Isolated Asian steppe element in the Balkans: habitats of <Emphasis Type="Italic">Proterebia afra</Emphasis> (Lepidoptera: Nymphalidae: Satyrinae) and associated butterfly communities

A characteristic butterfly of Asian steppes, Proterebia afra (Fabricius 1787), was studied in its two relic areas of occurrence within the Balkans—the Askion Mts (a single mountain massif in NW Greece) and Dalmatia (karstic inland S Croatia)—together with co-occurring butterfly communities during its early spring adult flight period. P. afra adults tolerate harsh continental conditions prevailing at its localities during its flight. Local densities were higher in the Askion Mts (up to 100 individuals per 50 m walk) than in Dalmatia (up to 30 individuals per 50 m). Within both areas of occurrence, it inhabits dry grasslands subject to intermediate grazing pressure that retains enough dry grass litter but still suppresses shrubs and trees. Hotter slopes are preferred in more northerly Dalmatia than in the more southerly Askion Mts. More co-occurring butterfly species and more Mediterranean species were recorded in the Askion Mts (69 vs 63; 23 vs 12), but more butterfly individuals and higher species’ richness per transect were observed in Dalmatia. In ordination analyses, the main gradients organising the grassland butterfly communities distinguished between grassy plains and rocky slopes containing more woody plants. Given the distribution extents, local densities and present land use conditions, the Balkan P. afra is not currently endangered, but this may swiftly change with grazing abandonment, especially in Dalmatia, and some conservation actions should be considered in the near future.     

Limited overlap of the community of bees and wasps (Hymenoptera: Aculeata) nesting in reed galls with those nesting in other cavities

Hymenopterans occurring in wetlands represent specific community with bioindicative characters but poorly understood nesting biology. We have studied the nesting preferences of these insects in ten reed beds—five represented by natural wetlands, and the other five localized to anthropogenic sites. We reared the hymenopterans from trap-nests consisting of reed stalks and goldenrod stems, which were installed at the localities through the nesting season, and compared them with quantitative data of hymenopterans reared from reed galls collected at the same localities. Most of the species that nested in reed galls accepted the reed stalk traps but not vice versa. Some of the species that accepted both these nesting resources strongly differed in their frequency of use of these two nesting resources. Moreover, the species composition differed substantially between goldenrod stems and either reed stalks or reed galls. The digger wasp Pemphredon fabricii was eudominant in reed galls with higher abundance at anthropogenic sites, while it was also observed in reed stalks but in much lower numbers. Hylaeus pectoralis was frequent in reed galls at both habitat types and only one individual was reared from reed stalks. Trypoxylon deceptorium was quite numerous in reed galls but much more frequent in reed stalks. Species unknown from reed galls (Psenulus pallipes, Hylaeus confusus, Gymnomerus laevipes) were numerous in reed stalks. We experimentally confirmed that P. fabricii and H. pectoralis show high preference of reed galls and are dependent on these nesting resources. The available evidence suggests that the management of both natural and anthropogenic sites needs to implement tools preserving reed beds, especially the terrestrial ones with reed galls.     

Strain‐specific consumption and transformation of alga‐derived dissolved organic matter by members of the Limnohabitans‐C and Polynucleobacter‐B clusters of Betaproteobacteria

We investigated changes in quality and quantity of extracellular and biomass‐derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass‐derived OM concentrations from each alga were approximately 20 mg l^?1 and 1 mg l^?1 respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%–61% of identified compounds of the extracellular OM from each alga. In biomass‐derived OM of Rhodomonas and Chlamydomonas 71%–77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga‐derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%–76% and 38%–82% of all identified extracellular and biomass‐derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga‐derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation.     

Successful invasion of the neotropical species Piper aduncum in rain forests in Papua New Guinea

Abstract. Piper aduncum is a neotropical invasive species which has spread throughout Papua New Guinea over the past three decades. It has become a most successful alien woody plant in New Guinea, occurring from sea level up to 2000 m a.s.l. The species prefers initial stages of forest succession and is particularly common in recently abandoned gardens representative of a system of swidden agriculture. It often attains high cover, suppresses other pioneer species and becomes the absolute dominant species in these habitats. The species is now also spreading into naturally disturbed habitats far from direct human influence, such as natural tree‐fall gaps, landslides and frequently flooded stream banks. It has, however, never been found in a closed primary forest. The species germinates from faeces of mammal and bird species, and we conclude that dispersal through endozoochory contributes to this species’ extraordinary success in Papua New Guinea. A similar invasion behaviour has been documented over a large geographic area, from Malaysia to Fiji. Piper aduncum has attributes which are common amongst successful invasive species: (1) a large native geographic range; (2) aggressively colonizing disturbed habitats in its native area; (3) relatively small seeds; (4) a short juvenile period; (5) a large seed production every year.     

Depleted genetic variation of the European ground squirrel in Central Europe in both microsatellites and the major histocompatibility complex gene: implications for conservation

Habitat fragmentation may influence the genetic make-up and adaptability of endangered populations. To facilitate genetic monitoring of the endangered European ground squirrel (EGS), we analyzed 382 individuals from 16 populations in Central Europe, covering almost half of its natural range. We tested how fragmentation affects the genetic architecture of presumably selectively neutral (12 microsatellites) and non-neutral (the major histocompatibility class II DRB gene) loci. Spatial genetic analyses defined two groups of populations, “western” and “eastern”, with a significantly higher level of habitat fragmentation in the former group. The highly fragmented western populations had significantly lower genetic diversity in both types of markers. Only one allele of the DRB gene predominated in populations of the western group, while four alleles were evenly distributed across the eastern populations. Coefficient of inbreeding values (F _IS) calculated from microsatellites were significantly higher in the western (0.27–0.79) than in eastern populations (−0.060–0.119). Inter-population differentiation was very high, but similar in both groups (western F _ST = 0.23, eastern F _ST = 0.25). The test of isolation by distance was significant for the whole dataset, as well as for the two groups analyzed separately. Comparison of genetic variability and structure on microsatellites and the DRB gene does not provide any evidence for contemporary selection on MHC genes. We suggest that genetic drift in small bottlenecked and fragmented populations may overact the role of balancing selection. Based on the resulting risk of inbreeding depression in the western populations, we support population management by crossbreeding between the western and eastern populations.     

Are blackcaps current winners in the evolutionary struggle against the common cuckoo?

Blackcaps Sylvia atricapilla reject artificial cuckoo eggs, and their eggs vary little in appearance within clutches, whereas among clutches eggs vary considerably. Low variation within clutches facilitates discrimination of parasitic eggs, whereas high variation among clutches makes it harder for the cuckoo to mimic the eggs of a certain host species. These traits have most probably evolved as counteradaptations against brood parasitism by the common cuckoo Cuculus canorus, even though blackcaps are not regularly parasitised today. In this study, we investigated how fine-tuned the rejection of parasitic eggs is in this species by introducing three types of eggs into their nests: a real non-mimetic egg the approximate size of a cuckoo egg, an artificial mimetic egg the size of a cuckoo egg and a real conspecific egg. As the rejection frequency of both mimetic and non-mimetic artificial cuckoo eggs has been shown to be high in previous studies, the variation in rejection behaviour between individuals is low, indicating that most individuals within the population are able to reject parasitic eggs. Thus, we predict that (1) the intraclutch variation in egg appearance should be generally low in all individuals, and that (2) regarding conspecific eggs, rejection decisions should be highly dependent on the degree of mimicry between parasitic and host eggs. We found support for these predictions, which indicates that due to their highly sophisticated countermeasures against brood parasitism, blackcaps can probably be regarded as current winners of the arms race with the common cuckoo. Furthermore, the high and consistent rejection frequency of cuckoo eggs found throughout Europe for this species supports the spatial habitat structure hypothesis, which claims that woodland-nesting species breeding near trees, like blackcaps, presumably experienced a high level of parasitism throughout their range in the past and, therefore, their rejection behaviour, once evolved, spread rapidly to all populations.