scholarly journals Revisiting Connell: competition but not as we know it

2017 ◽  
Vol 98 (6) ◽  
pp. 1253-1261 ◽  
Author(s):  
Jenna M. Gordon ◽  
Antony M. Knights
Keyword(s):  
Growth Rates ◽  
Natural Populations ◽  
Small Scale ◽  
Nearest Neighbour ◽  
Negative Effects ◽  
Lower Growth ◽  
Neighbour Distance ◽  
Lower Growth Rate ◽  
Pair Competition ◽  
Reduced Density

Space is one of the primary limiting resources for organisms on the intertidal rocky shore. This paper examined the effect of reduced density on key traits (mortality and growth) on the intertidal barnacles, Chthamalus montagui and Semibalanus balanoides, on the mid-shore in Plymouth, UK. Intra- and interspecific treatments comprising of C. montagui and S. balanoides were manipulated to reduce densities at two similar sites. Changes in mortality and operculum growth were assessed over an 8-week period using digital photography. Covariates of growth included nearest neighbour distance, competition between closest pairs and initial size. Conflicting patterns were observed when comparing growth rates between treatments and sites. At Site 1, interspecific treatments had a lower growth rate than intraspecific treatments, whereas at Site 2, interspecific growth rates were higher. ANCOVA showed that nearest neighbour distance had no significant effect on growth, but when comparing differences in growth of closest neighbouring pairs, C. montagui treatment showed evidence of competition whereas S. balanoides did not. ANCOVA analysis indicated no difference in growth between each outcome of pair competition, suggesting winners are initially bigger than losers. Comparisons of mortality between treatments indicated mortality over time with no significant differences observed between treatments, but response surface methodology (RSM) revealed no effects of competition on mortality of S. balanoides, but negative effects of both intra- and interspecific competition on C. montagui survivorship. Examination of natural populations of barnacles in the mid-shore indicated there was strong spatial variation in growth rates, perhaps driven by small-scale differences within sites.

scholarly journals Spatial micro-distribution of shoots in Posidonia oceanica (L.) Delile meadows

2015 ◽  
Author(s):  
Tiziano Bacci ◽  
Sante Francesco Rende ◽  
Domenico Rocca ◽  
Michele Scardi
Keyword(s):  
Spatial Distribution ◽  
Posidonia Oceanica ◽  
Small Scale ◽  
Nearest Neighbour ◽  
Data Set ◽  
Spatial Indices ◽  
Neighbour Distance ◽  
Point Patterns ◽  
Spatial Point ◽  
Spatial Point Patterns

Posidonia oceanica meadows contain huge numbers of shoots and their dynamics are strictly related to spatial distribution patterns of those shoots. In order to investigate the structure of P. oceanica meadows at very small spatial scale (i.e. in the 1 cm 2 -1 m 2 range), patterns in shoot distribution were analyzed. Spatial distribution of shoots was recorded by cutting all the leaves and by digitizing shoot location from images of 10 square frames (1 m 2 ), sampled in seemingly uniformly dense meadows at two sites in Southern Italy. Spatial point patterns have been explored testing the sensitivity and robustness through different spatial indices, based on i) nearest neighbour analysis, ii) quadrat counts analysis, iii) fractal dimension. Clark & Evans nearest neighbour distance index has been proved to be the most suitable for aim of the work and it has been selected for the further analysis. Data analysis of the 10 square frames (1 m 2 ) highlighted regular spatial point patterns (R>1; p<0.0001) in most cases (8 frames), while aggregated (R<1; p<0.01) and random (R=1) spatial point patterns were rare. In addition, mean value of nearest neighbour distance of shoots in each square frame analyzed has been shown to be always close to 2 cm (min: 1.73 cm; max: 2.21 cm). The potential implications of this type of data set were highlighted. Both nearest neighbour distance of shoots and spatial point pattern typology (aggregated, random or regular) could provide useful and integrative information for the study of P. oceanica macrostructure (e.g. implementation of shoot growth models, development of new descriptors). The raw data, provided by the authors as supplementary material, are currently the first and the only information available about shoot spatial micro-distribution. In this regard, although our data set cannot represent the whole spectrum of variability in P. oceanica meadows, it certainly shed some light on the small scale patterns of P. oceanica meadows and it prompts us many questions, some of which are still unanswered.

scholarly journals An examination of the effect of autumn closing date on over-winter herbage production and spring yield

2021 ◽  
Author(s):  
C. Looney ◽  
D. Hennessy ◽  
A. Wingler ◽  
A. Claffey ◽  
M. Egan
Keyword(s):  
Growth Rates ◽  
Lower Growth ◽  
Closing Date ◽  
Herbage Quality ◽  
High Feed ◽  
Lower Growth Rate ◽  
Dead Material ◽  
Grass Growth ◽  
Tiller Density ◽  
Spring Yield

Altering autumn management affects the herbage mass available in spring. An experiment was established to determine the effect of five autumn closing dates (CDs) on herbage production, herbage quality, leaf, stem and dead proportions and tiller density over winter. In the study 50% of the herbage available in spring was accounted for by autumn CD. Each 1 d extra a sward was closed from 25 September to 9 December increased herbage mass by 16 kg DM/ha in spring. Swards closed earlier (25 September–26 October) had consistently higher herbage masses in spring (1,301 kg DM/ha) compared to swards closed later (11 November–9 December; 703 kg DM/ha). Later closed swards had greater herbage quality compared to earlier closed swards (organic matter digestibility = 852 and 825 g/kg DM, respectively) due to increased stem and dead material in the grazing horizon of earlier closed swards. There was no effect of autumn CD on sward quality in the subsequent defoliation in spring. However, following the initial spring grazing there was an effect of autumn CD on subsequent grass growth rates; swards closed in October had a lower growth rate (33 kg DM/ha per day) compared to swards closed in November and early December (49 kg DM/ha per day). Results indicate that earlier autumn closing is beneficial to meet high-feed demand in spring but can affect sward quality and growth rates in spring.

scholarly journals Differences on allocation of available resources, in growth, reproduction, and survival, in an exotic gastropod of Physidae compared to an endemic one

2010 ◽  
Vol 100 (3) ◽  
pp. 275-279 ◽  
Author(s):  
Verónica Núñez
Keyword(s):  
Growth Rates ◽  
Native Species ◽  
Energy Allocation ◽  
Reproductive Period ◽  
Functional Requirements ◽  
Lower Growth ◽  
Physa Acuta ◽  
Local Species ◽  
Lower Growth Rate ◽  
Maximum Shell Length

Physa acuta Draparnaud, 1805 is an invasive gastropod that can affect local species. In Argentina, it is widespread and abundant, even in environments inhabited by the native species Stenophysa marmorata Guilding, 1828. Its predominance raises the question whether this could be explained by a more successful energy allocation in functional requirements (growth, reproduction and survival) compared to S. marmorata. This study was aimed at comparing growth rates, as well as survival and fecundity, between both species under laboratory conditions. Individuals born on the same day were grouped in four per aquaria and kept under controlled conditions of food, light, and temperature. Snails were weekly measured (maximum shell length), and growth rates were calculated using the Von Bertalanffy's equation. The number of eggs and survivors were grouped by week. Stenophysa marmorata was larger at birth than Physa acuta and invested more energy in growth, delaying sexual maturity. This resulted in a disadvantage in fecundity and survival compared to P. acuta, which had a lower growth rate but matured earlier and survived longer. Furthermore, the growth of P. acuta was not affected by reproduction, its reproductive period was longer, consequently with more eggs laid than S. marmorata.

scholarly journals Spatial micro-distribution of shoots in Posidonia oceanica (L.) Delile meadows

2015 ◽  
Author(s):  
Tiziano Bacci ◽  
Sante Francesco Rende ◽  
Domenico Rocca ◽  
Michele Scardi
Keyword(s):  
Spatial Distribution ◽  
Posidonia Oceanica ◽  
Small Scale ◽  
Nearest Neighbour ◽  
Data Set ◽  
Spatial Indices ◽  
Neighbour Distance ◽  
Point Patterns ◽  
Spatial Point ◽  
Spatial Point Patterns

Posidonia oceanica meadows contain huge numbers of shoots and their dynamics are strictly related to spatial distribution patterns of those shoots. In order to investigate the structure of P. oceanica meadows at very small spatial scale (i.e. in the 1 cm 2 -1 m 2 range), patterns in shoot distribution were analyzed. Spatial distribution of shoots was recorded by cutting all the leaves and by digitizing shoot location from images of 10 square frames (1 m 2 ), sampled in seemingly uniformly dense meadows at two sites in Southern Italy. Spatial point patterns have been explored testing the sensitivity and robustness through different spatial indices, based on i) nearest neighbour analysis, ii) quadrat counts analysis, iii) fractal dimension. Clark & Evans nearest neighbour distance index has been proved to be the most suitable for aim of the work and it has been selected for the further analysis. Data analysis of the 10 square frames (1 m 2 ) highlighted regular spatial point patterns (R>1; p<0.0001) in most cases (8 frames), while aggregated (R<1; p<0.01) and random (R=1) spatial point patterns were rare. In addition, mean value of nearest neighbour distance of shoots in each square frame analyzed has been shown to be always close to 2 cm (min: 1.73 cm; max: 2.21 cm). The potential implications of this type of data set were highlighted. Both nearest neighbour distance of shoots and spatial point pattern typology (aggregated, random or regular) could provide useful and integrative information for the study of P. oceanica macrostructure (e.g. implementation of shoot growth models, development of new descriptors). The raw data, provided by the authors as supplementary material, are currently the first and the only information available about shoot spatial micro-distribution. In this regard, although our data set cannot represent the whole spectrum of variability in P. oceanica meadows, it certainly shed some light on the small scale patterns of P. oceanica meadows and it prompts us many questions, some of which are still unanswered.

The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1190-1191
Author(s):  
David Cockayne ◽  
David McKenzie
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Density Function ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Materials ◽  
Nearest Neighbour ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Reduced Density ◽  
System F

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.

scholarly journals Effects of Modification of Light Parameters on the Production of Cryptophycin, Cyanotoxin with Potent Anticancer Activity, in Nostoc sp.

Toxins ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 809
Author(s):  
Alexandros Polyzois ◽  
Diana Kirilovsky ◽  
Thi-hanh Dufat ◽  
Sylvie Michel
Keyword(s):  
Light Stress ◽  
Red Light ◽  
Major Effect ◽  
High Light Intensity ◽  
Efficient Production ◽  
Lower Growth ◽  
Noticeable Increase ◽  
Lower Growth Rate ◽  
Industrial Use ◽  
Effect Of Light

Cryptophycin-1 is a cyanotoxin produced by filamentous cyanobacteria. It has been evaluated as an anticancer agent with great potential. However, its synthesis provides insufficient yield for industrial use. An alternative solution for metabolite efficient production is to stress cyanobacteria by modifying the environmental conditions of the culture (Nostoc sp. ATCC 53789). Here, we examined the effects of light photoperiod, wavelength, and intensity. In light photoperiod, photoperiods 24:0 and 16:8 (light:dark) were tested while in wavelength, orange-red light was compared with blue. Medium, high, and very high light intensity experiments were performed to test the effect of light stress. For a 10-day period, growth was measured, metabolite concentration was calculated through HPLC, and the related curves were drawn. The differentiation of light wavelength had a major effect on the culture, as orange-red filter contributed to noticeable increase in both growth and doubled the cyanotoxin concentration in comparison to blue light. Remarkably, constant light provides higher cryptophycin yield, but slightly lower growth rate. Lastly, the microorganism prefers medium light intensities for both growth and metabolite expression. The combination of these optimal conditions would contribute to the further exploitation of cryptophycin.

ELASTIC PROPERTIES OF STRAINED FCC AND HCP IRON

1993 ◽  
Vol 07 (01n03) ◽  
pp. 207-211
Author(s):  
T. KRAFT ◽  
M. METHFESSEL ◽  
M. VAN SCHILFGAARDE ◽  
M. SCHEFFLER
Keyword(s):  
Energy Cost ◽  
Interplanar Distance ◽  
Orbital Method ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Nearest Neighbour ◽  
Density Approximation ◽  
Neighbour Distance ◽  
Large Lattice ◽  
Fcc Phase

Using the full-potential linear muffin-tin orbital method within the local spin-density approximation we analyse the influence of the nearest neighbour distance on fcc(111) or hcp(0001) iron layers. The LDA-LSDA error in describing ferromagnetic phases is determined to be at least 15 mRy/atom. As a consequence of this error, our calculations favour paramagnetic ground states. In this sense, the reported results have some model character. However, our analysis of the elastic energy cost under distortions should hold for transition metals in general. Allowing relaxations of the interplanar distance the fcc phase can become energetically favourable over the hcp phase at large lattice mismatches. The main reason for this behaviour is the enhanced stiffness of the hcp interplanar bonds due to the shortening of the axial c/a ratio.

Effects of lice infestation on the growth of beef heifers in Victoria

1984 ◽  
Vol 24 (125) ◽  
pp. 140 ◽  
Author(s):  
PJ Bailey ◽  
WAD Carroll ◽  
B Knee
Keyword(s):  
Growth Rates ◽  
Beef Heifers ◽  
Lower Growth ◽  
High Rainfall ◽  
Main Species ◽  
Western Victoria ◽  
Linognathus Vituli

Ten experiments were carried out to examine some of the effects of lice infestation on heifers grazing on six commercial properties in the high rainfall areas of Victoria. In all experiments, famphur, a pour-on lousicide, effectively controlled lice populations (main species Linognathus vituli). Lice infestation was associated with lower growth rates in only two experiments. Significant correlations between lice infestation and liveweight gain of untreated heifers were found in three of ten experiments, but infestation accounted for only 23-30% of the variation in liveweight gain. The results support other studies conducted in Western Victoria, and the need for routine whole herd treatment against lice is questioned.

scholarly journals Widespread variation in heat tolerance and symbiont load are associated with growth tradeoffs in the coral Acropora hyacinthus in Palau

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Brendan Cornwell ◽  
Katrina Armstrong ◽  
Nia S Walker ◽  
Marilla Lippert ◽  
Victor Nestor ◽  
...  
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Habitat Restoration ◽  
Natural Resistance ◽  
Lower Growth ◽  
Coral Reef Resilience ◽  
The Face ◽  
Lower Growth Rate ◽  
Acropora Hyacinthus ◽  
The Cost

Climate change is dramatically changing ecosystem composition and productivity, leading scientists to consider the best approaches to map natural resistance and foster ecosystem resilience in the face of these changes. Here we present results from a large-scale experimental assessment of coral bleaching resistance, a critical trait for coral population persistence as oceans warm, in 221 colonies of the coral Acropora hyacinthus across 37 reefs in Palau. We find that bleaching resistant individuals inhabit most reefs but are found more often in warmer microhabitats. Our survey also found wide variation in symbiont concentration among colonies, and that colonies with lower symbiont load tended to be more bleaching resistant. By contrast, our data show that low symbiont load comes at the cost of lower growth rate, a tradeoff that may operate widely among corals across environments. Corals with high bleaching resistance have been suggested as a source for habitat restoration or selective breeding in order to increase coral reef resilience to climate change. Our maps show where these resilience corals can be found, but the existence of tradeoffs with heat resistance may suggest caution in unilateral use of this one trait in restoration.

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