Spatio-temporal genetic variation in sympatric and allopatric Mediterranean Cicada species (Hemiptera, Cicadidae)

Cicada barbara (Stål) and Cicada orni L. are two Mediterranean cicadas, very similar in morphology, that produce distinct acoustic mating signals and that have partially overlapping distribution ranges in the Iberian Peninsula, occurring in sympatry in several locations. In the present study, six microsatellite loci were analysed in C. barbara , four of which were also analysed in C. orni . Geographical and temporal genetic variation in these species was studied. No evidence of hybridization was found, enabling us to infer that the isolating barriers between these species are efficient. Partitioning of geographic variation in each species, revealed the following patterns: Iberian Peninsula and Northwestern African populations of C. barbara showed higher differentiation between than within each region, supporting C. barbara subspecific taxonomy ( C. barbara lusitanica in the Iberian Peninsula and C. barbara barbara in Northwestern Africa) and highlighting isolation coincident with the presence of physical barriers to gene-flow; differentiation between populations of C. orni from both sides of the Pyrenees was very low, and this mountain range may not constitute a significant barrier for the dispersal of this species; Greek populations of C. orni were found to be highly differentiated from Western European populations; and no pattern of isolation-by-distance was found in either species within the Iberian Peninsula.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 249–265.     

A novel parasitoid and a declining butterfly: cause or coincidence?

1. The small tortoiseshell butterfly (Aglais urticae L.) is considered to be a widespread and abundant generalist species in Northern Europe. However, it declined sharply in the U.K. between 2003 and 2008, coinciding with the arrival and spread of a parasitoid, Sturmia bella Meig. (Diptera: Tachinidae), which specialises on nymphalid butterflies. 2. Whether the decline in A. urticae is associated with the arrival of S. bella was investigated using data from a large‐scale butterfly monitoring scheme, and by collecting larvae to assess parasitoid incidence and parasitism frequency. Similar data were compiled for a related butterfly (Inachis io) which is also parasitised by S. bella but which is not declining. 3. Sturmia bella was recorded as far north as north Lincolnshire (53.53°N). Aglais urticae has declined significantly to the south of this latitude, but not to the north. 4. Sturmia bella was present in 26% and 15% of the larval groups of A. urticae and I. io, respectively, and now kills more individuals of A. urticae (but not I. io) than any native parasitoid. 5. Survival was 25–48% lower in batches of A. urticae larvae where S. bella was present, indicating that S. bella causes host mortality in addition to that caused by native parasitoids. 6. Our results suggest that S. bella may be playing a role in the recent decline of A. urticae. However, further research is needed to establish its effects relative to other potential drivers of trends in the abundance of this butterfly.     

Thermotropic Properties of Cellular Membranes in Dormant and Non-Dormant Echinochloa crus-galli(L.) Beauv. Seeds

Steady-state fluorescence polarization measurements with l,6-diphenyl-l,3,5-hexatriene(DPH) were used to monitor thermotropic transitions in microsomalfractions and plasma membrane vesicles isolated from barnyardgrass[Echinochloa crus-galli (L.) Beauv.] seeds during the transititionfrom dormancy to germination. The effect of dormancy-relievingor inactive alcohols on the thermotropic properties of the cellularmembranes was determined both in vivo and in vitro. Membranefractions isolated from dormant seeds showed some discontinuitiesin the Arrhenius plots. In non-dormant or germinating seedscellular membranes showed linear Arrhenius plots over the entirerange of temperature examined. Membrane preparations from imbibedseeds showed a similar pattern in their Arrhenius plots upontreatment with the various alcohols in vitro. The results suggestthat the release from dormancy in seeds is associated with somechanges in their cellular membranes. Key words: Germination, alcohols, thermotropic transition