The function and evolution of male and female genitalia in Phyllophaga Harris scarab beetles (Coleoptera: Scarabaeidae)

Genitalia diversity in insects continues to fuel investigation of the function and evolution of these dynamic structures. Whereas most studies have focused on variation in male genitalia, an increasing number of studies on female genitalia have uncovered comparable diversity among females, but often at a much finer morphological scale. In this study, we analysed the function and evolution of male and female genitalia in Phyllophaga scarab beetles, a group in which both sexes exhibit genitalic diversity. To document the interaction between male and female structures during mating, we dissected flash‐frozen mating pairs from three Phyllophaga species and investigated fine‐scale morphology using SEM. We then reconstructed ancestral character states using a species tree inferred from mitochondrial and nuclear loci to elucidate and compare the evolutionary history of male and female genitalia. Our dissections revealed an interlocking mechanism of the female pubic process and male parameres that appears to improve the mechanical fit of the copulatory position. The comparative analyses, however, did not support coevolution of male and female structures and showed more erratic evolution of the female genitalia relative to males. By studying a group that exhibits obvious female genitalic diversity, we were able to demonstrate the relevance of female reproductive morphology in studies of male genital diversity.     

Improved enantioselectivity of thermostable esterase ST0071 from archaeon Sulfolobus tokodaii by site-saturation mutagenesis

An archaeon GGG(A)X-type esterase (ST0071) can catalyze the hydrolysis of various acetates of secondary alcohols, but shows low enantioselectivity. Using structure-guided site-saturation mutagenesis, we successfully identified a G274W variant that has excellent selectivity compared with that of wild-type ST0071.     

The constant philopater hypothesis: a new life history invariant for dispersal evolution

Surprising invariance relationships have emerged from the study of social interaction, whereby a cancelling‐out of multiple partial effects of genetic, ecological or demographic parameters means that they have no net impact upon the evolution of a social behaviour. Such invariants play a pivotal role in the study of social adaptation: on the one hand, they provide theoretical hypotheses that can be empirically tested; and, on the other hand, they provide benchmark frameworks against which new theoretical developments can be understood. Here we derive a novel invariant for dispersal evolution: the ‘constant philopater hypothesis’ (CPH). Specifically, we find that, irrespective of variation in maternal fecundity, all mothers are favoured to produce exactly the same number of philopatric offspring, with high‐fecundity mothers investing proportionally more, and low‐fecundity mothers investing proportionally less, into dispersing offspring. This result holds for female and male dispersal, under haploid, diploid and haplodiploid modes of inheritance, irrespective of the sex ratio, local resource availability and whether mother or offspring controls the latter's dispersal propensity. We explore the implications of this result for evolutionary conflict of interests – and the exchange and withholding of contextual information – both within and between families, and we show that the CPH is the fundamental invariant that underpins and explains a wider family of invariance relationships that emerge from the study of social evolution.     

Pre‐adapting parasitic phages to a pathogen leads to increased pathogen clearance and lowered resistance evolution with Pseudomonas aeruginosa cystic fibrosis bacterial isolates

Recent years have seen renewed interest in phage therapy – the use of viruses to specifically kill disease‐causing bacteria – because of the alarming rise in antibiotic resistance. However, a major limitation of phage therapy is the ease at with bacteria can evolve resistance to phages. Here, we determined whether in vitro experimental coevolution can increase the efficiency of phage therapy by limiting the resistance evolution of intermittent and chronic cystic fibrosis Pseudomonas aeruginosa lung isolates to four different phages. We first pre‐adapted all phage strains against all bacterial strains and then compared the efficacy of pre‐adapted and nonadapted phages against ancestral bacterial strains. We found that evolved phages were more efficient in reducing bacterial densities than ancestral phages. This was primarily because only 50% of bacterial strains were able to evolve resistance to evolved phages, whereas all bacteria were able to evolve some level of resistance to ancestral phages. Although the rate of resistance evolution did not differ between intermittent and chronic isolates, it incurred a relatively higher growth cost for chronic isolates when measured in the absence of phages. This is likely to explain why evolved phages were more effective in reducing the densities of chronic isolates. Our data show that pathogen genotypes respond differently to phage pre‐adaptation, and as a result, phage therapies might need to be individually adjusted for different patients.     

Experimentally evolved and phenotypically plastic responses to enforced monogamy in a hermaphroditic flatworm

Sexual selection is considered a potent evolutionary force in all sexually reproducing organisms, but direct tests in terms of experimental evolution of sexual traits are still lacking for simultaneously hermaphroditic animals. Here, we tested how evolution under enforced monogamy affected a suite of reproductive traits (including testis area, sex allocation, genital morphology, sperm morphology and mating behaviour) in the outcrossing hermaphroditic flatworm Macrostomum lignano, using an assay that also allowed the assessment of phenotypically plastic responses to group size. The experiment comprised 32 independent selection lines that evolved under either monogamy or polygamy for 20 generations. While we did not observe an evolutionary shift in sex allocation, we detected effects of the selection regime for two male morphological traits. Specifically, worms evolving under enforced monogamy had a distinct shape of the male copulatory organ and produced sperm with shorter appendages. Many traits that did not evolve under enforced monogamy showed phenotypic plasticity in response to group size. Notably, individuals that grew up in larger groups had a more male‐biased sex allocation and produced slightly longer sperm than individuals raised in pairs. We conclude that, in this flatworm, enforced monogamy induced moderate evolutionary but substantial phenotypically plastic responses.     

Local adaptation to developmental density does not lead to higher mating success in Drosophila melanogaster

In this study, we investigate the effect of local adaptation to developmental density on male mating success in laboratory populations of Drosophila melanogaster. Mating success is known to be influenced by body condition which can in turn be influenced by local adaptation. We test the hypothesis that males adapted to a given environment have higher mating success when assayed in that environment. We used males selected for adaptation to high larval density and their controls which are reared at low larval density. We grew assay males in low and high densities whereas the focal females (raised at low larval density) used for the experiment belonged to the common ancestor of selected and control populations. We considered selected males grown at high density and control males grown at low density as ‘adapted’. Similarly, we considered selected males grown at low density and control males grown at high density as ‘nonadapted’. Selected male belonging to a given treatment (larval density) was made to compete with control male of the same treatment for mating with ancestral female. We quantified components of reproductive fitness: mating latency, copulation duration, mating success and number of progeny sired by the ‘adapted’ and ‘nonadapted’ males. The results show that local adaptation does not lead to higher mating success in populations adapted to their own larval rearing environment.     

One size fits all? Determinants of sperm transfer in a highly dimorphic orb‐web spider

The evolutionary significance of widespread hypo‐allometric scaling of genital traits in combination with rapid interspecific genital trait divergence has been of key interest to evolutionary biologists for many years and remains poorly understood. Here, we provide a detailed assessment of quantitative genital trait variation in males and females of the sexually highly dimorphic and cannibalistic orb‐weaving spider Argiope aurantia. We then test how this trait variation relates to sperm transfer success. In particular, we test specific predictions of the one‐size‐fits‐all and lock‐and‐key hypotheses for the evolution of genital characters. We use video‐taped staged matings in a controlled environment with subsequent morphological microdissections and sperm count analyses. We find little support for the prediction of the one‐size‐fits‐all hypothesis for the evolution of hypo‐allometric scaling of genital traits, namely that intermediate trait dimensions confer highest sperm transfer success. Likewise, our findings do not support the prediction of the lock‐and‐key hypothesis that a tight fit of male and female genital traits mediates highest sperm transfer success. We do, however, detect directional effects of a number of male and female genital characters on sperm transfer, suggesting that genital trait dimensions are commonly under selection in nature. Importantly, even though females are much larger than males, spermatheca size limits the number of sperm transferred, contradicting a previous hypothesis about the evolutionary consequences of genital size dimorphism in extremely size‐dimorphic taxa. We also find strong positive effects of male body size and copulation duration on the probability of sperm transfer and the number of sperm transferred, with implications for the evolution of extreme sexual size dimorphism and sexual cannibalism in orb weavers.     

Population differentiation in the context of Holocene climate change for a migratory marine species,the southern elephant seal

Understanding observed patterns of connectivity requires an understanding of the evolutionary processes that determine genetic structure among populations, with the most common models being associated with isolation by distance, allopatry or vicariance. Pinnipeds are annual breeders with the capacity for extensive range overlap during seasonal migrations, establishing the potential for the evolution of isolation by distance. Here, we assess the pattern of differentiation among six breeding colonies of the southern elephant seal, Mirounga leonina, based on mtDNA and 15 neutral microsatellite DNA markers, and consider measures of their demography and connectivity. We show that all breeding colonies are genetically divergent and that connectivity in this highly mobile pinniped is not strongly associated with geographic distance, but more likely linked to Holocene climate change and demographic processes. Estimates of divergence times between populations were all after the last glacial maximum, and there was evidence for directional migration in a clockwise pattern (with the prevailing current) around the Antarctic. We discuss the mechanisms by which climate change may have contributed to the contemporary genetic structure of southern elephant seal populations and the broader implications.     

植菌昆虫与其共生真菌协同进化分子机制

昆虫菌业（fungiculture）是一种类似于人类种植业的昆虫种植体系,包括种植、耕作、收获和营养依赖4个过程,可分为高级的社会性昆虫如切叶蚂蚁、白蚁等和低级的非社会性昆虫如食菌小蠹虫、卷叶象甲、蜥蜴甲虫、树蜂等,它们均能种植并取食真菌。近年来随着组学及微生物组技术的发展,植菌昆虫与其共生真菌协同进化的分子机制研究方面取得了重要进展。系统发育分析阐明了植菌昆虫的起源与进化历程,并显示出与共生真菌系统发育的一致性;共生真菌细胞核数量也从双核增加到最多17个核,而染色体倍型也从单倍体增加为二倍体甚至多倍体;组学分析则揭示了植菌昆虫与其共生真菌在精氨酸、碳水化合物、木质素及几丁质合成或降解等方面显示出了高度的协同进化。本文系统综述了植菌昆虫及其共生真菌的系统进化、核进化及基因组进化进展,并探讨这种协同进化机制的生物学意义。