Adjustment of fecundity and sex ratio in response to social environments in a haplodiploid mite

Animals can adjust reproductive strategies in favour of corporation or competition in response to local population size and density, the two key factors of social environments. However, previous studies usually focus on either population size or density but ignore their interactions. Using a haplodiploid spider mite, Tetranychus ludeni Zacher, we carried out a factorial experiment in the laboratory to examine how ovipositing females adjust their fecundity and offspring sex ratio during their early reproductive life under various population size and density. We reveal that females laid significantly more eggs with increasing population size and significantly fewer eggs with increasing population density. This suggests that large populations favour cooperation between individuals and dense populations increase competition. We demonstrate a significant negative interaction of population size and density that resulted in significantly fewer eggs laid in the large and dense populations. Furthermore, we show that females significantly skewed the offspring sex ratio towards female-biased in small populations to reduce the local mate competition among their sons. However, population density incurred no significant impact on offspring sex ratio, while the significant positive interaction of population size and density significantly increased the proportion of female offspring in the large and dense populations, which will minimise food or space competition as females usually disperse after mating at crowded conditions. These results also suggest that population density affecting sex allocation in T. ludeni is intercorrelated with population size. This study provides evidence that animals can manipulate their reproductive output and adjust offspring sex ratio in response to various social environments, and the interactions of different socio-environmental factors may play significant roles.

Impact of a nonnative parasitoid species on intraspecific interference and offspring sex ratio

In an assemblage of multiple predators sharing a single prey species, the combined effects of the component species may scale unpredictably because of emergent interspecific interactions. Prior studies suggest that chaotic but persistent community dynamics are induced by intra-/interspecific interactions between native and nonnative parasitoids competing over a shared host. Here, we test the impact of the nonnative parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) on the intraspecific interference and offspring sex ratio of the native parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae). We found that the nonnative parasitoid reduced intraspecific interference among native parasitoids and decreased the proportion of female offspring produced by the native parasitoid (predicted under conditions of reduced host availability). At higher host densities, the nonnative parasitoid contributed less to the total proportion of hosts parasitized, as its innate saturating Type II response changed to a dome-shaped Type IV response with increasing density of the native parasitoid, while the native parasitoid retained its increasing Type I response. This inverse host-density-dependent response between the two parasitoids and associated competitive superiority can explain the observed changes in parasitism; at high host densities, the searching efficiency of the native parasitoid increases via host feeding while the nonnative parasitoid experiences egg limitation. These results highlight the importance of the complementary top-down effects of multiple consumers on a single resource.

Modelling the incubation microclimate to predict offspring sex ratios and hatching phenology in tuatara (Sphenodon punctatus)

<p>Successful conservation of terrestrial biodiversity requires understanding and predicting the impacts of rapid climate warming on the suitability of both current and potential future habitats. Most predictions of range shifts and other population-scale effects of climate change rely to some extent on statistical links between a species' known geographical distribution and the suite of environmental conditions experienced within that space. However, species' responses to climate change are likely to be more complex than can be represented by the projection of current species-environment relationships into unknown environments. An important goal in biodiversity conservation is the development of quantitative tools with which to assess habitat suitability independently of distributions. In populations of oviparous species, climate change and habitat modification may have distinct effects on different life stages. Temperatures that are well within the thermal tolerance range of adults, for example, may affect embryonic development rates, hatching phenology, or offspring survival and phenotype. I examined how environmental variation may affect the thermal suitability of habitat for facilitating embryonic development and maintaining balanced sex ratios in tuatara (Sphenodon punctatus), an endemic New Zealand reptile with temperature-dependent sex determination (TSD). Once widespread throughout New Zealand, populations are now restricted to offshore islands and fenced mainland sanctuaries, though establishment of additional populations via translocation is ongoing. Due to intensive conservation efforts, tuatara are not classified as an endangered species, but, like other species in which hatchling sex is determined by the incubation environment, populations are potentially at risk from the detrimental effects of sex-ratio bias. I conducted two seasons of field work on the island of Takapourewa to quantify the relationship between rapid vegetation succession and selection of nesting areas. I then used a variety of predictive models to link data on nesting behaviour collected in the field with the microclimate conditions experienced by nesting female tuatara and developing embryos. Using mechanistically modelled soil temperature data, I generated predictions of incubation temperatures, offspring sex ratios, and hatching dates for two populations of tuatara on environmentally distinct islands, Takapourewa and Hauturu, under current and projected future climate scenarios. Finally, I classified the thermal suitability of sites on Hauturu for facilitating successful embryonic development and created geospatial surfaces defining suitable nesting locations adjacent to tuatara habitats. Offspring sex ratios on both islands are unlikely to become male-biased if the magnitude of climate warming observed over the next century more closely matches the minimum, rather than the maximum, projected warming scenario. On Takapourewa, the timing of nesting will be critical in determining whether sex ratios become male-biased under a scenario of maximum climate warming. Earlier nesting may also lead to shifts in hatching phenology under either scenario of climate warming. Warmer annual temperatures on Hauturu are more likely to lead to heavily male-biased offspring sex ratios under the maximum warming scenario. Female tuatara on Hauturu do not need to travel away from their current habitats to locate suitable nesting sites. Monitoring the population to quantify nesting behaviour on the island will be important for determining whether females' choices of incubation microclimates can compensate for the sex ratio-biasing effects of climate change.</p>

Modelling the incubation microclimate to predict offspring sex ratios and hatching phenology in tuatara (Sphenodon punctatus)

<p>Successful conservation of terrestrial biodiversity requires understanding and predicting the impacts of rapid climate warming on the suitability of both current and potential future habitats. Most predictions of range shifts and other population-scale effects of climate change rely to some extent on statistical links between a species' known geographical distribution and the suite of environmental conditions experienced within that space. However, species' responses to climate change are likely to be more complex than can be represented by the projection of current species-environment relationships into unknown environments. An important goal in biodiversity conservation is the development of quantitative tools with which to assess habitat suitability independently of distributions. In populations of oviparous species, climate change and habitat modification may have distinct effects on different life stages. Temperatures that are well within the thermal tolerance range of adults, for example, may affect embryonic development rates, hatching phenology, or offspring survival and phenotype. I examined how environmental variation may affect the thermal suitability of habitat for facilitating embryonic development and maintaining balanced sex ratios in tuatara (Sphenodon punctatus), an endemic New Zealand reptile with temperature-dependent sex determination (TSD). Once widespread throughout New Zealand, populations are now restricted to offshore islands and fenced mainland sanctuaries, though establishment of additional populations via translocation is ongoing. Due to intensive conservation efforts, tuatara are not classified as an endangered species, but, like other species in which hatchling sex is determined by the incubation environment, populations are potentially at risk from the detrimental effects of sex-ratio bias. I conducted two seasons of field work on the island of Takapourewa to quantify the relationship between rapid vegetation succession and selection of nesting areas. I then used a variety of predictive models to link data on nesting behaviour collected in the field with the microclimate conditions experienced by nesting female tuatara and developing embryos. Using mechanistically modelled soil temperature data, I generated predictions of incubation temperatures, offspring sex ratios, and hatching dates for two populations of tuatara on environmentally distinct islands, Takapourewa and Hauturu, under current and projected future climate scenarios. Finally, I classified the thermal suitability of sites on Hauturu for facilitating successful embryonic development and created geospatial surfaces defining suitable nesting locations adjacent to tuatara habitats. Offspring sex ratios on both islands are unlikely to become male-biased if the magnitude of climate warming observed over the next century more closely matches the minimum, rather than the maximum, projected warming scenario. On Takapourewa, the timing of nesting will be critical in determining whether sex ratios become male-biased under a scenario of maximum climate warming. Earlier nesting may also lead to shifts in hatching phenology under either scenario of climate warming. Warmer annual temperatures on Hauturu are more likely to lead to heavily male-biased offspring sex ratios under the maximum warming scenario. Female tuatara on Hauturu do not need to travel away from their current habitats to locate suitable nesting sites. Monitoring the population to quantify nesting behaviour on the island will be important for determining whether females' choices of incubation microclimates can compensate for the sex ratio-biasing effects of climate change.</p>

Paternal Borderline Symptoms and Offspring Outcomes in Young Adulthood

Borderline personality disorder symptoms (BPDsx) in mothers have been linked to psychopathology in their offspring. However, it is still unclear whether BPDsx in fathers influences offspring psychopathology and, if so, how this risk transmission may occur. A total of 448 father-mother-offspring triads completed a longitudinal study following children from birth until age 20 and included self-report questionnaires and clinical interviews when children were 15 and 20 years old. Results revealed that paternal BPDsx were predictive of youth BPDsx and internalizing symptoms, even after controlling for maternal BPDsx. Chronic family stress was a significant mediator of the relationship between paternal BPDsx and offspring BPDsx, internalizing symptoms, and externalizing symptoms. Fathers' expressed emotion and child temperament were not significant mediators. Although offspring sex predicted youth outcomes, it was not a significant moderator of the association between paternal BPDsx and offspring symptoms. Finally, controlling for comorbid paternal disorders weakened the association between paternal BPDsx and youth psychopathology.

Cannabis and tobacco use prior to pregnancy and subsequent offspring birth outcomes: a 20-year intergenerational prospective cohort study

There is increasing evidence that the life-course origins of health and development begin before conception. We examined associations between timing and frequency of preconception cannabis and tobacco use and next generation preterm birth (PTB), low birth weight (LBW) and small for gestational age. 665 participants in a general population cohort were repeatedly assessed on tobacco and cannabis use between ages 14–29 years, before pregnancy. Associations were estimated using logistic regression. Preconception parent (either maternal or paternal) daily cannabis use age 15–17 was associated with sixfold increases in the odds of offspring PTB (aOR 6.65, 95% CI 1.92, 23.09), and offspring LBW (aOR 5.84, 95% CI 1.70–20.08), after adjusting for baseline sociodemographic factors, parent sex, offspring sex, family socioeconomic status, parent mental health at baseline, and concurrent tobacco use. There was little evidence of associations with preconception parental cannabis use at other ages or preconception parental tobacco use. Findings support the hypothesis that the early life origins of growth begin before conception and provide a compelling rationale for prevention of frequent use during adolescence. This is pertinent given liberalisation of cannabis policy.

Impact of feeding experiences on oviposition and sex allocation of Neoseiulus californicus (Acari: Phytoseiidae)

Feeding experiences of predators during immature and adult stages may impact females’ reproduction. In the present study, we investigated reproductive performances of Neoseiulus californicus when both parents had different feeding experiences on Tetranychus urticae and Frankliniella occidentalis. Female and male immatures fed on either prey species. Each newly emerged female adult individually mated with a male had either the same or different feeding experience. Prey for mated females were either same as or different from that consumed during their immature stages. Therefore, eight reproductive treatments were created. The highest cumulative fecundity (57.5±3.3 eggs/female) was observed when both female and male fed on T. urticae with the lowest fecundity (34.2±2.7 eggs/female) observed when the parents fed on F. occidentalis. Daily fecundity and oviposition duration were mainly affected by prey of mated females. Mated females preyed on T. urticae had 56.6% higher daily fecundity and 22.3% shorter oviposition duration than those preyed on F. occidentalis. No significant difference in offspring sex ratio and egg hatch rate was detected between treatments. About 88% of the first-laid eggs developed to males. Impact of prey species consumed by male immatures was only observed on pre-oviposition duration. The average pre-oviposition duration of females who mated with males fed on T. urticae in their immaturity was 33.0% shorter than those females who mated with males fed on F. occidentalis in their immaturity. Results of the present study are valuable in optimizing N. californicus field release strategies, and will help further investigations into the nutritional requirements of this species.

Early and late fawn mortality in a remnant population of Arabian gazelles (Gazella arabica)

The Arabian gazelle (Gazella arabica) population in Israel has experienced a turbulent conservation history and repeatedly faced local extinction. Low fawn survival was considered the main cause for the constant decline. In our study, we analyzed instantaneous fawn mortality rates, using a binomial coding at three different developmental stages, i.e., mortality rates to 3 months after parturition (weaning age), to 5 months after parturition (male fawns leave their mothers), and to the age of reproductive maturity, i.e., recruitment (12 months). We used a dataset obtained from 20 individually discernible mothers and their fawns (49 females and 48 males) born between June 2006 and September 2019. To explore causes for the fawn mortality rates, parental- (age of the mother at parturition) and offspring-related attributes (offspring sex), year of birth, together with one weather variable (mean monthly maximum temperature) were included as independent variables into three independent mixed effects cox regression models. Out of 97 fawns, 92 survived to weaning age, 73 to the age of 5 months and only 7 to the age of reproductive maturity. Temperature had significant effects on instantaneous fawn mortality rates, suggesting that low temperatures were detrimental to the survival of fawns after weaning (4–5 months) and male dispersal age (6–12 months). Male offspring encountered a higher instantaneous mortality rate than female offspring at the age of 6–12 months. Moreover, fawns from less experienced mother (young age at parturition) experienced higher mortality. Our results were in line with previous studies on fawn mortality observed in other desert dwelling ungulates.