scholarly journals Frequency-dependent fitness and reproductive dynamics contribute to habitat segregation in sympatric jewelflowers

2020 ◽  
Vol 287 (1927) ◽  
pp. 20200559 ◽  
Author(s):  
Kyle Christie ◽  
Sharon Y. Strauss
Keyword(s):  
Resource Competition ◽  
Niche Partitioning ◽  
Seed Viability ◽  
Low Frequency ◽  
Habitat Segregation ◽  
Differential Survival ◽  
Habitat Patches ◽  
Heterospecific Pollen ◽  
Biogeographic History ◽  
Differential Adaptation

Coexistence results from a complex suite of past and contemporary processes including biogeographic history, adaptation, ecological interactions and reproductive dynamics. Here we explore drivers of local micro-parapatry in which two closely related and reproductively isolated Streptanthus species (jewelflower, Brassicaceae) inhabit continuous or adjacent habitat patches and occur within seed dispersal range, yet rarely overlap in fine-scale distribution. We find some evidence for abiotic niche partitioning and local adaptation, however differential survival across habitats cannot fully explain the scarcity of coexistence. Competition may also reduce the fitness of individuals migrating into occupied habitats, yet its effects are insufficient to drive competitive exclusion. Experimental migrants suffered reduced seed production and seed viability at sites occupied by heterospecifics, and we infer that heterospecific pollen transfer by shared pollinators contributes to wasted gametes when the two congeners come into contact. A minority disadvantage may reduce effective colonization of patches already occupied by heterospecifics, even when habitat patches are environmentally suitable. Differential adaptation and resource competition have often been evoked as primary drivers of habitat segregation in plants, yet negative reproductive interactions—including reproductive interference and decreased fecundity among low-frequency migrants—may also contribute to non-overlapping distributions of related species along local tension zones.

scholarly journals Viability of Neotyphodium endophytic fungus and endophyte-infected and noninfected Lolium multiflorum seeds

Botany ◽  
2009 ◽  
Vol 87 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Pedro E. Gundel ◽  
M. Alejandra Martínez-Ghersa ◽  
Lucas A. Garibaldi ◽  
Claudio M. Ghersa
Keyword(s):  
High Temperature ◽  
Water Content ◽  
Lolium Multiflorum ◽  
Seed Viability ◽  
Cool Season ◽  
Differential Survival ◽  
Factors Affecting ◽  
Neotyphodium Endophyte ◽  
Endophyte Fungi ◽  
Seed Water Content

Neotyphodium endophyte fungi are vertically transmitted symbionts of cool-season grasses. The seed phase of the grass’ life cycle appears to be critical for the persistence of the fungus. Endophyte viability decreases faster than seed viability, but little is known of the effects of this endophyte on seed viability. The endophyte could affect seed viability through changes in water content. Here, we assessed the effects of the endophyte on seed viability, the differential survival of endophyte and seed, and the effects of infection on seed water content. Viability of endophyte-infected and noninfected seeds and endophyte were evaluated over a period of 729 d under 12 controlled environmental conditions. Seed viability was reduced by the infection at high temperature and high relative humidity, but not under other conditions. Moreover, endophyte viability decreased faster than seed viability only under high humidity or high temperature. Seed water content was not affected by endophyte presence. The proportion of viable infected seeds was mainly affected by the loss in endophyte viability and secondly by the differential survival of infected and noninfected seeds. Knowledge on the relative importance of these processes is critical to understand the factors affecting the efficiency of endophyte vertical transmission and the frequency of endophyte-infected plants.

scholarly journals Phosphonate production by marine microbes: exploring new sources and potential function

2020 ◽  
Author(s):  
Marianne Acker ◽  
Shane L. Hogle ◽  
Paul M. Berube ◽  
Thomas Hackl ◽  
Ramunas Stepanauskas ◽  
...  
Keyword(s):  
Biological Function ◽  
Organic Phosphorus ◽  
Niche Partitioning ◽  
Low Frequency ◽  
Phosphorus Cycling ◽  
Global Ocean ◽  
Chemical Analyses ◽  
Marine Microbes ◽  
Surface Ocean ◽  
Phosphorus Source

AbstractPhosphonates, organic compounds with a C-P bond, constitute 20-25% of phosphorus in high molecular weight dissolved organic matter and are a significant phosphorus source for marine microbes. However, little is known about phosphonate sources, biological function, or biogeochemical cycling. Here, we determine the biogeographic distribution and prevalence of phosphonate biosynthesis potential using thousands of genomes and metagenomes from the upper 250 meters of the global ocean. Potential phosphonate producers are taxonomically diverse, occur in widely distributed and abundant marine lineages (including SAR11 and Prochlorococcus) and their abundance increases with depth. Within those lineages, phosphonate biosynthesis and catabolism pathways are mutually exclusive, indicating functional niche partitioning of organic phosphorus cycling in the marine microbiome. Surprisingly, one strain of Prochlorococcus (SB) can allocate more than 40% of its cellular P-quota towards phosphonate production. Chemical analyses and genomic evidence suggest that phosphonates in this strain are incorporated into surface layer glycoproteins that may act to reduce mortality from grazing or viral infection. Although phosphonate production is a low-frequency trait in Prochlorococcus populations (~ 5% of genomes), experimentally derived production rates suggest that Prochlorococcus could produce a significant fraction of the total phosphonate in the oligotrophic surface ocean. These results underscore the global biogeochemical impact of even relatively rare functional traits in abundant groups like Prochlorococcus and SAR11.

Foraging behaviour of insectivorous migrants and a resident songbird at a stopover site

Biologia ◽  
2015 ◽  
Vol 70 (1) ◽  
Author(s):  
Christoph Randler ◽  
Stefan Pentzold ◽  
Constanze Pentzold
Keyword(s):  
Foraging Behaviour ◽  
Resource Competition ◽  
Niche Partitioning ◽  
Hierarchical Cluster ◽  
Ficedula Albicollis ◽  
Resident Species ◽  
Stopover Site ◽  
Stopover Sites ◽  
Competition Hypothesis ◽  
Direct Competition

AbstractDuring their staging at stopover sites, migrants compete with resident species over food resources. This ‘resource competition hypothesis’ has often been examined in breeding areas of songbirds, but little is known about resource competition between migrants and resident species at stopover sites. We studied foraging behaviour and microhabitat of the endemic resident species Cyprus Wheatear Oenanthe cypriaca in comparison to eleven migrating species of the same genus or of the same flycatching guild during spring migration on Cyprus, a Mediterranean stopover site. We characterized microhabitats of congeneric Oenanthe species by less cover overhead and low perches and distinguished them from migrating Ficedula hypoleuca, Ficedula albicollis and Phoenicurus phoenicurus, which preferred high cover overhead and medium perches. In a hierarchical cluster analysis, O. cypriaca clustered together with three shrike species Lanius and the flycatcher Muscicapa striata, with less cover overhead, but high perches. During foraging, hopping behaviour discriminated best among the Oenanthe species. Multidimensional scaling on foraging behaviour showed that O. cypriaca is clearly distinct from the other species. Direct competition (aggressive encounters) between the resident species and migrants was rarely observed. Our results provide support for niche partitioning and coexistence between migrants and a resident species at a stopover site.

Pathology of conifer seed and timing of germination in high-elevation subalpine fir and Engelmann spruce forests of the southern interior of British Columbia

1999 ◽  
Vol 29 (2) ◽  
pp. 187-193 ◽  
Author(s):  
Jianwen Zhong ◽  
Bart J van der Kamp
Keyword(s):  
British Columbia ◽  
Forest Floor ◽  
Mineral Soil ◽  
Seed Viability ◽  
Low Frequency ◽  
High Elevation ◽  
Subalpine Fir ◽  
Engelmann Spruce ◽  
Black Mold ◽  
Nurse Logs

Unstratified seed of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in nylon mesh bags was placed on various natural and disturbed forest floor seed beds in the Engelmann Spruce - Subalpine Fir Zone in the southern interior of British Columbia in September 1995 and recovered just before snow melt in June 1996. Fifty-two and 86% of the viable spruce and fir seed, respectively, had germinated before snowmelt. Germination under snow may be an adaptation of these high-elevation species to short cool growing seasons. Seed viability at recovery was significantly lower on undisturbed forest floor seed beds (spruce, 13%; fir, 12%) than on exposed mineral soil (spruce, 57%; fir, 42%). Viability of seed placed on nurse logs was 38 and 23% for spruce and fir, respectively. Isolation from ungerminated seed yielded a Rhizoctonia sp., an as yet unidentified black mold at high frequencies, and several other seed pathogens at low frequency. Multiple linear regression of the frequency of isolation of Rhizoctonia and black mold on seed viability was highly significant for both tree species. Seed pathogens appear to cause a major loss of seed and seedlings in these forests, and this may explain both the common occurrence of regeneration on nurse logs and the requirement of mineral soil seed beds for adequate regeneration.

scholarly journals Niche partitioning among dead wood-dependent beetles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jakub Horák
Keyword(s):  
Dead Wood ◽  
Resource Competition ◽  
Niche Partitioning ◽  
Species Abundance ◽  
Landscape Scale ◽  
Habitat Requirements ◽  
Wood Material ◽  
Neutral Drift ◽  
Species Abundances

AbstractNiche partitioning among species with virtually the same requirements is a fundamental concept in ecology. Nevertheless, some authors suggest that niches have little involvement in structuring communities. This study was done in the Pardubice Region (Czech Republic) on saproxylic beetles with morphologically similar larvae and very specific requirements, which are related to their obligatory dependence on dead wood material: Cucujus cinnaberinus, Pyrochroa coccinea, and Schizotus pectinicornis. This work was performed on 232 dead wood pieces at the landscape scale over six years. Based on the factors studied, the relationships among these species indicated that their co-occurrence based on species presence and absence was low, which indicated niche partitioning. However, based on analyses of habitat requirements and species composition using observed species abundances, there was no strong evidence for niche partitioning at either studied habitat levels, the tree and the microhabitat. The most likely reasons for the lack of strong niche partitioning were that dead wood is a rich resource and co-occurrence of saproxylic community was not driven by resource competition. This might be consistent with the theory that biodiversity could be controlled by the neutral drift of species abundance. Nevertheless, niche partitioning could be ongoing, meaning that the expanding C. cinnaberinus may have an advantage over the pyrochroids and could dominate in the long term.

Habitat Segregation by Serotinous Shrubs in Heaths: Post-fire Emergence and Seedling Survival

1997 ◽  
Vol 45 (1) ◽  
pp. 31 ◽  
Author(s):  
Paul R. Williams ◽  
Peter J. Clarke
Keyword(s):  
Soil Moisture ◽  
Field Experiments ◽  
Seedling Survival ◽  
Habitat Segregation ◽  
Differential Survival ◽  
Shrub Species ◽  
Edge Zone ◽  
Drainage Channels ◽  
Germination Trial ◽  
Adult Plants

Seeds of two serotinous shrub species generally restricted to the drier edges, and two serotinous shrub species commonly confined to the wetter drainage channels of upland sedge–heaths were assessed for germinability and used in manipulative field experiments. In post-fire field experiments the effects of habitat and manipulated soil moisture were examined to test if the distribution of adult plants was influenced by soil moisture at seed germination. The effects of habitat on seedling survival for 11 months were also assessed. One species from the edge zone, Banksia marginata Cav., and one from the channel zone, Hakea microcarpa R.Br., had germination preferences corresponding to the distribution of adult plants. The other edge species, Hakea dactyloides (Gaertner) Cav., did not show a significant preference for either zone. The second channel species, Callistemon pityoides F.Muell., did not germinate in the field or in a laboratory germination trial. Some evidence for soil-stored dormancy related to temperature and or waterlogging was found in both Hakea species. Overall the results suggest that for two species habitat segregation occurs when seeds are incorporated into the seed-bed and germination occurs. No differential survival effects across habitats were found in the first year of growth.

scholarly journals Reproductive Interference and Niche Partitioning in Aphidophagous Insects

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Suzuki Noriyuki ◽  
Naoya Osawa
Keyword(s):  
Species Coexistence ◽  
Resource Competition ◽  
Habitat Preferences ◽  
Niche Partitioning ◽  
Reproductive Interference ◽  
Species Pairs ◽  
Specialist Species ◽  
Race Formation

The range and quality of prey species differ greatly among closely related species of predators. However, the factors responsible for this diversified niche utilization are unclear. This is because the predation and resource competition do not always prevent species coexistence. In this paper, we present evidence in support of reproductive interference as a driver of niche partitioning, focusing on aphidophagous insect. Firstly, we present closely related generalist and specialist species pairs in aphidophagous lacewings to compare the reproductive interference hypothesis with two other hypotheses that have been proposed to explain niche partitioning in lacewings and sympatric speciation through host race formation and sexual selection. Secondly, we present a case study that shows how reproductive interference can drive niche partitioning in sibling ladybird species. Thirdly, we show that many ladybird genera include species inhabiting the same region but having different food and habitat preferences, raising the possibility that reproductive interference might occur in these groups. Finally, we show that intraguild predation cannot always explain the niche partitioning in aphidophagous insects including hoverflies and parasitoids. On the basis of the evidence presented, we urge that future studies investigating predator communities should take account of the role of reproductive interference.

Capacity of Vertical VOR Adaptation in Squirrel Monkey

2002 ◽  
Vol 88 (6) ◽  
pp. 3194-3207 ◽  
Author(s):  
Y. Hirata ◽  
J. M. Lockard ◽  
S. M. Highstein
Keyword(s):  
Motor Learning ◽  
Head Movement ◽  
High Frequency ◽  
Low Frequency ◽  
Squirrel Monkeys ◽  
Head Motion ◽  
Vestibuloocular Reflex ◽  
Differential Adaptation ◽  
Vor Adaptation ◽  
Eye Velocity

Squirrel monkeys were trained using newly developed visual-vestibular mismatch paradigms to test the asymmetrical simultaneous induction of vertical vestibuloocular reflex (VOR) gain changes in opposite directions (high and low) either in the upward and downward directions or in response to high- and low-frequency stimuli. The first paradigm consists of sinusoidal head movement [ Asin(ω t)] and a full rectified sinusoidal optokinetic stimulus [±‖ A sin(ω t)‖], whereas the second paradigm consists of the sum of two sinusoids with different frequencies { A sin(ω1 t) + A sin(ω2 t) for head motion and ±[ Asin(ω1 t) − Asin(ω2 t)] for the optokinetic stimulus, ω1 = 0.1π, ω2 = 5π}. The first paradigm induced a half rectified sinusoidal eye-velocity trace, i.e., suppression of the VOR during upward head motion and enhancement during downward head motion or vise versa, whereas the second paradigm induced suppression of the VOR at the low-frequency ω1 and enhancement at the high-frequency ω2 or vise versa. After 4 h of exposure to these paradigms, VOR gains of up and down or high and low frequency were modified in opposite directions. We conclude that the monkey vertical VOR system is capable of up-down directionally differential adaptation as well as high-low frequency differential adaptation. However, experiments also suggest that these gain controls are not completely independent because the magnitudes of the gain changes during simultaneous asymmetrical training were less than those achieved by symmetrical training or training in only one of the two components, indicating an influence of the gain controls on each other. These results confine the adaptive site(s) responsible for vertical VOR motor learning to those that can process up and downward or low- and high-frequency head signal separately but not completely independently.

scholarly journals Resource partitioning of phytoplankton metabolites that support bacterial heterotrophy

2020 ◽  
Author(s):  
Frank Xavier Ferrer-González ◽  
Brittany Widner ◽  
Nicole R. Holderman ◽  
John Glushka ◽  
Arthur S. Edison ◽  
...  
Keyword(s):  
Resource Partitioning ◽  
Organic Molecules ◽  
Resource Competition ◽  
Heterotrophic Bacteria ◽  
Niche Partitioning ◽  
Marine Diatom ◽  
Organic Sulfur Compounds ◽  
Surface Ocean ◽  
Uptake Pattern ◽  
Bacterial Uptake

Abstract The communities of bacteria that assemble around marine microphytoplankton are predictably dominated by Rhodobacterales, Flavobacteriales, and families within the Gammaproteobacteria. Yet whether this consistent ecological pattern reflects the result of resource-based niche partitioning or resource competition requires better knowledge of the metabolites linking microbial autotrophs and heterotrophs in the surface ocean. We characterized molecules targeted for uptake by three heterotrophic bacteria individually co-cultured with a marine diatom using two strategies that vetted the exometabolite pool for biological relevance by means of bacterial activity assays: expression of diagnostic genes and net drawdown of exometabolites, the latter detected with mass spectrometry and nuclear magnetic resonance using novel sample preparation approaches. Of the more than 36 organic molecules with evidence of bacterial uptake, 53% contained nitrogen (including nucleosides and amino acids), 11% were organic sulfur compounds (including dihydroxypropanesulfonate and dimethysulfoniopropionate), and 28% were components of polysaccharides (including chrysolaminarin, chitin, and alginate). Overlap in phytoplankton-derived metabolite use by bacteria in the absence of competition was low, and only guanosine, proline, and N-acetyl-d-glucosamine were predicted to be used by all three. Exometabolite uptake pattern points to a key role for ecological resource partitioning in the assembly marine bacterial communities transforming recent photosynthate.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

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