). Vegetation characteristics were similar between edge and interior sites, which suggests that vegetation structure did not influence edge response. The variability in response indicates a need to assess patterns of predator distributions through long-term studies at multiple spatial scales. [ABSTRACT FROM AUTHOR]

Mode of development was determined for 130 of the nearly 250 species of shallow-water, benthic opisthobranchs known from the northeast Pacific Ocean. Excluding four introduced or cryptogenic species, 91% of the species have planktotrophic development, 5% have lecithotrophic development, and 5% have direct development. Of the 12 native species with non-feeding (i.e., lecithotrophic or direct) modes of development, 5 occur largely or entirely south of Point Conception, California, where surface waters are warmer, lower in nutrients, and less productive than those to the north; 4 are known from habitats, mainly estuaries, that are small and sparsely distributed along the Pacific coast of North America; and 1 is Arctic and circumboreal in distribution. The nudibranchs Doto amyra Marcus, 1961 and Phidiana hiltoni (O'Donoghue, 1927) were the only species with non-feeding development that were widespread along the outer coast. This pattern of distribution of developmental mode is consistent with the prediction that planktotrophy should be maintained at high prevalence in regions safe for larval feeding and growth and should tend to be selected against where the risks of larval mortality (from low- or poor-quality food, predation, and transport away from favorable adult habitat) are higher. However, direct development, which includes the most derived mode of non-feeding development, was also correlated with small adult size, reflecting an association common in marine invertebrates. Planktotrophic development also predominates in decapod Crustacea from the northeast Pacific, but is less common in echinoderms and prosobranch gastropods from this region owing to the presence of lineages constrained by phylogeny to non-feeding modes of development. [ABSTRACT FROM AUTHOR]

In the ground cricket Allonemobius socius (Scudder 1877), males provide females with a hemolymph-based nuptial gift. The size of the gift depends on when copulation is terminated, which can be controlled by either sex. Here we show that more immunocompetent males provide larger nuptial gifts, increasing their reproductive potential. To address if this pattern was the consequence of sexual selection for an honest signal (i.e., females assess mate immune quality through the hemolymph), we examined which sex controlled gift size. We found that the probability that males initiated the end of copulation increased when gift size was small (stereotypical of less immunocompetent males). Thus, early termination of copulation was the consequence of male behavior, suggesting that the association between immunocompetence and gift size was not due to sexual selection, but to natural selection for male vigor. [ABSTRACT FROM AUTHOR]

Natural enemies, including humans, play a major role in the diversification of species and the maintenance of biodiversity. Compared with humans, most enemies faced by the rest of biodiversity are restricted in the magnitude of their effects, the spatial extent of their distribution, and the variety of species that they influence. Recognition of the similarities and differences between natural and human enemies should help us preserve and manage biodiversity. [ABSTRACT FROM AUTHOR]