Silvicolous on a Small Scale: Possibilities and Limitations of Habitat Suitability Models for Small,Elusive Mammals in Conservation Management and Landscape Planning

Species distribution and endangerment can be assessed by habitat-suitability modelling. This study addresses methodical aspects of habitat suitability modelling and includes an application example in actual species conservation and landscape planning. Models using species presence-absence data are preferable to presence-only models. In contrast to species presence data, absences are rarely recorded. Therefore, many studies generate pseudo-absence data for modelling. However, in this study model quality was higher with null samples collected in the field. Next to species data the choice of landscape data is crucial for suitability modelling. Landscape data with high resolution and ecological relevance for the study species improve model reliability and quality for small elusive mammals like Muscardinus avellanarius. For large scale assessment of species distribution, models with low-detailed data are sufficient. For regional site-specific conservation issues like a conflict-free site for new wind turbines, high-detailed regional models are needed. Even though the overlap with optimally suitable habitat for M. avellanarius was low, the installation of wind plants can pose a threat due to habitat loss and fragmentation. To conclude, modellers should clearly state the purpose of their models and choose the according level of detail for species and environmental data.     

Phenotypic Plasticity and Population Differentiation in an Ongoing Species Invasion

The ability to succeed in diverse conditions is a key factor allowing introduced species to successfully invade and spread across new areas. Two non-exclusive factors have been suggested to promote this ability: adaptive phenotypic plasticity of individuals, and the evolution of locally adapted populations in the new range. We investigated these individual and population-level factors in Polygonum cespitosum, an Asian annual that has recently become invasive in northeastern North America. We characterized individual fitness, life-history, and functional plasticity in response to two contrasting glasshouse habitat treatments (full sun/dry soil and understory shade/moist soil) in 165 genotypes sampled from nine geographically separate populations representing the range of light and soil moisture conditions the species inhabits in this region. Polygonum cespitosum genotypes from these introduced-range populations expressed broadly similar plasticity patterns. In response to full sun, dry conditions, genotypes from all populations increased photosynthetic rate, water use efficiency, and allocation to root tissues, dramatically increasing reproductive fitness compared to phenotypes expressed in simulated understory shade. Although there were subtle among-population differences in mean trait values as well as in the slope of plastic responses, these population differences did not reflect local adaptation to environmental conditions measured at the population sites of origin. Instead, certain populations expressed higher fitness in both glasshouse habitat treatments. We also compared the introduced-range populations to a single population from the native Asian range, and found that the native population had delayed phenology, limited functional plasticity, and lower fitness in both experimental environments compared with the introduced-range populations. Our results indicate that the future spread of P. cespitosum in its introduced range will likely be fueled by populations consisting of individuals able to express high fitness across diverse light and moisture conditions, rather than by the evolution of locally specialized populations.     

Carriage of Staphylococcus aureus by Free-Living Wild Animals in Spain

The presence of methicillin-susceptible Staphylococcus aureus (MSSA) was analyzed in different free-living wild animals to assess the genetic diversity and predominant genotypes on each animal species. Samples were taken from the skin and/or nares, and isolates were characterized by spa typing, multilocus sequence typing (MLST) and antimicrobial susceptibility testing. The proportion of MSSA carriers were 5.00, 22.93, 19.78, and 17.67% in Eurasian griffon vulture, Iberian ibex, red deer, and wild boar, respectively (P = 0.057). A higher proportion of isolates (P = 0.000) were recovered from nasal samples (78.51%) than skin samples (21.49%), but the 9.26% of red deer and 18.25% of wild boar would have been undetected if only nasal samples had been tested. Sixty-three different spa types were identified, including 25 new spa types. The most common were t528 (43.59%) in Iberian ibex, t548 and t11212 (15.79% and 14.04%) in red deer, and t3750 (36.11%) in wild boar. By MLST, 27 STs were detected, of which 12 had not been described previously. The most frequent were ST581 for Iberian ibex (48.72%), ST425 for red deer (29.82%), and ST2328 for wild boar (42.36%). Isolates from Eurasian griffon vulture belong to ST133. Host specificity has been observed for the most frequent spa types and STs (P = 0.000). The highest resistance percentage was found against benzylpenicillin (average, 22.2%), although most of the S. aureus isolates were susceptible to all antimicrobial tested. Basically, MSSA isolates were different from those MRSA isolates previously detected in the same animal species.     

Endozoochory largely outweighs epizoochory in migrating passerines

Fruits and seeds are critical food sources for many European passerines during the autumn migration, which in turn contribute to disperse seeds either internally, i.e. after ingestion (endozoochory), or externally, when seeds adhere to the body surface (epizoochory). Despite the recognized importance of birds as seed dispersers, the vast majority of studies focused on endozoochory while the external transport of seeds is frequently invoked as being potentially important, but remains largely unexplored. This is particularly important during the post‐breeding migration of passerines, the most ubiquitous and diverse movement of potential seed carriers across Europe and into Africa, which coincides with the fruiting peak of many plant species (August–October). Our aim was to evaluate the role of migrating birds as potential long‐distance seed dispersers, and comparing the prevalence of epizoochory and endozoochory during post‐breeding migration. We sampled 926 wild birds in nine locations in Portugal, and retrieved 1833 seeds of 19 plant species dispersed internally and only three seeds externally attached to three birds (Serinus serinus, Locustella naevia and Turdus merula), showing an endozoochory prevalence 85 times higher than that of epizoochory. Migrating and non‐migrating passerines dispersed seeds equally. While two of the seeds transported externally had specific adaptations to epizoochory, namely spines (Torilis arvensis) and hooks (Galium aparine), the third is a large seed from a fleshy‐fruited plant, Frangula alnus (i.e. typical endozoochorous syndrome). These seeds were found on bird species with different diets, but similar behaviour (ground foragers) and in similar habitats (open agro‐ecosystems). Our results highlight the strong role of migrating passerines as potentially long‐distance seed dispersers and show that, at least in the autumn, the prevalence of epizoochory is several orders of magnitude lower than that of endozoochory.     

Effect of Temperature on the Biotic Potential of Honeybee Microsporidia

The biological cycle of Nosema spp. in honeybees depends on temperature. When expressed as total spore counts per day after infection, the biotic potentials of Nosema apis and N. ceranae at 33°C were similar, but a higher proportion of immature stages of N. ceranae than of N. apis were seen. At 25 and 37°C, the biotic potential of N. ceranae was higher than that of N. apis. The better adaptation of N. ceranae to complete its endogenous cycle at different temperatures clearly supports the observation of the different epidemiological patterns.Biotic potential represents the maximum reproductive capacity of a population under optimum environmental conditions. Thus, a species fulfilling its biotic potential would exhibit maximal exponential population growth, thereby augmenting the possibilities of transmission of the species. A wide range of factors affects the biotic potential of each species, and among the external factors, temperature clearly influences the life cycles of most parasitic species (4).Nosemosis is a common worldwide disease of adult honeybees (Apis mellifera) that is caused by microsporidia (19). Nosema apis was the only agent known to produce this disease in A. mellifera until N. ceranae was identified in this host in 2005, in Europe (11) and Taiwan (12). Both these microsporidia infect and multiply in the ventricular cells of A. mellifera, and they can be found under different environmental conditions in both the northern and southern hemispheres (17, 13). Significantly, N. ceranae seems to be more pathogenic than N. apis in caged worker bees (10, 18), and it has recently been related to significant losses of bees and colony collapses under field conditions (17, 8).Due to the lack of comparative studies of the factors affecting parasite virulence, trials were designed to determine the influence of temperature on the biotic potentials of both microsporidia. Only the deleterious effect of high exogenous temperature on spores of N. apis has been checked previously (16).In this work, purified N. apis and N. ceranae spores with a minimum viability of 99% (tested with 4% trypan blue) were obtained from experimentally infected honeybees always maintained at 33°C as described previously (9). The spores were counted using a hemocytometer chamber (19), while the Nosema species identification was confirmed by PCR (17).The experimental infection of bees was carried out as described previously (10). Briefly, young Nosema-free honeybees were starved for 2 h and fed 2 μl of 50% sucrose solution containing 100,000 viable N. ceranae or N. apis spores. Honeybees were anesthetized with CO₂, and later, a droplet of the spore solution was administered to each honeybee by touching a micropipette to its mouthparts until the entire droplet was consumed. The bees that did not consume the entire droplet were discarded. Uninfected control bees were fed 2 μl of 50% sucrose solution alone.Three trials were carried out for 1 week each at three different temperatures (25, 33, and 37°C). Each trial included four replicate cages of 30 N. apis-infected honeybees, four replicate cages of 30 N. ceranae-infected honeybees, and four replicate cages of 30 uninfected honeybees. Three different refrigerated incubators (Memmert) were used for N. ceranae- or N. apis-infected bees and controls.On days 1, 2, 3, 4, and 7 postinfection (p.i.), five living honeybees were removed from each of three cages (n = 15) in each incubator. Spore detection and counting were performed with each bee. To obtain the Nosema spore counts, the whole abdomen from each bee was placed into a sterile Eppendorf microtube in 200 μl of double-distilled water (PCR grade). After thorough grinding of the abdomen, the spore count for each bee was calculated with a hemocytometer. In addition, PCR was used to confirm the Nosema species identification. The biotic index was calculated as the total N. apis or N. ceranae spore count per day after infection.Finally, on the same days p.i., a histopathological study was performed with two honeybees from the fourth cage in each incubator. The ventriculus of each bee, with the Malpighian tubules attached, was processed as described previously (10).The daily spore count per bee and its relationship to the temperature were established with a nonparametric Mann-Whitney test for each Nosema species (level of significance, α = 0.05). Two curvilinear regression models for each temperature were established. The growth curves fitted predict the increases of the N. ceranae and N. apis spore counts over time (days p.i.), and the slopes and intercepts of the regression lines could be compared. SPSS (version 15.0) software was used to perform the tests and regression analysis.Throughout the study, Nosema infection was not evident in any of the control bees (Table ​(Table1),1), while N. ceranae was detected in all the bees (100%) exposed to this microsporidium. The proportion of the bees exposed to N. apis in which N. apis infection was detected varied during the period studied (0 to 100%).

TABLE 1.

Percentages of infected honey bees in the different test groups^a

Analysis of UV-induced mutation spectra in Escherichia coli by DNA polymerase eta from Arabidopsis thaliana

DNA polymerase eta belongs to the Y-family of DNA polymerases, enzymes that are able to synthesize past template lesions that block replication fork progression. This polymerase accurately bypasses UV-associated cis-syn cyclobutane thymine dimers in vitro and therefore may contributes to resistance against sunlight in vivo, both ameliorating survival and decreasing the level of mutagenesis. We cloned and sequenced a cDNA from Arabidopsis thaliana which encodes a protein containing several sequence motifs characteristics of Pol eta homologues, including a highly conserved sequence reported to be present in the active site of the Y-family DNA polymerases. The gene, named AtPOLH, contains 14 exons and 13 introns and is expressed in different plant tissues. A strain from Saccharomyces cerevisiae, deficient in Pol eta activity, was transformed with a yeast expression plasmid containing the AtPOLH cDNA. The rate of survival to UV irradiation in the transformed mutant increased to similar values of the wild type yeast strain, showing that AtPOLH encodes a functional protein. In addition, when AtPOLH is expressed in Escherichia coli, a change in the mutational spectra is detected when bacteria are irradiated with UV light. This observation might indicate that AtPOLH could compete with DNA polymerase V and then bypass cyclobutane pyrimidine dimers incorporating two adenylates.     

Larger aboveground neighbourhood scales maximise similarity but do not eliminate discrepancies with belowground plant diversity in a Mediterranean shrubland

Plant and Soil - An unresolved question in plant ecology is whether diversity of the aboveground and belowground compartments of a plant community is similar at different neighbourhood scales. We...     

MALDI-TOF mass spectrometry as a tool for differentiation of Bradyrhizobium species: Application to the identification of Lupinus nodulating strains

Genus Bradyrhizobium includes slow growing bacteria able to nodulate different legumes as well as species isolated from plant tumours. The slow growth presented by the members of this genus and the phylogenetic closeness of most of its species difficults their identification. In the present work we applied for the first time Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) to the analysis of Bradyrhizobium species after the extension of MALDI Biotyper 2.0 database with the currently valid species of this genus. With this methodology it was possible to identify strains belonging to phylogenetically closely related species of genus Bradyrhizobium allowing the discrimination among species with rrs gene identities higher than 99%. The application of MALDI-TOF MS to strains isolated from nodules of different Lupinus species in diverse geographical locations allowed their correct identification when comparing with the results of rrs gene and ITS analyses. The nodulation of Lupinus gredensis, an endemic species of the west of Spain, by B. canariense supports the European origin of this species.     

Host specificity in spinturnicid mites: do parasites share a long evolutionary history with their host?

Host specificity in parasites can be explained by spatial isolation from other potential hosts or by specialization and speciation of specific parasite species. The first assertion is based on allopatric speciation, the latter on differential lifetime reproductive success on different available hosts. We investigated the host specificity and cophylogenetic histories of four sympatric European bat species of the genus Myotis and their ectoparasitic wing mites of the genus Spinturnix. We sampled >40 parasite specimens from each bat species and reconstructed their phylogenetic COI trees to assess host specificity. To test for cospeciation, we compared host and parasite trees for congruencies in tree topologies. Corresponding divergence events in host and parasite trees were dated using the molecular clock approach. We found two species of wing mites to be host specific and one species to occur on two unrelated hosts. Host specificity cannot be explained by isolation of host species, because we found individual parasites on other species than their native hosts. Furthermore, we found no evidence for cospeciation, but for one host switch and one sorting event. Host‐specific wing mites were several million years younger than their hosts. Speciation of hosts did not cause speciation in their respective parasites, but we found that diversification of recent host lineages coincided with a lineage split in some parasites.