Leukocyte profile variation in Dupont’s Lark (Chersophilus duponti) in Spain and Morocco

Stress in birds has been widely studied through the measurement of heterophil-to-lymphocyte ratio (H/L ratio). In this study we aimed to assess for the first time the potential variation of stress, measured as H/L ratio, associated to geography (between-country variation) and seasonality (between seasons and within the breeding season), as well as the leukocyte profiles, in the threatened Dupont’s Lark (Chersophilus duponti), using samples from Spain and Morocco. Furthermore, we tested whether variation in H/L ratio was associated with variables such as population density, presence of blood parasites and individual body condition. We found that H/L ratio did not vary between countries, but individuals captured during the breeding season showed higher values of H/L compared to non-breeding ones. Neither male density, nor date within the breeding season had an effect on the H/L ratio. In Spain, individuals with higher body condition showed lower H/L ratio regardless of whether they were malaria-infected. In Morocco, malaria-infected individuals showed higher values of H/L ratio than the non-infected birds. Moreover, we found that our average values of H/L ratio in Morocco were within the ranges of other passerines, but not in Spain. Individuals with higher H/L ratios may be more stressed or present higher capability to face stressful situations. Although H/L ratio is a useful and relatively easy way to obtain measure of stress, the impact that the environment might have on stress and the way it is explained by H/L ratio must be addressed carefully. This study provides new insight for this species’ biology and provides useful reference information to test the status and survival of other populations.

Natural History Observations on a Population of Vesperus luridus (Coleoptera: Cerambycidae) in Central Italy

Natural history observations were made, during August–September 2021, on a population of the ecologically poorly known Vesperus luridus (Cerambycidae) at a hilly locality of Latium, Central Italy. These beetles were searched for by night along a 170 m long transect, with the help of hand torches. During the field surveys, we recorded a total of 130 individuals, of which 128 were males and 2 females. All individuals were observed between 21 h 45 and 01 h 15, with above-ground activity peaking from 22 h 45 to 23 h 45. The minimum observed density per day showed a rapid increase to a peak at the end of August, followed by a slower decrease in the following two weeks. Mean male density was 0.32 individuals per transect m2, whereas only two females were observed (mean density = 0.006 individuals per transect m2). Most individuals were found on trees, and they appeared to be highly attracted to artificial lights. One female, situated on a tree at a height of 170 cm, was surrounded by five courting males.

Juvenile Experience with Male Cues Triggers Cryptic Choice Mechanisms in Adult Female Redback Spiders

Female choice may be linked to population density if the expected encounter rates with potential mates affects choosiness (the energy and risk engaged to express mate preferences). Choosiness should covary with male availability, which could be assessed using the social cues available during development. We tested whether the exposure of juvenile females to cues of male density affected the mechanisms of choosiness of adult Latrodectus hasselti spiders in two experiments simulating natural contexts. The juvenile females were exposed to (1) volatile chemicals from two densities of adult males (airborne cues), and (2) tactile, vibrational and chemical cues from adult males or other females (cohabitation cues). As adults, the females mated readily, regardless of the treatment, but there was strong evidence for post-copulatory mechanisms of choosiness in females exposed to cues of high male availability. These included abbreviated matings (in both experiments), cannibalism of the males before the mating was complete (cohabitation), and, remarkably, a reduction in the successful placement of internal sperm plugs (cohabitation). These shifts decrease the likelihood that the first mate would monopolize paternity if the female chose to mate again. We conclude that female choosiness may impose a strong selection on males despite the high mating rates, and these effects can hinge on the cues of male availability detected by juveniles.

Male Impact on Female Reproductive Performance of the Larval Tephritid Parasitoid Diachasmimorpha tryoni (Hymenoptera: Braconidae)

Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae) is a larval parasitoid that has been mass-reared for augmentative biological control against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in Hawaii and other regions. To improve performance of female wasps in biological control programs, we conducted a series of experiments to investigate male wasp reproductive performance and its role in female reproductive success. The results showed that D. tryoni males remained close to the emergence (release) site following release. Males emerged earlier than females and male’s capacity to inseminate females reached the highest level (inseminated 9.2 ± 0.4 females/day) on the second day after eclosion in synchronization with female emergence peak; allowing males encountering most receptive females to enhance their mating success. Mating rates under normal rearing conditions (200 pairs per cage) reached optimum 100% insemination after 5 d. However, oviposition experience prior to mating impaired female’s receptivity as a percentage of inseminated females reduced to 17.5 ± 4.8%, while 70.0 ± 4.1% females without prior oviposition experience accepted mating. Mating reduced male’s survivorship and the potential lifetime fecundity of females, although multiple mating increased percentage of female offspring. Overall, influence of male density on the female oviposition rate and offspring sex ratio was not detected under captive rearing conditions. These results suggest that local and early mating is important for male’s reproductive success and females must be allowed to mate before they are exposed to hosts or released in the field to achieve their full reproductive potential.

Size-at-maturity shift in a male-only fishery: factors affecting molt-type outcomes in Newfoundland and Labrador snow crab (Chionoecetes opilio)

A sex-asymmetric downward shift in size-at-terminal-molt has recently occurred in males in some portions of the Newfoundland and Labrador (NL) snow crab stock range, a first known occurrence for such processes in snow crab (Chionoecetes opilio) stocks. This study examines plausible factors promoting the shift in size-at-terminal-molt [synonymous with size-at-maturity (SaM)] including individual size, temperature, population density, and sex ratio. Analyses highlight expanse of cold water and large male density as being significant predictors of molt-type outcomes. A confluence of cold conditions and low density of large males promoted the SaM shift. In turn, the low male density was associated with recently elevated fishery exploitation rates under quota-controlled management. It remains unknown the extent to which the reduction in terminal size reflects a phenotypic vs. genotypic process. Factors affecting skip-molting in male snow crab are investigated, and we find that skip-molting occurs most frequently under extreme cold and high population density conditions. Potential complications arising from altered growth dynamics are discussed. Overall, the results advance knowledge on intraspecific competition processes within snow crab populations and inform fisheries management systems that male-only harvest strategies do not provide full protection from biological harm to aquatic resources through fishing.

Time-course in attractiveness of pheromone lure on the smaller tea tortrix moth: a generalized additive mixed model approach

Long-term pest insect monitoring in agriculture and forestry has advanced population ecology. However, the discontinuation of research materials such as pheromone lure products jeopardizes data collection continuity, which constrains the utilization of the industrial datasets in ecology. Three pheromone lures against the smaller tea tortrix moth Adoxophyes honmai Yasuda (Lepidoptera; Tortricidae) were available but one was recently discontinued. Hence, a statistical method is required to convert data among records of moths captured with different lures. We developed several generalized additive mixed models (GAMM) separating temporal fluctuation in the background male density during trapping and attenuation of lure attractiveness due to aging or air exposure after settlement. We collected multisite trap data over four moth generations. The lures in each of these were unsealed at different times before trap settlement. We used cross-validation to select the model with the best generalization performance. The preferred GAMM had nonlinear density fluctuation terms and lure attractiveness decreased exponentially after unsealing. The attenuation rates varied among lures but there were no differences among moth generations (seasons). A light trap dataset near the pheromone traps was a candidate for a male density predictor. Nevertheless, there was only a weak correlation between trap yields, suggesting the difficulty of data conversion between the traps differing in attraction mechanisms.

Status of the Critically Endangered Bengal Florican Houbaropsis bengalensis (Gmelin, 1789) in Koshi Tappu Wildlife Reserve, Nepal

The Bengal Florican is one of the rarest bustard species and is listed ‘Critically Endangered’ by the IUCN. The species is restricted to the lowland grasslands of India, Nepal, and Cambodia with fewer than 1,000 mature individuals. To assess the species status in Koshi Tappu Wildlife Reserve, Nepal, we repeated our first comprehensive survey conducted during the 2012 breeding season. In spite of a larger area coverage we recorded only 41 adult Bengal Floricans in 2017 compared to 47 individuals in 2012. Detectability of this rare species is low in its Imperata-Saccharum grasslands. We, therefore, used a long pole with black and white clothing to mimic Bengal Florican’s display flight to stimulate male Bengal Florican. The number of adult males recorded was the same as in the 2012 survey and the adult male density remains one of the highest in the Indian subcontinent. Management recommendations for the long-term conservation of the species in Koshi Tappu include maintenance of Imperata-Saccharum grasslands in the reserve favoured by the Bengal Florican and working with farmers and communities adjacent to the reserve where the birds breed in order to maintain some agricultural lands with vegetation height suitable for the species especially during the species’ breeding season.

Exposure to high male density causes maternal stress and female-biased sex ratios in a mammal

A shift from the traditional perspective that maternal stress is invariably costly has instigated recent interest into its adaptive role in offspring sex allocation. Stress generated by social instability has been linked to offspring sex ratio biases that favour the production of female offspring, which converges with the theoretical prediction that mothers in the poor condition are better off investing in daughters rather than sons. However, previous research has failed to disentangle two different processes: the passive consequence of maternal stress on sex-specific mortality and the adaptive effect of maternal stress at the time of conception. Here, I show that exposure to high male density social conditions leads to elevated stress hormone levels and female-biased in utero offspring sex ratios in house mice ( Mus musculus domesticus ), and identify that sex-specific offspring production—not sex-specific mortality—is the mechanism accounting for these sex ratio skews. This outcome reflects the optimal fitness scenario for mothers in a male-dominated environment: the production of daughters, who are guaranteed high mate availability, minimizes male–male competition for their sons. Overall, this study supports the idea that maternal stress has the potential to be adaptive and advances our understanding of how exposure to different social conditions can influence sex allocation in mammals.

Direct and Indirect Effects of Overstory Canopy and Sex-Biased Density Dependence on Reproduction in the Dioecious Shrub Shepherdia canadensis (Elaeagnaceae)

This study assessed the reproductive success of a temperate dioecious shrub, Canada buffaloberry, Shepherdia canadensis (L.) Nutt., in central Alberta, Canada, by examining the effects of spatial patterns and overstory canopy on flower and fruit production. S. canadensis is more abundant and productive (more fruit) at forest edges and in forest gaps, suggesting a dependence on higher light conditions than is typical of late-seral forests. We used path analysis to demonstrate that flower and fruit production exhibited density-dependent effects at a scale of 50 m2 around focal female plants. Fruit production was positively affected by male intraspecific density (pollen supply) and negatively affected by female intraspecific density (pollen competition), but not correlated with overall intraspecific density. The effects of sex-differentiated density are partly due to pollinator responses to male plant density. Flower production was positively affected by overall intraspecific density. A pollen supplementation trial doubled fruit production relative to a control, demonstrating that local male density (pollen availability) and pollinator activity can limit fruit production in S. canadensis. Canopy cover was negatively related to both flower and total fruit production, with approximately one-third (34%) of the total effect of canopy on fruit production due to the effect of canopy on flower production. The commonly observed negative association between canopy cover and fruit production in buffaloberry, therefore, is partly a result of the reduction first in flower number and second in fruit set. This study clarifies the mechanisms associated with the often-noted observation, but not previously assessed at the level of individuals, that reproductive output in S. canadensis is density dependent, limited by canopy cover through reductions in both flowering and fruit set, and pollinator limited. These findings hold implications for managing animal species that depend on the fruit of S. canadensis and suggest future directions for research on dioecious and actinorhizal species.