scholarly journals Variable seed bed microsite conditions and light influence germination in Australian winter annuals

Oecologia ◽  
2022 ◽  
Author(s):  
Isaac R. Towers ◽  
David J. Merritt ◽  
Todd E. Erickson ◽  
Margaret M. Mayfield ◽  
John M. Dwyer
Keyword(s):  
Environmental Gradients ◽  
Light Availability ◽  
Canopy Cover ◽  
Niche Differentiation ◽  
Annual Plant ◽  
Light Requirement ◽  
Germination Response ◽  
Spatial Niche ◽  
Germination Behaviour ◽  
Species Specific

AbstractEnvironmentally cued germination may play an important role in promoting coexistence in Mediterranean annual plant systems if it causes niche differentiation across heterogeneous microsite conditions. In this study, we tested how microsite conditions experienced by seeds in the field and light conditions in the laboratory influenced germination in 12 common annual plant species occurring in the understorey of the York gum-jam woodlands in southwest Western Australia. Specifically, we hypothesized that if germination promotes spatial niche differentiation, then we should observe species-specific germination responses to light. In addition, we hypothesized that species’ laboratory germination response may depend on the microsite conditions experienced by seeds while buried. We tested the laboratory germination response of seeds under diurnally fluctuating light and complete darkness, which were collected from microsites spanning local-scale environmental gradients known to influence community structure in this system. We found that seeds of 6 out of the 12 focal species exhibited significant positive germination responses to light, but that the magnitude of these responses varied greatly with the relative light requirement for germination ranging from 0.51 to 0.86 for these species. In addition, germination increased significantly across a gradient of canopy cover for two species, but we found little evidence to suggest that species’ relative light requirement for germination varied depending on seed bank microsite conditions. Our results suggest that variability in light availability may promote coexistence in this system and that the microsite conditions seeds experience in the intra-growing season period can further nuance species germination behaviour.

scholarly journals Variable Seed Bed Microsite Conditions and Light Influence Germination in Australian Winter Annuals

2021 ◽  
Author(s):  
Isaac Ray Towers ◽  
David J Merritt ◽  
Todd E Erikson ◽  
Margaret M Mayfield ◽  
John M Dwyer
Keyword(s):  
Environmental Gradients ◽  
Light Availability ◽  
Canopy Cover ◽  
Niche Differentiation ◽  
Annual Plant ◽  
Germination Response ◽  
Spatial Niche ◽  
Germination Behaviour ◽  
Species Specific ◽  
Annual Plant Species

Abstract Environmentally-cued germination may play an important role in promoting coexistence in Mediterranean annual plant systems if it causes niche differentiation across heterogenous microsite conditions. In this study, we tested how microsite conditions experienced by seeds in the field and light conditions in the laboratory influenced germination in twelve common annual plant species occurring in the understorey of the York gum-jam woodlands in southwest Western Australia. Specifically, we hypothesized that if germination promotes spatial niche differentiation then we should observe species-specific germination responses to light. In addition, we hypothesized that species’ laboratory germination response may depend on the microsite conditions experienced by seeds while buried. We tested the laboratory germination response of seeds of species under diurnally fluctuating light and complete darkness which were retrieved from microsites spanning local-scale environmental gradients known to influence community structure in this system. We found that seeds of six out of the twelve focal species exhibited significant positive germination responses to light but that the magnitude of these responses varied greatly. In addition, maximum germinability increased significantly across a gradient of canopy cover for two species, but we found little evidence to suggest that species’ relative light requirement for germination varied depending on microsite conditions. Our results suggest that variability in light availability may promote coexistence in this system and that the microsite conditions seeds experience in the intra-growing season period can further nuance species germination behaviour.

Temperature as a Proximate Factor in Orientation Behavior

1977 ◽  
Vol 34 (5) ◽  
pp. 734-739 ◽  
Author(s):  
William W. Reynolds
Keyword(s):  
Temperature Response ◽  
Biotic Interactions ◽  
Niche Differentiation ◽  
Behavioral Thermoregulation ◽  
Size Segregation ◽  
Ecological Value ◽  
Thermal Requirements ◽  
Prey Location ◽  
Proximate Factor ◽  
Species Specific

Temperature serves as a proximate factor (cue, guidepost, sign stimulus, or directive factor) affecting locomotor responses of fishes. Although temperature can also serve as an ultimate ecological factor, as in behavioral thermoregulation, nonthermal factors may in some cases provide the ultimate adaptive or ecological value of a temperature response; some examples are habitat selection, intraspecific size segregation, interspecific niche differentiation, isolating mechanisms, predator avoidance, prey location, escape reactions, and migrations (thermoperiodic, diel, seasonal, spawning). Conversely, nonthermal variables such as light intensity or water depth may act as accessory proximate factors in thermoregulation. In spawning migrations, thermal requirements of eggs and larvae may take precedence over the (often different) preferenda or optima of adults. Although thermal responses of fishes are largely innate and species specific, ontogenetic and other changes can occur. Since temperature can serve as an unconditioned reinforcer in operant conditioning, thermal responses are not limited to simple kineses or taxes. Nonthermal factors such as photoperiod, circadian rhythms, currents, social and biotic interactions, stresses, infections, or chemicals can affect thermal responses, and may account for some lack of conformity between laboratory preferenda and field distributions and behaviors. Key words: thermoregulation, orientation, preferendum, selection, preference, avoidance, behavior, temperature, fish, responses

scholarly journals Nanopore amplicon sequencing reveals molecular convergence and local adaptation of opsin genes

2020 ◽  
Author(s):  
Katherine M. Eaton ◽  
Moisés A. Bernal ◽  
Nathan J.C. Backenstose ◽  
Trevor J. Krabbenhoft
Keyword(s):  
Local Adaptation ◽  
Environmental Gradients ◽  
Parallel Evolution ◽  
Amplicon Sequencing ◽  
Species Flock ◽  
Closely Related Species ◽  
Oxford Nanopore ◽  
Opsin Genes ◽  
Potential Case ◽  
Species Specific

AbstractLocal adaptation can drive diversification of closely related species across environmental gradients and promote convergence of distantly related taxa that experience similar conditions. We examined a potential case of adaptation to novel visual environments in a species flock (Great Lakes salmonids, genus Coregonus) using a new amplicon genotyping protocol on the Oxford Nanopore Flongle. Five visual opsin genes were amplified for individuals of C. artedi, C. hoyi, C. kiyi, and C. zenithicus. Comparisons revealed species-specific differences in the coding sequence of rhodopsin (Tyr261Phe substitution), suggesting local adaptation by C. kiyi to the blue-shifted depths of Lake Superior. Parallel evolution and “toggling” at this amino acid residue has occurred several times across the fish tree of life, resulting in identical changes to the visual systems of distantly related taxa across replicated environmental gradients. Our results suggest that ecological differences and local adaptation to distinct visual environments are strong drivers of both evolutionary parallelism and diversification.

Salt Marsh Light Use Efficiency is Driven by Environmental Gradients and Species‐Specific Physiology and Morphology

2021 ◽  
Author(s):  
Peter A. Hawman ◽  
Deepak R. Mishra ◽  
Jessica L. O’Connell ◽  
David L. Cotten ◽  
Caroline R. Narron ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Environmental Gradients ◽  
Light Use Efficiency ◽  
Use Efficiency ◽  
Species Specific

scholarly journals Germination response of invasive plants to soil burial depth and litter accumulation is species‐specific

2020 ◽  
Vol 31 (6) ◽  
pp. 1079-1087 ◽  
Author(s):  
Judit Sonkoly ◽  
Orsolya Valkó ◽  
Nóra Balogh ◽  
Laura Godó ◽  
András Kelemen ◽  
...  
Keyword(s):  
Invasive Plants ◽  
Burial Depth ◽  
Soil Burial ◽  
Litter Accumulation ◽  
Germination Response ◽  
Species Specific

scholarly journals Niche Models Differentiate Potential Impacts of Two Aquatic Invasive Plant Species on Native Macrophytes

Diversity ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 162
Author(s):  
Michael R. Verhoeven ◽  
Wesley J. Glisson ◽  
Daniel J. Larkin
Keyword(s):  
Native Species ◽  
Invasive Plant ◽  
Environmental Gradients ◽  
Myriophyllum Spicatum ◽  
Light Availability ◽  
Niche Overlap ◽  
Growth Cycle ◽  
Potamogeton Crispus ◽  
Starting Point ◽  
Niche Models

Potamogeton crispus (curlyleaf pondweed) and Myriophyllum spicatum (Eurasian watermilfoil) are widely thought to competitively displace native macrophytes in North America. However, their perceived competitive superiority has not been comprehensively evaluated. Coexistence theory suggests that invader displacement of native species through competitive exclusion is most likely where high niche overlap results in competition for limiting resources. Thus, evaluation of niche similarity can serve as a starting point for predicting the likelihood of invaders having direct competitive impacts on resident species. Across two environmental gradients structuring macrophyte communities—water depth and light availability—both P. crispus and M. spicatum are thought to occupy broad niches. For a third dimension, phenology, the annual growth cycle of M. spicatum is typical of other species, whereas the winter-ephemeral phenology of P. crispus may impart greater niche differentiation and thus lower risk of native species being competitively excluded. Using an unprecedented dataset comprising 3404 plant surveys from Minnesota collected using a common protocol, we modeled niches of 34 species using a probabilistic niche framework. Across each niche dimension, P. crispus had lower overlap with native species than did M. spicatum; this was driven in particular by its distinct phenology. These results suggest that patterns of dominance seen in P. crispus and M. spicatum have likely arisen through different mechanisms, and that direct competition with native species is less likely for P. crispus than M. spicatum. This research highlights the utility of fine-scale, abundance-based niche models for predicting invader impacts.

scholarly journals Differentiation in Leaf Physiological Traits Related to Shade and Drought Tolerance Underlies Contrasting Adaptations of Two Cyclobalanopsis (Fagaceae) Species at the Seedling Stage

Forests ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 844 ◽  
Author(s):  
Ai-Ying Wang ◽  
Guang-You Hao ◽  
Jing-Jing Guo ◽  
Zhi-Hui Liu ◽  
Jiao-Lin Zhang ◽  
...  
Keyword(s):  
Drought Tolerance ◽  
Environmental Gradients ◽  
High Irradiance ◽  
Tree Seedlings ◽  
Physiological Mechanisms ◽  
Full Sunlight ◽  
Leaf Hydraulics ◽  
Naturally Occurring ◽  
Species Specific ◽  
Distinct Distribution

Adaptation and acclimation of tree seedlings to different combinations of light and water conditions can determine the species-specific patterns of distribution along environmental gradients and the underlying physiological mechanisms are fundamental to the understanding of such patterns. Seedlings of two Cyclobalanopsis species naturally occurring in southwest China, with distinct distribution and regeneration characteristics, were grown under 100%, 50% and 4% sunlight conditions and traits related to shade and drought tolerance were studied. Particularly, we investigated whether leaf hydraulics, photosynthetic traits and their functional coordination play an important role in determining seedling environmental adaptation and acclimation of the two species. Seedlings of C. helferiana showed characteristics adapted to high irradiance while C. rex had traits adapted to partially shaded environments. Cyclobalanopsis helferiana had significantly higher maximum net photosynthetic rate (Amax), light compensation point and light saturation point than C. rex and the contrasts were particularly large when they were grown under full sunlight. Cyclobalanopsis helferiana showed the highest Amax when grown under 100% sunlight, while C. rex exhibited the highest Amax at 50% sunlight. Similarly, under full sunlight conditions C. helferiana showed significantly higher leaf hydraulic conductance (Kleaf) than C. rex, i.e., 13.37 vs. 7.09 mmol m−2 s−1 MPa−1 (p < 0.01). The correlation between Kleaf and Amax followed a unified positive correlation across different light treatments of both species. Moreover, leaves of C. helferiana showed greater resistance to drought-induced hydraulic dysfunction and to desiccation than C. rex. The contrasts in functional traits between the two Cyclobalanopsis species are consistent with the hypothesis that there is a trade-off between shade tolerance and drought tolerance. Findings of the present study contribute to a deeper understanding of mechanisms of divergence between closely related (congeneric) species with respect to key ecophysiology associated with natural regeneration.

scholarly journals Plant survival in relation to seed size along environmental gradients: a long-term study from semi-arid and Mediterranean annual plant communities

2010 ◽  
Vol 98 (3) ◽  
pp. 697-704 ◽  
Author(s):  
Johannes Metz ◽  
Pierre Liancourt ◽  
Jaime Kigel ◽  
Danny Harel ◽  
Marcelo Sternberg ◽  
...  
Keyword(s):  
Seed Size ◽  
Plant Communities ◽  
Environmental Gradients ◽  
Annual Plant ◽  
Term Study ◽  
Plant Survival ◽  
Long Term Study ◽  
Semi Arid

scholarly journals A framework to bridge scales in distribution modeling of soil microbiota

2020 ◽  
Vol 96 (5) ◽  
Author(s):  
Jonas J Lembrechts ◽  
L Broeders ◽  
J De Gruyter ◽  
D Radujković ◽  
I Ramirez-Rojas ◽  
...  
Keyword(s):  
Environmental Gradients ◽  
Spatial Scales ◽  
Biotic Interactions ◽  
Environmental Niche ◽  
Distribution Models ◽  
Soil Microbiota ◽  
Soil Microbial ◽  
Critical Issues ◽  
Multiple Species ◽  
Species Specific

ABSTRACT Creating accurate habitat suitability and distribution models (HSDMs) for soil microbiota is far more challenging than for aboveground organism groups. In this perspective paper, we propose a conceptual framework that addresses several of the critical issues holding back further applications. Most importantly, we tackle the mismatch between the broadscale, long-term averages of environmental variables traditionally used, and the environment as experienced by soil microbiota themselves. We suggest using nested sampling designs across environmental gradients and objectively integrating spatially hierarchic heterogeneity as covariates in HSDMs. Second, to incorporate the crucial role of taxa co-occurrence as driver of soil microbial distributions, we promote the use of joint species distribution models, a class of models that jointly analyze multiple species’ distributions, quantifying both species-specific environmental responses (i.e. the environmental niche) and covariance among species (i.e. biotic interactions). Our approach allows incorporating the environmental niche and its associated distribution across multiple spatial scales. The proposed framework facilitates the inclusion of the true relationships between soil organisms and their abiotic and biotic environments in distribution models, which is crucial to improve predictions of soil microbial redistributions as a result of global change.

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