Optimising Seagrass Conservation for Ecological Functions

Ecosystems - Animals are central to numerous ecological processes that shape the structure and function of ecosystems. It follows that species that are strongly linked to specific functions can...     

Regional differences in foraging behaviour of invasive green crab (<Emphasis Type=Italic>Carcinus maenas</Emphasis>) populations in Atlantic Canada

Invasive green crab populations initially established in Canada within the Bay of Fundy, New Brunswick in the 1950s and were present in all five Atlantic provinces by 2007. Genetic evidence suggests that the Atlantic Canadian populations originated from two separate introductions with differences in time of establishment among regions and possible population-level behavioural differences. In this study, we examine intraspecific foraging behaviour among crabs from different populations, and interspecific foraging behaviour between genetically similar crabs and juvenile lobsters. Both sets of foraging experiments involved competition for a limited food source over a 1-h period. In intraspecific match-ups, recent invaders from Newfoundland (NL) were significantly superior foragers than long-established invaders from Nova Scotia (NS) and New Brunswick (NB) populations; however, we found no differences between NL and Prince Edward Island (PE) invaders. Crabs from PE were better competitors than those from NS and NB, but these differences were not significant. Interspecific competition experiments indicated that the feeding behaviour of recent invaders (NL) and genetically similar, but long-established invaders (NS), differed in the presence of juvenile lobsters. Our study documents striking behavioural differences among populations of green crab from a small geographic region, which may reflect a combination of both genetic differences and time since establishment. These differences may result in varying impacts on newly invaded habitats.     

Nuclear magnetic resonance and molecular modeling studies on O-beta-D-galactopyranosyl-(1----4)-O-beta-D-xylopyranosyl-(1----0)-L-se rine, a carbohydrate-protein linkage region fragment from connective tissue proteoglycans

The solution conformation of O-beta-D-galactopyranosyl-(1----4)-O-beta-D-xylopyranosyl-(1----0)-L-ser ine (GXS), a carbohydrate-protein linkage region fragment from connective tissue proteoglycans, was investigated by two-dimensional NMR spectroscopy and molecular modeling calculations. Specifically, the 1H and 13C resonances were assigned by 2D-COSY and by 1H-13C heteronuclear correlation spectroscopy methods. 2D-NOESY was used to generate distance constraints between the galactose and xylose and between the xylose and serine residues. The 1H vicinal coupling constants for the sugars and the serine were also determined. A general molecular modeling methodology suitable for complex carbohydrates was developed. This methodology employed molecular dynamics and energy minimization procedures together with the application of inter-residue spatial constraints across the linkages derived from 2D-NOESY. The first step in this methodology is the generation of a wide variety of starting conformations that span the (phi, psi) space for each linkage. In the present study, nine such conformations were constructed for each linkage using the torsion angles phi and psi corresponding to the gauche+, gauche-, and trans configurations across each of the two bonds constituting the linkage. These conformations were subjected to a combined molecular dynamics/energy minimization refinement using the NOESY derived constraints as pseudoenergy functions. Families of conformations for the whole molecule were then constructed from the structures derived for each linkage. Characterization of GXS using this methodology identified a single family of conformations that are consistent with the solution phase NMR data on this molecule.     

Monitoring and adaptive resistance management in Australia for Bt-cotton: current status and future challenges

In the mid-1990 s the Australian Cotton industry adopted an insect-resistant variety of cotton (Ingard) which expresses the Bt toxin Cry1Ac that is specific to a group of insects including the target Helicoverpa armigera. A conservative resistance management plan (RMP), that restricted the area planted to Ingard, was implemented to preserve the efficacy of Cry1Ac until two-gene transgenic cotton was available. In 2004/05 Bollgard II replaced Ingard as the transgenic cotton available in Australia. It improves on Ingard by incorporating an additional insecticidal protein (Cry2Ab). If an appropriate refuge is grown, there is no restriction on the area planted to Bollgard II. In 2004/05 and 2005/06 the Bollgard II acreage represented approximately 80 of the total area planted to cotton in Australia. The sensitivity of field-collected populations of H. armigera to Bt products was assayed before and subsequent to the widespread deployment of Ingard cotton. In 2002 screens against Cry2Ab were developed in preparation for replacement of Ingard with Bollgard II. There have been no reported field failures of Bollgard II due to resistance. However, while alleles that confer resistance to H. armigera in the field are rare for Cry1Ac, they are surprisingly common for Cry2Ab. We present an overview of the current approach adopted in Australia to monitor and adaptively manage resistance to Bt-cotton in field populations of H. armigera and discuss the implications of our findings to date. We also highlight future challenges for resistance management in Australia, many of which extend to other Bt-crop and pest systems.     

Climate,Colonisation and Celibacy: Population Structure in Central European Trichomanes speciosum (Pteridophyta)

The Killarney fern Trichomanes speciosum Willd. (Hymenophyllaceae) is unique in possessing both extensive sexual (sporophyte and gametophyte generations present) and asexual (gametophyte only) ranges. It was first discovered in central Europe in 1993 and is represented in this area only by its perennial, vegetatively propagating gametophyte generation. Genetic variation has been investigated at 35 sites. Allozyme diversity is partitioned primarily between, not within, sites. Although genetic variation exists at a fine scale (lt 5 m) within some populations, the results suggest that clones were not intimately associated in these cases. The majority of sites support unique multilocus phenotypes. Where phenotypes were present at more than one site they tended to recur at the next closest site. However, similar phenotypes link eastern and western Pfälzerwald sites up to c. 70 km apart. This pattern of diversity suggests that colonisation was not solely of a “stepping stone” or “leading edge” type. We suggest that during a climatically favourable period, probably the Atlantic hypsithermal, there may have been an explosive colonisation by long-distance dispersal from refugial areas. This was followed by a short period during which sporophyte production, sexual reproduction and local spread were possible. With climatic change, reduction in the available habitat and the loss of the sporophyte generation, different individual genets became fixed within small, favourable, but scattered, sites. The possibility that some central European sites north of the Alps acted as periglacial refugia cannot be discounted, but would appear less likely than (re-) colonisation from the Atlantic fringe.     

Differential responses of three Agriotes click beetle species to pheromone traps

1 Previous work had suggested that adult male click beetles (Agriotes spp.) show differential responses to species specific pheromone traps. This hypothesis was tested using mark–release–recapture methods to estimate the maximum sampling range and the effective sampling area of traps for three species. 2 Captured beetles of the species Agriotes lineatus, Agriotes obscurus and Agriotes sputator were marked to show the direction of release, the distance of the release point from the trap and the replicate. Analysis of variance showed that there were significant differences in recapture rates between species and release distances. There were no significant differences between release direction and replicates. 3 Calculated linear speeds suggested differences in movement rates in the order: A. lineatus > A. obscurus > A. sputator. There were also substantial differences between the species in the maximum sampling ranges and effective sampling areas of the traps. These placed the species in the same order. 4 The results are used to estimate the minimum cost of mass trapping programmes to prevent males from mating, giving values of €165/ha/year (A. lineatus), €247.5/ha/year (A. obscurus) and €2343/ha/year (A. sputator). 5 Implications for the use of pheromone traps in wireworm pest management are discussed. It is concluded that current U.K. recommendations based on the cumulative total catch of the three species over a sampling season can be improved by considering the spatial relationships between the adult trapping system and larval distribution. The current constraint to this is the general inability to separate wireworms into species.     

On Hybrid Formation in the Rock Fern Asplenium x alternifolium (Aspleniaceae,Pteridophyta)

Length polymorphism in a non-coding spacer (trnL_UAA-trnF_GAA) in the chloroplast DNA was used in the investigation of the origin of the most common and conspicuous European fern hybrid, Asplenium x alternifolium (Aspleniaceae, Pteridophyta). The origins of A. x alternifolium, the hybrid between A. trichomanes s.l. and A. septentrionale s.l. was studied at three ploidy levels, diploid, triploid and tetraploid. The cpDNA technique allowed us to investigate the mode of hybrid formation between sexual species for the first time over a wide geographic range and with a large sample size. Morphological variation in this hybrid has previously been attributed to different reciprocal parental combinations, and to the influence of chloroplast genes on morphogenesis. Our results demonstrate that one parent, A. septentrionale s.l., acts predominantly as the female parent in these hybrids, with only one population of A. x alternifolium showing reciprocal hybridity. The discovery of predominantly unidirectional hybrid formation in this hybrid may be explained by the different breeding systems of the parental taxa. The role of gametophyte ecology is also assessed.