Sexual Selection: Signals to Die for

SummarySexual signals are conspicuous and are typically assumed to be energetically costly, which keeps them honest. A recent study on fireflies has found that signal production is energetically cheap, but signalling remains expensive because of eavesdropping predators

Monitoring the Effects of Tenofovir Disoproxil Fumarate to Tenofovir Alafenamide Switch for Tubulotoxicity in Highly Treatment-Experienced or in Very Sick Individuals Infected with HIV

Tenofovir disoproxil fumarate (TDF) is a common antiretroviral utilised in the treatment of human immunodeficiency virus (HIV) and hepatitis B infections. It is associated with the development of tubulotoxicity and tubulopathies, and is not recommended in the treatment of patients with baseline chronic kidney disease. Until now, guidelines have suggested frequent monitoring of serum biochemistry to detect the development of such complications. In recent trials, a new prodrug formulation of tenofovir alafenamide (TAF) has been shown to exhibit less tubular toxicity than its counterpart due to a lower serum concentration of its metabolites. In this article, we share our experience with two patients who developed tubulotoxicity following the commencement of TDF-based regimens in HIV, and its improvement following its change to TAF, and review the available literature regarding tenofovir-based nephrotoxicity

Male water striders attract predators to intimidate females into copulation

Despite recent advances in our understanding of sexual conflict and antagonistic coevolution between sexes, the role of interspecific interactions, such as predation, in these evolutionary processes remains unclear. In this paper, we present a new male mating strategy whereby a male water strider Gerris gracilicornis intimidates a female by directly attracting predators as long as she does not accept the male's coercive copulation attempt. We argue that this male strategy is a counteradaptation to the evolution of the female morphological shield protecting her genitalia from coercive intromission by water strider males. The G. gracilicornis mating system clearly represents an effect expected from models of the coevolutionary arms race between sexes, whereby one sex causes a decrease in the fitness component of the other sex. Moreover, our study demonstrates a crucial role that interspecific interactions such as predation can have in the antagonistic coevolution between sexes

Pleiotropic Effects of DDT Resistance on Male Size and Behaviour

Understanding the evolution and spread of insecticide resistance requires knowing the relative fitness of resistant organisms. In the absence of insecticides, resistance is predicted to be costly. The Drosophila melanogaster DDT resistance allele (DDT-R) is associated with a male mating cost. This could be because resistant males are generally smaller, but DDT-R may also alter courtship behaviours. Here we tested for body size and courtship effects of DDT-R on mating success in competitive and non-competitive mating trials respectively. We also assessed relative aggression in resistant and susceptible males because aggression can also influence mating success. While the effect of DDT-R on male size partly contributed to reduced mating success, resistant males also had lower rates of courtship and were less aggressive than susceptible males. These differences contribute to the observed DDT-R mating costs. Additionally, these pleiotropic effects of DDT-R are consistent with the history and spread of resistance alleles in nature

Polyandry Is a Common Event in Wild Populations of the Tsetse Fly Glossina fuscipes fuscipes and May Impact Population Reduction Measures

Glossina fuscipes fuscipes is the most common tsetse species in Uganda where it is responsible for transmitting Trypanosoma brucei rhodensiense and Trypanosoma brucei gambiense parasites causing sleeping sickness in humans in addition to related trypanosomes that cause Nagana in cattle. An understanding of the reproductive biology of this vector is essential for the application of sustainable control/eradication methods such as Sterile Insect Technique (SIT). We have analysed the number of times a female mates in the wild as this aspect of the reproductive behaviour may affect the stability and size of populations. We provide evidence that remating is a common event in the wild and females store sperm from multiple males, which may potentially be used for insemination. In vector eradication programmes, re-infestation of cleared areas and/or in cases of residual populations, the occurrence of remating may unfortunately enhance the reproductive potential of the re-invading propagules. We suggest that population age structure may influence remating frequency. Considering the seasonal demographic changes that this fly undergoes during the dry and wet seasons, control programmes based on SIT should release large numbers of sterile males, even in residual surviving target populations, in the dry season

Infectious Speciation Revisited: Impact of Symbiont-Depletion on Female Fitness and Mating Behavior of Drosophila paulistorum

The neotropical Drosophila paulistorum superspecies, consisting of at least six geographically overlapping but reproductively isolated semispecies, has been the object of extensive research since at least 1955, when it was initially trapped mid-evolution in flagrant statu nascendi. In this classic system females express strong premating isolation patterns against mates belonging to any other semispecies, and yet uncharacterized microbial reproductive tract symbionts were described triggering hybrid inviability and male sterility. Based on theoretical models and limited experimental data, prime candidates fostering symbiont-driven speciation in arthropods are intracellular bacteria belonging to the genus Wolbachia. They are maternally inherited symbionts of many arthropods capable of manipulating host reproductive biology for their own benefits. However, it is an ongoing debate as to whether or not reproductive symbionts are capable of driving host speciation in nature and if so, to what extent. Here we have reevaluated this classic case of infectious speciation by means of present day molecular approaches and artificial symbiont depletion experiments. We have isolated the α-proteobacteria Wolbachia as the maternally transmitted core endosymbionts of all D. paulistorum semispecies that have coevolved towards obligate mutualism with their respective native hosts. In hybrids, however, these mutualists transform into pathogens by overreplication causing embryonic inviability and male sterility. We show that experimental reduction in native Wolbachia titer causes alterations in sex ratio, fecundity, and mate discrimination. Our results indicate that formerly designated Mycoplasma-like organisms are most likely Wolbachia that have evolved by becoming essential mutualistic symbionts in their respective natural hosts; they have the potential to trigger pre- and postmating isolation. Furthermore, in light of our new findings, we revisit the concept of infectious speciation and discuss potential mechanisms that can restrict or promote symbiont-induced speciation at post- and prezygotic levels in nature and under artificial laboratory conditions

Successful breeding predicts divorce in plovers

When individuals breed more than once, parents are faced with the choice of whether to re-mate with their old partner or divorce and select a new mate. Evolutionary theory predicts that, following successful reproduction with a given partner, that partner should be retained for future reproduction. However, recent work in a polygamous bird, has instead indicated that successful parents divorced more often than failed breeders (Halimubieke et al. in Ecol Evol 9:10734–10745, 2019), because one parent can benefit by mating with a new partner and reproducing shortly after divorce. Here we investigate whether successful breeding predicts divorce using data from 14 well-monitored populations of plovers (Charadrius spp.). We show that successful nesting leads to divorce, whereas nest failure leads to retention of the mate for follow-up breeding. Plovers that divorced their partners and simultaneously deserted their broods produced more offspring within a season than parents that retained their mate. Our work provides a counterpoint to theoretical expectations that divorce is triggered by low reproductive success, and supports adaptive explanations of divorce as a strategy to improve individual reproductive success. In addition, we show that temperature may modulate these costs and benefits, and contribute to dynamic variation in patterns of divorce across plover breeding systems

The overseas mail service of the colony of South Australia 1836-1901

© 1951 Margaret Ch. de CrespignyIntroduction: Before the first contract was made with a steamship company for the carriage of mails between England and Australia in 1852, no attempt was made by the British Government to provide a regular mail service to each of the Australian colonies. A contract was signed in 1843 for a monthly service of sailing ships to carry the mails to Sydney and back, but no provision was made for the other colonies, and the official packet service was usually slower than the service given by private vessels carrying mails. The colonies were therefore dependent upon the traders and transport sailing vessels calling at their ports, and forwarded their mails by them direct, or else to neighbouring colonies for onward transmission. Their mails were received in a similar manner. Opportunities were not very frequent in South Australia during the first few years after its settlement, but they increased during the forties, and by the turn of the half century opportunities were most frequent. Arrangements were made in 1842 for mails to be forwarded from and to England from South Australia via India and Suez by the P. and O. Company, or between Bombay and Suez by the East India Company, various persons in India acting as forwarding agents. This route, which was subsequently improved by the mails being forwarded across France between Marseilles and Calais, took longer that the direct all-sea route. The Sydney packet service, after a three year trial, also proved unsatisfactory for South Australian mails. So that the carriage of mails between Adelaide and England and the continent was entirely subject to the vagaries of the shipping traffic of traders and transports, all of which were compelled by law to accept and deliver mails, but whose movements were uncontrolled and unreliable. The average time taken for transporting mails to or from England between 1840 and 1850 was about 158 days; towards the end of the forties the usual time taken was from 120 to 130 days. The voyage out was on average quicker than the voyage home. During the forties, agitation, both in Australia and England, for the inception of a steamship mail service, grew with increasing vigour until the British Government was finally induced to contract with the Australian Royal Mail Steam Navigation Company in 1852 for the carriage of mails to the Australian colonies. The discovery of gold in Australia, and the repeal of the Navigation Laws in 1850, doubtless influence the decision of the authorities, but in any case it would not have been possible for them to have withstood the demands voiced both in England and Australia for what was obviously a most essential requisite for England’s relationship, social, economic, and administrative, with Australia, viz. a regular steamship mail service