Species‐specific microsatellite markers to monitor gene flow between exotic poplars and their natural relatives in eastern North America

Species‐specific microsatellite markers were obtained for the unambiguous recognition of five poplar species of ecological and commercial importance to eastern North America: the native species Populus balsamifera and Populus deltoides, the exotic species Populus maximowiczii, Populus nigra, Populus trichocarpa and their interspecific hybrids. Forty‐four of 71 tested primer pairs amplified simple sequence repeat (SSR) loci for all five taxa. Six of these loci showed non‐overlapping allelic diversity between species, including fixed differences. Together, they were useful to identify unambiguously the five taxa and to validate parental contributions in a group of hybrid progeny. These markers will be invaluable to detect gene flow from plantations of exotic poplar into adjacent stands of native species and between the two potentially hybridizing native species P. balsamifera and P. deltoides.     

Styloid crystals in Claoxylon (Euphorbiaceae) and allies (Claoxylinae) with notes on leaf anatomy

Claoxylon and Micrococca are the only Euphorbiaceae genera that have rough dried leaves (fresh ones are smooth) because of protruding styloid (needle-like) crystals more or less perpendicular to the leaf surface, which perforate the epidermis and cuticle. A broad leaf anatomical study of the subtribes Claoxylinae, the monogeneric Lobaniliinae, and Mercurialis of the Mercurialinae (95 of a possible 235 species in all six genera) showed that styloids are present in Claoxylon , Discoclaoxylon , Erythrococca , Lobanilia , and Micrococca , and lacking in Claoxylopsis and Mercurialis . Contrary to Claoxylon , the dried leaves of Discoclaoxylon , Erythrococca , Lobanilia , and Micrococca are not rough, because the styloids do not perforate the epidermis during drying and therefore herbarium leaves generally remain smooth. The presence of styloids supports a clade in a recent molecular phylogenetic study that unites subtribes Claoxylinae and Lobaniliinae as Claoxylinae s.l. Mercurialis (no styloids) is sister to all other taxa (with styloids) in the monophyletic Claoxylinae s.l. The styloids form a synapomorphy for a monophyletic part of the Claoxylinae ( Claoxylon , Discoclaoxylon , Erythrococca , Lobanilia , and Micrococca ). Other leaf anatomical notes are provided, together with an overview of the occurrence of styloids, stomata, and druse crystals for most species in the Claoxylinae. The indumentum ranges from (virtually) absent to a sparse or dense tomentum of straight and thick- or thin-walled unicellular hairs (most common), curly hairs, or two-armed hairs ('Malpighiaceous hairs'). The last two hair types probably form diagnostic characters for species groups within the genus Claoxylon .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 445–457.     

Evolutionary radiation of Asteromyia carbonifera (Diptera: Cecidomyiidae) gall morphotypes on the goldenrod Solidago altissima (Asteraceae)

Population divergence of phytophagous insects is often coupled to host‐plant shifts and is frequently attributed to the divergent selective environments associated with alternative host‐plants. In some cases, however, divergence is associated with the use of alternative host‐plant organs of a single host species. The basis of within‐host radiations such as these remains poorly understood. In the present stusy, we analysed the radiation of Asteromyia gall midges occurring both within one host plant species and within a single organ on that host. In this system, four morphologically distinct Asteromyia gall forms (morphs) coexist on the leaves of goldenrod Solidago altissima. Our analyses of amplified fragment length polymorphism and DNA sequence data confirm the genetic differentiation among midges from three gall morphs and reveal evidence of a genetically distinct fourth gall morph. The absence of clear gall morph related clades in the mitochondrial DNA derived phylogenies is indicative of incomplete lineage sorting or recent gene flow, suggesting that population divergence among gall forms is recent. We assess the likely history of this radiation and use the results of phylogenetic analyses along with ecological data on phenology and parasitism rates to evaluate potential hypotheses for the mode of differentiation. These preliminary analyses suggest that diversification of the Asteromyia gall morphs is likely shaped by interactions between the midge, a symbiotic fungus, and parasitoid enemies. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 840–858.     

Investigating the effects of predator removal and habitat management on nest success and breeding population size of a farmland passerine: a case study

Passerines are especially vulnerable to predation at the pre-independence stage. Although the role of nest success in British farmland passerine declines is contentious, improvement in nest success through sympathetic management could play a role in their reversal. Because habitat is known to interact with predation, management options for mitigation will need to consider effects of nest predation. We present results from an observational study of a population of Common Blackbird Turdus merula on a farm which has experienced a range of agri-environment and game-management options, including a period with nest predator control, as a case study to address some of these issues. We used an information theoretic model comparison procedure to look for evidence of interactions between habitat and nest predation, and then asked whether habitat management and nest predator abundances could explain population trends at the site through their effects on nest success. Interactions were detected between measures of predator abundance and habitat variables, and these varied with nest stage – habitat within the vicinity of the nest appeared to be important at the egg stage, and nest-placement characteristics were important at the nestling stage. Although predator control appeared to have a positive influence on Blackbird breeding population size, the non-experimental set-up meant we could not eliminate other potential explanations. Variation in breeding population size did not appear to be influenced by variation in nest success alone. Our study demonstrates that observational data can only go so far in detection of such effects, and we discuss how it might be taken further. Agri-environment and game-management techniques are likely to influence nest predation pressure on farmland passerines, but the patterns, mechanisms and importance to population processes remain not wholly understood.     

POPULATION DENSITY-PHYSICAL CONDITION RELATIONSHIPS IN WHITE-TAILED DEER

Abstract: Management of white-tailed deer (Odocoileus virginianus) populations is important because of the popularity of this species for sport hunting and the ecological and economic damage deer can cause. Managers traditionally have collected data from hunter-harvested deer to provide information for making these harvest management decisions. We tested for predictive relationships between these data and density using long-term (15–31 years duration, median = 26 years) harvest data for 9 populations in the southeastern United States that spanned several physiographic provinces and a wide range of densities (3–32 deer/km²) that varied by a factor of 1.67–5.50 within populations over the study period. Mean annual harvest for these populations ranged from 265–5,242 animals (median = 626). We tested 8 physical and 3 recruitment measures commonly collected on harvested deer for their relationship to reconstructed herd density estimates using correlation and linear regression models. Yearling male dressed body weights (range of average annual sample sizes: 53–260, median = 146) proved to be the parameter most consistently (7 of 9 populations) related to density (P < 0.05) among those tested. Yearling antler points (sample sizes the same as for yearling male weights) and yearling female dressed body weights (range of average annual sample sizes: 17–126, median = 72) also were related to density (P < 0.05). The most appropriate models were based on 2-year lags for density. Three-year running averages for both dependent and independent variables were used to smooth annual variability. Using data from 3 additional, independent populations validated that predicted and observed densities were highly correlated (r = 0.71–0.96; P < 0.01). The efficacy of time lags should serve to caution managers not to look for immediate responses in herds. The populations examined in this study provided long-term data that captured stochasticity resulting from density-independent factors. Despite any potential impact from these factors, we detected significant density-dependent relationships.     

Inferring the history of speciation in house mice from autosomal,X‐linked,Y‐linked and mitochondrial genes

Patterns of genetic differentiation among taxa at early stages of divergence provide an opportunity to make inferences about the history of speciation. Here, we conduct a survey of DNA‐sequence polymorphism and divergence at loci on the autosomes, X chromosome, Y chromosome and mitochondrial DNA in samples of Mus domesticus, M. musculus and M. castaneus. We analyzed our data under a divergence with gene flow model and estimate that the effective population size of M. castaneus is 200 000–400 000, of M. domesticus is 100 000–200 000 and of M. musculus is 60 000–120 000. These data also suggest that these species started to diverge approximately 500 000 years ago. Consistent with this recent divergence, we observed considerable variation in the genealogical patterns among loci. For some loci, all alleles within each species formed a monophyletic group, while at other loci, species were intermingled on the phylogeny of alleles. This intermingling probably reflects both incomplete lineage sorting and gene flow after divergence. Likelihood ratio tests rejected a strict allopatric model with no gene flow in comparisons between each pair of species. Gene flow was asymmetric: no gene flow was detected into M. domesticus, while significant gene flow was detected into both M. castaneus and M. musculus. Finally, most of the gene flow occurred at autosomal loci, resulting in a significantly higher ratio of fixed differences to polymorphisms at the X and Y chromosomes relative to autosomes in some comparisons, or just the X chromosome in others, emphasizing the important role of the sex chromosomes in general and the X chromosome in particular in speciation.     

Global decomposition experiment shows soil animal impacts on decomposition are climate‐dependent

Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region‐ or biome‐scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity.     

Invertebrate community patterns in Mediterranean temporary wetlands along hydroperiod and salinity gradients

1. Temporary aquatic habitats often are inhabited by a unique fauna and flora and contribute significantly to regional diversity. Temporary wetlands around the world are disappearing rapidly. The individual and interacting impacts of factors influencing community structure and dynamics in temporary wetlands are not always well known.
2. Camargue wetlands are mainly characterized by variable salinity and hydroperiod. The individual and combined impacts of these local factors, together with regional variables, on invertebrate communities remain unknown. We therefore characterized and sampled invertebrates in 30 temporary wetlands along salinity and hydroperiod gradients in the Camargue (Southern France) 3, 5 and 7 months after inundation.
3. Over the three sampling occasions, a total of 17 cladoceran species and 49 macroinvertebrate taxa were identified. Hydroperiod and salinity were the most important variables explaining variation in taxonomic composition and can be considered key factors shaping the invertebrate communities in Camargue wetlands. The impact on taxon richness was significantly positive for hydroperiod but significantly negative for salinity. Regional factors had no significant effect on the structure of the studied invertebrate communities, suggesting that dispersal was not limiting and that species sorting was the most important structuring process.
4. The results of this study suggest that the combined and interacting effects of salinization and hydrological modification of Mediterranean temporary wetlands (due to water management, climate change, etc.) can result in reduced diversity in large numbers of Mediterranean wetlands and induce a considerable decline in regional diversity of aquatic invertebrates.     

Phylogenetic relationships among microgastrine braconid wasp genera based on data from the 16S, COI and 28S genes and morphology

Abstract Phylogenetic relationships among the genera of the large braconid wasp subfamily Microgastrinae were explored using DNA sequence data from the mitochondrial large ribosomal subunit (16S), nuclear large ribosomal subunit (28S) and mitochondrial cytochrome oxidase (COI) genes, along with morphological characters, both new and from previous studies. The taxonomic history of this group of wasps is reviewed, along with a critique of previous phylogenetic studies on the group. Molecular data were sampled from forty-six species representing twenty-six genera of microgastrines, plus three species representing the close outgroup taxa Cardiochilinae and Miracinae. Some 2300 base pairs of aligned sequence were obtained per taxon from the three genes. In addition, fifty-three morphological characters were coded for all known genera, including two undescribed genera, except Semionis Nixon (known from only a single male type specimen). Relationships among several groups of genera are clarified and challenge some major assumptions made in earlier classifications. In particular, it is clear that dependence on one or a few major morphological character systems oversimplifies relationships, and can lead to misleading results. Despite the large amount of data analysed, basal divergences within the subfamily remain poorly resolved and essentially unsupported in any rigorous statistical sense.     

Genetic characterization of Artemia tibetiana (Crustacea: Anostraca)

The brine shrimp Artemia consists of a number of bisexual species and a large number of parthenogenetic forms, which collectively, inhabit a wide range of hypersaline habitats. A recently described species (A. tibetiana) from a carbonate lake (Lagkor Co) in Tibet at an altitude of 4490 m has been tested with New World (A. franciscana USA, and A. franciscana feral population Vietnam) and Old World species (A. salina, A. urmiana, A. sinica) for cross fertility. These tests show complete infertility between A. tibetiana and A. franciscana . Between A. tibetiana and A. urmiana, A. sinica partial fertility through to F₂ and F₃ generations is evident. Allozyme and RAPD comparison of A. tibetiana with A. franciscana (USA), A. franciscana (Vietnam), A. sinica (Mongolia) and A. urmiana (Iran) show that A. tibetiana is similar to other bisexual species in mean heterozygosity (0.074) but has a somewhat higher proportion of polymorphic loci (40%, similar to that of A. urmiana ). The genetic distance between A. tibetiana and A. franciscana is 0.730, between A. tibetiana and A. urmiana is 0.475 and that between A. tibetiana and A. sinica is 0.114. F_IS estimates for A. tibetiana differ significantly from zero for six loci, mainly because of lack of fit to Hardy-Weinberg expectations. This may suggest that even within the limited area of Lagkor Co there are Genétically distinct populations. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 333–344.