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Saturday, 25 October 2014

PubMed papers: Week 2, October 2014

1. Am Nat. 2014 Nov;184(5):E101-E114. Epub 2014 Sep 22.

Sexual Selection and Diversification: Reexamining the Correlation between Dichromatism and Speciation Rate in Birds.

Huang H1, Rabosky DL.
Author information:
1Department of Ecology and Evolutionary Biology, Museum of Zoology, University of Michigan, Ann Arbor, Michigan 48109.


Abstract Theory predicts that sexual selection can serve as an important driver of speciation, but phylogenetic comparative analyses have failed to demonstrate a consistent effect of sexual selection on species richness at macroevolutionary scales. Sexual dichromatism in birds is an example of a phenotypic trait that is hypothesized to reflect the intensity of sexual selection, yet previous studies have reached ambiguous conclusions regarding its role in promoting species diversification. Here, we revisit this problem by pairing published spectrophotometer estimates of plumage dichromatism in the bird-visible range with a newly developed method for modeling speciation rates on phylogenetic trees that explicitly accounts for diversification rate variation through time and among clades. We find little evidence linking dichromatism to speciation across birds, using several measures of dichromatism and macroevolutionary diversification. These results suggest that sexual dichromatism plays a limited role in determining speciation rates at macroevolutionary scales in birds.
PMID: 25325752 [PubMed - as supplied by publisher]

2. Am Nat. 2014 Nov;184(5):624-635. Epub 2014 Oct 1.

Reciprocal Specialization in Multihost Malaria Parasite Communities of Birds: A Temperate-Tropical Comparison.

Svensson-Coelho M1, Ellis VA, Loiselle BA, Blake JG, Ricklefs RE.
Author information:
1Department of Biology, University of Missouri, St. Louis, Missouri 63121.


Abstract How specialization of consumers with respect to resources varies with respect to latitude is poorly understood. Coexistence of many species in the tropics might be possible only if specialization also increases. Alternatively, lower average abundance of more diverse biotic resources in the tropics might force consumers to become more generalized foragers. We examine levels of reciprocal specialization in an antagonistic system-avian malaria-to determine whether the number of host species used and/or parasite lineages harbored differ between a temperate and a tropical assemblage. We evaluate the results of network analysis, which can incorporate both bird and parasite perspectives on specialization in one quantitative index, in comparison to null models. Specialization was significantly greater in both sample sites than predicted from null models. We found evidence for lower per-host species parasite diversity in temperate compared to tropical birds. However, specialization did not differ between the tropical and temperate sites from the parasite perspective. We supplemented the network analysis with estimates of specialization that incorporate phylogenetic relationships of associates and found no differences between sites. Thus, our analyses indicate that specialization within an antagonistic host-parasite (resource-consumer) system varies little between tropical and temperate localities.
PMID: 25325746 [PubMed - as supplied by publisher]

3. Am Nat. 2014 Nov;184(5):593-608. Epub 2014 Oct 1.

Unraveling the Interplay of Community Assembly Processes Acting on Multiple Niche Axes across Spatial Scales.

Trisos CH1, Petchey OL, Tobias JA.
Author information:
1Edward Grey Institute, Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom.


Abstract How the relative importance of community assembly processes varies with spatial scale is the focus of intensive debate, in part because inferring the scales at which specific niche-based processes act is difficult. One obstacle is that standard phylogenetic and functional diversity metrics may integrate the signals of multiple processes when combining separate niche axes into one variable (multiple-niche-axis metrics), potentially obscuring overlapping niche-based processes. We use simulations to evaluate the power of these metrics to detect competition and habitat filtering when these processes operate across multiple niche axes and vary in their relative importance. We then test for both processes at a range of spatial scales in a Neotropical bird assemblage. Simulations revealed that multiple-niche-axis metrics had low power to detect competition and habitat filtering when a mix of both processes acts across niche axes, whereas metrics focused on single-niche axes were better able to deal with this complexity. We found the same contrast in bird communities, where both competition and habitat filtering were detected at the scale of individual territories, but only by single-niche-axis metrics focused on specific niche axes (e.g., foraging traits). Our results suggest that multiple-niche-axis metrics may produce misleading evidence that niche-based processes are partitioned, particularly across scales, and highlight the importance of analyzing functional diversity patterns on individual niche axes when testing assembly models.
PMID: 25325744 [PubMed - as supplied by publisher]

4. J Exp Biol. 2014 Oct 16. pii: jeb.112946. [Epub ahead of print]

Developmental variation in sound production in water and air in the blue catfish Ictalurus furcatus.

Ghahramani ZN1, Mohajer Y2, Fine ML3.
Author information:
1Brooklyn College, City University of New York; Virginia Commonwealth University, US;
2Virginia Commonwealth University, US.
3Virginia Commonwealth University, US


Blue catfish Ictalurus furcatus Lesueur, the largest catfish in North America, produces pectoral stridulation sounds (distress calls) when attacked and held. They have both fish and bird predators, and the frequency spectrum of their sounds is better matched to hearing of birds than to that of unspecialized fish predators with low frequency hearing. It is unclear whether their sounds evolved to function in air or water. We categorized the calls and how they change with fish size in air and water and compared developmental changes in call parameters with stridulation motions captured with a high-speed camera. Stridulation sounds consist of a variable series of pulses produced during abduction of the pectoral spine. Pulses are caused by quick rapid spine rotations (jerks) of the pectoral spine that do not change with fish size although larger individuals generate longer, higher amplitude pulses with lower peak frequencies. There are longer pauses between jerks, and therefore fewer jerks and fewer pulses in larger fish that take longer to abduct their spines and therefore produce a longer series of pulses per abduction sweep. Sounds couple more effectively to water (1400 times greater pressure in Pascals at 1m), are more sharply tuned and have lower peak frequencies than in air. Blue catfish stridulation sounds appear to be specialized to produce under-water signals although most of the sound spectrum includes frequencies matched to catfish hearing but largely above the hearing range of unspecialized fishes.
PMID: 25324337 [PubMed - as supplied by publisher]

5. Glob Chang Biol. 2014 Oct 16. doi: 10.1111/gcb.12740. [Epub ahead of print]

Climate change in our backyards: the reshuffling of North America's winter bird communities.

Princé K1, Zuckerberg B.
Author information:
1Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, 53706, USA.


Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species-specific responses are resulting in community-wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm-adapted species. To do this, we quantified changes in community composition using a functional index - the Community Temperature Index (CTI) - which measures the balance between low- and high-temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (n = 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22-year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm-adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.
© 2014 John Wiley & Sons Ltd.
PMID: 25322929 [PubMed - as supplied by publisher]

6. PeerJ. 2014 Oct 9;2:e621. doi: 10.7717/peerj.621. eCollection 2014.

A vision physiological estimation of ultraviolet window marking visibility to birds.

Håstad O1, Odeen A2.
Author information:
1Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences , Uppsala , Sweden.
2Department of Animal Ecology, Uppsala University , Norbyvägen, Uppsala , Sweden.


Billions of birds are estimated to be killed in window collisions every year, worldwide. A popular solution to this problem may lie in marking the glass with ultraviolet reflective or absorbing patterns, which the birds, but not humans, would see. Elegant as this remedy may seem at first glance, few of its proponents have taken into consideration how stark the contrasts between ultraviolet and human visible light reflections or transmissions must be to be visible to a bird under natural conditions. Complicating matters is that diurnal birds differ strongly in how their photoreceptors absorb ultraviolet and to a lesser degree blue light. We have used a physiological model of avian colour vision to estimate the chromatic contrasts of ultraviolet markings against a natural scene reflected and transmitted by ordinary window glass. Ultraviolets markings may be clearly visible under a range of lighting conditions, but only to birds with a UVS type of ultraviolet vision, such as many passerines. To bird species with the common VS type of vision, ultraviolet markings should only be visible if they produce almost perfect ultraviolet contrasts and are viewed against a scene with low chromatic variation but high ultraviolet content.
PMID: 25320684 [PubMed]

7. J Exp Biol. 2014 Oct 15;217(Pt 20):3700-7. doi: 10.1242/jeb.106344.

Impacts of extreme climatic events on the energetics of long-lived vertebrates: the case of the greater flamingo facing cold spells in the Camargue.

Deville AS1, Labaude S2, Robin JP3, Béchet A2, Gauthier-Clerc M4, Porter W5, Fitzpatrick M5, Mathewson P5, Grémillet D6.
Author information:
1Centre de Recherche de la Tour du Valat, Le Sambuc, 13200 Arles, France Centre d'Ecologie Fonctionnelle et Evolutive (CEFE-CNRS), 1919 Route de Mende, 34090 Montpellier, France.
2Centre de Recherche de la Tour du Valat, Le Sambuc, 13200 Arles, France.
3Institut Pluridisciplinaire Hubert Curien, Département Ecologie, Physiologie et Ethologie, Unité Mixte de Recherche 7178 CNRS-ULP, 23 Rue Becquerel, 67087 Strasbourg Cedex 2, France.
4Centre de Recherche de la Tour du Valat, Le Sambuc, 13200 Arles, France Departement Chrono-Environnement, UMR UFC/CNRS 6249 USC INRA, Université de Franche-Comté, 25030 Besançon, France.
5Department of Zoology, University of Wisconsin, Madison, 250 N. Mills Street, Madison, WI 53706, USA.
6Centre d'Ecologie Fonctionnelle et Evolutive (CEFE-CNRS), 1919 Route de Mende, 34090 Montpellier, France FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa


Most studies analyzing the effects of global warming on wild populations focus on gradual temperature changes, yet it is also important to understand the impact of extreme climatic events. Here we studied the effect of two cold spells (January 1985 and February 2012) on the energetics of greater flamingos (Phoenicopterus roseus) in the Camargue (southern France). To understand the cause of observed flamingo mass mortalities, we first assessed the energy stores of flamingos found dead in February 2012, and compared them with those found in other bird species exposed to cold spells and/or fasting. Second, we evaluated the monthly energy requirements of flamingos across 1980-2012 using the mechanistic model Niche Mapper™. Our results show that the body lipids of flamingos found dead in 2012 corresponded to 2.6±0.3% of total body mass, which is close to results found in woodcocks (Scolopax rusticola) that died from starvation during a cold spell (1.7±0.1%), and much lower than in woodcocks which were fed throughout this same cold spell (13.0±2%). Further, Niche Mapper™ predicted that flamingo energy requirements were highest (+6-7%) during the 1985 and 2012 cold spells compared with 'normal' winters. This increase was primarily driven by cold air temperatures. Overall, our findings strongly suggest that flamingos starved to death during both cold spells. This study demonstrates the relevance of using mechanistic energetics modelling and body condition analyses to understand and predict the impact of extreme climatic events on animal energy balance and winter survival probabilities.
© 2014. Published by The Company of Biologists Ltd.
PMID: 25320270 [PubMed - in process]

8. J R Soc Interface. 2014 Dec 6;11(101). pii: 20140645. doi: 10.1098/rsif.2014.0645.

Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis.

Reynolds KV1, Thomas AL1, Taylor GK2.
Author information:
1Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
2Department of Zoology, University of Oxford, Oxford OX1 3PS, UK


Turbulent atmospheric conditions represent a challenge to stable flight in soaring birds, which are often seen to drop their wings in a transient motion that we call a tuck. Here, we investigate the mechanics, occurrence and causation of wing tucking in a captive steppe eagle Aquila nipalensis, using ground-based video and onboard inertial instrumentation. Statistical analysis of 2594 tucks, identified automatically from 45 flights, reveals that wing tucks occur more frequently under conditions of higher atmospheric turbulence. Furthermore, wing tucks are usually preceded by transient increases in airspeed, load factor and pitch rate, consistent with the bird encountering a headwind gust. The tuck itself immediately follows a rapid drop in angle of attack, caused by a downdraft or nose-down pitch motion, which produces a rapid drop in load factor. Positive aerodynamic loading acts to elevate the wings, and the resulting aerodynamic moment must therefore be balanced in soaring by an opposing musculoskeletal moment. Wing tucking presumably occurs when the reduction in the aerodynamic moment caused by a drop in load factor is not met by an equivalent reduction in the applied musculoskeletal moment. We conclude that wing tucks represent a gust response precipitated by a transient drop in aerodynamic loading.
Free Article
PMID: 25320064 [PubMed - in process]

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9. Biol Lett. 2014 Oct;10(10). pii: 20140665. doi: 10.1098/rsbl.2014.0665.

European starlings recognize the location of robotic conspecific attention.

Butler SR1, Fernández-Juricic E2.
Author information:
1Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
2Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.


Looking where others are allocating attention can facilitate social interactions by providing information about objects or locations of interest. We asked whether European starlings follow the orientation behaviour of conspecifics owing to their highly gregarious behaviour. Starlings reoriented their attention to follow that of a robot around a barrier more often than when the robot's attention was directed elsewhere. This is the first empirical evidence of reorienting in response to conspecific attention in a songbird. Starlings may use this behaviour to obtain fine-tuned spatial information from conspecifics (e.g. direction of predator approach, spatial location of food patches), enhancing group cohesion.
© 2014 The Author(s) Published by the Royal Society. All rights reserved.
PMID: 25319821 [PubMed - in process]

10. Biol Lett. 2014 Oct;10(10). pii: 20140647. doi: 10.1098/rsbl.2014.0647.

Reproductive niche conservatism in the isolated New Zealand flora over 23 million years.

Conran JG1, Lee WG2, Lee DE3, Bannister JM4, Kaulfuss U3.
Author information:
1ACEBB & SGC, School of Earth and Environmental Sciences, DX 650-312, The University of Adelaide, Adelaide, South Australia 5005, Australia
2Landcare Research, Private Bag 1930, Dunedin 9054, New Zealand School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1010, New Zealand.
3Department of Geology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
4Department of Botany, University of Otago, PO Box 56, Dunedin 9054, New Zealand.


The temporal stability of plant reproductive features on islands has rarely been tested. Using flowers, fruits/cones and seeds from a well-dated (23 Ma) Miocene Lagerstätte in New Zealand, we show that across 23 families and 30 genera of forest angiosperms and conifers, reproductive features have remained constant for more than 20 Myr. Insect-, wind- and bird-pollinated flowers and wind- and bird-dispersed diaspores all indicate remarkable reproductive niche conservatism, despite widespread environmental and biotic change. In the past 10 Myr, declining temperatures and the absence of low-latitude refugia caused regional extinction of thermophiles, while orogenic processes steepened temperature, precipitation and nutrient gradients, limiting forest niches. Despite these changes, the palaeontological record provides empirical support for evidence from phylogeographical studies of strong niche conservatism within lineages and biomes.
© 2014 The Author(s) Published by the Royal Society. All rights reserved.
PMID: 25319820 [PubMed - in process]

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