The influence of landscape on population structure of four invertebrates in groundwater springs

1. The unique aquatic fauna of the island‐like groundwater springs of arid inland Australia raises important questions as to how aquatic species persist in very isolated and fragmented habitats and the role that dispersal may play in mitigating/mediating the influence of landscape structure and determining population structure. By determining the relationship between genetics and geography (i.e. phylogeography), the historical processes responsible for population structure can be determined. 2. We undertook comparative phylogeographic studies of invertebrates from springs south of Lake Eyre. Clusters of springs lying within and between surface drainage catchments (which provide a potential connection between springs) were sampled, and the phylogeographic structure of four coexisting species, an ostracod Ngarwa dirga, a snail Fonscochlea accepta, an isopod Phreatomerus latipes and an amphipod Wangiannachiltonia guzikae, was examined. 3. Clear differences in the geographic patterns of genetic structure were found amongst the four species. No discernable genetic structure was found in ostracod and snail populations, even amongst springs lying 20 km apart in separate surface catchments; isopod populations were highly genetically structured amongst springs located in separate catchments, but not within catchments, whilst amphipod populations were highly genetically structured amongst springs both within and between catchments. 4. The results suggest that differences in dispersal ability of each species, and not the overall fragmented nature of the springs, may have led to large differences in phylogeographic history. Interestingly, the relative dispersal ability of these species may be related to their vulnerability to and recovery from large‐scale flood events. Therefore, despite the highly isolated and fragmented nature of the springs, the landscape has not strongly influenced the population structure of the aquatic invertebrate community as a whole nor has it led to the evolution of common life histories.     

Epstein-Barr Virus (EBV)-derived BARF1 encodes CD4- and CD8-restricted epitopes as targets for T-cell immunotherapy

Background aims

EBV type II latency tumors, such as Hodgkin lymphoma (HL), Non-Hodgkin lymphoma (NHL) and nasopharyngeal carcinoma, express a limited array of EBV antigens including Epstein-Barr nuclear antigen (EBNA)1, latent membrane protein (LMP)1, LMP2, and BamH1-A right frame 1 (BARF1). Adoptive immunotherapy for these malignancies have focused on EBNA1, LMP1 and LMP2 because little is known about the cellular immune response to BARF1.

Evidence for parasitoid‐induced premature mortality in the Argentine stem weevil

The Argentine stem weevil Listronotus bonariensis Kuschel (Coleoptera: Curculionidae) is an exotic pest of New Zealand ryegrass and the adult‐stage is parasitized by the introduced solitary endoparasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae: Euphorinae). This biological control agent is effective, although, under both laboratory and field conditions, an unexplained source of premature mortality in the weevils is observed after exposure to M. hyperodae. This premature mortality may be affected to varying degrees by the length of time of parasitoid exposure, the physiological conditions of the host, and the host to parasitoid ratios, although it occurs naturally without any physical interruption to the parasitoid ovipositional process. In the present study, the premature mortality reported in earlier studies is confirmed and it is conjectured to be the result of injection of parasitoid venom without an egg. Moreover, the lack of premature mortality resulting from longer exposure periods indicates that there might be a curative effect resulting from subsequent oviposition; the egg reverses the toxic effect induced by the injection of venom only. As discussed, this phenomenon may not be restricted to the L. bonariensis/M. hyperodae system and, accordingly, there are evolutionary, biosecurity and general pest management questions to be considered.     

Phylogenetic relationships of North American Gomphidae and their close relatives

Intrafamilial relationships among clubtail dragonflies (Gomphidae) have been the subject of many morphological studies, but have not yet been systematically evaluated using molecular data. Here we present the first molecular phylogeny of Gomphidae. We include six of the eight subfamilies previously suggested to be valid, and evaluate generic relationships within them. We have included examples of all genera reported from the Nearctic except Phyllocycla. This sample includes all North American species of Ophiogomphus, which has allowed us to explore intrageneric relationships in that genus. Our particular focus is on the closest relatives of the genus Gomphus, especially those North American species groups that have been commonly treated as subgenera of Gomphus. The Gomphus complex is split into additional genera, supported by molecular and morphological evidence: Phanogomphus, Stenogomphurus, Gomphurus and Hylogomphus are here considered to be valid genera. The genus Gomphus, in our restricted sense, does not occur in the western hemisphere; in addition, G. flavipes is transferred to Stylurus.     

Adaptation to host plants may prevent rapid insect responses to climate change

We must consider the role of multitrophic interactions when examining species' responses to climate change. Many plant species, particularly trees, are limited in their ability to shift their geographic ranges quickly under climate change. Consequently, for herbivorous insects, geographic mosaics of host plant specialization could prohibit range shifts and adaptation when insects become separated from suitable host plants. In this study, we examined larval growth and survival of an oak specialist butterfly (Erynnis propertius) on different oaks (Quercus spp.) that occur across its range to determine if individuals can switch host plants if they move into new areas under climate change. Individuals from Oregon and northern California, USA that feed on Q. garryana and Q. kelloggii in the field experienced increased mortality on Q. agrifolia, a southern species with low nutrient content. In contrast, populations from southern California that normally feed on Q. agrifolia performed well on Q. agrifolia and Q. garryana and poorly on the northern, high elevation Q. kelloggii. Therefore, colonization of southern E. propertius in higher elevations and some northern locales may be prohibited under climate change but latitudinal shifts to Q. garryana may be possible. Where shifts are precluded due to maladaptation to hosts, populations may not accrue warm‐adapted genotypes. Our study suggests that, when interacting species experience asynchronous range shifts, historical local adaptation may preclude populations from colonizing new locales under climate change.     

Dinucleotide microsatellite primers designed for a critically endangered primate,the black lion tamarin (Leontopithecus chrysopygus)

Black lion tamarin (BLT) monkeys (Leontopithecus chrysopygus) have suffered a severe reduction in their natural range and are consequently critically endangered. Because allozyme data showed very low levels of variation, it was not clear if these monkeys had much genetic diversity. We designed microsatellite primers for BLTs, and from them we identified nine polymorphic loci, seven of which were tested on golden lion tamarins (GLTs) (Leontopithecus rosalia). All of the seven polymorphic loci and two other monomorphic BLT loci were polymorphic in GLTs. The microsatellite markers identified here are directly applicable to ongoing lion tamarin population and conservation genetics studies.     

The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink

Despite the success of breeding programmes focused on increasing fruit size, relatively little is known about the anatomical and physiological changes required to increase reproductive allocation. To address this gap in knowledge, we compared fruit/ovary anatomy, vascular structure and phloem transport of two varieties of giant pumpkins, and their smaller fruited progenitor under controlled environmental conditions. We also modelled carbon transport into the fruit of competitively grown plants using data collected in the field. There was no evidence that changes in leaf area or photosynthetic capacity impacted fruit size. Instead, giant varieties differed in their ovary morphology and contained more phloem on a cross‐sectional area basis in their petioles and pedicels than the ancestral variety. These results suggest that sink activity is important in determining fruit size and that giant pumpkins have an enhanced capacity to transport carbon. The strong connection observed between carbon fixation, phloem structure and fruit growth in field‐grown plants indicates that breeding for large fruit has led to changes throughout the carbon transport system that could have important implications for how we think about phloem transport velocity and carbon allocation.     

The ecology and phylogeny of oomycete infections in Asplanchna rotifers

1. Recently, the potential for parasites to influence the ecology and evolution of their zooplankton hosts has been the subject of increasing study. However, most research to date has focussed on Daphnia hosts, and the potential for parasites to influence other zooplankton taxa remains largely unstudied. 2. During routine sampling of zooplankton in a eutrophic lake, we observed that the rotifer Asplanchna girodi was often infected with a parasitic oomycete. Epidemics of this parasite occurred frequently, with three separate events in a single year. Prevalence at peak infection ranged from 29 to 41% and epidemics lasted from 17 to 56 days. Our data indicate that high densities of the host population are required for epidemics to occur. 3. Our morphological and molecular analyses suggest that this parasite is in the genus Pythium. Most Pythium spp. are plant pathogens, but our study supports recent work on Daphnia, suggesting that Pythium spp. are also important parasites of zooplankton. 4. As the parasite in this study was recalcitrant to cultivation, we developed an alternative method to verify its identity. Our approach used quantitative PCR to show that the ribosomal sequences identified increased with increasing density of infected hosts and, thus, were associated with the parasite. This approach should be generally applicable to other plankton parasites that are difficult to cultivate outside their hosts. 5. Infections significantly reduced host fecundity, lifespan and population growth rate. As a result of the virulence of this parasite, it is likely to influence the population ecology and evolution of its Asplanchna host, and may be a useful model system for studies on host–parasite coevolutionary dynamics.     

Floral color variation and associations with fitness‐related traits in Malva moschata (Malvaceae)

Genetic polymorphisms for floral color are interesting phenomena to study because they are likely to be maintained by opposing selective forces. Pollinator preferences may exert direct selection on floral color; however, floral color might also be the indirect target of selection through genetic associations with other traits under selection. Malva moschata (Malvaceae) is a North American species that produces either red or white flowers. In the present study, we present reflectance spectrophotometry data that characterize the nature of floral color variation in this species and show that honey bees and bumble bees should be able to distinguish between the morphs through differential sensitivity at the green (long‐wavelength) photoreceptor. Second, we use a series of phenotypic measures to investigate whether the color morphs differ with respect to other floral traits, vegetative traits or female reproductive success, and use a series of correlation analyses to infer the relative independence of color from these other traits. We found that red‐flowered morphs produced more anthers per flower and had greater leaf area, and that white‐flowered morphs had greater percentage fruit set; however, there were no reproductive success differences between the morphs. The relationship between flower size and anther number was the only correlation that differed between the morphs. Finally, a series of pollinator‐choice experiments showed that bumble bees strongly prefer red morphs in terms of visit frequency and duration, but honey bees have no preference. Taken together, our results suggest that color is rather independent of other phenotypic traits, and that honey bee abundance is likely to play a role in maintaining color variation in this system.