Spatial and temporal patterns of abundance of the potato leafhopper among red maples

A study was conducted in the 2001 growing season to examine the relative abundance, dispersion and distribution of the potato leafhopper (Empoasca fabae) among trees of 24 red maple (Acer rubrum) clonal selections. Yellow sticky traps hung from the trees were used to estimate the relative number of aerial potato leafhoppers among trees, starting on 1 May 2001 and stopping on 4 September 2001. More insects were collected from the east side of the plot than from the other sides in May, but no differences were significant late in the season. Few leafhoppers were collected during May, but the number of leafhoppers collected on traps rapidly increased and peaked during June. Afterwards, populations decreased and just a few individuals were trapped late in the season. Overall, significantly more leafhoppers were caught on traps hanging from trees of clone 56026 and 55410 than on trees of the other clones. Dispersion of the potato leafhopper changed from being aggregated in May, to being random in August, and also differed among the different clones. Populations tended to aggregate with increases in population numbers. Positive significant autocorrelations were detected at short distances in May, suggesting an aggregated spatial pattern early in the season. Yet, different autocorrelation patterns were detected within each block later in the season. Our results indicate that management practices could be developed to minimise pesticide use by targeting smaller areas with the highest populations at the right time of the season.     

Spatial and temporal gene expression patterns occur during corm development.

We investigated gene expression patterns that occur during taro corm development. Two-dimensional gel electrophoresis identified several different prevalent proteins that accumulate during corm development. Microsequencing studies indicated that some of these proteins are related to taste-modifying proteins, such as curculin and miraculin, and proteins found in other storage organs, such as sporamin and the Kunitz trypsin inhibitor. A curculin-encoding cDNA clone, designated as TC1, was identified that corresponds to a highly prevalent 1-kb corm mRNA. The TC1 mRNA accumulates during corm development, is more prevalent in corm apical than basal regions, and is either absent, or present at low concentrations, in other vegetative organs such as the leaf and root. In situ hybridization experiments showed that the TC1 mRNA is highly concentrated in corm storage parenchyma cells and is absent, or present in reduced concentrations, in other corm cells and tissues. Our results show that corm development is associated with the differentiation of specialized cells and tissues, and that these differentiation events are coupled with the temporal and spatial expression of corm-specific genes.     

Spatial and temporal patterns of phenotypic variation in a Neotropical frog

Aim Studies of the spatial and temporal patterns of phenotypic diversity help to elucidate the fine‐scale evolutionary and ecological mechanisms underlying geographical differentiation. The red‐eyed tree frog, Agalychnis callidryas, is a widespread Neotropical frog that exhibits a broad range of polymorphism of coloration and flank‐stripe pattern. The goal of this study was two‐fold: first, to investigate the stability of polymorphisms over a 38‐year period; and second, to evaluate biogeographical hypotheses of diversification between lower Central American populations through quantification of phenotypic diversity on a fine geographical scale. Location This study was conducted at 12 sites across four biogeographical regions in Costa Rica and Panama. Methods We quantified colour, categorized flank‐stripe pattern from digital photos taken during field sampling, and measured body size for each individual. We compared the regional frequency of each flank‐stripe pattern in 2005 with the frequency distribution from a previous study of the same sites in 1967 using logistic regression analyses. We determined the geographical signal of leg coloration by employing linear discriminant function analyses to generate a classification matrix based on covariance similarities, and by comparison of the average hue values within and between regions. Results We found a temporal shift in the frequency of flank‐stripe patterns in three of four regions over 38 years. Based on measures of leg coloration, the frequency distribution of flank‐stripe patterns and body size, we conclude that A. callidryas populations are easily distinguishable at a regional scale. Main conclusions Agalychnis callidryas exhibits regional differentiation in all phenotypic traits measured in this study, supporting the role of three major biogeographical barriers to gene exchange. We found evidence of a putative contact zone between polytypic regions in Costa Rica. In addition, we report temporal instability of the relative frequency of stripe patterns located on the flanks. The ecological and evolutionary mechanisms that may underlie this variation include sexual selection and avoidance of predators.     

Spatial and temporal patterns of species richness in a riparian landscape

Aim To test for control of vascular plant species richness in the riparian corridor by exploring three contrasting (although not mutually exclusive) hypotheses: (1) longitudinal patterns in riparian plant species richness are governed by local, river‐related processes independent of the regional species richness, (2) riparian plant species richness is controlled by dispersal along the river (longitudinal control), and (3) the variation in riparian plant species richness mirrors variation in regional richness (lateral control). Location The riparian zones of the free‐flowing Vindel River and its surrounding river valley, northern Sweden. Methods We used data from three surveys, undertaken at 10‐year intervals, of riparian reaches (200‐m stretches of riverbank) spanning the entire river. In addition, we surveyed species richness of vascular plants in the uplands adjacent to the river in 3.75‐km² large plots along the same regional gradient. We explored the relationship between riparian and upland flora, and various environmental variables. We also evaluated temporal variation in downstream patterns of the riparian flora. Results Our results suggest that local species richness in boreal rivers is mainly a result of local, river‐related processes and dispersal along the corridor. The strongest correlation between species richness and the environment was a negative one between species number and soil pH, but pH varied within a narrow range. We did not find evidence for a correlation between species richness on regional and local scales. We found that the local patterns of species richness for naturally occurring vascular plants were temporally variable, probably in response to large‐scale disturbance caused by extreme floods. Most previous studies have found a unimodal pattern of species richness with peaks in the middle reaches of a river. In contrast, on two of three occasions corresponding to major flooding events, we found that the distribution of species richness of naturally occurring vascular plants resembled that of regional diversity: a monotonic decrease from headwater to coast. We also found high floristic similarity between the riparian corridor and the surrounding landscape. Main conclusions These results suggest that local processes control patterns of riparian species richness, but that species composition is also highly dependent on the regional species pool. We argue that inter‐annual variation in flood disturbance is probably the most important factor producing temporal variability of longitudinal species richness patterns.     

Spatial and temporal patterns of morel fruiting

The biotic and abiotic factors conditioning morel fruit body production are incompletely known. We examined spatial and temporal patterns of Morchella esculenta fruiting over five years in a wooded site in Missouri, USA. Fruiting onset was inversely correlated with spring air and soil temperatures, whereas abundance was positively correlated with rain events (>10 mm) during the 30 d preceding fruiting. The two years with the greatest fruiting had the shortest fruiting seasons (6–7 d). Fruiting season length was positively correlated with soil warming, suggesting that a narrow range of optimum soil temperatures favour the explosive production of fruit bodies. All woody stems of at least 1 cm diam were mapped and stem diameter and crown condition were noted. Morel fruit bodies were significantly closer to stems of Carya spp., Tilia americana and Ulmus americana than predicted by the frequencies of these woody species or their contribution to the total basal area on the site. Although intra-annual clustering of fruit bodies was often observed, inter-annual clustering was not. The spatial pattern of M. esculenta fruiting appears to be associated with vegetation pattern, whereas the onset and abundance of fruiting are determined by the interaction of spring temperatures with availability of supporting precipitation.     

Spatial and temporal patterns in Arctic mosquito abundance

1. Organisms that undergo a shift in ontogeny and habitat type often change their spatial distribution throughout their life cycle, but how this affects population dynamics remains poorly understood.
2. We examined spatial and temporal patterns in Aedes nigripes abundance, a widespread univoltine Arctic mosquito species (Diptera: Culicidae), hypothesizing that the spatial distribution of adults would be closely tied to aquatic habitat.
3. We tracked adult densities of A. nigripes near Kangerlussuaq, Greenland using emergence traps, CO₂-baited traps, and sweep-nets.
4. In back-to-back years of sampling (2017 and 2018) we found two-fold variation in overall abundance.
5. Adults were spatially patchy when first emerging from aquatic habitats but within a week, mean capture rates for host-seeking adult females were similar across locations, even in places far from larval habitat.
6. Daily variation in mosquito captures was primarily explained by weather, with virtually no mosquito activity when temperatures averaged less than 8°C or wind speeds exceeded 6 m/s. Gravid females (3% of resting adults) were spatially patchy on the landscape, but not always in the same places where most adults emerged.
7. The spatial distribution of adults is quickly uncoupled from the spatial distribution of larvae because A. nigripes females may disperse far from their natal habitats in search of a blood-meal and high-quality oviposition habitat.

8. This research highlights the value of studying ecological processes that act at disparate life stages for understanding the population biology of organisms with complex life cycles.     

Differential expression within a family of novel wound-induced genes in potato

Summary Wounding in higher plants leads to an increased synthesis of specific messenger RNAs. A cDNA clone complementary to a wound-induced message from potato tubers was used to isolate a lambda clone from a genomic library of Salanum tuberosum var. Maris Piper. DNA sequence analysis has shown that this single genomic clone contains two novel wound-induced genes, called win1 and win2, organised in close tandem array. The coding sequences of these two genes are highly homologous and are interrupted by a single intron. However, the sequences of the introns and flanking regions have diverged widely. Win1 and win2 encode cysteine-rich proteins of 200 and 211 amino-acids, respectively, which show striking homologies to several chitin-binding proteins. Southern analysis of genomic DNA has shown that win1 and win2 are members of a small multi-gene family which is estimated to have a minimum of five members per haploid genome of Maris Piper and appears to be conserved within the Solanaceae. We have shown by Northern analysis and S1 mapping that the two genes exhibit differential organ-specific expression after the wounding of a potato plant.     

Spatial and temporal expression patterns of Xenopus Nkx-2.3 gene in skin epidermis during metamorphosis

Using PCR cloning, the mRNA of XNkx-2.3 gene, a Xenopus tinman homologue, was identified in a cDNA library prepared from thyroid hormone (T(3))-treated tadpole skin. Quantitative RT-PCR and RNase Protection Assay confirmed the expression of XNkx-2.3 in adult frog skin and its amount was similar to the amount found in heart. In situ hybridization indicated that XNkx-2.3 was expressed in the frog epidermis. Further analysis of XNkx-2.3 expression patterns demonstrates that it shares great similarities with a 63 kDa keratin, a well-characterized marker for skin maturation, in the following aspects. First, XNkx-2.3 was expressed in tadpole skin during metamorphosis (stages 55-59), but not in pre-metamorphic (stage 54) skin. Secondly, XNkx-2.3 expression in skin responded to T(3) stimulation because it could be precociously induced by T(3) at pre-metamorphic stage, both in tadpoles and in cultures of skin explants. Finally, the T(3)-induced appearance of XNkx-2.3 in head skin occurred earlier and at higher level than that in tail skin. These data suggest that XNkx-2.3 may be an important factor for skin maturation and may also serve as a good marker to indicate the maturation of Xenopus epidermis.     

Spatial and temporal expression of a Polysphondylium spore-specific gene

In the cellular slime mold Polysphondylium spherical masses of cells are periodically released from the base of the culminating sorogen. These whorls undergo a morphogenetic transformation from spherical to radial symmetry, marked by the early emergence of a radially symmetric prepattern on the whorl surface. In previous experiments, morphogenesis was followed by observing prestalk cell markers. Here we describe the isolation and characterization of a spore coat gene whose expression pattern is the negative image of the prestalk pattern. To study the molecular mechanism of sp-45 gene regulation, we have cloned and analyzed the sp-45 promoter. Deletion analysis localized a single positive regulatory element (PRE) to a 106-bp fragment between positions -246 and -352 of the upstream coding sequence. This fragment can be further divided into a promoter-proximal and promoter-distal PRE and a 29-bp sequence between them. The distal PRE can regulate prespore expression when fused to a nonfunctioning basal promoter. The distal PRE contains two adjacent essential elements, a Gr box (GTGATATAGTGG) and a TA box (TAATATATT). Each element can drive prespore cell-specific reporter gene expression independently when incorporated into a nonfunctional promoter. Our results also show that prespore cell-specific gene expression is solely under positive regulation, with no evidence for spore-specific enhancers or cis-acting negative regulatory elements. By fusing GFP to the C-terminus of sp-45, we have demonstrated that the graded gene expression of SP45 in the sorogen is regulated by a sequence lying within the sp-45 coding sequence. The temporal and spatial expression pattern of this protein, taken together with the prestalk expression pattern, demonstrates unambiguously that the radial symmetries that emerge in the whorl are established by a system of positional coordinates and that cell sorting plays little if any role in this process.     

Spatial and temporal patterns of root activity in a species-rich alluvial grassland

Summary The time and depth of activity of a number of co-existing grassland plants was measured using a technique involving the simultaneous injection to different depths in soil of 3 chemical tracers — Li, Rb and Sr. Root activity at a particular depth was assessed from the concentration of each tracer in leaf tissue.The seven most constant species showed very similar patterns of root activity, which was greater at 5 than at 15 or 25 cm except towards the end of the growth period in late June. Maximum root activity generally occurred earlier than maximum shoot productivity but there was little evidence of differentiation between species. When root activity was assessed as a proportion of total community root activity, by combining tracer concentration and biomass data, seasonal differences between species were more obvious. Using both root activity and productivity data, species were grouped into two main guilds, one active in spring (April-May) and one in summer (June).Correlations of above-ground biomass with root activity at different depths revealed that species of the spring guild were more active in the 5–15 cm horizons and those of the summer guild at 15–25 cm.These patterns suggest that rooting depth and time of activity are strongly linked: early-active species tend to be less productive and shallower-rooted and this combination of characters allows them to escape from competition with more productive species, by being active at a time when deeper soil layers are less hospitable.     

Kinetics and localization of wound-induced DNA biosynthesis in potato tuber

Tuber wounding induces a cascade of biological responses that are involved in processes required to heal and protect surviving plant tissues. Little is known about the coordination of these processes, including essential wound-induced DNA synthesis, yet they play critical roles in maintaining marketability of the harvested crop and tubers cut for seed. A sensitive “Click-iT EdU Assay” employing incorporation of the thymidine analog, 5-ethynyl-2′-deoxyuridine (EdU), in conjunction with 4′,6-diamindino-2-phenylindole (DAPI) counter labeling, was employed to objectively identify and determine the time course and spatial distribution of tuber nuclei that were wound-induced to enter S-phase of the cell cycle. Both labeling procedures are rapid and sensitive in situ. Following wounding, EdU incorporation (indicating DNA synthesis) was not detectable until after 12 h, rapidly reached a maximum at about 18 h and then declined to near zero at 48 h. About 28% of the nuclei were EdU labeled at 18 h reflecting the proportion of cells in S-phase of the cell cycle. During the ∼30 h in which induced cells were progressing through S-phase, de novo DNA synthesis extended 7–8 cell layers below the wound surface. Cessation of nuclear DNA synthesis occurred about 4 d prior to completion of wound closing layer formation. Initiation of wound periderm development followed at 7 d, i.e. about 5 d after cessation of nuclear DNA biosynthesis; at this time the phellogen developed and meristematic activity was detected via the production of new phellem cells. Collectively, these results provide new insight into the coordination of wound-induced nucleic acid synthesis with associated tuber wound-healing processes.     

Spatial and temporal distribution patterns of flying Diptera

The temporal and spatial distributions of flying Diptera have been studied using suction traps hung at three levels and two distances from an emergent hedgerow tree. Most families were far more abundant in 1987 than in 1986, but patterns of spatial and temporal abundance were basically the same. Most families showed a marked concentration close to the tree. Scatopsidae accumulated away from the tree in large numbers. Most families concentrated at the mid-level, except the Anisopodidae and Mycetophilidae (top and bottom levels, respectively). Vertical distributions showed discontinuities for almost all families. It is suggested that the emergent hedgerow tree plays a very important part in the life of flying insects.     

Vacuolar localization of wound-induced carboxypeptidase inhibitor in potato leaves

The wound-induced carboxypeptidase inhibitor in potato leaves was shown to be localized in the central vacuoles of the cells. The inhibitor was quantified by immunological assays (ELISA) in protoplasts and vacuoles isolated from upper unwounded leaves of 5- to 6-week old potato plants that had been wounded on their lower leaves 48 hours earlier to induce the accumulation of the carboxypeptidase inhibitor. The regulation of the synthesis and compartmentation of the inhibitor is similar to that of wound-induced serine proteinase Inhibitors I and II in potato and tomato leaves and appears to be part of an induced defense response against attacking pests.     

Spatial and temporal patterns of sexual reproduction in a hybrid Daphnia species complex

Evidence for extensive interspecific hybridization among speciesof the genus Daphnia has been accumulating on a global scale.Although there is evidence for limited gene flow between taxavia hybridization, many species still maintain discrete morphologicaland molecular characteristics. We studied temporal and spatialpatterns of sexual reproduction within the Daphnia galeata–hyalina–cucullatahybrid species complex in a lake (Plußsee), located innorthern Germany. Allozyme electrophoresis allowed us to trackseasonal changes in taxon composition as well as the quantificationof back-crosses. Sexually-reproducing animals (ephippial femalesand males) were mainly found in autumn. The simultaneous presenceof sexual morphs of D. galeata and D. galeata x hyalina withthe dominant D. hyalina taxa makes recent hybridization, aswell as back-crossing, plausible. Males and ephippial femalesof D. hyalina were not back-crossed as were the parthenogeneticfemales. The low number of sexual clones of the hybrid D. galeatax hyalina might reflect its reduced fertility, although thesefew clones were detected in high densities. Only hybrid-clonesthat had a back-cross genotype (towards D. hyalina) exhibitedephippial females and males. This indicates that male and ephippialfemale production within the Daphnia taxa is not random, whichmight increase the chance for the parental Daphnia species toremain distinct.     

Spatial and temporal patterns of invertebrate drift in streams draining a Neotropical landscape

1. Invertebrate drift in streams draining a tropical landscape in Costa Rica was studied to assess differences in assemblage composition above and below a major gradient break in geomorphic landform and to assess temporal patterns of drift in lowland reaches below the gradient break. The gradient break (～50 m a.s.l.) is the point at which the foothills of the Costa Rican Cordillera Central (piedmont) merge with the Caribbean coastal plain (lowlands).
2. Spatial patterns were assessed along two streams by sampling drift over 24 h once a month for 3 months in both the piedmont (90 m a.s.l.) and lowlands (30 m a.s.l.). Temporal patterns of drift were assessed through monthly diel sampling of three lowland sites over 8–10 months, encompassing both ‘dry’ (<400 mm precipitation per month, November to May) and wet (July to October) seasons.
3. Drift composition was insect dominated in piedmont sites and larval shrimp dominated in the lowlands. Percent similarity of assemblages between piedmont and lowland sites was low (range 26–43%) because of high larval shrimp densities in lowland versus piedmont sites.
4. Drift densities were higher during night than day, with peaks at sunset on all dates and at all sites. Diel patterns in drift agree with previous observations for the study area and support the ‘risk of predation’ hypothesis.
5. Analysis of monthly patterns in lowland sites showed high variability in drift densities; however, all major taxa were found every month. Overall, there was a trend for high invertebrate densities during the ‘dry’ season, but these trends were not significant.
6. Observed changes in drift composition support the concept of river zonation, which predicts a change in community composition along the stream continuum due to geomorphic features. Drift at lowland sites below the gradient break was dominated by shrimps, which are linked to marine environments via their migratory behaviour.     

Spatial and temporal distribution patterns of three trophic levels in a saline lake

Horizontal distribution patterns of three trophic levels wereinvestigated at Mono Lake, California, USA during the autumnsof 1980 and 1981. Coefficients of variation for Anemia monicaand grebes peaked in October of both years, whereas coefficientsof variation for phytoplankton declined from August to November.Stable population gradients were observed in the Anemia population.In contrast, grebes were very mobile and their distributionalpatterns changed between sampling dates. Anemia and phytoplanktonwere negatively correlated during 1980, but no significant correlationsoccurred in 1981. Grebes and Artemia were positively correlatedin October 1980 and 1981, suggesting active prey tracking bythe grebes. Interactions between trophic levels may have contributedto the creation and maintenance of patchiness, although theseeffects appeared to be intermittent.     

Spatial and temporal patterns in the activity of European moles

 Using ratio-tracking data obtained at three sites, we assessed the effects of season and of neighbour avoidance on the activity and patterns of home range use by European moles (Talpa europaea). The home ranges of non-breeding male and female moles did not differ significantly in size, and averaged 2324 m² (minimum convex polygon). Although overlap between ranges was small (an average of 12.8% of each range being shared with neighbours and an average of only 3.3% of 2×2 m grid cells were shared with an individual neighbour, ranges were not oriented to avoid neighbours. Non-breeding male/female neighbours tended to share more of their grid cells (3.9±5.7%) mean ±SD than did neighbours of the same sex (male:male 1.2±0.95%; female:female 1.1±1.3%), but there was no significant difference in overlap between any combination of sex pairings. On average, each mole spent only 0.9% of its time within 6 m of another mole, and only 3 out of 46 dyads showed evidence of being attracted to each other; there was no evidence from the simultaneous movement patterns of neighbouring moles that they avoided each other. Although moles tended to return to the same part of their range at the same time on successive days, there was also some indication of gradual changes in the spatial pattern of daily home range use. Moles had a triphasic pattern of activity, but this became tetraphasic under drought conditions. There were significant differences between sites, but not between sexes, in sleeping behaviour and activity patterns. These differences could be related to seasonal differences in soil moisture and thus probably to prey renewal rates. We conclude that in our sites, the activity patterns and movements of moles depend on the temporal and spatial dispersion of food, rather than on short-term interactions between the movements of neighbours. Received: 13 January 1996 / Accepted: 26 June 1996     

Spatial and temporal patterns in the hydrogeochemistry of a poor fen in northern Wisconsin

We studied the factors causing spatial and temporal patterning of interstitial water chemistry in Crystal Bog, a 7 ha northern Wisconsin kettle-hole peatland. Over the course of the snow-free season Crystal Bog exhibited spatial and temporal patterns in chemistry, especially hydrogen-ion, dissolved organic carbon, and specific conductance. The peatland contains a 0.5 ha pond that has water more dilute than the interstitial water of the surrounding peatland. The direction of groundwater flow between the lake and the peatland was seasonally dependent. In the spring and early summer, flow was from the lake into the peatland, especially on the eastern side of the lake. This flow resulted in a plume of relatively dilute surface interstitial water in the peatland. In mid and late summer direction of groundwater flow was from the peatland into the lake and the dilute plume was reduced in areal extent. By fall the direction of water flow was again from the lake to the peatland.The spatial and temporal heterogeneity in water chemistry produced by the seasonal variation in the direction of horizontal water flow was substantial. Minimum and maximum observed concentrations of dissolved organic carbon (DOC) in the interstitial water of the peatland, for example, differed by more than a factor of three, and pH ranged between 3.8 and 5.0. Correlations of DOC with anion deficit and hydrogen ion concentration and experiments of photo-oxidation of water samples showed that organic acids were the primary cause of acidity in the peatland. Specific conductance was highly correlated with DOC, probably because of DOC's correlation with the very conductive hydrogen ion. In Crystal Bog it was possible to use the relatively simple measure of specific conductance to estimate the temporal and spatial distribution of the more difficult to determine DOC.     

Nutrient fluxes in a snow-dominated, semi-arid forest: Spatial and temporal patterns

We tested five hypotheses regarding the potential effects of precipitation change on spatial and temporal patterns of water flux, ion flux, and ion concentration in a semiarid, snowmelt-dominated forest in Little Valley, Nevada. Variations in data collected from 1995 to 1999 were used to examine the potential effects of snowpack amount and duration on ion concentrations and fluxes. Soil solution NO₃ ^–, NH₄ ⁺, and ortho-phosphate concentrations and fluxes were uniformly low, and the variations in concentration bore no relationship to snowmelt water flux inputs of these ions. Weathering and cation exchange largely controlled the concentrations and fluxes of base cations from soils in these systems; however, soil solution base cation concentrations were affected by cation concentrations during snowmelt episodes. Soil solution Cl^– and SO₄ ^2– concentrations closely followed the patterns in snowmelt water, suggesting minimal buffering of either ion by soils. In contrast to other studies, the highest concentration and the majority of ion flux from the snowpack in Little Valley occurred in the later phases of snowmelt. Possible reasons for this include sublimation of the snowpack and dry deposition of organic matter during the later stages of snowmelt. Our comparison of interannual and spatial patterns revealed that variation in ion concentration rather than water flux is the most important driver of variation in ion flux. Thus, it is not safe to assume that changes in total precipitation amount will cause concomitant changes in ion inputs to this system.