Nesting habitat use and partitioning of three sympatric ninespine sticklebacks (genus <Emphasis Type="Italic">Pungitius</Emphasis>): implications for reproductive isolation

The nest site characteristics and distribution patterns of nests of three sympatric ninespine sticklebacks, the brackish- and fresh-water types and Pungitius tymensis, were investigated in the Shiomi River, eastern Hokkaido, Japan. In this river, most of the males of the brackish-water type were found to build their nests in the lower reach with higher salinity (mean 13.5‰) and water temperature (mean 13.3°C), whereas the males of the freshwater type and P. tymensis built their nests in the upper reach with lower salinity (mean 0.6 and 0.8‰, respectively) and water temperature (both mean 11.3°C). The ranges of their nesting areas, however, overlapped within the river, because the nests of the brackish-water type were widely distributed in the river. A comparison of the nest site characteristics in the area where nest overlapped indicated that there were no significant differences for all of five characteristics (the distance from the nest to the shore, the distance from the nest to the bottom, the distance to the nearest nest, the nest density and the amount of cover around the nest). Using canonical discriminant analysis, the nests of the three sticklebacks could not be distinguished using the five nest characteristics. These results suggest that habitat isolation through physical factors functions as an important mechanism of reproductive isolation between the brackish-water type and the other two sticklebacks.     

蜂桶寨自然保护区小熊猫对生境的选择

2002年4月至11月,在邛崃山系宝兴蜂桶寨自然保护区设点,应用资源选择函数和资源选择指数研究了小熊猫对生境的选择和利用。结果表明,影响小熊猫生境选择的关键因子是水源距离、竹子基径、灌木密度;次关键因子是坡位、树桩密度、倒木密度;次要因子是坡向、乔木密度;而郁闭度、坡度、植被类型、乔木高度、灌木高度、树桩高度、树洞密度、人为干扰的影响不明显。小熊猫喜欢在水源较近(<250m)、竹子长势良好(基径大于4 0mm)、灌木和乔木密度大(大于1 5株 20m2)、树桩和倒木数量多(>1根 400m2)、中上坡位、南坡的针叶林或针阔混交林活动。小熊猫的生境资源选择函数为:logit(P)=-13 527-3 180×水源距离 2 702×竹子基径 2 582×灌木密度 2 134×树桩密度 2 104×坡位 1 622×倒木密度-1 066×坡向 0 934×乔木密度……小熊猫对生境的选择概率为:P=elogit(P) (1 elogit(P))     

Philopatry, Dispersal Patterns and Nest-site Reuse in Lesser Grey Shrikes (Lanius minor)

To nest in the same breeding area, territory or even nest-site in successive years may provide a possibility to look at mechanisms involved in breeding habitat selection and could also be an important tool for conservation, management and restoration attempts. In this study we examine site fidelity towards the breeding area as well as the nesting site in a dense and stable population of the Lesser Grey Shrike Lanius minor, a long-distance migrant and highly endangered passerine species, at its present northern border of its breeding range. Overall we recovered 48 out of 146 (32.8%) adults between 1996 and 2000. Recovery rate is significantly higher for males (31 of 77, 40.25%) than for females (17 of 69, 24.6%). Recovery rate of nestlings is much lower since only 51 of 790 (6.5%) were recovered and there is no significant sex difference. Furthermore, our results from 1989 to 2000 revealed that more than 30% (97/319) of the nests were built in the same nest tree in successive years and more than half (183/319 = 57.4%) of the nests in the same or neighboring trees (up to 20 m), but very seldom by the same individuals. The fact that nest reuse in successive years is almost exclusively done by different individuals suggests habitat copying and public information of individual birds. Due to optimal ecological breeding conditions other parameters like inbreeding avoidance or increased genetic variability could be important factors in nest-site selection strategies and consequently result in a “disperse over stay strategy”.     

The role of male contest competition over mates in speciation

Research on the role of sexual selection in the speciation process largely focuses on the diversifying role of mate choice.In particular,much attention has been drawn to the fact that population divergence in mate choice and in the male traits subject to choice directly can lead to assortative mating.However,male contest competition over mates also constitutes an important mechanism of sexual selection.We review recent empirical studies and argue that sexual selection through male contest competition can affect speciation in ways other than mate choice.For example,biases in aggression towards similar competitors can lead to disruptive and negative frequency-dependent selection on the traits used in contest competition in a similar way as competition for other types of limited resources.Moreover,male contest abilities often trade-off against other abilities such as parasite resistance,protection against predators and general stress tolerance.Populations experiencing different ecological conditions should therefore quickly diverge non-randomly in a number of traits including male contest abilities.In resource based breeding systems,a feedback loop between competitive ability and habitat use may lead to further population divergence.We discuss how population divergence in traits used in male contest competition can lead to the build up of reproductive isolation through a number of different pathways.Our main conclusion is that the role of male contest competition in speciation remains largely scientifically unexplored.     

Fine scale site fidelity in sea kraits: implications for conservation

The shores of coral reef islands are major sites for biodiversity, but unfortunately they are also subject to strong anthropogenic disturbances. Indeed vast arrays of organisms live exclusively in these very narrow and well structured zones, many others depend on the rich and diverse micro-habitats for essential part of their life cycle (to reproduce, forage, etc.). Sea kraits are sea snakes that depend on the shore of coral islets; they forage at sea but digest, reproduce and rest on land. They have been killed in extremely large numbers in many places, causing local extinctions. In the current study we demonstrate through recapture and translocation studies that these snakes exhibit a strong and fine-scale fidelity for particular segments of the shore. Consequently, these specific areas should be under strong protection, as it the case for the breeding beaches used by marine mammals, birds or turtles.     

Ecological character displacement caused by reproductive interference

We carried out a theoretical investigation of whether ecological character displacement can be caused by reproductive interference. Our model assumes that a quantitative character is associated with both resource use and species recognition, and that heterospecific mating incurs costs. The model shows that ecological character displacement can occur as a consequence of evolution of premating isolation; this conclusion is based on the premise that resource competition is less intense between species than within species and that the ecological character also contributes to premating isolation. When resource competition between species is intense, extinction of either species may occur by competitive exclusion before ecological character divergence. Some observational studies have shown that character displacement in body size is associated with not only resources use but also species recognition. We propose that body size displacement can occur as a consequence of evolution of premating isolation. Our results suggest that ecological character displacement results from reproductive character displacement.     

Survey of Alouatta caraya, the black-and-gold howler monkey, and Alouatta guariba clamitans, the brown howler monkey, in a contact zone, State of Rio Grande do Sul, Brazil: evidence for hybridization

Sympatry and natural hybridization between howler monkey taxa (Alouatta spp.) has only recently being confirmed in the wild. Surveys in areas of potential contact between the distribution of two taxa have shown that sympatry is rare, although more common than previously known. Here we report the results of a survey conducted in a contact zone between the only two sexually dichromatic howler monkey taxa, Alouatta caraya and A. guariba clamitans, in São Francisco de Assis, State of Rio Grande do Sul, Brazil. Our survey, covering an area of about 400 ha at the Cerro dos Negros (29°33′50″–29°35′10″S, 54°58′40″–54°59′50″W; ~100–279 m a.s.l.), was successful in locating seven black-and-gold and one brown howler monkey social groups living syntopically. Black-and-gold group size ranged from 5 to 15 individuals, whereas the brown group was composed of 7 individuals. The pelage color of three adult males belonging to different black-and-gold groups and another adult male belonging to the brown howler group presented a mosaic of red or rufous and black. These adult males and an adult female living in another black-and-gold group are putative hybrids. Therefore, it appears that pre-zygotic reproductive isolation has not evolved, at least not completely, between these howler monkey species, corroborating previous reports for these and other Alouatta taxa. Future genetic studies need to confirm the occurrence of hybridization in this contact zone, and to determine the viability and fertility of hybrids and their possible offspring. In addition, there is no evidence supporting the existence of significant segregation in habitat and resource utilization by black-and-gold and brown howler monkeys.     

Natal location influences movement and survival of a spatially structured population of snail kites

Despite the accepted importance of the need to better understand how natal location affects movement decisions and survival of animals, robust estimates of movement and survival in relation to the natal location are lacking. Our study focuses on movement and survival related to the natal location of snail kites in Florida and shows that kites, in addition to exhibiting a high level of site tenacity to breeding regions, also exhibit particular attraction to their natal region. More specifically, we found that estimates of movement from post-dispersal regions were greater toward natal regions than toward non-natal regions (differences were significant for three of four regions). We also found that estimates of natal philopatry were greater than estimates of philopatry to non-natal regions (differences were statistically significant for two of four regions). A previous study indicated an effect of natal region on juvenile survival; in this study, we show an effect of natal region on adult survival. Estimates of adult survival varied among kites that were hatched in different regions. Adults experienced mortality rates characteristic of the region occupied at the time when survival was measured, but because there is a greater probability that kites will return to their natal region than to any other regions, their survival was ultimately influenced by their natal region. In most years, kites hatched in southern regions had greater survival probabilities than did kites hatched in northern regions. However, during a multiregional drought, one of the northern regions served as a refuge from drought, and during this perturbation, survival was greater for birds hatched in the north. Our study shows that natal location may be important in influencing the ecological dynamics of kites but also highlights the importance of considering temporal variation in habitat conditions of spatially structured systems when attempting to evaluate the conservation value of habitats. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Female and male visually based mate preferences are consistent with reproductive isolation between populations of the Lake Malawi endemic Labeotropheus fuelleborni

Sexual selection via female mate choice is thought to have played a key role in the speciation of haplochromine cichlids, but a dominant role for visual signals in such processes has lately been called into question. In addition, the possible role of male mating preferences in haplochromine speciation has been little studied. We studied patterns of both female and male mate choice, based exclusively on visual signals, in order to evaluate potential reproductive isolation between two populations of the Lake Malawi haplochromine Labeotropheus fuelleborni. In the first experiment, females were allowed to choose between two males, one from the same population and the other allopatric with respect to the female. Females in this experiment responded more frequently to males from their own population. Similarly, the males in these trials displayed more frequently when presented with females of their own population. In the second experiment, a female was allowed to choose between two males, either both from her own population or both allopatric. In these trials, both males and females from the Katale population interacted significantly more frequently in settings in which all three individuals were from the same population (same-population trios), and those from the Chipoka population showed a similar trend. Thus, patterns in both male and female courtship behavior suggest that visual signals contribute to at least incipient reproductive isolation between populations of L. fuelleborni [Current Zoology 56 (1): 65-72 2010].     

Habitat selection and home range in the Blanford's fox,Vulpes cana: compatibility with the resource dispersion hypothesis

Summary This paper presents analyses of habitat-use and home range size in the Blanford's fox. We predicted, from the resource dispersion hypothesis (RDH), that home ranges would encompass similar areas of combined fruitful habitats, but widely different areas of useless habitats, and thus that home ranges would be larger where such fruitful patches are fragmented and widely dispersed. Home range estimates of 0.5–2.0 km² were calculated for 16 adult Blanford's foxes, using three different methods. There were no significant differences in home range size between sexes or study sites. One habitat, dry creekbed, was the most frequently visited in all home ranges. Dry creekbed provided abundant prey for the foxes and only sparse cover for their predators. Both the available area of creekbed in each range, and the area of creekbed patches that was used by the foxes, were independent of home range size. However, the variance in home range size was explained by the mean distance between the main denning area and the most frequently used patches of creekbed. These results are in accord with some predictions of the resource dispersion hypothesis.     

Influence of digestive morphology on resource partitioning in Amazonian ungulates

Summary Resource partitioning of diet and habitat use was studied in the entire Amazonian ungulate community of Northeastern Peru, which comprises the red brocket deer (Mazama americana), grey brocket deer (M. gouazoubira), collared peccary (Tayassu tajacu), white-lipped peccary (T. pecari), and lowland tapir (Tapirus terrestris). Each ungulate species partitioned at least one type of resource from every other species. Digestive morphology had a greater influence on resource partitioning of diet than body size. Neither digestive morphology nor body size were related to segregation of habitats. However, species with similar diets partitioned habitats, whereas species with different diets often used the same type of forest. Increases in habitat breadth of ungulates were positively correlated with increases in dietary breadth.     

American legacies and the variable life histories of women and men

Sex differences in behavior are most interesting when they are the result of inherent differences in the operational rules motivating behavior and not merely a reflection of differing life history experiences. American men and women exhibit a few differences in testamentary patterns of property allocation that appear to be due to inherently different rules of allocation. Even when analyses control for resources and surviving kin configurations, women distribute their property among a greater number of individual beneficiaries than do men. The most striking differences in property allocation between men and women occur within the nuclear family and reflect differences in reproductive life span and the resulting reproductive conflicts between spouses that can endure beyond death. The initial research for this paper was funded by a grant to Sarah Blaffer Hrdy and the author from the Rockefeller Foundation Program in Changing Gender Roles. Debra Judge is associated with the Ecology Graduate Group and the Department of Anthropology at the University of California at Davis. Her interests focus on human demography, reproductive strategies, and the ecological conditions influencing human mating and parenting strategies—especially intergenerational resource transfer.     

Comparisons between the influence of habitat type, season and body size on the dietary compositions of fish species in nearshore marine waters

Fish were collected from over bare sand in nearshore shallow waters at three sites that varied in the extent to which they were exposed to wave activity and which were located within a 45-km stretch on the lower west coast of Australia. Sampling was undertaken within a 4-6-week period in each season. The volumetric contributions of different prey to the stomach contents and the mouth characteristics of four species, i.e. Sillago bassensis and Sillago vittata (Sillaginidae), Spratelloides robustus (Clupeidae) and Pseudorhombus jenynsii (Bothidae), were determined. Overall, the dietary compositions of the four species differed significantly from each other and those of fish at both the three different sites and in four consecutive seasons were also significantly different. In comparison with S. bassensis, the morphologically similar S. vittata fed to a relatively greater extent on polychaetes than zooplankters, presumably reflecting in part its greater ability to extend its upper jaw downwards towards the benthos. S. robustus typically targeted calanoid copepods in the plankton, whereas P. jenynsii fed on larger benthic prey taxa, reflecting the large differences in mouth morphology and feeding behaviour of these species. Although the diets of S. bassensis and S. vittata were strongly influenced by habitat type and season, the former variable was slightly more important for both of these species. However, the reverse applied with S. robustus. Season strongly influenced the dietary composition of P. jenynsii at the one site at which it was regularly caught. The diets of the two Sillago species and P. jenynsii underwent pronounced size-related changes, which would help distribute the food resources among the individuals of the different size classes of each of these species. In contrast, all size classes of S. robustus fed predominantly or exclusively on calanoid copepods at all sites and in all seasons, except at the most sheltered site in winter when these zooplankters were not found in samples taken from the water column. The seasonal and habitat variations recorded in the diets of the fish species in this study imply that these species are able to feed opportunistically, a characteristic that would be of particular value to fish that live in nearshore waters where the relative abundance of the different prey types varies with habitat type and season.     

Factors influencing stable nitrogen isotope ratios in wing membranes of insectivorous bat species: A field study

Nitrogen stable isotope analysis studies have become a useful tool in dietary studies to quantify differences in diet composition among species or individuals. However, laboratory studies have revealed several factors that influence the nitrogen isotope ratios (δ¹⁵N) in animal tissues (e.g. habitat, amount of ingested food, and metabolic rate). The influence of these factors has not been validated for free-ranging bat species, which is important for interpreting nitrogen isotope data in field studies. In this study, we measured δ¹⁵N from wing membranes (δ¹⁵N_w) and habitat samples (δ¹⁵N_h; soil and leaf, or sediment) to test for effects of diet, age, and individual energy demand in three free-living bat species (Myotis daubentonii, Nyctalus noctula and Nyctalus leisleri). We hypothesised that based on differences in diet composition δ¹⁵N_w values should increase in the sequence M. daubentonii, N. leisleri, and highest N. noctula. Furthermore, juveniles should have significantly lower δ¹⁵N_w compared to their mothers. Thirdly, the δ¹⁵N_w values of reproductively active individuals should be significantly higher than those of non-reproductive individuals. Values of δ¹⁵N_w were significantly influenced by differences in feeding ecology among species and individual reproductive status, but not by animal age. Our results show that species feeding on primary consumers have lower δ¹⁵N_w values than species feeding on secondary and tertiary consumers. Further, independent young did not differ in their δ¹⁵N_w values from adults suggesting that their tissues already reflect the insect diet. The effect of reproductive status varied among species which might reflect intra-specific differences in foraging behaviour of generalist vs. specialist species. In this study, we demonstrated that δ¹⁵N can provide information on the dietary range of bats, but researchers should account for variation owing to reproductive status, habitat, and species.