scholarly journals The impact of diet, habitat use, and behaviour on head shape evolution in homalopsid snakes

2016 ◽  
Vol 118 (3) ◽  
pp. 634-647 ◽  
Author(s):  
Anne-Claire Fabre ◽  
David Bickford ◽  
Marion Segall ◽  
Anthony Herrel
Keyword(s):  
Habitat Use ◽  
Shape Evolution ◽  
Head Shape ◽  
The Impact

Warning signals promote morphological diversification in fossorial uropeltid snakes (Squamata: Uropeltidae)

2020 ◽  
Author(s):  
Vivek Philip Cyriac ◽  
Ullasa Kodandaramaiah
Keyword(s):  
Body Size ◽  
Free Space ◽  
Morphological Evolution ◽  
Environmental Constraints ◽  
Shape Evolution ◽  
Head Shape ◽  
Warning Signals ◽  
Morphological Diversification ◽  
Niche Expansion ◽  
Antipredator Defences

Abstract Many species possess warning colourations that signal unprofitability to predators. Warning colourations are also thought to provide prey with a ‘predator-free space’ and promote niche expansion. However, how such strategies release a species from environmental constraints and facilitate niche expansion is not clearly understood. Fossoriality in reptiles imposes several morphological limits on head and body size to facilitate burrowing underground, but many fossorial snakes live close to the surface and occasionally move above ground, exposing them to predators. In such cases, evolving antipredator defences that reduce predation on the surface could potentially relax the morphological constraints associated with fossoriality and promote morphological diversification. Fossorial uropeltid snakes possess varying degrees of conspicuous warning colourations that reduce avian predation when active above ground. We predicted that species with more conspicuous colourations will exhibit more robust body forms and show faster rates of morphological evolution because constraints imposed by fossoriality are relaxed. Using a comparative phylogenetic approach on the genus Uropeltis, we show that more conspicuous species tend to have more robust morphologies and have faster rates of head-shape evolution. Overall, we find that the evolution of warning colourations in Uropeltis can facilitate niche expansion by influencing rates of morphological diversification.

scholarly journals The impact of fire on habitat use by the short-snouted elephant shrew (Elephantulus brachyrhynchus) in North West Province, South Africa

2008 ◽  
Vol 43 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Richard W. Yarnell ◽  
Daniel J. Metcalfe ◽  
Nigel Dunstone ◽  
Niall Burnside ◽  
Dawn M. Scott
Keyword(s):  
South Africa ◽  
Habitat Use ◽  
North West ◽  
North West Province ◽  
Elephant Shrew ◽  
The Impact

Holding ground in the face of invasion: native fence lizards (Sceloporus undulatus) do not alter their habitat use in response to introduced fire ants (Solenopsis invicta)

2009 ◽  
Vol 87 (7) ◽  
pp. 626-634 ◽  
Author(s):  
T. Langkilde
Keyword(s):  
Habitat Use ◽  
Solenopsis Invicta ◽  
Native Species ◽  
Fire Ants ◽  
Sceloporus Undulatus ◽  
The Face ◽  
Solenopsis Invicta Buren ◽  
The Usa ◽  
Adaptive Shifts ◽  
The Impact

The introduction of non-native species is becoming increasingly common. Understanding the impact of invaders on native populations is critical for effective management. Red imported fire ants ( Solenopsis invicta Buren, 1972) were introduced to the USA in the 1930s. They will attack, and can kill, native fence lizards ( Sceloporus undulatus (Bosc and Daudin in Sonnini and Latreille, 1801)), which co-occur with these ants across much of their invasive range. I determined whether fence lizards minimize encounters with S. invicta by altering their habitat use following invasion or avoiding cues of the presence of these fire ants. I recorded the habitat use of fence lizards and S. invicta mounds across four sites with different histories of invasion, and quantified lizard avoidance of S. invicta scent. I found that lizards do not alter their habitat use following S. invicta invasion, nor do they spatially avoid their mounds. Fence lizards do avoid S. invicta scent, but this was only evident in naïve or recently invaded populations. The lack of avoidance of S. invicta by fence lizards could be explained by the high prevalence of these fire ants, making them difficult to avoid, and adaptive shifts in the escape behaviour and morphology of these lizards following invasion that permit them to survive fire ant attack.

scholarly journals Does aquatic foraging impact head shape evolution in snakes?

2016 ◽  
Vol 283 (1837) ◽  
pp. 20161645 ◽  
Author(s):  
Marion Segall ◽  
Raphaël Cornette ◽  
Anne-Claire Fabre ◽  
Ramiro Godoy-Diana ◽  
Anthony Herrel
Keyword(s):  
Aquatic Environment ◽  
Anterior Part ◽  
Three Dimensional ◽  
Shape Evolution ◽  
Head Shape ◽  
Evolutionary Trajectory ◽  
Biomechanical Models ◽  
Historical Factors ◽  
Evolutionary Trajectories ◽  
Do So

Evolutionary trajectories are often biased by developmental and historical factors. However, environmental factors can also impose constraints on the evolutionary trajectories of organisms leading to convergence of morphology in similar ecological contexts. The physical properties of water impose strong constraints on aquatic feeding animals by generating pressure waves that can alert prey and potentially push them away from the mouth. These hydrodynamic constraints have resulted in the independent evolution of suction feeding in most groups of secondarily aquatic tetrapods. Despite the fact that snakes cannot use suction, they have invaded the aquatic milieu many times independently. Here, we test whether the aquatic environment has constrained head shape evolution in snakes and whether shape converges on that predicted by biomechanical models. To do so, we used three-dimensional geometric morphometrics and comparative, phylogenetically informed analyses on a large sample of aquatic snake species. Our results show that aquatic snakes partially conform to our predictions and have a narrower anterior part of the head and dorsally positioned eyes and nostrils. This morphology is observed, irrespective of the phylogenetic relationships among species, suggesting that the aquatic environment does indeed drive the evolution of head shape in snakes, thus biasing the evolutionary trajectory of this group of animals.

scholarly journals Oceanographic, ecological, and socio-economic impacts of an unusual summer storm in the Mackenzie Estuary

2020 ◽  
Vol 6 (2) ◽  
pp. 62-76 ◽  
Author(s):  
Kevin C. Scharffenberg ◽  
Dustin Whalen ◽  
Shannon A. MacPhee ◽  
Marianne Marcoux ◽  
John Iacozza ◽  
...  
Keyword(s):  
Habitat Use ◽  
Marine Mammals ◽  
Storm Surges ◽  
Open Water ◽  
Water Levels ◽  
Environmental Drivers ◽  
Mackenzie Delta ◽  
Arctic Ecosystems ◽  
Significant Drop ◽  
The Impact

With increased warming and open water due to climate change, the frequency and intensity of storm surges is expected to increase. Although studies have shown that strong storms can negatively impact Arctic ecosystems, the impact of storms on Arctic marine mammals is relatively unknown. In July 2016, an unusually large storm occurred in the Mackenzie Delta while instrumented seabed moorings equipped with hydrophones and oceanographic sensors were in place to study environmental drivers of beluga habitat use during their summer aggregation. The storm lasted up to 88 h, with maximum wind speeds reaching 60 km/h; historical wind data from Tuktoyaktuk revealed a storm of similar duration has not occurred in July in at least the past 28 years. This provided a unique opportunity to study the impacts of large storms on oceanographic conditions, beluga habitat use, and the traditional subsistence hunt that occurs annually in the delta. The storm resulted in increased water levels and localized flooding as well as a significant drop in water temperature (∼10 °C) and caused belugas to leave the area for 5 days. Although belugas returned after the storm ended, the subsistence hunt was halted resulting in the lowest beluga harvest between 1978 and 2017.

An experimental and simulation study of impact resistance in sandwich structures casing

2018 ◽  
Vol 233 (10) ◽  
pp. 3635-3648
Author(s):  
Shuyi Yang ◽  
Cang Chen ◽  
Guiwen Liu
Keyword(s):  
Double Layer ◽  
Simulation Study ◽  
Sandwich Structure ◽  
Sandwich Structures ◽  
Layer Structure ◽  
Impact Resistance ◽  
Head Shape ◽  
Double Layer Structure ◽  
Single Structure ◽  
The Impact

As the main force component on the aeroengine, casing is one of bases of the whole aeroengine, but it is extremely difficult to analyze the capacity of aeroengine casing impact resistance. An experimental and simulation study of impact resistance has been conducted on sandwich structures casing with aluminum honeycombs to identify and improve aeroengine casing impact resistance. Firstly, a Rent–Ipson model has been applied to analyze the energy of broken blades with impacting casing. Based on a sensing test technology, the experimental research on the impact of aluminum honeycomb sandwich panel with a conical head shape bullet and a hemispherical head shape bullet have been carried out. The experimental results provide a basis for subsequent simulation research. Then the impact resistance have been compared and analyzed from single structure casing, double layer structure casing, and sandwich structure casing, according to their loss of blade kinetic energy, casing deformation, and the variation of casing internal energy. Finally, the variation of energy has been discussed during blade impacting casing with various oblique angles. Our results show that the impact resistance of sandwich structure casing is better than single structure casing and double layer structure casing. Most importantly, the impact resistance of casing has been improved with the increase of blade impact oblique angle.

scholarly journals Factors influencing outcomes of the treatment of positional plagiocephaly in infants: a 7-year experience

2017 ◽  
Vol 19 (3) ◽  
pp. 273-281 ◽  
Author(s):  
Sandi Lam ◽  
I-Wen Pan ◽  
Ben A. Strickland ◽  
Caroline Hadley ◽  
Bradley Daniels ◽  
...  
Keyword(s):  
Univariate Analysis ◽  
Retrospective Chart Review ◽  
Treatment Recommendation ◽  
Sudden Infant ◽  
Multiple Gestation ◽  
Head Shape ◽  
Positional Plagiocephaly ◽  
Recommended Treatment ◽  
The Impact ◽  
Orthotic Treatment

OBJECTIVE Following institution of the Back to Sleep Campaign, the incidence of sudden infant death syndrome decreased while the prevalence of positional skull deformation increased dramatically. The management of positional deformity is controversial, and treatment recommendations and outcomes reporting are variable. The authors reviewed their institutional experience (2008–2014) with the treatment of positional plagiocephaly to explore factors associated with measured improvement. METHODS A retrospective chart review was conducted with risk factors and treatment for positional head shape deformity recorded. Univariate and multivariate analyses were used to assess the impact of these variables on the change in measured oblique diagonal difference (ODD) on head shape surface scanning pre- and posttreatment. RESULTS A total of 991 infants aged less than 1 year were evaluated for cranial positional deformity in a dedicated clinical program. The most common deformity was occipital plagiocephaly (69.5%), followed by occipital brachycephaly (18.4%) or a combination of both deformities (12.1%). Recommended treatment included repositioning (RP), physical therapy (PT) if indicated, or orthotic treatment with a customized cranial orthosis (CO) according to an age- and risk factor–dependent algorithm that the authors developed for this clinic. Of the 991 eligible patients, 884 returned for at least 1 follow-up appointment. A total of 552 patients were followed to completion of their treatment and had a full set of records for analysis: these patients had pre- and posttreatment 2D surface scanner evaluations. The average presenting age was 6.2 months (corrected for prematurity for treatment considerations). Of the 991 patients, 543 (54.8%) had RP or PT as first recommended treatment. Of these 543 patients, 137 (25.2%) transitioned to helmet therapy after the condition did not improve over 4–8 weeks. In the remaining cases, RP/PT had already failed before the patients were seen in this program, and the starting treatment recommendation was CO. At the end of treatment, the measured improvements in ODD were 36.7%, 33.5%, and 15.1% for patients receiving CO, RP/PT/CO, and RP/PT, respectively. Univariate analysis showed that sex, race, insurance, diagnosis, sleep position preference, torticollis history, and multiple gestation were not significantly associated with magnitude of ODD change during treatment. On multivariate analysis, corrected age at presentation and type of treatment received were significantly associated with magnitude of ODD change. Orthotic treatment corresponded with the largest ODD change, while the RP/PT group had the least change in ODD. Earlier age at presentation corresponded with larger ODD change. CONCLUSIONS Earlier age at presentation and type of treatment impact the degree of measured deformational head shape correction in positional plagiocephaly. This retrospective study suggests that treatment with a custom CO can result in more improvement in objective measurements of head shape.

scholarly journals Influence of Forest Structure and Composition on Summer Habitat Use of Wildlife in an Upland Hardwood Forest

Diversity ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 160 ◽  
Author(s):  
Brent S. Pease ◽  
Eric J. Holzmueller ◽  
Clayton K. Nielsen
Keyword(s):  
Habitat Use ◽  
Forest Structure ◽  
Sugar Maple ◽  
Management Practices ◽  
Negative Relationship ◽  
Hardwood Forest ◽  
Forest Composition ◽  
Gray Squirrel ◽  
The Impact ◽  
Eastern Gray Squirrel

Oak-hickory (Quercus-Carya spp.) forest types are widespread across the midwestern United States, but changes in forest disturbance regimes are resulting in little to no oak recruitment and a compositional shift to shade-tolerant, mesophytic species, such as American beech (Fagus grandifolia) and sugar maple (Acer saccharum). We conducted camera trap surveys in a mature upland hardwood forest of southern Illinois, USA during May to August 2015–2016 to document mammal summer habitat use in relation to forest structure and composition to further understand how regional shifts in forests may affect mammal communities. With nearly 4000 camera days of effort, we modeled occupancy patterns for white-tailed deer (Odocoileus virginianus), raccoon (Procyon lotor), and eastern gray squirrel (Sciurus canadensis). Forest composition models outcompeted forest structure models for white-tailed deer, where we observed a statistically significant negative relationship between white-tailed deer habitat use and beech dominance. Further, we found a strong, positive association between deer and oak dominance. Model selection indicated little support for within-stand forest structure or composition characteristics influencing habitat use for raccoons. Eastern gray squirrel occurrence was best described by forest composition, revealing a positive relationship with beech–maple importance values. Our predictive models indicated that the impact of forest changes underway will have varying impacts on wildlife species. We can expect changes in habitat use patterns to be more pronounced with time barring revised forest management practices, and these changes are likely to be most influential at the landscape-scale. We conclude that a patchwork mosaic of forest conditions will likely best support a diverse and abundant mammal community across the region.

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