A comparison of the host preference of monarch butterflies (Danaus plexippus) for milkweed (Asclepias syriaca) over dog-strangler vine (Vincetoxicum rossicum)

Observations in the field indicate that monarch butterflies will oviposit on dog‐strangler vine, an invasive introduced species in the same family as milkweed (Asclepias spp.), the principal larval host of monarchs. The potential impact of this behaviour depends on the strength of the preference of monarch adults to oviposit on these two hosts and the relative ability of larvae to survive on each. We determined the preference for milkweed vs. dog‐strangler vine of ovipositing adults and first instar larvae in choice and no‐choice tests. We also compared the ability of larvae to consume, develop, and survive on either host. In the presence of both hosts, adults exhibited a strong preference to oviposit on milkweed over dog‐strangler vine (mean 80.7 eggs compared to 0.4 eggs over 48 h, respectively). In the absence of milkweed, adults ceased oviposition (mean 0.9 eggs in 48 h), but resumed oviposition when the dog‐strangler vine was replaced with milkweed (mean 99.1 eggs in 48 h). Given a choice between hosts over 24 h, 92% of larvae moved to milkweed leaves and consumed 3.94 cm² of milkweed leaves compared to 2% of larvae that moved to dog‐strangler vine and consumed negligible amounts of leaf material (0.01 cm²). Without a choice, larvae on dog‐strangler vine never consumed more than mean 0.02 cm² larva^?1 in a 24‐h period, did not develop beyond the first instar, and died within 96 h. We obtained no data in support of an effect of the presence of dog‐strangler vine on monarch butterfly populations.     

Local adaptation to different phytogeographic regions: habitat‐related variations in seed germination in response to temperature and salinity for two medicinal Salvia species from Jordan

Salvia spinosa L. and Salvia syriaca L. are perennial medicinal herbs that occur in the Mediterranean, Irano‐Turanian and Saharo‐Arabian phytogeographic regions of Jordan. With respect to the seed germination requirements, prevailing environmental conditions in each phytogeographic region may promote local adaptation and consequently affect the distribution range of the species. Using seeds of both species collected from populations across the three regions, we tested responses to variations in temperature and salinity under laboratory conditions. Both species showed significant differences in cumulative germination percentages and germination rates (modified Timson Index) with temperature, while origin only significantly affected S. spinosa seeds. Both species germinated best under the highest temperature regime (32/20°C). The low temperature regime (8/4°C) completely inhibited germination in S. syriaca, wheras it led to 80% to 95% germination in S. spinosa, with significant variation being recorded between the phytogeographic regions. For both species, salt solutions of 0, 25 and 50 mM NaCl yielded the highest germination percentages and rates, which sharply and significantly declined at higher concentrations (100 and 200 mM NaCl). Our results provide evidence of local adaptation of the study species to salinity and temperature in the respective maternal environments, particularly in the Irano‐Turanian and Saharo‐Arabian regions. Such differentiation should be accounted for in future conservation planning.     

Monarchs in decline: a collateral landscape‐level effect of modern agriculture

We review the postulated threatening processes that may have affected the decline in the eastern population of the monarch butterfly, Danaus plexippus L. (Lepidoptera: Nymphalidae), in North America. Although there are likely multiple contributing factors, such as climate and resource‐related effects on breeding, migrating, and overwintering populations, the key landscape‐level change appears to be associated with the widespread use of genetically modified herbicide resistant crops that have rapidly come to dominate the extensive core summer breeding range. We dismiss misinterpretations of the apparent lack of population change in summer adult count data as logically flawed. Glyphosate‐tolerant soybean and maize have enabled the extensive use of this herbicide, generating widespread losses of milkweed (Asclepias spp.), the only host plants for monarch larvae. Modeling studies that simulate lifetime realized fecundity at a landscape scale, direct counts of milkweeds, and extensive citizen science data across the breeding range suggest that a herbicide‐induced, landscape‐level reduction in milkweed has precipitated the decline in monarchs. A recovery will likely require a monumental effort for the re‐establishment of milkweed resources at a commensurate landscape scale.     

Pollination genetics of hybridization in sympatric populations of asclepias exaltata and a. syriaca (asclepiadaceae)

Enzyme electrophoresis of pollinia and seeds was used to identify pollinia on pollinators, interspecific pollinations, and hybrid seed production in sympatric populations of Asclepias exaltata and A. syriaca. The frequency of mixed pollinia loads on pollinators was low. Only 4.1% (N= 169 pollinia) and 8% (N= 244 pollinia) of the pollinia collected from pollinators of A. syriaca and A. exaltata, respectively, were identified as pollinia from the other species. Natural levels of interspecific pollination, 3.6% (N = 166 pollinia) on A. syriaca and 3.1% (N = 228 pollinia) on A. exaltata, were typically lower than the number of foreign pollinia carried by pollinators. Hybrid seeds were identified in only two of 208 A. syriaca fruits and one of 178 A. exaltata fruits. Hybrid seeds were largely underdeveloped in the single A. exaltata fruit. High fruit set (34.7%) and near normal seed set following hand-pollination of A. syriaca with A. exaltata pollinia suggest that hybridization is more likely between these taxa when A. syriaca is the maternal parent. Our findings indicate that the likelihood of hybridization between A. exaltata and A. syriaca is remote. Nevertheless, introgressive hybridization has been documented in these species, which suggests that hybridization remains a strong evolutionary force even for species that infrequently interbreed.     

Next generation sequencing of Apis mellifera syriaca identifies genes for Varroa resistance and beneficial bee keeping traits

Apis mellifera syriaca exhibits a high degree of tolerance to pests and pathogens including varroa mites. This native honey bee subspecies of Jordan expresses behavioral adaptations to high temperature and dry seasons typical of the region. However, persistent honey bee imports of commercial breeder lines are endangering local honey bee population. This study reports the use of next‐generation sequencing (NGS) technology to study the A. m. syriaca genome and to identify genetic factors possibly contributing toward mite resistance and other favorable traits. We obtained a total of 46.2 million raw reads by applying the NGS to sequence A. m. syriaca and used extensive bioinformatics approach to identify several candidate genes for Varroa mite resistance, behavioral and immune responses characteristic for these bees. As a part of characterizing the functional regulation of molecular genetic pathway, we have mapped the pathway genes potentially involved using information from Drosophila melanogaster and present possible functional changes implicated in responses to Varroa destructor mite infestation toward this. We performed in‐depth functional annotation methods to identify ～600 candidates that are relevant, genes involved in pathways such as microbial recognition and phagocytosis, peptidoglycan recognition protein family, Gram negative binding protein family, phagocytosis receptors, serpins, Toll signaling pathway, Imd pathway, Tnf, JAK‐STAT and MAPK pathway, heamatopioesis and cellular response pathways, antiviral, RNAi pathway, stress factors, etc. were selected. Finally, we have cataloged function‐specific polymorphisms between A. mellifera and A. m. syriaca that could give better understanding of varroa mite resistance mechanisms and assist in breeding. We have identified immune related embryonic development (Cactus, Relish, dorsal, Ank2, baz), Varroa hygiene (NorpA2, Zasp, LanA, gasp, impl3) and Varroa resistance (Pug, pcmt, elk, elf3‐s10, Dscam2, Dhc64C, gro, futsch) functional variations genes between A. mellifera and A. m. syriaca that could be used to develop an effective molecular tool for bee conservation and breeding programs to improve locally adapted strains such as syriaca and utilize their advantageous traits for the benefit of apiculture industry.     

Structure of asclepin and some observations on the NMR spectra of Calotropis glycosides

Asclepin has been shown to be 3′-O-acetylcalotropin using various chemical and physical methods. The NMR data of all the Calotropis glycosides have been analysed in conjunction with that of asclepin, certain anomalies have been pointed out and revised structures have been proposed for the acetylated glycosides.     

Zawan and tares in the Bible

Farmers in Jordan and Syria refer to two weeds in wheat fields as zawan in Arabic. These are Cephalaria syriaca (L.) Schrad. (Dipsacaceae) and Lolium temulentum L (Poaceae). The Greek word zizanion in the parable in Matthew 13 is translated variously as tares, darnel, and weed. According to the biblical text, tares must have a life cycle like wheat and easily contaminate wheat seed. To better understand which plant is zawan, field and threshing sites in Jordan and Syria were surveyed. Four grain fields and four threshing sites had Cephalaria, one field and one threshing site had Lolium. Early botanical explorers noted C. syriaca as a weed in wheat in Syria. There are few records of C. syriaca as contaminants of grain caches at archeological sites while L. temulentum is common.     

Hybrid bridges to gene flow: a case study in milkweeds (Asclepias)

Natural hybridization occurs throughout areas of sympatry for the North American milkweeds Asclepias exaltata and A. syriaca (Asclepiadaceae), even though the formation of F1 hybrid seed is a rare event. For introgressive hybridization to proceed, F1 and advanced hybrids must be released from reproductive barriers and successfully mate with one or both parental species. I investigated the mating system of natural hybrids between A. exaltata and A. syriaca in three populations in Shenandoah National Park, Virginia. Allozyme data and a maximum-likelihood procedure were used to estimate the frequency of six genotypic classes (parentals, F1, F2, and backcrosses) of the hybridizing populations, the pollinia received by hybrid plants, and the paternal parents of seeds produced by hybrids. F1 hybrids, backcross A. syriaca, and parental A. syriaca individuals were common in three hybrid populations. Even though self-pollinations and interhybrid pollinations were common, F2 seed production and the occurrence of F2 individuals were rare in hybrid populations. Hybrid plants received more pollen from A. syriaca than A. exaltata, which resulted in the production of more backcross-A. syriaca seed than backcross-A. exaltata seed. Asclepias exaltata was rare in the hybrid populations, but A. exaltata pollinia were received by hybrids and this species sired between 15% and 36% of the seeds produced on hybrids. The potential for introgression with A. exaltata populations is lower because this species is unsuccessful as the maternal parent in interspecific and backcross hand-pollinations. The asymetry of hybridization with A. syriaca as the maternal parent is further supported by the incorporation of maternally inherited chloroplast DNA markers in hybrids. Hybrid milkweeds frequently backcross with both parental species and may be released from the reproductive barriers that limit the formation of F1 hybrids in natural populations. The direction of interspecific gene flow and introgression in milkweeds is influenced by the reproductive biology of hybrids, the constituency of the surrounding population, and failure of some crosses to produce seeds. Finally, introgressive hybridization remains an important evolutionary force even when the initial formation of F1 hybrids in natural populations is rare.     

Postglacial migration and the loss of allozyme variation in northern populations of Asclepias exaltata (Asclepiadaceae)

The recent Wisconsin glaciation has provided opportunities for examining the effects of postglacial recolonization on the population genetics of plant and animal communities. In this study allozyme Variation was examined in 19 populations of the herbaceous perennial Asclepias exaltata occurring in previously glaciated regions of North America. These northern populations of A. exaltata possess significantly fewer polymorphic loci (46.31 ± 2.7; mean ± 1 SD), alleles per polymorphic locus (1.84 ± 0.24), and expected heterozygosity (0.133 ± 0.031) than populations found in the Pleistocene refugium in the southern Appalachians. Population-level allozyme diversity decreased linearly from south to north and from east to west. Nineteen uncommon alleles previously observed in southern Appalachian populations were undetected in the northern region. Seven common alleles exhibited a clinal change in allele frequency. Of these, only Pgd-1a and Mnr-1c were at low-frequency in the southern Appalachians and increased significantly with increasing latitude and longitude, respectively. Despite this loss of allozyme diversity following postglacial migration, northern populations of A. exaltata have higher allozyme diversity and lower population differentiation (G" = 0.1 17) than mean values for other long-lived herbaceous perennials. Increased habitat fragmentation in northern regions and potential habitat loss in the southern Appalachians are likely to reduce the historically rich gene pool that has provided the genetic stock for postglacial recoveries.