Strong influences of a dominant,ground‐nesting ant on recruitment,and establishment of ant colonies and communities

Many factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant ground‐nesting ant (Pheidole synanthropica) on (1) arboreal twig‐nesting, (2) ground‐foraging, and (3) coffee‐foraging ant communities in coffee agroecosystems. We surveyed these communities in high‐ and low‐density areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between high‐ and low‐density sites of P. synanthropica. High‐density sites also had significantly lower recruitment of twig ants and had species‐specific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the high‐density sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.     

Interpreting colonization of the Calathus (Coleoptera: Carabidae) on the Canary Islands and Madeira through the application of the parametric bootstrap

The Canary Islands have proven to be an interesting archipelago for the phylogeographic study of colonization and diversification with a number of recent studies reporting evolutionary patterns and processes across a diversity of floral and faunal groups. The Canary Islands differ from the Hawaiian and Galapagos Islands by their close proximity to a continental land mass, being 110 km from the northwestern coast of Africa. This close proximity to a continent obviously increases the potential for colonization, and it can be expected that at the level of the genus some groups will be the result of more than one colonization. In this study we investigate the phylogeography of a group of carabid beetles from the genus Calathus on the Canary Islands and Madeira, located 450 km to the north of the Canaries and 650 km from the continent. The Calathus are well represented on these islands with a total of 29 species, and on the continent there are many more. Mitochondrial cytochrome oxidase I and II sequence data has been used to identify the phylogenetic relationships among the island species and a selection of continental species. Specific hypotheses of monophyly for the island fauna are tested with parametric bootstrap analysis. Data suggest that the Canary Islands have been colonized three times and Madeira twice. Four of these colonizations are of continental origin, but it is possible that one Madeiran clade may be monophyletic with a Canarian clade. The Calathus faunas of Tenerife and Madeira are recent in origin, similar to patterns previously reported for La Gomera, El Hierro, and Gran Canaria.     

Perturbation of maize rhizosphere microflora following seed bacterization with Burkholderia cepacia MCI 7

Introduction of a large quantity of exogenous microorganisms may disrupt a local ecosystem and affect the natural microflora. In this work we investigated the effects of the introduction of a plant growth promoting strain of Burkholderia cepacia into the rhizosphere of maize on both indigenous B. cepacia populations and microbial community structure of total culturable bacteria using the concept of r/K strategy. Moreover we studied the distribution of bacterial populations in the root system at various soil depths. Seed bacterization was used as application method. Root colonization of the introduced strain occurred mainly on roots close to the plant stem, whereas indigenous B. cepacia was recovered at higher amounts from the lower parts of root systems of mature plants. As far as total culturable bacteria are concerned, an almost uniform distribution in the root system of mature plants was observed. The release of the exogenous bacterial strain affected mainly the microbial populations of young growing plants rather than mature plants. Indeed it caused only short-term perturbations in the microbial community of maize rhizosphere. Colonization of maize roots by indigenous B. cepacia was not significantly affected by the presence of the exogenous strain.     

Translation elongation factor-3 (EF-3): An evolving eukaryotic ribosomal protein?

Fungi appear to be unique in their requirement for a third soluble translation elongation factor. This factor, designated elongation factor 3 (EF-3), exhibits ribosome-dependent ATPase and GTPase activities that are not intrinsic to the fungal ribosome but are nevertheless essential for translation elongation in vivo. The EF-3 polypeptide has been identified in a wide range of fungal species and the gene encoding EF-3 (YEF3) has been isolated from four fungal species (Saccharomyces cerevisiae, Candida albicans, Candida guillermondii, andPneumocystis carinii). Computer-assisted analysis of the predictedS. cerevisiae EF-3 amino acid sequence was used to identify several potential functional domains; two ATP binding/catalytic domains conserved with equivalent domains in members of the ATP-Binding Cassette (ABC) family of proteins, an aminoterminal region showing significant similarity to theE. coli S5 ribosomal protein, and regions of predicted interaction with rRNA, tRNA, and mRNA. Furthermore, EF-3 was also found to display amino acid similarity to myosin proteins whose cellular function is to provide the motive force of muscle. The identification of these regions provides clues to both the evolution and function of EF-3. The predicted functional regions are conserved among all known fungal EF-3 proteins and a recently described homologue encoded by the Chlorella virus CVK2. We propose that EF-3 may play a role in the ribosomal optimization of the accuracy of fungal protein synthesis by altering the conformation and activity of a ribosomal accuracy center, which is equivalent to the S4-S5-S12 ribosomal protein accuracy center domain of theE. coli ribosome. Furthermore, we suggest that EF-3 represents an evolving ribosomal protein with properties analogous to the intrinsic ATPase activities of higher eukaryotic ribosomes, which has wider implications for the evolutionary divergence of fungi from other eukaryotes. Correspondence to: M.F. Tuite     

Glomalean mycorrhizal fungi from tropical Australia

 A comparison of different methods for isolation of vesicular-arbuscular mycorrhizal (VAM) fungi into open-pot cultures was undertaken as part of a study of the diversity of these fungi. Four different isolation techniques using spores separated from soil, soil trap cultures, root samples, or transplanted seedlings grown in intact soil cores were used to obtain as many fungi as possible from each site. Isolation methods were compared using paired samples from the same locations within natural (savanna, rocky hill, wetland, rainforest) and disturbed (minesite) habitats in a seasonally dry tropical region in the Northern Territory of Australia. There were large differences in (i) the efficiency (rate of increase in mycorrhizal colonisation), (ii) the proportion of successful cultures, (iii) fungal diversity (number of fungal species in each culture) and (iv) specificity (identity of species isolated) between these four procedures. However, the less-efficient procedures generally resulted in a higher proportion of cultures of one fungus, which could be used without further isolation steps. Most species of Scutellospora, Acaulospora and Gigaspora were obtained primarily from field-collected spores, but only 50% of these culture attempts were successful. Spores from these initial cultures produced mycorrhizas much more rapidly and successfully when used to start second-generation cultures. Several species of fungi, rarely recovered as living spores from field soils, were dominant in many trap cultures started from soil or roots. Most of these fungi were Glomus species, that were first distinguished by colonisation patterns in roots and eventually identified after sporulation in second- or third-generation trap cultures. These experiments demonstrated that glomalean fungi in the habitats sampled belonged to two functional categories, based on whether or not spores were important propagules. The "non-sporulating" fungi were dominant in many trap cultures, which suggests that these fungi had higher total inoculum levels in soils than other fungi. Pot-culturing methods provided additional information on fungal diversity which complemented spore occurrence data obtained using the same soil samples and provided valuable new information about the biology of these fungi. Accepted: 26 December 1998     

Spatio-temporal variation in post-recovery dynamics in a large Peregrine Falcon (Falco peregrinus) population in the Jura mountains 2000–2020†

After spectacular population crashes in the 1960 and 1970s, Peregrine Falcon Falco peregrinus populations recovered worldwide, and in the 2000s many study populations were back to normal. However, post-recovery trends have been documented less well. We combined three long-term population studies covering the entire Jura mountain range (16 304 km²) to examine spatio-temporal variation in population dynamics during 2000–2020 in 420 known nesting sites in five regions: Ain, Jura and Doubs in France, and Jura Sud and Jura Nord in Switzerland. Every year about 60% of all sites were surveyed at least once, and this proportion increased over time. We used Bayesian occupancy modelling to investigate site persistence and colonization probabilities and correct status and trend estimates for bias due to non-random site coverage. Based on the average of two models correcting for preferential sampling, we estimated that population size peaked in 2002 (Jura), 2005 (Doubs), 2007 (Ain, Jura Nord) and in 2007 for the Jura as a whole. Thereafter, the population declined significantly in four regions and in the Jura as a whole, with the strongest decline found in the Jura Nord ( –38%, 95% credible interval –34%/–41%) during 2007–2020. Thus, we found considerable spatial heterogeneity in post-recovery trends and widespread post-recovery declines. Reasons for the latter may include Eagle Owl Bubo bubo predation, illegal persecution and human disturbance. Our results illustrate how quickly positive population trends may be reversed, such that continuous long-term monitoring even for species seemingly ‘out of danger’ remains invaluable. Our study also emphasizes the importance of correcting for both coverage bias in general and preferential sampling in particular when assessing population trends in studies where not every territory can be surveyed in all years.     

From the Apennines to the Alps: colonization genetics of the naturally expanding Italian wolf (Canis lupus) population

Wolves in Italy strongly declined in the past and were confined south of the Alps since the turn of the last century, reduced in the 1970s to approximately 100 individuals surviving in two fragmented subpopulations in the central-southern Apennines. The Italian wolves are presently expanding in the Apennines, and started to recolonize the western Alps in Italy, France and Switzerland about 16 years ago. In this study, we used a population genetic approach to elucidate some aspects of the wolf recolonization process. DNA extracted from 3068 tissue and scat samples collected in the Apennines (the source populations) and in the Alps (the colony), were genotyped at 12 microsatellite loci aiming to assess (i) the strength of the bottleneck and founder effects during the onset of colonization; (ii) the rates of gene flow between source and colony; and (iii) the minimum number of colonizers that are needed to explain the genetic variability observed in the colony. We identified a total of 435 distinct wolf genotypes, which showed that wolves in the Alps: (i) have significantly lower genetic diversity (heterozygosity, allelic richness, number of private alleles) than wolves in the Apennines; (ii) are genetically distinct using pairwise F(ST) values, population assignment test and Bayesian clustering; (iii) are not in genetic equilibrium (significant bottleneck test). Spatial autocorrelations are significant among samples separated up to c. 230 km, roughly correspondent to the apparent gap in permanent wolf presence between the Alps and north Apennines. The estimated number of first-generation migrants indicates that migration has been unidirectional and male-biased, from the Apennines to the Alps, and that wolves in southern Italy did not contribute to the Alpine population. These results suggest that: (i) the Alps were colonized by a few long-range migrating wolves originating in the north Apennine subpopulation; (ii) during the colonization process there has been a moderate bottleneck; and (iii) gene flow between sources and colonies was moderate (corresponding to 1.25-2.50 wolves per generation), despite high potential for dispersal. Bottleneck simulations showed that a total of c. 8-16 effective founders are needed to explain the genetic diversity observed in the Alps. Levels of genetic diversity in the expanding Alpine wolf population, and the permanence of genetic structuring, will depend on the future rates of gene flow among distinct wolf subpopulation fragments.