Herbarium specimens show patterns of fruiting phenology in native and invasive plant species across New England

Premise of the Study

Patterns of fruiting phenology in temperate ecosystems are poorly understood, despite the ecological importance of fruiting for animal nutrition and seed dispersal. Herbarium specimens represent an under‐utilized resource for investigating geographical and climatic factors affecting fruiting times within species, patterns in fruiting times among species, and differences between native and non‐native invasive species.

Methods

We examined over 15,000 herbarium specimens, collected and housed across New England, and found 3159 specimens with ripe fruits, collected from 1849–2013. We examined patterns in fruiting phenology among 37 native and 18 invasive woody plant species common to New England. We compared fruiting dates between native and invasive species, and analyzed how fruiting phenology varies with temperature, space, and time.

Key Results

Spring temperature and year explained a small but significant amount of the variation in fruiting dates. Accounting for the moderate phylogenetic signal in fruiting phenology, invasive species fruited 26 days later on average than native species, with significantly greater standard deviations.

Conclusions

Herbarium specimens can be used to detect patterns in fruiting times among species. However, the amount of intraspecific variation in fruiting times explained by temporal, geographic, and climatic predictors is small, due to a combination of low temporal resolution of fruiting specimens and the protracted nature of fruiting. Later fruiting times in invasive species, combined with delays in autumn bird migrations in New England, may increase the likelihood that migratory birds will consume and disperse invasive seeds in New England later into the year.     

Straight Walk: A modified method of ligation-mediated genome walking for plant species with large genomes

Polymerase chain reaction (PCR)-based genome walking techniques are commonly used to clone unknown genomic regions flanking known sequences. However, these methods are typically problematic when applied to highly complex DNA templates isolated from plants with large genomes. Here we describe a reliable and efficient genome walking method that is particularly effective for plants with large genomes. Our ligation-mediated PCR method, Straight Walk, has improved sensitivity and specificity due to optimization of sequences of adaptors and adaptor primers. Successful genome walking in lily, which has one of the largest genomes in plants, indicates that Straight Walk is applicable for most plant species.     

Warming, plant phenology and the spatial dimension of trophic mismatch for large herbivores

Temporal advancement of resource availability by warming in seasonal environments can reduce reproductive success of vertebrates if their own reproductive phenology does not also advance with warming. Indirect evidence from large-scale analyses suggests, however, that migratory vertebrates might compensate for this by tracking phenological variation across landscapes. Results from our two-year warming experiment combined with seven years of observations of plant phenology and offspring production by caribou (Rangifer tarandus) in Greenland, however, contradict evidence from large-scale analyses. At spatial scales relevant to the foraging horizon of individual herbivores, spatial variability in plant phenology was reduced--not increased--by both experimental and observed warming. Concurrently, offspring production by female caribou declined with reductions in spatial variability in plant phenology. By highlighting the spatial dimension of trophic mismatch, these results reveal heretofore unexpected adverse consequences of climatic warming for herbivore population ecology.     

A new method of survey and data analysis in phenology

Abstract. A new, computerized method is presented for the survey and analysis of phenological data on the vegetative cycle of tree species in complex forest structures. It is based on the principles of classical phenology, phytosociological sampling techniques and the main concepts of growth analysis. The method considers the development of phenological phases as a stochastic process, and allows a quantitative and mathematical-statistical comparisonbetweenphenorhythms of trees and crown sections, and correlations with environmental variables.     

Rhizosphere respiration varies with plant species and phenology: A greenhouse pot experiment

Assessment of particulate (>53-m) and mineral-associated (<53-m) soil organic matter (SOM) fractions is a useful approach to understand the dynamic of organic matter in soils. This study aimed to compare the long-term (9-yr) effects of no-tillage (NT) and conventional tillage (CT) on C and N stocks in the two above mentioned organic fractions in a Brazilian Acrisol. The degree of SOM humification, which has been associated with the concentration of semiquinone-type free radicals (`spin') determined by electron spin resonance (ESR), was also evaluated. Soil under no-tillage had 7.55 Mg ha<sup>–1</sup> (25%) more C and 741 kg ha<sup>–1</sup> (29%) more N than conventionally tilled soil in the 0–175-mm depth. Both particulate and mineral-associated SOM increased in the no-tilled soil. The increase of C and N stocks in the mineral-associated SOM accounted for 75% and 91% of the difference in total soil C and N stocks between NT and CT, respectively. Averaged across tillage systems, C and N stocks were respectively 4.6 and 16.8 times higher in the mineral-associated SOM than in particulate SOM. The higher C and N stocks were associated with greater recalcitrance of mineral-associated SOM to biological decomposition, resulting, probably, from its interaction with variable charge minerals. This is corroborated by a positive relationship between concentrations of C and iron oxides and kaolinite in the 53–20, 20–2 and <2-m particle size classes, of the 0–25-mm soil layer. The degree of SOM humification, assessed by ESR, decreased in both the 53–20 and 20–2-m fractions under NT. However, it was unaffected by tillage in the <2-m fraction, which normally presented the lowest `spin' concentration. Since quality as well as quantity of SOM improved in the no-tillage soil, adoption of this system is highly recommended for amelioration of degraded tropical and subtropical soils.     

A new technique for reconstructing Montgomery's tubercles

Although Montgomery's tubercles are often prominent structures on the areola, little attention has been paid to their reconstruction. Present techniques for nipple-areola reconstruction result in a flat-appearing surface that is usually not characteristic of a normal areola with its projecting Montgomery's tubercles. We describe a technique for creating Montgomery's tubercles that has resulted in a more normal-appearing nipple-areola complex and a higher degree of patient satisfaction.     

Flowering phenology of invasive alien plant species compared with native species in three Mediterranean-type ecosystems

Background and Aims

Flowering phenology is a potentially important component of success of alien species, since elevated fecundity may enhance invasiveness. The flowering patterns of invasive alien plant species and related natives were studied in three regions with Mediterranean-type climate: California, Spain and South Africa''s Cape region.

Methods

A total of 227 invasive–native pairs were compared for seven character types across the regions, with each pair selected on the basis that they shared the same habitat type within a region, had a common growth form and pollination type, and belonged to the same family or genus.

Key Results

Invasive alien plant species have different patterns of flowering phenology from native species in the three regions. Whether the alien species flower earlier, later or at the same time as natives depends on the climatic regime in the native range of the aliens and the proportion of species in the invasive floras originating from different regions. Species invading at least two of the regions displayed the same flowering pattern, showing that flowering phenology is a conservative trait. Invasive species with native ranges in temperate climates flower earlier than natives, those from Mediterranean-type climates at the same time, and species from tropical climates flower later. In California, where the proportion of invaders from the Mediterranean Basin is high, the flowering pattern did not differ between invasive and native species, whereas in Spain the high proportion of tropical species results in a later flowering than natives, and in the Cape region early flowering than natives was the result of a high proportion of temperate invaders.

Conclusions

Observed patterns are due to the human-induced sympatry of species with different evolutionary histories whose flowering phenology evolved under different climatic regimes. The severity of the main abiotic filters imposed by the invaded regions (e.g. summer drought) has not been strong enough (yet) to shift the flowering pattern of invasive species to correspond with that of native relatives. It does, however, determine the length of the flowering season and the type of habitat invaded by summer-flowering aliens. Results suggest different implications for impacts at evolutionary time scales among the three regions.Key words: Biological invasions, flowering phenology, genetic inertia, Cape Floristic Region, California, Spain, Mediterranean-type ecosystems, water availability, climatic origin     

A method for reconstructing three-dimensional positions of swarming mosquitoes

We developed a new field method for reconstructing the three-dimensional positions of swarming mosquitoes. This method overcame certain inherent difficulties accompanied by conventional stereoscopic methods and is applicable to three-dimensional measurements of other insect species. Firstly, we constructed a probabilistic model for stereoscopy; if mosquitoes and six reference points with known coordinates were photographed simultaneously from two or more perspectives, then from the positions of images of mosquitoes and the reference points on the photographs, 1) the position of each camera with respect to the reference points is estimated; 2) stereo images which correspond to an identical real mosquito are matched; and 3) the spatial positions of the mosquitoes are determined. We automated the processes 1), 2) and 3), developing computer programs based on our model. We then constructed a portable system for three-dimensional measurements of swarming mosquitoes in the field. Initial data that illustrate the application of our method to studying mosquito swarming were presented.     

A new method for breath-to-breath determination of oxygen flux across the alveolar membrane

A new method for breath-to-breath determination of the oxygen flux across the alveolar membrane is described. The principle of the method is to integrate the product of oxygen concentration and flow in the respiratory gas over an interval, which covers a complete respiratory cycle. The result is corrected for the change in oxygen content of the lungs through a formula, which, in contrast to those used in other methods, is independent of the residual capacity of the lungs. The method was evaluated with respect to repeatability by repetitive measurement of oxygen flux in twenty volunteer subjects, and with respect to accuracy by comparing the measured oxygen fluxes with those obtained by the gas collection method. The coefficient of variation was found to be 8% and the breath to breath determinations were, on an average, 6% lower than those of the gas collection method.     

A method for reconstructing climate from fossil beetle assemblages

Fossil beetle remains have been used to reconstruct temperatures. One method by which these reconstructions are made--the Mutual Climatic Range method--is based on the overlap of the observed modern climatic ranges of the beetles present in a fossil sample. A limitation of this method is that it does not exploit variations in the rate of occurrence of a species within its climatic range. We present an alternative method that uses observed variations in this rate in modern data for climate reconstruction. The method is shown to perform well in an experiment using modern data from North America.     

Random local neighbor joining: a new method for reconstructing phylogenetic trees

We have developed a new method for reconstructing phylogenetic trees called random local neighbor-joining (RLNJ). Our method is different from the neighbor-joining method (NJ) of Saitou and Nei and affords a more thorough sampling of solution space by randomly searching for local pair of neighbors in each step. Results using the RLNJ method to analyze yeast data show an increasing possibility to get a smaller S value (sum of branch lengths) compared with the NJ method as cases with more taxa are analyzed and many individual runs using the RLNJ method usually generate more than one topology with small S values. Computer simulation shows the fact that the RLNJ method can improve the possibility of recovering correct topology significantly by affording more than one topology. In addition, when using the RLNJ method, computer simulation also shows that the proportion of correct topologies (P(C)) will increase as the number of different topologies decreases and as the proportion of "most frequent topology" increases. Thus, the number of different topologies and the proportion of "most frequent topology" can be used as auxiliary criteria to evaluate reliability of a phylogenetic tree.     

Assessment of potential indigenous plant species for the phytoremediation of arsenic-contaminated areas of Bangladesh

Soil and water contaminated with arsenic (As) pose a major environmental and human health problem in Bangladesh. Phytoremediation, a plant-based technology, may provide an economically viable solution for remediating the As-polluted sites. The use of indigenous plants with a high tolerance and accumulation capacity for As may be a very convenient approach for phytoremediation. To assess the potential of native plant species for phytoremediation, plant and soil samples were collected from four As-contaminated (groundwater) districts in Bangladesh. The main criteria used for selecting plants for phytoremediation were high bioconcentration factors (BCFs) and translocation factors (TFs) of As. From the results of a screening of 49 plant species belonging to 29 families, only one species of fern (Dryopteris filix-mas), three herbs (Blumea lacera, Mikania cordata, and Ageratum conyzoides), and two shrubs (Clerodendrum trichotomum and Ricinus communis) were found to be suitable for phytoremediation. Arsenic bioconcentration and translocation factors > 1 suggest that these plants are As-tolerant accumulators with potential use in phytoextraction. Three floating plants (Eichhornia crassipes, Spirodela polyrhiza, and Azolla pinnata) and a common wetland weed (Monochoria vaginalis) also showed high BCF and TF values; therefore, these plants may be promising candidates for cleaningup As-contaminated surface water and wetland areas. The BCF of Oryza sativa, obtained from As-contaminated districts was > 1, which highlights possible food-chain transfer issues for As-contaminated areas in Bangladesh.     

Use of animal and plant phenology for flight safety

The relationship between the appearance of small soil animals, number of birds and the season makes it possible to judge flight safety risks. The phenological phase of special plant species also controls the appearance of birds, for particular birds prefer particular states of vegetation, e.g. in pastured areas. This may suggest the possibilities for flight safety in the airfields and their vicinity. During low and high level flights of aircraft it has been necessary to forecast the beginning and course of migration. Beginning of migration is a function of fat deposit in the bird's body which in turn is a function of food uptake. Weather situations and single meteorological parameters influence the course of migration. By observing bird migration by radar and by combining radar data with weather data it has been possible to publish not only medium and long-scale forecasts but also actual warnings. Modern radar technique rendered the observation more difficult but this problem can be solved by introducing new methods.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, IsraelHerrn Dr. Fritz Schnelle zum 80. Geburtstag gewidmet.     

Flowering phenology and reproduction of a forest understorey plant species in response to the local environment

Temperate forest understorey plants are subjected to a strong seasonality in their optimal growing conditions. In winter and early spring, low temperatures are suboptimal for plant growth while light becomes limited later in spring season. We can thus expect that differences in plant phenology in relation to spatiotemporal environmental variation will lead to differences in reproductive output, and hence selection. We specifically studied whether early flowering, a paradoxical pattern that is observed in many plant species, is an adaptive strategy, and whether selection for early flowering was confounded with selection for flower duration or was attributable to environmental variables. We used Geum urbanum as a study species to investigate the effect of relevant environmental factors on the species’ flowering phenology and the consequences for plant reproductive output. We monitored the phenology of four to six plants in each of ten locations in a temperate deciduous forest (Belgium). We first quantified variation in flowering time within individuals and related this temporal variation to individual flower reproductive output. Then, we studied inter-individual variation here-in and linked this to reproduction at the plant level, hence studying the selection differential. We found that flowering within individual plants of Geum urbanum was spread over a long period from June to October. Reproductive output of individual flowers, measured as total seed mass per flower, declined during the season. We found no indication for selection for early flowering but rather for longer flower duration. Larger plants had an earlier flowering onset and a higher seed mass, which suggests that these factors covary and are condition dependent. None of the studied environmental variables could explain plant size, although soil pH and to a lesser extent light availability had a positive direct effect on seed mass per plant. Finally, we suggest that the high intra-individual variation in flowering time, which might be a risk spreading strategy of the plant in the presence of seed predation, limits the potential for selection on flowering phenology.

     

Consistency in the habitat degree of invasion for three invasive plant species across Mediterranean islands

Habitats are known to vary in their vulnerability to invasion by alien plants and different species often colonise distinct habitats. To assess the consistency in the degree of invasion of particular habitats, this study examined the frequency of occurrence and local abundance of three invasive plant taxa: Ailanthus altissima, Carpobrotus spp., and Oxalis pes-caprae across different habitat types on four representative Mediterranean islands. We conducted systematic field surveys recording the presence-absence and cover of these taxa on the islands of Mallorca, Corsica, Sardinia and Crete. Drawing on the results of 5,285 sample points, the frequency of occurrence of the three invaders tends to be higher than expected in urban, ruderal and roadside habitats. In contrast, scrub habitats rarely contain any of the three invaders, indicating that they may be more resistant to invasion. The degree of invasion, determined by the local abundance of an invasive plant in any one habitat, varies according to the identity of the invader and the island. However, based on average abundance, Oxalis pes-caprae exhibits the highest degree of invasion, and Carpobrotus spp. the least. There is no indication that any one of the four islands is more prone to either higher frequencies or abundances of the three invaders. These patterns suggest that anthropogenic changes in Mediterranean islands will increase the vulnerability of certain habitats to invasion and increase the distribution of these three invasive taxa at any of the four islands.