Interactive effects of body size and environmental gradient on the trophic ecology of sea stars in an Antarctic fjord

2021 ◽  
Author(s):  
B Le Bourg ◽  
P Kuklinski ◽  
P Balazy ◽  
G Lepoint ◽  
LN Michel
Keyword(s):  
Body Size ◽  
Environmental Gradient ◽  
Trophic Ecology ◽  
Interactive Effects ◽  
Sea Stars

Body size and trophic divergence of two large sympatric elapid snakes (Notechis scutatus and Austrelaps superbus) (Serpentes:Elapidae) in Tasmania

2012 ◽  
Vol 60 (3) ◽  
pp. 159 ◽  
Author(s):  
S. Fearn ◽  
J. Dowde ◽  
D. F. Trembath
Keyword(s):  
Body Size ◽  
High Frequency ◽  
Field Data ◽  
Trophic Ecology ◽  
Competitive Exclusion ◽  
Head Size ◽  
Large Prey ◽  
Potential Prey ◽  
Island State ◽  
Species Being

Tiger snakes (Notechis scutatus) and lowland copperheads (Austrelaps superbus) are both large viviparous elapid snakes confined to the cooler, mesic regions of southern Australia. In spite of both species being common and widespread in the island state of Tasmania, no quantified studies on the trophic ecology of these two snakes from the main island has been published. During a two-year period we collected field data from 127 adult A. superbus and 74 adult N. scutatus from throughout eastern Tasmania. For both species, males were larger than females with respect to all measured parameters, including mass and head size. Reproduction in females was strongly seasonal and clutch size was not related to maternal body size. N. scutatus has a larger head than A. superbus and consequently ingests both small and large prey. N. scutatus in our study displayed the most catholic diet of any Australian elapid studied to date and consumed mammals (possum, bandicoot, antechinus, rats, mice), birds (fairy wrens), fish (eel, trout) and frogs. A. superbus shows a more specialist diet of large volumes of predominately ectothermic prey (frogs, lizards, snakes) even at maximal sizes and was more likely to contain ingested prey than specimens of N. scutatus. Distinctive rodent bite scars were common on N. scutatus but rare on A. superbus. The high frequency of rodent bite scars on N. scutatus further supports our findings of a primarily endothermic diet for mature specimens. We suggest that significant differences in head size, and hence diet, as well as a taxonomically diverse suite of potential prey in Tasmania allow both these large snakes to coexist in sympatry and avoid interspecific competitive exclusion.

scholarly journals A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry

2020 ◽  
Vol 117 (30) ◽  
pp. 17932-17936 ◽  
Author(s):  
Christian F. Kammerer ◽  
Sterling J. Nesbitt ◽  
John J. Flynn ◽  
Lovasoa Ranivoharimanana ◽  
André R. Wyss
Keyword(s):  
Body Size ◽  
Fossil Record ◽  
Evolutionary History ◽  
Trophic Ecology ◽  
Upper Triassic ◽  
Important Group ◽  
Size Evolution ◽  
Stem Lineage ◽  
Body Size Evolution

Early members of the dinosaur–pterosaur clade Ornithodira are very rare in the fossil record, obscuring our understanding of the origins of this important group. Here, we describe an early ornithodiran (Kongonaphon kelygen. et sp. nov.) from the Mid-to-Upper Triassic of Madagascar that represents one of the smallest nonavian ornithodirans. Although dinosaurs and gigantism are practically synonymous, an analysis of body size evolution in dinosaurs and other archosaurs in the context of this taxon and related forms demonstrates that the earliest-diverging members of the group may have been smaller than previously thought, and that a profound miniaturization event occurred near the base of the avian stem lineage. In phylogenetic analysis,Kongonaphonis recovered as a member of the Triassic ornithodiran clade Lagerpetidae, expanding the range of this group into Africa and providing data on the craniodental morphology of lagerpetids. The conical teeth ofKongonaphonexhibit pitted microwear consistent with a diet of hard-shelled insects, indicating a shift in trophic ecology to insectivory associated with diminutive body size. Small ancestral body size suggests that the extreme rarity of early ornithodirans in the fossil record owes more to taphonomic artifact than true reflection of the group’s evolutionary history.

scholarly journals The Combined Effects of Warming and Body Size on the Stability of Predator-Prey Interactions

2022 ◽  
Vol 9 ◽  
Author(s):  
Pavel Kratina ◽  
Benjamin Rosenbaum ◽  
Bruno Gallo ◽  
Elena L. Horas ◽  
Eoin J. O’Gorman
Keyword(s):  
Body Size ◽  
Trophic Interactions ◽  
Handling Time ◽  
Size Ratio ◽  
Interactive Effects ◽  
Functional Responses ◽  
Ample Evidence ◽  
Predator Prey ◽  
The Stability ◽  
Prey Populations

Environmental temperature and body size are two prominent drivers of predation. Despite the ample evidence of their independent effects, the combined impact of temperature and predator-prey body size ratio on the strength and stability of trophic interactions is not fully understood. We experimentally tested how water temperature alters the functional response and population stability of dragonfly nymphs (Cordulegaster boltonii) feeding on freshwater amphipods (Gammarus pulex) across a gradient of their body size ratios. Attack coefficients were highest for small predators feeding on small prey at low temperatures, but shifted toward the largest predators feeding on larger prey in warmer environments. Handling time appeared to decrease with increasing predator and prey body size in the cold environment, but increase at higher temperatures. These findings indicate interactive effects of temperature and body size on functional responses. There was also a negative effect of warming on the stability of predator and prey populations, but this was counteracted by a larger predator-prey body size ratio at higher temperatures. Here, a greater Hill exponent reduced feeding at low prey densities when predators were much larger than their prey, enhancing the persistence of both predator and prey populations in the warmer environment. These experimental findings provide new mechanistic insights into the destabilizing effect of warming on trophic interactions and the key role of predator-prey body size ratios in mitigating these effects.

Interactive effects of ocean acidification and warming on subtidal mussels and sea stars from Atlantic Canada

2014 ◽  
Vol 11 (4) ◽  
pp. 337-348 ◽  
Author(s):  
Elise A. Keppel ◽  
Ricardo A. Scrosati ◽  
Simon C. Courtenay
Keyword(s):  
Ocean Acidification ◽  
Interactive Effects ◽  
Atlantic Canada ◽  
Sea Stars

scholarly journals Isotopic niche reflects stress-induced variability in physiological status

2018 ◽  
Vol 5 (2) ◽  
pp. 171398 ◽  
Author(s):  
Agnes M. L. Karlson ◽  
Martin Reutgard ◽  
Andrius Garbaras ◽  
Elena Gorokhova
Keyword(s):  
Body Size ◽  
Stable Isotope ◽  
Trophic Ecology ◽  
Physiological Stress ◽  
Isotope Composition ◽  
Stress Factors ◽  
Physiological Status ◽  
Isotopic Niche ◽  
Control Groups ◽  
Oxygen Conditions

The isotopic niche has become an established concept in trophic ecology. However, the assumptions behind this approach have rarely been evaluated. Evidence is accumulating that physiological stress can affect both magnitude and inter-individual variability of the isotopic signature in consumers via alterations in metabolic pathways. We hypothesized that stress factors (inadequate nutrition, parasite infestations, and exposure to toxic substances or varying oxygen conditions) might lead to suboptimal physiological performance and altered stable isotope signatures. The latter can be misinterpreted as alterations in isotopic niche. This hypothesis was tested by inducing physiological stress in the deposit-feeding amphipod Monoporeia affinis exposed to either different feeding regimes or contaminated sediments. In the amphipods, we measured body condition indices or reproductive output to assess growth status and δ 13 C and δ 15 N values to derive isotope niche metrics. As hypothesized, greater isotopic niche estimates were derived for the stressed animals compared to the control groups. Moreover, the δ 15 N values were influenced by body size, reproductive status and parasite infestations, while δ 13 C values were influenced by body size, oxygen conditions and survival. Using regression analysis with isotope composition and growth variables as predictors, we were able to discriminate between the amphipods exposed to nutritionally or chemically stressful conditions and those in the control groups. Thus, interpretation of isotopic niche can be confounded by natural or anthropogenic stressors that may induce an apparent change in isotopic niche. These findings stress the importance of including measures of growth and health status when evaluating stable isotope data in food web studies.

scholarly journals Interactive effects of shifting body size and feeding adaptation drive interaction strengths of protist predators under warming

2017 ◽  
Author(s):  
K. E. Fussmann ◽  
B. Rosenbaum ◽  
U. Brose ◽  
B.C. Rall
Keyword(s):  
Body Size ◽  
Functional Response ◽  
Interactive Effects ◽  
Experimental Temperature ◽  
Foraging Efficiency ◽  
Positive Energy ◽  
Feeding Rates ◽  
Mixed Response ◽  
Different Temperatures ◽  
The Impact

AbstractGlobal change is heating up ecosystems fuelling biodiversity loss and species extinctions. High-trophic-level predators are especially prone to extinction due to an energetic mismatch between increasing feeding rates and metabolism with warming. Different adaptation mechanisms such as decreasing body size to reduce energy requirements (morphological response) as well as direct effects of adaptation to feeding parameters (physiological response) have been proposed to overcome this problem. Here, we use protist-bacteria microcosm experiments to show how those adaptations may have the potential to buffer the impact of warming on predator-prey interactions. After adapting the ciliate predator Tetrahymena pyriformis to three different temperatures (15°C, 20°C and 25°C) for approximately 20 generations we conducted functional response experiments on bacterial prey along an experimental temperature gradient (15°C, 20°C and 25°C). We found an increase of maximum feeding rates and half-saturation densities with rising experimental temperatures. Adaptation temperature had on average slightly negative effects on maximum feeding rates, but maximum feeding rates increased more strongly with rising experimental temperature in warm adapted predators than in cold adapted predators. There was no effect of adaptation temperature on half-saturation densities characterising foraging efficiency. Besides the mixed response in functional response parameters, predators also adapted by decreasing body size. As smaller predators need less energy to fulfil their energetic demands, maximum feeding rates relative to the energetic demands increased slightly with increased adaptation temperature. Accordingly, predators adapted to 25°C showed the highest feeding rates at 25°C experimental temperature, while predators adapted to 15°C showed the highest maximum feeding rate at 15°C. Therefore, adaptation to different temperatures potentially avoids an energetic mismatch with warming. Especially a shift in body size with warming additionally to an adaptation of physiological parameters potentially helps to maintain a positive energy balance and prevent predator extinction with rising temperatures.

Interactive effects of body-size structure and adaptive foraging on food-web stability

2012 ◽  
Vol 15 (3) ◽  
pp. 243-250 ◽  
Author(s):  
Lotta Heckmann ◽  
Barbara Drossel ◽  
Ulrich Brose ◽  
Christian Guill
Keyword(s):  
Body Size ◽  
Food Web ◽  
Size Structure ◽  
Interactive Effects ◽  
Adaptive Foraging
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