A major goal of modern neuroscience is to understand how variation in behavior, cognition, and emotion relates to underlying neural mechanisms. These breeds possess distinct traits related to morphology, which include body size, skull shape, tail phenotype, fur type, body . A phylogeny is a branch of Biology that specially deals with Phylogenesis. We were interested in the possibility that human-driven selection on external craniofacial morphology may have had on the internal dimensions of the skull. Furthermore, recent genetic research indicates that this behavioral variation is highly heritable (MacLean et al., 2019). It should be noted that phylogenetic approaches such as pGLS and pANCOVA are interpreted in the same way as standard least-squares approaches. Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships. Table 1 lists the breed, breed group, and other data for all dogs included in the study. Importantly, we cannot say from the current analyses whether variation in skull morphology drives variation in brain morphology, the reverse, or both. A general diagram illustrating the overall processing pipeline is included in Fig. Consistent with this possibility, one study has already found that border collies and Siberian huskies respond significantly differently to intranasal oxytocin (Kovcs et al., 2016). Therefore, we stress that the functional roles of these networks, and their relationship to selection on behavior in specific breeds, should at this point still be considered an open question. We observed the latter (Fig. whole tree (PD whole tree) metrics. The results were published in Celljournal (PDF). Plotted points represent breed averages, not individuals. We therefore used phylogenetic comparative methods that account for phylogenetic nonindependence by including expected phylogenetic variance-covariance among species into the error term of generalized least-squares [phylogenetic generalized least squares (pGLS)] linear models (Rohlf, 2001). Cell Reports, Provided by (S) Briard/continental herder (by Mary Bloom). Relationship between morphologically covarying regional brain networks and ostensible behavioral specializations. Some dog traits also cropped up more than once, according to the researchers' analysis. (C) Icelandic sheepdog/Nordic spitz (by Veronica Druk). By comparing the differences at 150,000 spots on each dog's genome, they built a family tree. The signature separation point in European and American dogs occurs in a hidden genome. or. "What we noticed is that there are groups of American dogs that separated somewhat from the European breeds," says study co-author Heidi Parker of the NIH. Terms & Conditions. The images show structural similarity and differences between the three species as well. Colors indicate partial correlation coefficients resulting from multiple regression analysis on source-based morphometry results. Using both an identity-by-state distance matrix and a neighbor-joining tree algorithm, the researchers developed a bootstrapped cladogram with 23 well-supported clades. DNA-DNA hybridization data show that the dog family Canidae diverged about 50 million years ago from other carnivore families. In mammals, head shape is commonly measured using cephalic index (also known as skull index), calculated as maximum head width divided by maximum head length. Breeds from the Middle East, such as the Saluki, and from Asia, such as Chow Chows and Akitas, seem to. A significant relationship with total brain volume was present for all but component 6, where it was marginal but did not meet significance (component 1: t = 3.663, p = 0.001; component 2: t = 2.608, p = 0.014; component 3: t = 6.219, p < 0.001; component 4: t = 6.325, p < 0.001; component 5: t = 3.938, p < 0.001; component 6: t = 1.845, p = 0.076). Also, here we questioned whether grade shifts in this allometry exist, putatively showing differences among breeds. The majority of changes that occur in these components take place on the terminal branches of the phylogenetic tree. Cell Press. This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. The phylogenetic tree based on the whole genomic SNPs of different dog breeds. For instance, the flat-coated, golden, and the Labrador retrievers were grouped together. This procedure identified six components, each of which were thresholded at Z scores >1.96 or below 1.96. This approach estimates phenotypic change along individual lineages of a tree and has been shown to provide more accurate estimates than traditional ancestral estimation methods (Smaers and Mongle, 2017). (O) Basset hound/scent hound (by Mary Bloom). No eLetters have been published for this article. This was accomplished using the GIFT software package (Xu et al., 2009). Each of the six components showed significant correlation with at least one behavioral specialization (Fig. This document is subject to copyright. Color: Gray and white or brown and white. We also investigated the relationship between these covarying morphological components and the phylogenetic tree. These findings have relevance to both basic and applied science. Although we know that modern organisms evolved from ancient organisms, the pathway of this evolution is sometimes a best guess based on the amount of evidence available at the time. However, this study uncovered evidence that some breeds from Central and South America such as the fascinating Peruvian Hairless Dog and the Xoloitzcuintle breeds are probably descendants of the so-called New World Dog. This ancient subspecies is thought to have migrated with the ancestors of Native Americans across the Bering Strait. Finally, the cropped transverse and sagittal images were then rescaled so that the robust mean intensity of both images was 100, the images were averaged together, and then the brain mask applied to this combined image. Particularly in the case of our network 4, it may be tempting to jump to conclusions about parallels with human cortical regions that are located in approximately the same location and are involved in similar tasks; for example, the fusiform face area, Wernicke's area, or the mirror system. Why Does My Dog Sleep with His Eyes Open? We first questioned whether significant variation in dog brain morphology even exists. "We've been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome.". Last, we use multiregime Ornstein-Uhlenbeck (OU) approaches to estimate phylogenetic shifts in mean value directly from the data. Some of its branches are curved, making this tree appear circular. Image 1 Credit: Rodrigo Muoz . Neuroanatomical variation is plainly visible across breeds. All life on Earth is part of a single phylogenetic tree, indicating common ancestry.. Apart from any fair dealing for the purpose of private study or research, no Species Name: Canis lupus familiaris. Those dogs clustered closely together on the phylogenetic tree, as did the spaniel breeds. pGLS analyses on gross brain, body, and skull measurements. For instance, US-based Tibetan mastiffs exhibited an importation bottleneck and less diverse gene pool than Tibetan mastiffs in China. Furthermore, the anatomy of these networks correlates significantly with different behavioral specialization(s) such as sight hunting, scent hunting, guarding, and companionship. We identified six such networks (Fig. In other words, these approaches allow estimating directly from the data where in a phylogeny a shift in mean value of a trait has occurred. Medical research advances and health news, The latest engineering, electronics and technology advances, The most comprehensive sci-tech news coverage on the web. However, a surprising result was that the herding breeds from Europe are unexpectedly diverse. Humans have bred different lineages of domestic dogs for different tasks such as hunting, herding, guarding, or companionship. (credit "plant . We further investigated the relationship between morphological components and the phylogenetic tree by estimating the amount of change that occurs on each lineage using a multiple variance Brownian motion approach (Smaers et al., 2016; Smaers and Mongle, 2018). "We've been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome." This work was supported by the National Science FoundationDivision of Integrative Organismal Systems (Grant NSF-IOS 1457291). Nearly all of the identified variation occurs in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds. T2-weighted MRI images were acquired on a 3.0 T GE Healthcare HDx MRI unit with a GE Healthcare 51471372 3.0T HD T/R Quad Extremity Coil. We do not retain these email addresses. Network 4 involves higher-order cortical regions that may be involved in social action and interaction. In all six of the regionally covarying networks that we found, significant correlations were found with at least one behavioral specialization. Collectively, these phylogenies are divided into two overlapping networks of breed types: (1) terriers, mastiffs, and setters; and (2) hounds, herding breeds, and spaniels. Second, and perhaps most importantly, a priori comparisons of regional gray matter volumes presuppose that experimenters can identify meaningful borders between regions. Dogs represent a natural experiment in behavioral selection that has been ongoing for thousands of years; it seems remarkable that attempts to observe the neurological results of this experiment have so far been fairly minimal. For this study, researcher Elaine Ostrander and her team have recruited the breeds from dog shows (where the cream of the crop in each breed can be found). We tested this hypothesis by estimating putative grade shifts in the brain to body allometry directly from the data using an OU modeling approach (Khabbazian et al., 2016). There is substantial diversification of skull shape across dog breeds, and this has been linked to behavioral differences (Drake and Klingenberg, 2010; McGreevy et al., 2013). All scans were re-reviewed by a board-certified veterinary neurologist before inclusion. The more we uncover about the lineage of a set of organisms, the more accurate the phylogenetic trees become. As they reported today in Cell Reports, the researchers were able to trace recent admixture between different clades and examine the effects of migration. Those dogs clustered closely together on the phylogenetic tree, as did the spaniel breeds. Importantly, this grade difference in the neurocephalic to cephalic index aligns with a significant difference in body size (pANOVA: F = 9.73, p < 0.01; average body size 11 kg vs 23 kg in other breeds). To determine whether this variation was randomly distributed across the brain or focused in specific areas, we applied Monte Carlo permutation testing on the demeaned Jacobian determinant images. The colour red represents the breeds with short-tail phenotype, while the colour yellow denotes for the. (J) Rat terrier/American terrier (by Stacy Zimmerman). Figure 2B shows the relationship between neurocephalic and cephalic index. Additional support was provided by NIH OD P51OD11132 to the Yerkes National Primate Research Center. Therefore, shifts in relative brain size may be related to expansion or contraction of specific networks, potentially leading to the presence or absence of correlations between body size and behavior depending on the specific breeds or behaviors being studied. Our last common ancestor with dogs likely had a fairly smooth, simple brain (Kaas, 2011), and higher-order cortical association areas, along with whatever complex perceptual and cognitive abilities they support, have evolved independently in dogs and humans. Not all networks showed a significant relationship with either cephalic index or neurocephalic index, indicating that variation in dog brain morphology is partially but not totally dependent on variation in skull morphology. The behavioral specialization associated with the most components (four of six) was explicit companionship, and the component associated with the most behavioral specializations (six of 10) was component 4, which involves regions involved in social action and interaction. Network 6 includes early sensory processing regions for olfaction and vision, including the olfactory peduncle and part of the lateral gyrus, which is the location of primary visual cortex (Evans and de Lahunta, 2013). Conceptual schematic of neuroimaging analysis. Code is available online at. Importantly, a phylogenetic analysis revealed that most change has occurred in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds. Gray matter segmentations were warped to the study-specific template and modulated by their log Jacobian determinants to produce per-subject maps of the degree of morphological divergence from the study-specific group-average template. Wouldn't you like it to represent your breed in the dog genome sequence database?' We found that the majority of changes that occur in these components take place in the tree's terminal branches (i.e., individual breeds). It helps them walk, play, and continue through their day, bringing smiles to everyones faces. Analysis of Proven Benefits, 4 Worst and Most Dangerous Ingredients to Avoid Used in Dog Foods. ", More information: part may be reproduced without the written permission. B, Unbiased group-average template for this dataset. We produced a study-specific template representing the average brain morphology across the entire group, equally unbiased toward any particular image. Our goal was to determine whether significant nonrandom variation in brain anatomy exists across dogs and, if so, to differentiate between the competing and possibly interacting explanations for this variation. This is consistent with a previous analysis linking foreshortening of the skull to ventral pitching of the brain and olfactory bulb, resulting in a more spherical brain (Roberts et al., 2010). Cephalic index is a significant predictor of neurocephalic index (pGLS: b = 0.37, t = 3.70, p < 0.01). She worked as a veterinary assistant and technician in shelters, rescues, boarding facilities, doggy daycares and animal hospitals in New York and Chicago throughout her teens and twenties, and now resides as a pet foster mom in Upstate New York. Place a star next to any coyote traits that are similar to the dog. The map of dog breeds, which is the largest to date, unearths new . This suggests that brain evolution in domestic dog breeds follows a late burst model, with directional changes in brain organization being primarily lineage specific. Neither your address nor the recipient's address will be used for any other purpose. All Rights Reserved. A phylogenetic analysis of 736 base pairs (bp) of the cytochrome b gene showed that gray wolves are the only direct ancestor to the domestic dog with dog-wolf sequences differing in only about 0-12 substitutions [10]. Researchers are now one step closer toward discovering which genes denote New World ancestry. The diagram below shows a tree of 3 . Therefore, the current study took a totally data-driven, whole-brain, agnostic approach to assessing morphological variation across dog brains. A dog breed is a particular strain of dog that was purposefully bred by humans to perform specific tasks, such as herding, hunting, and guarding. Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships. "If we see a breed that we haven't had a good sample of to sequence, we definitely make a beeline for that owner," says Ostrander. Download, NiPype pipeline for merging axial and sagittal images from each dog before registration to the template. To our knowledge, the dogs in the current study were all house pets. B, Neurocephalic index vesus cephalic index. Your email address is used only to let the recipient know who sent the email. All rights reserved. Herding breeds, though largely European in origin, proved to be surprisingly diverse. Conversely, if brain organization is strongly tied to selective breeding for behavioral traits, then morphological traits should be divorced from the structure of the tree (i.e., low phylogenetic signal). Speaking in terms of evolutionary history, humans have been migrating across continents and all over the world for millennia, and they took their dogs with them. S3 and S6). A phylogenetic tree constructed from the mitogenomes indicated that all sampled precontact dogs (PCDs) (from time frames spanning ~9000 years) formed a monophyletic group within dog haplogroup A ( Fig. To maximize the use of all available anatomical information, the transverse and sagittal images were combined as follows. This variation is distributed nonrandomly across the brain. in Argentina and used published data for 175 recognized domestic dog breeds and two wild dog species to create a phylogenetic tree. The current study took a comprehensive, data-driven, agnostic approach to investigating neuroanatomical variation in domestic dogs. A phylogenetic tree is a diagrammatic representation of the development of biological species. (Phylogenetic tree is from Parker et al., 2017.). The precruciate and prorean gyri house premotor and prefrontal cortex, respectively, while the gyrus rectus is part of medial prefrontal cortex. These were grouped into 10 different breed groups as defined by American Kennel Club (AKC), which ostensibly represent groupings that were developed for similar behavioral specializations, such as herding or hunting. 1A). Additionally, on a practical level, our findings open the door to brain-based assessment of the utility of different dogs for different tasks. In comparative animal cognition research, total brain size is often used as a gross index of cognitive capacity. But science has made a breakthrough in this endeavor. For many scans in our database, the exterior of the skull was not visible, but a large database of skull measurements is publicly available (Stone et al., 2016). Looking at the genetic stories of dogs has some practical applications for humans, too. Thank you for taking time to provide your feedback to the editors. However, based on their positions on the cladogram, the researchers suspect that the Peruvian Hairless dog and the Xoloitzcuintle likely descend in part from those New World dogs. We also assessed whether these networks were related to selective breeding, as evidenced by the ostensible behavioral specialization(s) of each breed as noted by the AKC. They combined that information with data from 405 additional dogs that had been genotyped using the same chip and whose data was publicly available. The answer is a clear yes: differences in gross brain anatomy are readily appreciable (Fig. The ideas and opinions expressed in JNeurosci do not necessarily reflect those of SfN or the JNeurosci Editorial Board. 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Hecht at. Variation in these networks is not simply the result of variation in total brain size, total body size, or skull shape. The transverse image and transverse brain mask were then cropped using the computed ROI coordinates. The consensus haplotype sharing of phased, ten-SNP windows spanning the genome is used to construct this dog phylogenetic tree. This component also involves regions of medial frontal cortex, which is involved in downstream or higher-order processing of chemosensation and shows activation in response to olfactory stimulation in awake but not sedated dogs (Jia et al., 2014). Specific associations between associated brain networks and behavioral specializations are also apparent. And of course, people are always very flattered to say, "Yes. The thing Be amazed at Norways national dog, the Norwegian Elkhound! (W) English mastiff/European mastiff (by Mary Bloom). Therefore, rather using AKC breed groups, we identified each individual breed's ostensible behavioral specialization(s) as noted on the AKC website (www.akc.org). To provide a common spatial reference for measuring this variation, we created an unbiased, diffeomorphic template using the ANTS software package (Avants et al., 2009). Breeds from the Middle East, such as the Saluki, and from Asia, such as Chow Chows and Akitas, seem to have diverged well before the "Victorian Explosion" in Europe and the United States. Additionally, a study that used a single scaling metric across breeds found that larger-brained (i.e., larger-bodied) dogs performed better on tests of executive function (Horschler et al., 2019).
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