Interclonal variability in the photoperiodic responses of the pea aphid Acyrthosiphon pisum and intraclonal differences between wingless viviparous females (=apterae) and winged viviparous females (=alatae) were studied. In 7 clones collected from peas near St.Petersburg the effect of constant diel photoperiods (from 0L : 24D to 24L : 0D at 20°C) on sexual morph determination and dynamics of morph production were recorded. Apterae of 5 clones and apterae and alatae of 2 clones were studied. The mean and age-dependent fecundity of apterae and alatae were compared. The clones studied in detail can be divided in two groups. The first includes clones that produced winged males and had critical photoperiods for female morph determination around 12L : 12D. The second includes clones with critical photoperiods for female morph determination around 17L : 7D; these clones produced wingless males, and one clone produced only oviparae. The intraclonal differences in the photoperiodic limits for ovipara and male production depended on the clone-specific abundance of males. The shapes of the photoperiodic curves for male production also depended on the clone-specific abundance of males. In short-day conditions alatae produced more oviparae and fewer males, and the range of photoperiods that induced ovipara production in alatae was nearly twice as wide as that in apterae. The photoperiodic limits for ovipara and male production differed for apterae and alatae. The fecundity of alatae was lower, although they reproduced for longer and lived longer than apterae. Both apterae and alatae reproduced more intensively over the first 2 weeks. Apterae and alatae began to produce males at the same age. Because of their late onset of larviposition, the reproductive pause that divides female and male production was obscured in alatae. Both apterae and alatae tended to produce initially and finally batches of viviparous offspring, possibly reflecting age-dependent endogenous changes in the hormonal titres in the parents.
Selected life-history traits of an oonopid spider, Triaeris stenaspis Simon, which has been introduced into greenhouses in Europe, were investigated. Spiders were reared in the laboratory under constant physical and dietary conditions, and followed from egg to death. The spiders passed through 3 juvenile instars, each lasting approximately a month. The adult stage lasted on average 6 months, which is 54% of the entire life cycle. The mortality in each juvenile instar was similar. Five morphological characters were recorded for each instar, which provided a reliable means of identifying the developmental stages. All spiders developed into females and although kept isolated they laid fertile eggs, which indicates thelytokous parthenogenesis. Eggs were always enclosed in a disc-shaped egg-sac, each containing 2 eggs. Total fecundity was on average 27 eggs and rate of laying eggs decreased with age. Fecundity was positively correlated with adult longevity. Fertility was rather low, approximately 59%. It was negatively correlated with fecundity but not related to longevity. Low fertility appears to be the only cost of parthenogenetic reproduction. There was considerable genotypic variation in all traits studied compared to that in sexually reproducing spiders. There were no apparent maternal effects on all the traits studied. Using molecular methods proved that parthenogenesis in T. stenaspis is not induced by the endosymbiotic bacteria, Wolbachia sp. or Cardinium sp.
a1_This study describes the parasitoid species complex associated with seven closely related species of sexual (Siederia rupicollella, S. listerella, Dahlica lazuri, D. charlottae and D. lichenella) and parthenogenetic (Dahlica fennicella and D. triquetrella) Naryciinae (Lepidoptera: Psychidae) in Central Finland. A thorough ecological analysis of all the species of parasitoids recorded was combined with analyses of molecular data. Mitochondrial and nuclear DNA data were obtained from all the species in order to (1) detect cryptic species associated with host specialization, (2) assign undescribed males to females, and (3) verify the morphological identification of closely related species. A DNA barcoding technique was employed to identify host species from parasitized larval remains. By sampling more than 10,000 host larvae, of which 25.7% were parasitized, nine parasitoid species were identified morphologically, including both koinobionts (Ichneumonidae: Diadegma incompletum, Macrus parvulus, Trachyarus borealis, T. solyanikovi, T. fuscipes, T. brevipennis and Braconidae: Meteorus affinis) and idiobionts (Ichneumonidae: Orthizema flavicorne, Gelis fuscicornis). Ecological characteristics such as time and mode of host attack, time of emergence and level of specialization differed widely. The results show that differences in parasitoid biology need to be taken into account when studying differences in percentage parasitism of sexual and parthenogenetic Naryciinae. The molecular data revealed that one parasitoid species M. parvulus may consist of two cryptic forms associated with the sexual and parthenogenetic hosts, respectively. The data further establishes that T. brevipennis and some T. fuscipes are in fact morphotypes of one species. The large variation in mitochondrial DNA within species and its inconsistency with nuclear DNA demonstrate that current species and genus delimitation is inadequate in the, a2_Trachyarus species group. Our study shows that it is essential to use DNA barcoding methods when investigating host-parasitoid complexes., and Jelmer A. Elzinga, Kees Zwakhals, Johanna Mappes, Alessandro Grapputo.
This paper reviews recent use of flow cytometry in studies on apomictic plant taxa. The most of apomictic angiosperms are polyploid, often differing in ploidy level from their sexual counterparts within the agamic complex. Flow cytometry is widely used for screening the ploidy levels of mature plants and their seed generated both in the field and in experiments. Routine ploidy screening often accompanied by molecular markers distinguishing individual genotypes are used to reveal novel insights into the biosystematics and population biology of apomictic taxa. Apomixis (asexual seed formation) is mostly facultative, operating together with other less frequent reproductive pathways within the same individual. The diversity in modes of reproduction in apomicts is commonly reflected in the ploidy structure of their progeny in mixed-cytotype populations. Thus, flow cytometry facilitates the detection and quantification of particular progeny classes generated by different reproductive pathways. The specific embryo/endosperm ploidy ratios, typical of the different reproductive pathways, result from modifications of double fertilization in sexual/apomictic angiosperms.Thus, the reproductive origin of seed can be identified, including autonomous or pseudogamous apomixis, haploid parthenogenesis and sexual reproduction, involving either reduced or unreduced gametes. Collectively, flow cytometry has been used to address the following research topics: (i) assessing the variation in ploidy levels and genome sizes in agamic complexes, (ii) detection and quantification of different reproductive modes in facultative apomicts, (iii) elucidation of processes in populations with coexisting sexual and apomictic biotypes, (iv) evolution of agamic complexes, and (v) genetic basis of apomixis. The last topic is of paramount importance to crop breeding: the search for candidate gene(s) responsible for apomixis is the main objective of many research programmes. A list of the angiosperm taxa that could provide model systems for such research is provided.
Co je dobré umět, chcete-li obstát v polárních krajích? Půdní vířníky nic nepřekvapí. Odpovědí na extrémní podmínky jsou anhydrobióza či partenogeneze., What is good to know if you want to survive in a polar region? Anhydrobiosis and/or parthenogenesis improve the ability of hydrobionts to adapt to extremes., and Miloslav Devetter.