Genetic diversity among asexual and sexual progenies of Phytophthora capsici detected with ISSR markers

The population structure of Phytophthora capsici among asexual and sexual progenies was analyzed using ISSR. Thirty asexual progenies of one parent and three sexual populations were assayed for genetic diversity using 5 ISSR primers and DNA from 120 offspring of P. capsici was amplified. In total, 71 reproducible ISSR fragments were obtained, of which 100% were polymorphic, revealing high polymorphism among the isolates. Among them, the percentages of polymorphism of sexual and asexual progeny isolates were 100.00 and 77.46%, respectively. Genetic similarity coefficients among all the isolates ranged from 0.54 to 0.73. The sexual offspring population showed much more variability than the asexual offspring population with 76.26% variability attributed to diversity within populations as compared with 23.74% among populations. This research reveals that the sexual progeny population of P. capsici contributes more genetic diversity than that of asexual progeny population.

The Inquiline Ant Myrmica karavajevi Uses Both Chemical and Vibroacoustic Deception Mechanisms to Integrate into Its Host Colonies

Social parasitism represents a particular type of agonistic interaction in which a parasite exploits an entire society instead of a single organism. One fascinating form of social parasitism in ants is the “inquilinism”, in which a typically worker-less parasitic queen coexists with the resident queen in the host colony and produces sexual offspring. To bypass the recognition system of host colonies, inquilines have evolved a repertoire of deceiving strategies. We tested the level of integration of the inquiline Myrmica karavajevi within the host colonies of M. scabrinodis and we investigated the mechanisms of chemical and vibroacoustic deception used by the parasite. M. karavajevi is integrated into the ant colony to such an extent that, in rescue experiments, the parasite pupae were saved prior to the host’s brood. M. karavajevi gynes perfectly imitated the cuticular hydrocarbon profiles of M. scabrinodis queens and the parasite vibroacoustic signals resembled those emitted by the host queens eliciting the same levels of attention in the host workers during playback experiments. Our results suggest that M. karavajevi has evolved ultimate deception strategies to reach the highest social status in the colony hierarchy, encouraging the use of a combined molecular and behavioural approach when studying host–parasite interactions.

Eusociality and the evolution of aging in superorganisms

Eusocial insects ants, bees, wasps and termites are being recognized as model organisms to unravel the evolutionary paradox of aging for two reasons: (1) queens (and kings, in termites) of social insects outlive similar sized solitary insects by up to several orders of magnitude; (2) all eusocial taxa show a divergence of long queen and shorter worker lifespans, despite their shared genomes and even under risk-free laboratory environments. Traditionally, these observations have been explained by invoking classical evolutionary aging theory: well-protected inside their nests, queens are much less exposed to external hazards than foraging workers, and this provides natural selection the opportunity to favor queens that perform well at advanced ages. Although quite plausible, these verbal arguments have not been backed up by mathematical analysis. Here, for the first time, we provide quantitative models for the evolution of caste specific aging patterns. We show that caste-specific mortality risks are in general neither sufficient nor necessary to explain the evolutionary divergence in lifespan between queens and workers and the extraordinary queen lifespans. Reproductive monopolization and the delayed production of sexual offspring in highly social colonies lead natural selection to inherently favor queens that live much longer than workers, even when exposed to the same external hazards. Factors that reduce a colony's reproductive skew, such as polygyny and worker reproduction, tend to reduce the evolutionary divergence in lifespan between queens and workers. Caste-specific extrinsic hazards also affect lifespan divergence but to a much smaller extent than reproductive monopolization.

OPTIMAL RATIO OF MALE AND SEXUAL FEMALE IN THE MATING OF MOINA MACROCOPA (CRUSTACEA, MONIDAE)

Moina macrocopa is a natural feed that can be cultured to producing ephippia as a bioproduct for fish and shrimp larvae feed. The number of males in the population affects the quality and quantity of ephippia produced. This study was conducted with the purpose of examining the female age in M. macrocopa mating and examining the ratio male-female M. macrocopa in the mating on the quantity and quality of ephippia produced. The treatment in this research was the ratio male-female sex of 1:30, 3:30, 5:30, 7: 30. 9:30., 12:30, 15: 30. Male and female sexual offspring M macrocopa were produced from cultured using a combination of induction factors such as density, feed concentration, kairomones and dissolved oxygen. male and female offspring produced were cultured with a density of 1000 ind/ L. This mating culture was using a container with a volume of water of 2 ml per individual. The results of this study were indicated that mating M. macrocopa using 70-hour old sexual females resulted in the highest ephippia production. Mating M. macrocopa with a sex ratio of 9:30 (male and female sexual) ware resulted in ephippia containing two eggs of 100%, with ephippia hatching degree of 35.4- 38.3%.

Hybrid forms of mandarin (Citrus reticulata blanco var. Unchiu tan.) from interspecific crosses and their characteristics

Representatives of the genus Citrus L., which includes C. limon, C. sinensis, C. reticulata, C. paradisi, C. maxima, C. medica, C. aurantifolia and other species are the most important fruit crops in countries with subtropical and tropical climates. Cross-pollination, variability of sexual offspring fixed by apomixis, preserved during vegetative propagation contributed to the appearance of intergeneric and interspecific hybrids combining characters and properties of different species. The aim of this work was to carry out interspecific crosses to create biodiversity of Citrus reticulata Blanco var. unchiu Tan. and create new forms with breeding valuable traits. Six interspecific combinations of crossings with the involvement of different varieties were carried out, and a large variety of seedlings was obtained. In sexual offspring from interspecific crosses, a high degree of phenotypic variability is observed on the leaf blade, in shape, size, color of the fruit, thickness and separability of the peel, the presence and absence of seeds, as well as organoleptic properties. All these characteristics represent important criteria for the variety. According to the totality of morphological characters, 24 promising forms were selected. The combination of C. reticulata × C. maxima crossing is the most productive, which allowed us to identify the largest number of forms with breeding valuable traits. Forms Yub - P Nmik; Yub – P Nmik - 1; MV - P Azah; MV - P Azah - 1; MV - P Azah - 2; Kr - P Azah; Cr - P Azah – 1 are promising and are important for the creation of new large-fruited varieties of mandarin. From combination of crossbreeding with C. sinensis such forms as KV - ApV, KV-ApV-2, MV-ApV-1were identified, characterized by large-fruited, fruits with high organoleptic properties. Hybrids bred with C. medica, C. aurantifolia, C. limon meyer are important for creating citrus biodiversity with valuable traits.

Lower bumblebee colony reproductive success in agricultural compared with urban environments

Urbanization represents a rapidly growing driver of land-use change. While it is clear that urbanization impacts species abundance and diversity, direct effects of urban land use on animal reproductive success are rarely documented. Here, we show that urban land use is linked to long-term colony reproductive output in a key pollinator. We reared colonies from wild-caught bumblebee ( Bombus terrestris ) queens, placed them at sites characterized by varying degrees of urbanization from inner city to rural farmland and monitored the production of sexual offspring across the entire colony cycle . Our land-use cluster analysis identified three site categories, and this categorization was a strong predictor of colony performance. Crucially, colonies in the two clusters characterized by urban development produced more sexual offspring than those in the cluster dominated by agricultural land. These colonies also reached higher peak size, had more food stores, encountered fewer parasite invasions and survived for longer. Our results show a link between urbanization and bumblebee colony reproductive success, supporting the theory that urban areas provide a refuge for pollinator populations in an otherwise barren agricultural landscape.

Asplanchna-kairomone induces life history shifts in Brachionus angularis (Rotifera)

Predator-derived kairomones play an important role in ecological and evolutionary processes that enable the prey to survive predation pressure. In the presence of predatory Asplanchna, some Brachionus and Keratella species develop morphological and behavioral defenses, but whether rapid population growth and diapause are inducible defenses largely remains unknown. In the present study, parental B. angularis females cultured at 1.0 × 106 and 2.0 × 106 cells · mL−1 of Scenedesmus obliquus were indirectly exposed to 0, 40, 80 and 160 ind. L−1 of A. brightwelli using mesh enclosure, and their life-table demographic parameters, population growth rates and morphological characters were calculated and measured. The results showed that Asplanchna-released kairomone decreased significantly average lifespan, life expectancy at hatching, generation time and net reproduction rate, but increased the proportion of sexual offspring of parental B. angularis females. The threshold Asplanchna density required for significant effects varied with food level. Kairomone released by Asplanchna at 80 ind. L−1 increased significantly the intrinsic rate of population increase of B. angularis cultured at 2.0 × 106 cells · mL−1 of S. obliquus, which would offset the mortality of exposed females from predation. The accumulation of kairomone in aquatic environments enhanced the indirect effect of Asplanchna on the population growth of B. angularis. The present results indicated that rapid population growth of B. angularis induced by Asplanchna kairomone might facilitate the coexistence of preys with predators, and higher proportion of sexual offspring and then resting egg production might help the preys avoid the predator in time instead of facing the enemy through defenses.

Is meiosis a fundamental cause of inviability among sexual and asexual plants and animals?

Differences in viability between asexually and sexually generated offspring strongly influence the selective advantage and therefore the prevalence of sexual reproduction (sex). However, no general principle predicts when sexual offspring will be more viable than asexual offspring. We hypothesize that when any kind of reproduction is based on a more complex cellular process, it will encompass more potential failure points, and therefore lower offspring viability. Asexual reproduction (asex) can be simpler than sex, when offspring are generated using only mitosis. However, when asex includes meiosis and meiotic restitution, gamete production is more complex than in sex. We test our hypothesis by comparing the viability of asexual and closely related sexual offspring across a wide range of plants and animals, and demonstrate that meiotic asex does result in lower viability than sex; without meiosis, asex is mechanistically simple and provides higher viability than sex. This phylogenetically robust pattern is supported in 42 of 44 comparisons drawn from diverse plants and animals, and is not explained by the other variables included in our model. Other mechanisms may impact viability, such as effects of reproductive mode on heterozygosity and subsequent viability, but we propose the complexity of cellular processes of reproduction, particularly meiosis, as a fundamental cause of early developmental failure and mortality. Meiosis, the leading cause of inviability in humans, emerges as a likely explanation of offspring inviability among diverse eukaryotes.

Sex as a strategy against rapidly evolving parasites

Why is sex ubiquitous when asexual reproduction is much less costly? Sex disrupts coadapted gene complexes; it also causes costs associated with mate finding and the production of males who do not themselves bear offspring. Theory predicts parasites select for host sex, because genetically variable offspring can escape infection from parasites adapted to infect the previous generations. We examine this using a facultative sexual crustacean, Daphnia magna, and its sterilizing bacterial parasite, Pasteuria ramosa . We obtained sexually and asexually produced offspring from wild-caught hosts and exposed them to contemporary parasites or parasites isolated from the same population one year later. We found rapid parasite adaptation to replicate within asexual but not sexual offspring. Moreover, sexually produced offspring were twice as resistant to infection as asexuals when exposed to parasites that had coevolved alongside their parents (i.e. the year two parasite). This fulfils the requirement that the benefits of sex must be both large and rapid for sex to be favoured by selection.