Molecular evidence for hybridization in Colias (Lepidoptera: Pieridae): are Colias hybrids really hybrids?

Gene flow and hybridization among species dramatically affect our understanding of the species as a biological unit, species relationships, and species adaptations. In North American Colias eurytheme and Colias eriphyle, there has been historical debate over the extent of hybridization occurring and the identity of phenotypically intermediate individuals as genetic hybrids. This study assesses the population structure of these two species to measure the extent of hybridization and the genetic identity of phenotypic intermediates as hybrids. Amplified fragment length polymorphism (AFLP) marker analysis was performed on 378 specimens collected from northern California and Nevada. Population structure was inferred using a Bayesian/Markov chain Monte Carlo method, which probabilistically assigns individuals to genetic clusters. Three genetic clusters provided the best fit for the data. C. eurytheme individuals were primarily assigned to two closely related clusters, and C. eriphyle individuals were mostly assigned to a third, more distantly related cluster. There appeared to be significant hybridization between the two species. Individuals of intermediate phenotype (putative hybrids) were found to be genetically indistinguishable from C. eriphyle, indicating that previous work based on the assumption that these intermediate forms are hybrids may warrant reconsideration.     

Living in isolation – population structure,reproduction, and genetic variation of the endangered plant species Dianthus gratianopolitanus (Cheddar pink)

The endangered plant species Dianthus gratianopolitanus exhibits a highly fragmented distribution range comprising many isolated populations. Based upon this pattern of distribution, we selected a study region in Switzerland with a lower magnitude of isolation (Swiss Jura) and another study region in Germany with a higher degree of isolation (Franconian Jura). In each region, we chose ten populations to analyze population structure, reproduction, and genetic variation in a comparative approach. Therefore, we determined population density, cushion size, and cushion density to analyze population structure, investigated reproductive traits, including number of flowers, capsules, and germination rate, and analyzed amplified fragment length polymorphisms to study genetic variation. Population and cushion density were credibly higher in German than in Swiss populations, whereas reproductive traits and genetic variation within populations were similar in both study regions. However, genetic variation among populations and isolation by distance were stronger in Germany than in Switzerland. Generally, cushion size and density as well as flower and capsule production increased with population size and density, whereas genetic variation decreased with population density. In contrast to our assumptions, we observed denser populations and cushions in the region with the higher magnitude of isolation, whereas reproductive traits and genetic variation within populations were comparable in both regions. This corroborates the assumption that stronger isolation must not necessarily result in the loss of fitness and genetic variation. Furthermore, it supports our conclusion that the protection of strongly isolated populations contributes essentially to the conservation of a species' full evolutionary potential.     

Host‐associated differentiation in a highly polyphagous,sexually reproducing insect herbivore

Insect herbivores may undergo genetic divergence on their host plants through host‐associated differentiation (HAD). Much of what we know about HAD involves insect species with narrow host ranges (i.e., specialists) that spend part or all their life cycle inside their hosts, and/or reproduce asexually (e.g., parthenogenetic insects), all of which are thought to facilitate HAD. However, sexually reproducing polyphagous insects can also exhibit HAD. Few sexually reproducing insects have been tested for HAD, and when they have insects from only a handful of potential host‐plant populations have been tested, making it difficult to predict how common HAD is when one considers the entire species' host range. This question is particularly relevant when considering insect pests, as host‐associated populations may differ in traits relevant to their control. Here, we tested for HAD in a cotton (Gossypium hirsutum) pest, the cotton fleahopper (CFH) (Pseudatomoscelis seriatus), a sexually reproducing, highly polyphagous hemipteran insect. A previous study detected one incidence of HAD among three of its host plants. We used Amplified fragment length polymorphism (AFLP) markers to assess HAD in CFH collected from an expanded array of 13 host‐plant species belonging to seven families. Overall, four genetically distinct populations were found. One genetically distinct genotype was exclusively associated with one of the host‐plant species while the other three were observed across more than one host‐plant species. The relatively low degree of HAD in CFH compared to the pea aphid, another hemipteran insect, stresses the likely importance of sexual recombination as a factor increasing the likelihood of HAD.     

Field performance evaluation and genetic integrity assessment of cryopreserved papaya clones

This paper is the first report of field performance and evaluation of morphological traits following cryopreservation in four genotypes of Carica papaya (Z6, 97, TS2 and 35). It also describes the successful establishment of in vitro plantlets following vitrification-based cryopreservation of shoot tips and their acclimatisation through to field establishment. Cloned plants resulting from untreated controls, as well as controls taken at three other stages of the cryopreservation process (dissection, pre-treatment, plant vitrification solution 2 (PVS2) treatment) and cryopreserved plants were established to ensure a rigorous appraisal of any variation. Results indicate no differences between any of the control plants or cryopreserved plants for either growth performance or morphology. In addition, both randomly amplified DNA fingerprinting and amplified DNA methylation polymorphism markers were used to assess any genomic or methylation changes in genotype 97 at four different developmental stages post cryopreservation (in vitro, acclimatisation and field). Only small genomic DNA modifications (0–8.3%) were detected in field stage plants and methylation modifications (0–4.3%) were detected at both the in vitro and field stages for samples treated with PVS2 or cryopreservation.     

苦丁茶冬青的RAPD影响因素及实验条件的优化

以苦丁茶冬青为材料研究随机扩增多态DNA(RAPD)的影响因素及各种实验条件优化。研究结果表明：模板DNA的浓度适宜范围为20ng／反应-80ng／反应RAPD均可得到一致的结果;dNTVs的适宜浓度范围为200μmol／L-400μmol／L;Mg^2 适宜浓度范围为1．5mmol／L-2．0mmol／L;其合适的复性温度为35—37℃;2min的延伸时间,45次热循环。按照此优化的RAPD条件进行重复实验,实验结果重现性良好,因而确定了苦丁茶冬青RAPD反应体系之最佳的实验条件。     

Use of DNA markers to study bird migration

The molecular methods that are presently being used for studying phylogenetics, phylogeography and population genetics can also be applied to study bird migration. They are powerful and can supplement the information obtained from ringing, telemetry, morphometrics, ringing, radar tracking and isotope analysis. This short review describes the principles, scopes and limitations DNA methods and DNA markers that are relevant for migration research, such as DNA sequences, short tandem repeats (microsatellites), single nucleotide polymorphisms, amplified fragment length polymorphism, inter simple sequence repeats and molecular sexing.     

Impacts of Catastrophic Earthquakes on the Insect Communities in Estuarine Mangroves, Northern Taiwan

As a catastrophic earthquake is unpredictable and occurs only occasionally, impacts on biotic communities are seldom known. Monthly changes in insect communities in the mangroves along the Danshui Estuary were monitored for more than 3 years from before and after two catastrophic earthquakes in Taiwan the Chi–Chi earthquake (M_L = 7.3) of September 21, 1999 and the 3–31 earthquake (M_L = 6.8) of March 31, 2002. Here we show that the Chi–Chi earthquake not only caused large declines in total individual number but also total species number of insects. It also resulted in greater variability among samples, and shifts in insect communities. Non-biting midges and rove beetles, whose immatures inhabited the riparian underground or aquatic sediments, were most severely affected. By 7 months after the Chi–Chi earthquake, the insect communities had recovered to a level comparable to that before the earthquake. However, the influence of the 3–31 earthquake on the insect communities was less severe. It is concluded that the more-severe impacts of the Chi–Chi earthquake than the 3–31 earthquake can be attributable to differences in ground shaking, occurrence time, biodiversity, and growing conditions of insects at those times.     

Hybridisation in Jacobaea – characterisation of hybrids between Jacobaea aquatica and J. vulgaris in Austria

Background: Hybridisation in Senecio/Jacobaea is frequent and of significance in speciation and evolution. Moreover, these genera are model systems for studying the evolution of pyrrolizidine alkaloids (PAs). Hybrids between Jacobaea aquatica and J. vulgaris have been reported from north-western Europe.

Aims: Our aim was to determine whether hybrids between Jacobaea aquatica and J. vulgaris also occurred in Austria, and if these hybrids could be responsible for the presumed increase of J. aquatica-like plants in this part of Europe. Furthermore, we tested if such hybrids showed an altered PA spectrum compared with parental species.

Methods: We used amplified fragment length polymorphisms (AFLPs) to analyse genetic diversity and structure, and gas chromatography–mass spectrometry (GC–MS) to identify PAs.

Results: We were able to identify genetically one hybrid population adjacent to a large J. aquatica population. The AFLP phenotypes of hybrids demonstrated a closer relationship to J. aquatica, suggesting frequent backcrossing. All hybrid individuals contained the same set of PAs as the parental species, but in differing amounts, plus four additional PAs, one of which may be novel.

Conclusions: Although hybridisation in Jacobaea is common, we were able to confirm only one hybrid population in Austria. Therefore, it seems unlikely that hybridisation plays a role in the presumed increase of J. aquatica in this area.     

AFLP analysis shows high incongruence between genetic differentiation and morphology‐based taxonomy in a widely distributed tortoise

Morphology has traditionally been used to diagnose the taxa of various taxonomic ranks. However, there is growing evidence that morphology is not always able to reveal cryptic taxa, and that pronounced morphological variation could reflect phenotypic plasticity rather than evolutionary divergence. Spur‐thighed tortoises (the Testudo graeca complex), distributed in the western Palaearctic region, are characterized by high morphological variability and complicated taxonomy, which are under debate. Previous molecular studies using mainly mitochondrial DNA (mtDNA) sequences have revealed incongruence between genetic differentiation and morphology‐based taxonomy, suggesting that morphological variability is the result of phenotypic plasticity and stabilizing selection, which masks the true genealogies. In the present study, we used a range‐wide sampling and nuclear Amplified fragment length polymorphism (AFLP) markers to investigate genetic differentiation within the T. graeca complex. We found that spur‐thighed tortoises are differentiated into four geographically well‐defined AFLP groups: Balkans–Middle Eastern, western Mediterranean, Caucasian and central‐eastern Iranian. Compared with the distribution of mtDNA lineages, the groups are largely concordant, although the AFLP markers are less sensitive and distinguish fewer groups than do mtDNA sequences. The AFLP groups show an allopatric or parapatric distribution. The AFLP differentiation conflicts with the previously proposed morphology‐based taxonomy of the complex, suggesting that local adaptation to different environmental conditions may have led to the great extent of morphological variation within the same lineages. We propose a re‐evaluation of the taxa that were confirmed genetically using a thorough morphological analysis corrected for phenotypic plasticity. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.