scholarly journals Titi monkey neophobia and visual abilities allow for fast responses to novel stimuli

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Allison R. Lau ◽  
Mark N. Grote ◽  
Madison E. Dufek ◽  
Tristan J. Franzetti ◽  
Karen L. Bales ◽  
...  
Keyword(s):  
Mixed Models ◽  
Negative Binomial ◽  
Event Time ◽  
Snake Skin ◽  
Venomous Snakes ◽  
Visual Systems ◽  
Titi Monkey ◽  
Titi Monkeys ◽  
Snake Detection ◽  
Fast Responses

AbstractThe Snake Detection Theory implicates constricting snakes in the origin of primates, and venomous snakes for differences between catarrhine and platyrrhine primate visual systems. Although many studies using different methods have found very rapid snake detection in catarrhines, including humans, to date no studies have examined how quickly platyrrhine primates can detect snakes. We therefore tested in captive coppery titi monkeys (Plecturocebus cupreus) the latency to detect a small portion of visible snake skin. Because titi monkeys are neophobic, we designed a crossover experiment to compare their latency to look and their duration of looking at a snake skin and synthetic feather of two lengths (2.5 cm and uncovered). To test our predictions that the latency to look would be shorter and the duration of looking would be longer for the snake skin, we used survival/event time models for latency to look and negative binomial mixed models for duration of looking. While titi monkeys looked more quickly and for longer at both the snake skin and feather compared to a control, they also looked more quickly and for longer at larger compared to smaller stimuli. This suggests titi monkeys’ neophobia may augment their visual abilities to help them avoid dangerous stimuli.

scholarly journals The use of disturbed and undisturbed forest by masked titi monkeys Callicebus personatus melanochir is proportional to food availability

Oryx ◽  
2002 ◽  
Vol 36 (2) ◽  
pp. 133-139 ◽  
Author(s):  
Stefanie Heiduck
Keyword(s):  
Home Range ◽  
Atlantic Rainforest ◽  
Forest Types ◽  
Clear Cut ◽  
Titi Monkey ◽  
Eastern Brazil ◽  
Titi Monkeys ◽  
Undisturbed Forest ◽  
Disturbed Forest ◽  
One Year

The masked titi Callicebus personatus melanochir is a threatened primate, endemic to the Atlantic rainforest of eastern Brazil. The Atlantic rainforest has been reduced to only 5% of its former extent, and only 2% consists of undisturbed forest. The survival of the masked titi monkey is therefore dependent on its ability to utilise disturbed forest habitat. A group of four masked titi monkeys was observed for one year in a plot that contained both disturbed and undisturbed forest. The group used a home range of 22 ha, which comprised 58% undisturbed forest, 31% selectively logged forest and 11% forest that was regrowing after a clear-cut. The titi monkeys did not use the different forest types in proportion to the availability of each within their home range: undisturbed forest was used more than expected from its proportional availability, and disturbed forest was used less than expected. Use of forest types appeared to be determined by the availability of food resources. Undisturbed forest had the most food per unit area and regrowing forest had the least. This study shows that masked titi monkeys may be able to survive in disturbed forest habitats if these areas are of high enough quality to contain sufficient food and other resources.

scholarly journals Monkeying around with venom: an increased resistance to α-neurotoxins supports an evolutionary arms race between Afro-Asian primates and sympatric cobras

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Richard J. Harris ◽  
K. Anne-Isola Nekaris ◽  
Bryan G. Fry
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Selection Pressure ◽  
Arms Race ◽  
Last Common Ancestor ◽  
Geographic Ranges ◽  
Venomous Snakes ◽  
Snake Detection ◽  
Coevolutionary Arms Race

Abstract Background Snakes and primates have a multi-layered coevolutionary history as predators, prey, and competitors with each other. Previous work has explored the Snake Detection Theory (SDT), which focuses on the role of snakes as predators of primates and argues that snakes have exerted a selection pressure for the origin of primates’ visual systems, a trait that sets primates apart from other mammals. However, primates also attack and kill snakes and so snakes must simultaneously avoid primates. This factor has been recently highlighted in regard to the movement of hominins into new geographic ranges potentially exerting a selection pressure leading to the evolution of spitting in cobras on three independent occasions. Results Here, we provide further evidence of coevolution between primates and snakes, whereby through frequent encounters and reciprocal antagonism with large, diurnally active neurotoxic elapid snakes, Afro-Asian primates have evolved an increased resistance to α-neurotoxins, which are toxins that target the nicotinic acetylcholine receptors. In contrast, such resistance is not found in Lemuriformes in Madagascar, where venomous snakes are absent, or in Platyrrhini in the Americas, where encounters with neurotoxic elapids are unlikely since they are relatively small, fossorial, and nocturnal. Within the Afro-Asian primates, the increased resistance toward the neurotoxins was significantly amplified in the last common ancestor of chimpanzees, gorillas, and humans (clade Homininae). Comparative testing of venoms from Afro-Asian and American elapid snakes revealed an increase in α-neurotoxin resistance across Afro-Asian primates, which was likely selected against cobra venoms. Through structure-activity studies using native and mutant mimotopes of the α-1 nAChR receptor orthosteric site (loop C), we identified the specific amino acids responsible for conferring this increased level of resistance in hominine primates to the α-neurotoxins in cobra venom. Conclusion We have discovered a pattern of primate susceptibility toward α-neurotoxins that supports the theory of a reciprocal coevolutionary arms-race between venomous snakes and primates.

Negative binomial loglinear mixed models

2003 ◽  
Vol 3 (3) ◽  
pp. 179-191 ◽  
Author(s):  
James G Booth ◽  
George Casella ◽  
Herwig Friedl ◽  
James P Hobert
Keyword(s):  
Mixed Models ◽  
Negative Binomial

Chromosome Painting in Callicebus nigrifrons Provides Insights into the Genome Evolution of Titi Monkeys and the Ancestral Callicebinae Karyotype

2017 ◽  
Vol 151 (2) ◽  
pp. 82-88 ◽  
Author(s):  
Naiara Pereira Araújo ◽  
Alice Alves do Espírito Santo ◽  
Valéria do Socorro Pereira ◽  
Roscoe Stanyon ◽  
Marta Svartman
Keyword(s):  
Human Chromosome ◽  
Chromosome Painting ◽  
Human Chromosomes ◽  
Molecular Cytogenetic ◽  
Monkey Species ◽  
Titi Monkey ◽  
Painting Analysis ◽  
Titi Monkeys ◽  
Callicebus Nigrifrons ◽  
Cytogenetic Methods

We studied the chromosomes of Callicebus nigrifrons with conventional and molecular cytogenetic methods. Our chromosome painting analysis in C. nigrifrons together with previous reports allowed us to hypothesize an ancestral Callicebinae karyotype with 2n = 48. The associations of human chromosomes (HSA) 2/22, 7/15, 10/11, and the inverted HSA2/16 would link Callicebus, Cheracebus, and Plecturocebus and would thus be present in the ancestral Callicebinae karyotype. Four fusions (HSA1b/1c, 3c/8b, 13/20, and 14/15/3/21) and 1 fission (HSA2/22) are synapomorphies of Callicebus. The associations HSA3/15 and HSA3/9 are chromosome features linking Callicebus and Cheracebus, whereas the association HSA13/17 would represent a link between Callicebus and the moloch group (Plecturocebus). Only 6 of the 33 recognized titi monkey species have now been painted with human chromosome-specific probes. Further analyses are needed to clarify the phylogenomic relationships in this species-rich group.

A note on the analysis of germination data from complex experimental designs

2017 ◽  
Vol 27 (4) ◽  
pp. 321-327 ◽  
Author(s):  
Signe M. Jensen ◽  
Christian Andreasen ◽  
Jens C. Streibig ◽  
Eshagh Keshtkar ◽  
Christian Ritz
Keyword(s):  
Random Effects ◽  
Mixed Models ◽  
Mixed Model ◽  
Experimental Designs ◽  
Germination Test ◽  
Random Effects Models ◽  
Event Time ◽  
Sources Of Variation ◽  
Germination Experiments ◽  
Time Point

AbstractIn recent years germination experiments have become more and more complex. Typically, they are replicated in time as independent runs and at each time point they involve hierarchical, often factorial experimental designs, which are now commonly analysed by means of linear mixed models. However, in order to characterize germination in response to time elapsed, specific event-time models are needed and mixed model extensions of these models are not readily available, neither in theory nor in practice. As a practical workaround we propose a two-step approach that combines and weighs together results from event-time models fitted separately to data from each germination test by means of meta-analytic random effects models. We show that this approach provides a more appropriate appreciation of the sources of variation in hierarchically structured germination experiments as both between- and within-experiment variation may be recovered from the data.

scholarly journals Extension and Application of Credibility Models in Predicting Claim Frequency

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Yuan-tao Xie ◽  
Zheng-xiao Li ◽  
Rahul A. Parsa
Keyword(s):  
Mixed Models ◽  
Negative Binomial ◽  
Generalized Linear Mixed Models ◽  
Linear Mixed Models ◽  
Actuarial Science ◽  
Underlying Assumption ◽  
Binomial Distributions ◽  
Numerical Studies ◽  
Proposed Model ◽  
Claim Frequency

In nonlife actuarial science, credibility models are one of the main methods of experience ratemaking. Bühlmann-Straub credibility model can be expressed as a special case of linear mixed models (LMMs) with the underlying assumption of normality. In this paper, we extend the assumption of Bühlmann-Straub model to include Poisson and negative binomial distributions as they are more appropriate for describing the distribution of a number of claims. By using the framework of generalized linear mixed models (GLMMs), we obtain the generalized credibility premiums that contain as particular cases another credibility premium in the literature. Compared to generalized linear mixed models, our extended credibility models also have an advantage in that the credibility factor falls into the range from 0 to 1. The performance of our models in comparison with an existing model in the literature is also evaluated through numerical studies, which shows that our approach produces premium estimates close to the optima. In addition, our proposed model can also be applied to the most commonly used ratemaking approach, namely, the net, the optimal Bonus-Malus system.

scholarly journals Zero-Inflated gaussian mixed models for analyzing longitudinal microbiome data

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242073
Author(s):  
Xinyan Zhang ◽  
Boyi Guo ◽  
Nengjun Yi
Keyword(s):  
16S Rrna ◽  
Em Algorithm ◽  
Mixed Models ◽  
Fixed Effects ◽  
Negative Binomial ◽  
Longitudinal Design ◽  
Linear Mixed Models ◽  
Shotgun Sequencing ◽  
Zero Inflation ◽  
Microbiome Data

Motivation The human microbiome is variable and dynamic in nature. Longitudinal studies could explain the mechanisms in maintaining the microbiome in health or causing dysbiosis in disease. However, it remains challenging to properly analyze the longitudinal microbiome data from either 16S rRNA or metagenome shotgun sequencing studies, output as proportions or counts. Most microbiome data are sparse, requiring statistical models to handle zero-inflation. Moreover, longitudinal design induces correlation among the samples and thus further complicates the analysis and interpretation of the microbiome data. Results In this article, we propose zero-inflated Gaussian mixed models (ZIGMMs) to analyze longitudinal microbiome data. ZIGMMs is a robust and flexible method which can be applicable for longitudinal microbiome proportion data or count data generated with either 16S rRNA or shotgun sequencing technologies. It can include various types of fixed effects and random effects and account for various within-subject correlation structures, and can effectively handle zero-inflation. We developed an efficient Expectation-Maximization (EM) algorithm to fit the ZIGMMs by taking advantage of the standard procedure for fitting linear mixed models. We demonstrate the computational efficiency of our EM algorithm by comparing with two other zero-inflated methods. We show that ZIGMMs outperform the previously used linear mixed models (LMMs), negative binomial mixed models (NBMMs) and zero-inflated Beta regression mixed model (ZIBR) in detecting associated effects in longitudinal microbiome data through extensive simulations. We also apply our method to two public longitudinal microbiome datasets and compare with LMMs and NBMMs in detecting dynamic effects of associated taxa.

scholarly journals Extension of the geographic distribution of Plecturocebus baptista (Pitheciidae, Primates) and a possible hybrid zone with Plecturocebus hoffmannsi: evolutionary and conservation implications

2019 ◽  
Vol 49 (4) ◽  
pp. 330-333
Author(s):  
Alessandro ROCHA ◽  
Adrian P.A. BARNETT ◽  
Wilson R. SPIRONELLO
Keyword(s):  
Geographic Distribution ◽  
New Record ◽  
Evolutionary Relationships ◽  
Neotropical Primates ◽  
Conservation Implications ◽  
Titi Monkey ◽  
Titi Monkeys ◽  
Hybrid Animal ◽  
Wide Geographic Distribution ◽  
Occurrence Records

ABSTRACT Titi monkeys (family Pitheciidae) are Neotropical primates highly diversified in morphology, ecology and genetics, with a wide geographic distribution, including the Amazon, Atlantic Forest, Cerrado, Pantanal and Caatinga. This diversity, together with knowledge gaps, generates uncertainties in titi monkey taxonomy and distribution. An example is Plecturocebus baptista, with only 14 occurrence records and an ill-defined distribution based on untested geographical barriers. Here, we report the occurrence of this species at a new locality outside its known range, across the Paraná-Urariá River, which was considered a distributional limit for the species. The new record implies an overlap of P. baptista with the range of P. hoffmannsi. We document the sighting of an apparent hybrid animal. Our observations suggest that i) the distribution of P. baptista needs to be reviewed, and ii) the evolutionary relationships between P. baptista and P. hoffmannsi may be more complex than previously assumed. Since both species share contiguous areas of potential hybridization, we question whether the two species arose via allopatric speciation.

scholarly journals Within- and Between-cluster Effects in Generalized Linear Mixed Models: A Discussion of Approaches and the Xthybrid command

2017 ◽  
Vol 17 (1) ◽  
pp. 89-115 ◽  
Author(s):  
Reinhard Schunck ◽  
Francisco Perales
Keyword(s):  
Random Effects ◽  
Mixed Models ◽  
Fixed Effects ◽  
Negative Binomial ◽  
Generalized Linear Mixed Models ◽  
Linear Mixed Models ◽  
Consistent Estimation ◽  
Random Effects Models ◽  
Fixed Effects Models ◽  
Correlated Random Effects

One typically analyzes clustered data using random- or fixed-effects models. Fixed-effects models allow consistent estimation of the effects of level-one variables, even if there is unobserved heterogeneity at level two. However, these models cannot estimate the effects of level-two variables. Hybrid and correlated random-effects models are flexible modeling specifications that separate within-and between-cluster effects and allow for both consistent estimation of level-one effects and inclusion of level-two variables. In this article, we elaborate on the separation of within- and between-cluster effects in generalized linear mixed models. These models present a unifying framework for an entire class of models whose response variables follow a distribution from the exponential family (for example, linear, logit, probit, ordered probit and logit, Poisson, and negative binomial models). We introduce the user-written command xthybrid, a shell for the meglm command. xthybrid can fit a variety of hybrid and correlated random-effects models.

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