Although it is advantageous for males to express costly sexually selected signals when females are present, they may also benefit from suppressing these signals to avoid costly interactions with rival males. Cuticular chemical profiles frequently function as insect sexual signals; however, few studies have asked whether males alter these signals in response to their social environment. In Drosophila serrata, an Australian fly, there is sexual selection for a multivariate combination of male cuticular hydrocarbons (CHCs). Here, we show that the ratio of females to males that an adult male experiences has a strong effect on his CHC expression, with female-biased adult sex ratios eliciting greater expression of CHC profiles associated with higher male mating success. Classical models predict that male reproductive investment should be highest when there is a small but nonzero number of rivals, but we found that males expressed the most attractive combination of CHCs when there were no rivals. We found that male CHCs were highly sensitive to adult sex ratio, with males expressing higher values of CHC profiles associated with greater mating success as the ratio of females to males increased. Moreover, sex ratio has a stronger effect on male CHC expression than adult density. Finally, we explore whether sex ratio affects the variance among a group of males in their CHC expression, as might be expected if individuals respond differently to a given social environment, but find little effect. Our results reveal that subtle differences in social environment can induce plasticity in male chemical signal expression.
Urban free-roaming dog populations in the developing world are managed by a patchwork of local veterinary practitioners, government programs, and non-governmental organizations with varied effectiveness. While lethal removal is still commonly practiced, vaccination and fertility control methods are increasingly being adopted. Identifying which method(s) provides the most cost effective management is needed to inform dog population managers who seek to limit conflicts like dog bites, the spread of disease, and predation on wildlife. Here we describe an agent-based model that simulates the population of free-roaming dogs in Jaipur, a northwestern Indian city. We then apply various lethal and fertility control methodologies to identify which most effectively lowered the dog population size. This spatially explicit model includes temporal and demographic details of street dog populations modeled after data from the study city. We tested each pairing of control type (lethal or fertility) with search method (how to target efforts) to see their efficacy at altering the city’s dog population size, age structure, sterilization coverage, as well as the number of dogs handled. Models were run for 15 years to assess the long term effects of intervention. We found that the fertility control method that targets areas of the city with the highest percentage of intact bitches outperforms all other fertility control and lethal removal programs at reducing the population size while sterilizing a significantly higher proportion of the population. All lethal program methods skewed population demographics towards significantly younger dogs, thus likely increasing the frequency of conflict with humans. This work demonstrates the benefits of modeling differing management policies in free-roaming dogs.
Changes in microRNA abundance may regulate diapause in the flesh fly, Sarcophaga bullata
Diapause, an alternative developmental pathway characterized by changes in developmental timing and metabolism, is coordinated by molecular mechanisms that are not completely understood. MicroRNA (miRNA) mediated gene silencing is emerging as a key component of animal development and may have a significant role in initiating, maintaining, and terminating insect diapause. In the present study, we test this possibility by using high-throughput sequencing and qRT-PCR to discover diapause-related shifts in miRNA abundance in the flesh fly, Sarcophaga bullata. We identified ten evolutionarily conserved miRNAs that were differentially expressed in diapausing pupae compared to their nondiapausing counterparts. miR-289-5p and miR-1-3p were overexpressed in diapausing pupae and may be responsible for silencing expression of candidate genes during diapause. miR-9c-5p, miR-13b-3p, miR-31a-5p, miR-92b-3p, miR-275-3p, miR-276a-3p, miR-277-3p, and miR-305-5p were underexpressed in diapausing pupae and may contribute to increased expression of heat shock proteins and other factors necessary for the enhanced environmental stress-response that is a feature of diapause. In S. bullata, a maternal effect blocks the programming of diapause in progeny of females that have experienced pupal diapause, and in this study we report that several miRNAs, including MiR-263a-5p, miR-100-5p, miR-125-5p, and let-7-5p were significantly overexpressed in such nondiapausing flies and may prevent entry into diapause. Together these miRNAs appear to be integral to the molecular processes that mediate entry into diapause.
Typification of Hyobanche sanguinea (Orobanchaceae) and the identity of Hyobanche calvescens and Hyobanche glabrata
Hyobanche sanguinea (Orobanchaceae) is a member of a small genus of holoparasitic plants endemic to southern Africa. The description by Linnaeus in 1771 did not include a designated holotype, and no such material has been located in the Linnaean herbaria housed in London or Uppsala. After studying the Linnaean collection of Hyobanche specimens, and researching the history of botany in South Africa, a lectotype is here designated, and an epitype from the Cape Peninsula assigned. In addition, a study of type specimens for H. calvescens, H. glabrata, and H. rubra reveals that the type specimens for H. calvescens and H. glabrata fall within the circumscription of H. rubra, resulting in synonymization of both names.
Dehydration resistance and tolerance in the brush-legged wolf spider (Schizocosa ocreata): A comparison of survivorship, critical body water content, and water loss rates between sexes.
Small-bodied terrestrial animals like spiders face challenges maintaining water reserves essential for homeostasis. They may experience dry microclimates and/or seasonal variation in water availability, so dehydration is a common stressor that may help explain movement, foraging, and other behaviors. This study examines aspects of dehydration resistance and tolerance in the brush-legged wolf spider, Schizocosa ocreata (Hentz, 1844) (Aranaea: Lycosidae), commonly found in the leaf litter of eastern deciduous forests of North America. Sexes differ in morphology, physiology, reproductive strategy, and life history, likely resulting in divergent abilities to resist and tolerate dehydration. We used humidity-controlled chambers to examine relative survivorship by sex under varying humidity regimes, water loss rates, body water content, and critical water mass. Spiders survived significantly longer in higher humidity regimes (≥50% RH). Females had significantly better survivorship overall, lower body loss rates, and lower critical mass, though males had greater percent body water content, indicating that females have greater dehydration resistance and tolerance than males. Although sex based differences in survival time and water loss rates are likely an effect of relative body mass, females should be more successful than males during periods of episodic drought, and are likely selected to survive later in the season while caring for offspring.