Maternal Testosterone and Offspring Sex-Ratio in Birds and Mammals: A Meta-Analysis

Sex allocation theory predicts that parents should bias offspring sex to maximize their fitness in a given context. Quantifying the fitness benefits of offspring sex-ratio biases would be facilitated by a better knowledge of their underlying mechanism(s) and associated costs. The hypothesis that steroid hormones are involved in sex determination has gained in popularity recently. Being influenced by external stimuli and involved in a range of physiological processes, they could be a ubiquitous mediator of environmental conditions influencing sex-ratio with low fitness costs. Previous studies indicated that higher maternal testosterone levels led to the overproduction of sons around conception in both birds and mammals. We conducted a systematic review (including meta-analysis) of these studies and, as predicted, we found a weak positive and significant overall effect of maternal testosterone on the proportion of sons. Neither taxa, nor the type of study (experimental/observational), or the timing of timing testosterone manipulation/measure were significant predictors of offspring sex-ratio, which may be explained by low statistical power in addition to low variability between effect sizes. Our meta-analysis provides evidence for a general positive influence of maternal testosterone around conception on the proportion of sons across birds and mammals, although less confidently so for the latter. It begs for more large-scale experimental studies, especially on mammals, and ideally in the wild. It may also have some important consequences for the poultry industry.     

Local Competition, Inbreeding, and the Evolution of Sex-Biased Dispersal

Using game theory, we developed a kin-selection model to investigate the consequences of local competition and inbreeding depression on the evolution of natal dispersal. Mating systems have the potential to favor strong sex biases in dispersal because sex differences in potential reproductive success affect the balance between local resource competition and local mate competition. No bias is expected when local competition equally affects males and females, as happens in monogamous systems and also in polygynous or promiscuous ones as long as female fitness is limited by extrinsic factors (breeding resources). In contrast, a male-biased dispersal is predicted when local mate competition exceeds local resource competition, as happens under polygyny/promiscuity when female fitness is limited by intrinsic factors (maximal rate of processing resources rather than resources themselves). This bias is reinforced by among-sex interactions: female philopatry enhances breeding opportunities for related males, while male dispersal decreases the chances that related females will inbreed. These results meet empirical patterns in mammals: polygynous/promiscuous species usually display a male-biased dispersal, while both sexes disperse in monogamous species. A parallel is drawn with sex-ratio theory, which also predicts biases toward the sex that suffers less from local competition. Optimal sex ratios and optimal sex-specific dispersal show mutual dependence, which argues for the development of coevolution models.     

Sex-Biased Dispersal at Different Geographical Scales in a Cooperative Breeder from Fragmented Rainforest

Dispersal affects both social behavior and population structure and is therefore a key determinant of long-term population persistence. However, dispersal strategies and responses to spatial habitat alteration may differ between sexes. Here we analyzed spatial and temporal variation in ten polymorphic microsatellite DNA loci of male and female Cabanis’s greenbuls ( Phyllastrephus cabanisi ), a cooperative breeder of Afrotropical rainforest, to quantify rates of gene flow and fine-grained genetic structuring within and among fragmented populations. We found genetic evidence for female-biased dispersal at small spatial scales, but not at the landscape level. Local autocorrelation analysis provided evidence of positive genetic structure within 300 m distance ranges, which is consistent with behavioral observations of short-distance natal dispersal. At a landscape scale, individual-based autocorrelation values decreased over time while levels of admixture increased, possibly indicating increased gene flow over the past decade.     

Phylogenetic Analysis of Phaeosphaeria Species Using Mating Type Genes and Distribution of Mating Types in Iran

Phaeosphaeria species are pathogenic on wheat, barley and a wide range of wild grasses. To analyze mating type loci of the Phaeosphaeria species and investigate mating type distribution in Iran, we sequenced mating type loci of 273 Phaeosphaeria isolates including 67 isolates obtained from symptomatic leaves and ears of wheat, barley, and wild grasses from two wheat-growing region in Iran as well as 206 isolates from our collection from other regions in Iran which were isolated in our previous studies. Mating type genes phylogeny was successfully used to determine the species identity and relationships among isolates within the Phaeosphaeria spp. complex. In this study, we reported seven new host records for Phaeosphaeria species and the Phaeosphaeria avenaria f. sp. tritici 3 group was first reported from Iran in this study. Mating type distribution among Phaeosphaeria species was determined. Both mating types were present in all sampling regions from Iran. We observed skewed distribution of mating types in one region (Kohgiluyeh va Boyer-Ahmad) and equal distribution in the other region (Bushehr). However, when considering our entire dataset of 273 Iranian Phaeosphaeria isolates, the ratio of mating types was not deviated significantly from 1:1 suggesting possibilities for isolates of opposite mating type to interact and reproduce sexually, although the sexual cycle may infrequently occur in some regions especially when the climatic conditions are unfavorable for teleomorph development.     

Chlorpyrifos: Ecotoxicological Risk Assessment for Birds and Mammals in Corn Agroecosystems

A tiered risk assessment was conducted for the use of granular and liquid formulations of chlorpyrifos in corn agroecosystems in the U.S. The initial screening Tier I assessment suggested that under high-exposure scenarios the granular and some spray formulations present potential hazards to birds. Higher tiered probabilistic risk assessments were conducted separately for the granular and liquid formulations. The probabilistic assessment indicated that risk to birds from exposure to granular formulation is small and that this route of exposure would not be a significant source of mortality. Similarly, the assessment of potential exposure of birds to food items contaminated with chlorpyrifos showed that the risk from exposure via food was small, even if it was assumed that birds feed only on the treated fields. Although they have potentially greater sensitivity to chlorpyrifos, effects in nestling birds consuming food items from fields treated with granular chlorpyrifos were negligible. However, risks to young birds may be greater where the major source of food is from fields treated with liquid formulations of chlorpyrifos. A review of field studies showed that wildlife mortality incidents associated with use of either granular or liquid formulations of chlorpyrifos are not widely apparent in agroecosystems. Based on the multiple lines of evidence, we conclude that the presumption that chlorpyrifos use in corn agroecosystems will result in extensive mortality of terrestrial wildlife, particularly birds and mammals, is not supported by the scientific evidence.     

Gastrointestinal Bacteria of Certain Antarctic Birds and Mammals

An investigation was carried out of the aerobic gram-negative intestinal flora of 158 penguins, 30 skuas, and 66 seals from the Antarctic and sub-Antarctic zones and Phillip Island. Among penguins and seals, 17% and 11%, respectively, were devoid of aerobic enteric organisms, but microscopic examination showed the presence of other bacteria. The coliforms outnumbered the paracolons and nonlactosefermenting bacteria; irregular coliform types and Escherichia coli were predominant. The present study indicated the effect of diet on the composition of the intestinal flora of the birds and mammals examined.     

Patterns of Seed Dispersal and Dispersal Failure in a Hawaiian Dry Forest Having Only Introduced Birds

Dry forests are among the most endangered natural communities in the Hawaiian Islands. Most have been reduced to isolated trees and small forest fragments in which native tree species reproduce poorly. The replacement of native birds by introduced generalists may be contributing to dry forest decline through modification of seed dispersal patterns. To document seed dispersal by introduced birds, we conducted foraging observations on fleshy-fruited trees and measured seed rain under trees and in adjacent open areas for 1 year in a dry forest dominated by native trees. Although trees covered only 15.2 percent of the study area, 96.9 percent of the bird-dispersed seeds were deposited beneath them. The Japanese white-eye (Zosterops japonicus) was the principal dispersal agent. Among bird-dispersed seeds, those of the invasive tree Bocconia frutescens accounted for 75 percent of all seeds collected beneath trees (14.8 seeds/m²/yr) and the invasive shrub Lantana camara accounted for 17 percent. Although nearly 60 percent of the reserve's native woody species possess fleshy fruits, introduced birds rarely disperse their seeds. Native trees accounted for <8 percent of all bird-dispersed seeds and are consequently experiencing dispersal failure by falling directly under parent trees. Smaller-seeded non-native plants, in contrast, may be benefiting from dispersal by introduced birds. Current dispersal patterns suggest that these readily disseminated non-native plants may eventually replace the remaining native flora.     

Stepparental Behavior as Mating Effort in Birds and Other Animals

In many animal species, widowed or divorced parents may remate before young of the prior union are independent. In such circumstances, stepparents may kill their predecessors' offspring, may tolerate them without providing care, or may invest in them more or less as genetic parents do. Rohwer proposed that all three of these responses may be understood as mating tactics, adapted to different social and ecological circumstances. We discuss the selection pressures that would favor each of these alternatives and review relevant evidence on nonhuman stepparenting, especially in birds. Stepparental tolerance and (partial or full) care, which are the predominant human responses, are common in nonhuman animals too, and in many cases there is evidence supporting their interpretation as stepparental mating effort adaptations. In general, however, this interpretation is not as well established for tolerance and care as it is for stepparental infanticide. Because tolerance and care are not distinct modes of behavior peculiar to stepparents, the hypothesis that they are nonadaptive by-products of parental psychology often remains tenable. We discuss the kinds of evidence needed to choose between by-product and stepparental adaptation hypotheses.     

Phylogeography and Sex-Biased Dispersal across Riverine Manatee Populations (Trichechus inunguis and Trichechus manatus) in South America

Phylogeographic patterns and sex-biased dispersal were studied in riverine populations of West Indian (Trichechus manatus) and Amazonian manatees (T. inunguis) in South America, using 410bp D-loop (Control Region, Mitochondrial DNA) sequences and 15 nuclear microsatellite loci. This multi-locus approach was key to disentangle complex patterns of gene flow among populations. D-loop analyses revealed population structuring among all Colombian rivers for T. manatus, while microsatellite data suggested no structure. Two main populations of T. inunguis separating the Colombian and Peruvian Amazon were supported by analysis of the D-loop and microsatellite data. Overall, we provide molecular evidence for differences in dispersal patterns between sexes, demonstrating male-biased gene flow dispersal in riverine manatees. These results are in contrast with previously reported levels of population structure shown by microsatellite data in marine manatee populations, revealing low habitat restrictions to gene flow in riverine habitats, and more significant dispersal limitations for males in marine environments.     

Identifying Environmental Determinants of Diurnal Distribution in Marine Birds and Mammals

Marine birds and mammals move between various habitats during the day as they engage in behaviors related to resting, sleeping, preening, feeding, and breeding. The per capita rates of movement between these habitats, and hence the habitat occupancy dynamics, often are functions of environmental variables such as tide height, solar elevation, wind speed, and temperature. If the system recovers rapidly after disturbance, differential equation models of occupancy dynamics can be reduced to algebraic equations on two time scales. Identification of environmental factors that influence movement between habitats requires time series census data collected in both the absence and presence of disturbance.     

Competition Among Insects, Birds and Mammals for Conifer Steeds

Species of at least 5 orders of insects, 6 families of birds,and 2 orders of mammals, in various combinations, can exploitthe cones and seeds of most species of conifers. Lodgepole pineis the exception to this pattern of broad taxonomic diversityof seed predators in that only pine squirrels and coreid bugsattack its serotinous cones. The contrast between lodgepolepine and other conifers demonstrates that large intrinsic variationin the abundance of a resource fosters the evolution of a broadrange of taxonomic groups to exploit the resource. The diversegroups'are limited by different predators and alternate resourceswhen conifer seeds independently decrease in abundance.     

Local Mating,Dispersal and Sex Ratio in a Gregarious Parasitoid Wasp

Parasitoid sex ratios can be greatly influenced by mating and dispersal behaviour. Many sex ratio models assume that mating is strictly local (only mated females disperse from the natal patch) and that a single male is sufficient to inseminate all females in a brood. Bethylids (aculeate parasitoids) have been used to test predictions of these models, but less attention has been paid to testing their underlying assumptions. We investigated the timing of eclosion, mating and dispersal in mixed-sex and single-sex broods of the bethylid wasp Goniozus nephantidis. In mixed-sex broods, almost all females mate before dispersal and a single male is sufficient to inseminate virtually all females, even when brood sizes are large. Males disperse from both mixed-sex and all-male broods, but males in all-male broods disperse more slowly. Virgin females disperse from all-female broods, which are common. Virgin females can produce a brood, mate with their own sons and subsequently produce mixed-sex broods, but their success rate is very low. Virgin females could potentially circumvent sex allocation constraints by superparasitizing mixed-sex broods, but when presented with hosts bearing mixed-sex broods they destroy all members of the initial brood before ovipositing. Because of the high prevalence of single-sex broods and dispersal of both sexes, the mating structure of G. nephantidis is unlikely to conform to the assumption of strict local mating.     

基于红外相机技术对陕西老县城国家级自然保护区大中型兽类及林下鸟类资源分析

兽类和鸟类多样性的监测是生物多样性保护中的重要一环。2017年4月至2018年5月,按照网格法在位于陕西省西安市周至县的老县城国家级自然保护区布设了36台红外相机,对保护区内大中型兽类和林下鸟类多样性进行调查。累积7 835个相机工作日,获得野生动物独立有效照片1 915张,共鉴定出32种鸟类和兽类物种,隶属8目18科,其中被IUCN红色名录评估为濒危(EN)、易危(VU)和近危(NT)的物种分别有2种、4种和3种。相对丰富度指数最高的为羚牛(Budorcas taxicolor)(IRA=36.81);夏季(7.68)和秋季(7.81)物种拍摄率大于春季(4.65)和冬季(4.30),不同季节拍摄到的物种数和物种多样性指数差异不显著。不同海拔段物种拍摄率、物种数和物种多样性指数均不具有明显差异。濒危物种中的羚牛不同海拔段拍摄率存在明显差异。主成分分析表明,拍摄物种与相机位点之间相关性较强,这与相机位点附近的生境条件有关。研究结果初步掌握了老县城保护区内大中型兽类和林下鸟类种类组成、相对多度及分布状况,为未来保护区野生动物资源保护和管理提供基础资料。     

Comparative Biochemistry of the Pineal Glands of Birds and Mammals

Melatonin is synthesized from serotonin in the pineal glandby N-acetyltransferase and hydroxyindole-O-methyltransferase(HIOMT). The activities of these two enzymes have been comparedin the pineal glands of rats, hamsters, chickens, and sparrows.Three different patterns of pineal biochemistry have been observedin the four species. Evidence for the regulation of pineal N-acetyltransferaseactivity by a noradrenergic system exists in rats but not inchickens, hamsters, and sparrows.     

Seed Dispersal Patterns by Large Frugivorous Mammals in a Degraded Mosaic Landscape

Seed dispersal by Red fox (Vulpes vulpes), Stone marten (Martes foina), and Wild boar (Sus scrofa) was analyzed in an extensively degraded mosaic landscape in Sierra Nevada (SE Spain). The main objective was to determine whether seed dispersal by mammals was related to habitat degradation within a mosaic of adjacent degraded patches mixed with native forest and thereby to determine the potential role of mammals as seed dispersers in degraded landscape units. For three consecutive years, mammal feces were collected in the fruit production period, extracting all seeds of woody species found therein and analyzing their viability. Feces were collected in three different plots for each of five different landscape units: shrubland, native forest, and dense, cleared, and fenced reforestation stands. Seeds from 16 woody species (which represent more than a half of the total fleshy‐fruited woody species available) were recorded, although some agrarian species are also introduced in a low percentage of the scats. Seeds showed a high viability rate for all dispersed species, irrespective of the mammal disperser. No differences in species composition appeared in the overall landscape units or in the seed density between degraded habitats. Due to the small patch size, the high viability of dispersed seeds, and the large home range of the large mammals, these three animal species act as efficient seed dispersers for a diverse assemblage of woody plant species regardless of the habitat type within this degradation framework. This fact has important consequences for the biodiversity recuperation in these degraded habitats, principally in pine plantations.     

Independent Evolution of Transcriptional Inactivation on Sex Chromosomes in Birds and Mammals

X chromosome inactivation in eutherian mammals has been thought to be tightly controlled, as expected from a mechanism that compensates for the different dosage of X-borne genes in XX females and XY males. However, many X genes escape inactivation in humans, inactivation of the X in marsupials is partial, and the unrelated sex chromosomes of monotreme mammals have incomplete and gene-specific inactivation of X-linked genes. The bird ZW sex chromosome system represents a third independently evolved amniote sex chromosome system with dosage compensation, albeit partial and gene-specific, via an unknown mechanism (i.e. upregulation of the single Z in females, down regulation of one or both Zs in males, or a combination). We used RNA-fluorescent in situ hybridization (RNA-FISH) to demonstrate, on individual fibroblast cells, inactivation of 11 genes on the chicken Z and 28 genes on the X chromosomes of platypus. Each gene displayed a reproducible frequency of 1Z/1X-active and 2Z/2X-active cells in the homogametic sex. Our results indicate that the probability of inactivation is controlled on a gene-by-gene basis (or small domains) on the chicken Z and platypus X chromosomes. This regulatory mechanism must have been exapted independently to the non-homologous sex chromosomes in birds and mammals in response to an over-expressed Z or X in the homogametic sex, highlighting the universal importance that (at least partial) silencing plays in the evolution on amniote dosage compensation and, therefore, the differentiation of sex chromosomes.     

Seed Dispersal by Birds and Bats in Lowland Philippine Forest Successional Area

In the tropical forests of SE Asia, only a few studies have dealt with the role animal dispersal plays in early forest succession and rehabilitation, and a comparison of bird and bat dispersal is even rarer. We investigated seed dispersal by birds and bats in a successional area in the lowland dipterocarp forest of the Subic Watershed Forest Reserve (SWFR) in Luzon Island, Philippines. Using pairs of day and night traps, we collected seeds during 3 mo of wet season and 3 mo of dry season in a 1.2-ha study site. Bird-dispersed seeds predominated over those dispersed by bats in terms of both seed abundance and number of seed species. The most abundant endozoochorous seed species were significantly biased toward either bird or bat dispersal. Birds and bats appeared to compete more strongly for fruit resources during the dry season than during the wet season, and bats responded more to changes in the seasons than birds did. GLM analyses showed that the factor that had the strongest influence on overall seed distribution was the number of fleshy-fruited trees surrounding the traps, and that the distribution pattern of day-dispersed seeds was affected by more physical factors (number of trees, size of trees, presence of fleshy-fruited and conspecific trees) in the study site than the pattern of night-dispersed seeds were. Given that birds are the more important dispersers in the study site, restoration efforts in SWFR might benefit by focusing on attracting these dispersers into its degraded habitats.