Spatial and genetic structure of host-associated differentiation in the parasitoid Copidosoma gelechiae.

Host-associated differentiation (HAD) appears to be an important driver of diversification in the hyperdiverse phytophagous and parasitoid insects. The gallmaking moth Gnorimoschema gallaesolidaginis has undergone HAD on two sympatric goldenrods (Solidago), and HAD has also been documented in its parasitoid Copidosoma gelechiae, with the intriguing suggestion that differentiation has proceeded independently in multiple populations. We tested this suggestion with analysis of Amplified Fragment Length Polymorphism (AFLP) markers for C. gelechiae collections from the midwestern and northeastern United States and eastern Canada. AFLP data were consistent with the existence of HAD, with between-host F(ST) significant before Bonferroni correction in two of seven sympatric populations. amova analysis strongly rejected a model of HAD with a single historical origin, and thus supported the repeated-HAD hypothesis. Copidosoma gelechiae shows significant host-associated divergence at a number of allozyme loci (Stireman et al., 2006), but only weak evidence via AFLPs for genome-wide differentiation, suggesting that this species is at a very early stage of HAD.

Not just vicariance: phylogeography of a Sonoran Desert euphorb indicates a major role of range expansion along the Baja peninsula.

To examine the generality of population-level impacts of ancient vicariance identified for numerous arid-adapted animal taxa along the Baja peninsula, we tested phylogeographical hypotheses in a similarly distributed desert plant, Euphorbia lomelii (Euphorbiaceae). In light of fossil data indicating marked changes in the distributions of Baja floristic assemblages throughout the Holocene and earlier, we also examined evidence for range expansion over more recent temporal scales. Two classes of complementary analytical approaches - hypothesis-testing and hypothesis-generating - were used to exploit phylogeographical signal from chloroplast DNA sequence data and genotypic data from six codominant nuclear intron markers. Sequence data are consistent with a scenario of mid-peninsular vicariance originating c. 1 million years ago (Ma). Alternative vicariance scenarios representing earlier splitting events inferred for some animals (e.g. Isthmus of La Paz inundation, c. 3 Ma; Sea of Cortez formation, c. 5 Ma) were rejected. Nested clade phylogeographical analysis corroborated coalescent simulation-based inferences. Nuclear markers broadened the temporal spectrum over which phylogeographical scenarios could be addressed, and provided strong evidence for recent range expansions along the north-south axis of the Baja peninsula. In contrast to previous plant studies in this region, however, the expansions do not appear to have been in a strictly northward direction. These findings contribute to a growing appreciation of the complexity of organismal responses to past climatic and geological changes - even when taxa have evolved in the same landscape context.

Granular media filtration: old process, new thoughts.

The design of granular media filters has evolved over many years so that modern filters have larger media sizes and higher filtration velocities than in earlier times. The fundamental understanding of filtration has also improved over time, with current models that account reasonably for all characteristics of the media, the suspension and the filter operation. The methodology for design, however, has not kept pace with these improvements; current designs are based on pilot plants, past experience, or a simple guideline (the ratio of the bed depth to media grain size). We propose that design should be based universally on a characteristic removal length, with the provision of a bed depth that is some multiple of that characteristic length. This characteristic removal length is calculated using the most recent (and most complete) fundamental model and is based on the particle size with the minimum removal efficiency in a filter. The multiple of the characteristic length that yields the required bed depth has been calibrated to existing, successful filters.

Geographic differentiation in the house fly estimated by microsatellite and mitochondrial variation.

Gene flow over very large geographic scales has been investigated in few species. Examples include Drosophila melanogaster, Drosophila subobscura, Drosophila simulans, and the Mediterranean fruit fly (Ceratitis capitata). The cosmopolitan house fly, a highly vagile, fecund, colonizing species offers an additional exemplar. Genotypes at seven microsatellite loci were scored in 14 widely separated natural house fly populations from the Nearctic, neotropics, Afrotropics, Palearctic, and Asia. Allelic diversities and heterozygosities differed significantly among populations. Averaged over all populations, Weir and Cockerham's theta = 0.13 and RST = 0.20. Pairwise genetic distance measures were uncorrelated with geographic distance. Microsatellite frequencies were compared with mitochondrial data from 13 of the same populations in which theta = 0.35 and Nei's GST = 0.72. Mitochondrial variation indicated up to threefold greater indices of genetic differentiation than the microsatellites. We were unable to draw any biogeographical inferences from these results or from tree or network topologies constructed from the genetic data. It is likely that high microsatellite diversities, mutation rates, and homoplasy greatly compromised their usefulness in estimating gene flow. House fly colonization dynamics include a large number of primary and secondary colonizations coupled with substantial genetic drift, but no detectable bottlenecks.

The scientific basis of flocculator design.

A new guideline for the design of flocculators is proposed. This guideline is to design continuous flow flocculators on the basis of the characteristic reaction time for the loss of one micrometre particles in the suspension. The most commonly used guideline at the present time is that of Camp, but later proposals by Ives and O'Melia expanded the Camp guideline and incorporated more complete knowledge of flocculation. The suggestion here continues that process, by accounting explicitly for the heterodisperse nature of typical suspensions and the multiple collision mechanisms for particles in determining a characteristic reaction time. While the historical guidelines have served the water treatment industry well for reasonably similar size distributions in waters destabilized by precipitating metal hydroxides, the proposed guideline should be more robust in considering other suspensions. In particular, the new guideline can account explicitly for the effects of nanoparticles on flocculation.

Temporal aspects of the fine-scale genetic structure in a population of Cinnamomum insularimontanum (Lauraceae).

Cinnamomum insularimontanum Hayata (Lauraceae) is an insect-pollinated, broad-leaved evergreen tree with bird-dispersed seeds. We used allozyme loci, Wright's fixation index, spatial autocorrelation statistics (Moran's I), and coancestry measures to examine changes in genetic structure among four age-classes within a recently founded study population (60 x 100 m area) in southern Korea. There were no significant differences in expected heterozygosity among age classes. However, significant genetic differentiation among age classes was detected (P<0.0001). Fixation indices within age classes showed significant deficits of observed heterozygosity, which may be caused by partial selfing. The homogeneity of genetic structure among four age-classes may reflect similar spatial patterns of seed immigration from surrounding populations occurring year after year. Finally, the average Moran's I and coancestry estimates indicated essentially random spatial distributions of alleles for each of the four age-classes and between seedlings and 2-4 year juveniles vs adult trees. These findings are very similar to those observed in the same study area for another member of the Lauraceae, Neolitsea sericea, which has a very similar life history and ecological characteristics (ie, bird-dispersed fruits, insect pollination, and a similar age structure). Together, these results suggest that the fleshy drupes of lauraceous species represent an adaptation to aid in the independent dispersal of seed by birds, which in turn may increase the genetic diversity of founders colonizing new habitats.

Spatial population genetic structure in Trillium grandiflorum: the roles of dispersal, mating, history, and selection.

The roles of the various potential ecological and evolutionary causes of spatial population genetic structure (SPGS) cannot in general be inferred from the extant structure alone. However, a stage-specific analysis can provide clues as to the causes of SPGS. We conducted a stage-specific SPGS analysis of a mapped population of about 2000 Trillium grandiflorum (Liliaceae), a long-lived perennial herb. We compared SPGS for juvenile (J), nonreproductive (NR), and reproductive (R) stages. Fisher's exact test showed that genotypes had Hardy-Weinberg frequencies at all loci and stage classes. Allele frequencies did not differ between stages. Bootstrapped 99% confidence intervals (99%CI) indicate that F-statistic values are indistinguishable from zero, (except for a slightly negative FIT for the R stage). Spatial autocorrelation was used to calculate f the average kinship coefficient between individuals within distance intervals. Null hypothesis 99%CIs for f were constructed by repeatedly randomizing genotypic locations. Significant positive fine-scale genetic structure was detected in the R and NR stages, but not in the J stage. This structure was most pronounced in the R stage, and declined by about half in each remaining stage: near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively. For R and NR, the near-neighbor f lies outside the null hypothesis 99%CI, indicating kinship at approximately the level of half-sibs and first cousins, respectively. We also simulated the expected SPGS of juveniles post dispersal, based on measured R-stage SPGS, the mating system, and measured pollen and seed dispersal properties. This provides a null hypothesis expectation (as a 99%CI) for the J-stage correlogram, against which to test the likelihood that post-dispersal events have influenced J-stage SPGS. The actual J correlogram lies within the null hypothesis 99%CI for the shortest distance interval and nearly all other distance intervals indicating that the observed low recruitment, random mating and seed dispersal patterns are sufficient to account for the disappearance of SPSG between the R and the J stages. The observed increase in SPGS between J and R stages has two potential explanations: history and local selection. The observed low total allelic diversity is consistent with a past bottleneck: a possible historical explanation. Only a longitudinal stage-specific study of SPGS structure can distinguish between historical events and local selection as causes of increased structure with increasing life history stage.

Fine-scale genetic structure in Pinus clausa (Pinaceae) populations: effects of disturbance history.

Spatial autocorrelation analyses of 12 allozyme loci were used to compare genetic structure within populations of two varieties of Pinus clausa. P. clausa var. immuginata populations tend to be uneven-aged, with continuous recruitment in small gaps created by wind damage, whereas P. clausa var. clausa populations are more even-aged, with recruitment postdating periodic canopy fires. Three var. immuginata populations and three matched pairs of var. clausa populations, including both a mature and a nearby recently burned population, were examined. Aggregation of multilocus genotypes at small distances was evident in all young var. clausa populations. Little inbreeding was apparent among juveniles or adults in these populations; their genetic structure is likely to have resulted from limited seed dispersal. Genotypes were not significantly spatially structured in nearby matched mature populations. Genetic structure was less evident in var. immuginata populations. Aggregated genotypes were only apparent in the population where patches included juveniles of similar ages; dense juvenile clumps in the other two var. immuginata populations comprised a variety of ages. Interannual variability in allele frequencies of surviving seedlings may account for the absence of genetic structure in these populations.

Skewed paternity and sex allocation in hermaphroditic plants and animals.

Models predict a reduced allocation to sperm when females preferentially use one of two males' sperm and the males do not know who is favoured. An analogous discounting occurs in plants when their paternity success is skewed by random, non-heritable factors such as location in the population and pollinator behaviour. We present a model that shows that skewed paternity can affect the sex allocation of hermaphrodites, that is it leads to a female-biased investment. The model highlights the close links between local mate competition and sperm competition. We use paternity data from Ficus in order to illustrate that skews in paternity success can lead to a high degree of sibling gamete competition in an apparently open breeding system. Since skews in paternity are ubiquitous in hermaphroditic plants and animals these findings should apply broadly.

Extensive ribosomal DNA genic variation in the columnar cactus Lophocereus.

Sequence analysis of the hypervariable internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) is commonly used to gain insights into plant and animal population structure and phylogeny. We characterized ITS1, ITS2, and the 5.8S coding region of 18 senita (Lophocereus) individuals from 12 different populations in Baja as well as from closely related cactus species. Analyses of multiple clones demonstrated extensive paralogy in the senita rDNA gene family. We identified at least two putatively non-recombining rDNA operons in senita as well as multiple paralogous sequences within each operon. Usage of PCR, reverse transcriptase (RT)-PCR, Southern blot, primary sequence analyses of the 18S rDNA gene, and secondary structure analyses of the 5.8S rRNA showed that one of the operons encodes rDNA pseudogenes in a low copy-number (Truncated), whereas the second operon encodes an expressed rRNA (Functional). Surprisingly, we found extensive paralogy not only in the ITS regions but also in the 5.8S coding regions in senita both within and between operons. Phylogenetic analyses suggest that the second rDNA operon originated prior to the divergence of Lophocereus. A significant (p < 0.05) divergence-rate acceleration was found in the Lophocereus 5.8S rDNA coding region in the Functional operon in comparison to Pereskiopsis porteri (Cactaceae) and Portulaca molokiniensis (Portulacaceae) with Silene dioica and Spinacia oleracea as the outgroups.

Breeding population size of a fragmented population of a Costa Rican dry forest tree species.

Pollen immigration can offset the effects of genetic drift and inbreeding in small populations. To understand the genetic consequences of forest fragmentation, estimates of pollen flow into remnant fragments are essential. Such estimates are straightforward for plants with singly sired, multiseeded fruits, since the pollen donor genotype for each fruit can be unambiguously reconstructed through full-sib genealogical analyses. Allozyme analyses were used to estimate pollen donor numbers from the progeny of fruits of the tropical dry forest tree Enterolobium cyclocarpum in a small (9.8 ha) fragmented population (N = 11) over three reproductive seasons (1994, 1995, and 1996). These analyses indicate that each tree receives pollen from many pollen donors. When data are pooled for the site, estimated maximum pollen donor pool sizes in all years exceed the number of individuals (56) in the 227 ha study area. Although unidentified pollen donors may be located as close as 250 m to the study trees, the number of unidentified pollen donors indicates that individuals in this forest fragment are part of a large network of reproductively active individuals.

Widespread occurrence of spliceosomal introns in the rDNA genes of ascomycetes.

Spliceosomal (pre-mRNA) introns have previously been found in eukaryotic protein-coding genes, in the small nuclear RNAs of some fungi, and in the small- and large-subunit ribosomal DNA genes of a limited number of ascomycetes. How the majority of these introns originate remains an open question because few proven cases of recent and pervasive intron origin have been documented. We report here the widespread occurrence of spliceosomal introns (69 introns at 27 different sites) in the small- and large-subunit nuclear-encoded rDNA of lichen-forming and free-living members of the Ascomycota. Our analyses suggest that these spliceosomal introns are of relatively recent origin, i.e., within the Euascomycetes, and have arisen through aberrant reverse-splicing (in trans) of free pre-mRNA introns into rRNAs. The spliceosome itself, and not an external agent (e.g., transposable elements, group II introns), may have given rise to these introns. A nonrandom sequence pattern was found at sites flanking the rRNA spliceosomal introns. This pattern (AG-intron-G) closely resembles the proto-splice site (MAG-intron-R) postulated for intron insertions in pre-mRNA genes. The clustered positions of spliceosomal introns on secondary structures suggest that particular rRNA regions are preferred sites for insertion through reverse-splicing.

Landscape approaches to historical and contemporary gene flow in plants.

Growing interest in metapopulation dynamics and dispersal at a landscape level is promoting new approaches to the study of contemporary gene flow. These approaches have been fostered by the development of new genetic markers and statistical methods, as well as an awareness that contemporary gene flow cannot be reliably estimated by conventional methods based on genetic structure. Estimation of the spatial and temporal dynamics of pollen and seed movement with respect to extant landscape features can aid evolutionary and conservation biologists in predicting the demographic and genetic responses of species to naturally occurring or human-mediated population subdivision.

Detection of APGWamide-like immunoreactivity in the sea scallop, Placopecten magellanicus.

In pulmonate gastropods, the peptide, Ala-Pro-Gly-Trp-NH2 (APGWamide), appears to be located nearly exclusively in the neural circuitry controlling the male reproductive organs. This neuropeptide and related neuropeptides are also present and apparently bioactive in bivalve molluscs, although their physiological role in these latter animals is unknown. The present report uses immunohistochemistry to examine the distribution of APGWamide and/or related peptides within the tissues of the deep sea scallop, Placopecten magellanicus. Much of the APGWamide-like immunoreactivity (APGWa-LIR) was detected in the central nervous system (CNS) of both juvenile and adult scallops, where it was concentrated in the cerebral, pedal and parietovisceral ganglia, particularly in the cortex of ganglionic cells and their axons which extend into the central neuropilar region. APGWa-LIR was also detected in the nerves ramifying from these ganglia. In addition, strong APGWa-LIR was localized in what appeared to be axonal terminals within peripheral tissues including the striated adductor muscle, foot, gills, labial palps, lips, tentacles and gonads of the juvenile scallops. The presence of APGWa-LIR was also confirmed in the gonads of adults of both sexes. Cursory examinations of the CNS of the mussel, Mytilus edulis, and the oyster, Crassostrea virginica, revealed the presence of APGWa-LIR in cell bodies and processes in these bivalve species as well. It is concluded that APGWamide and/or related peptides are probably important neurotransmitters and/or neuromodulators of several central and peripheral functions in P. magellanicus and other bivalves. Future work must focus on the possible roles for APGWamide in the physiological processes of these and other bivalve species.

Gene flow among small populations of a self-incompatible plant: an interaction between demography and genetics.

We assessed the effects of population size and genetic relatedness on rates of pollen gene flow into experimental populations of the insect-pollinated, self-incompatible plant Raphanus sativus. We created synthetic populations of sizes 2, 5, 10, and 20 with three genetic structures (full siblings, half siblings, and unrelated plants). Following pollination in a natural setting, we conducted a simple paternity exclusion analysis using the allozyme genotypes of progeny to measure apparent gene flow and Monte Carlo simulations to estimate total gene flow. Estimates of apparent pollen gene flow rates ranged from 0 to 100% and were similar in rank to estimates of total gene flow. There were significant effects of population size and relatedness on the rate of apparent gene flow, and there were significant population size by relatedness interactions. Populations of size 2 had higher gene flow rates than larger populations, gene flow being negatively associated with the level of cross-compatibility (as measured by hand pollinations). Gene flow into populations of size 2 was also negatively associated with the distance to the nearest population of size 10 or 20. These results suggest that interactions among demography (population size), genetics (cross-compatibility), and ecology (pollinator behavior) are important influences on pollen gene flow rates into small plant populations.

On teaching psychotherapy in a community mental health center.

The author discusses some of the unique problems related to teaching psychotherapy in a community mental health center. These problems arise principally from the diversity of philosophies and backgrounds of the health center staff and the lack of an overriding institutional tradition of psychotherapy. They often result in increased anxiety among trainees and require special attention from the teacher of psychotherapy in this setting.

Sardines and other fried fish. The consumption of alcoholic beverages on a Micronesian island.

Drinking parties are an integral aspect of life on Etal Island, despite official sanctions against them. The parties help to preserve certain traditional community values and provide an outlet for tension caused by political and social change.