scholarly journals On the relationship between enamel band complexity and occlusal surface area in Equids (Mammalia, Perissodactyla)

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2181 ◽  
Author(s):  
Nicholas A. Famoso ◽  
Edward Byrd Davis
Keyword(s):  
Body Size ◽  
Least Squares ◽  
Surface Area ◽  
Phylogenetic Signal ◽  
Negative Relationship ◽  
Generalized Least Squares ◽  
Occlusal Surface ◽  
Last Common Ancestor ◽  
Occlusal Surfaces ◽  
The Relationship

Enamel patterns on the occlusal surfaces of equid teeth are asserted to have tribal-level differences. The most notable example compares the Equini and Hipparionini, where Equini have higher crowned teeth with less enamel-band complexity and less total occlusal enamel than Hipparionini. Whereas previous work has successfully quantified differences in enamel band shape by dividing the length of enamel band by the square root of the occlusal surface area (Occlusal Enamel Index, OEI), it was clear that OEI only partially removes the effect of body size. Because enamel band length scales allometrically, body size still has an influence on OEI, with larger individuals having relatively longer enamel bands than smaller individuals. Fractal dimensionality (D) can be scaled to any level, so we have used it to quantify occlusal enamel complexity in a way that allows us to get at an accurate representation of the relationship between complexity and body size. To test the hypothesis of tribal-level complexity differences between Equini and Hipparionini, we digitally traced a sample of 98 teeth, one tooth per individual; 31 Hipparionini and 67 Equini. We restricted our sampling to the P3-M2 to reduce the effect of tooth position. After calculating theDof these teeth with the fractal box method which uses the number of boxes of various sizes to calculate theDof a line, we performed at-test on the individual values ofDfor each specimen, comparing the means between the two tribes, and a phylogenetically informed generalized least squares regression (PGLS) for each tribe with occlusal surface area as the independent variable andDas the dependent variable. The slopes of both PGLS analyses were compared using at-test to determine if the same linear relationship existed between the two tribes. Thet-test between tribes was significant (p< 0.0001), suggesting differentDpopulations for each lineage. The PGLS for Hipparionini was a positive but not significant (p= 0.4912) relationship betweenDand occlusal surface area, but the relationship for Equini was significantly negative (p= 0.0177).λwas 0 for both tests, indicating no important phylogenetic signal is present in the relationship between these two characters, thus the PGLS collapses down to a non-phylogenetic generalized least squares (GLS) model. Thet-test comparing the slopes of the regressions was not significant, indicating that the two lineages could have the same relationship betweenDand occlusal surface area. Our results suggest that the two tribes have the same negative relationship betweenDand occlusal surface area but the Hipparionini are offset to higher values than the Equini. This offset reflects the divergence between the two lineages since their last common ancestor and may have constrained their ability to respond to environmental change over the Neogene, leading to the differential survival of the Equini.

scholarly journals Habitat productivity is a poor predictor of body size in rodents

2019 ◽  
Vol 66 (2) ◽  
pp. 135-143 ◽  
Author(s):  
Bader H Alhajeri ◽  
Lucas M V Porto ◽  
Renan Maestri
Keyword(s):  
Body Size ◽  
Least Squares ◽  
Body Mass ◽  
Resource Availability ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Positive Association ◽  
Generalized Least Squares ◽  
Habitat Productivity ◽  
Resource Availability Hypothesis

Abstract The “resource availability hypothesis” predicts occurrence of larger rodents in more productive habitats. This prediction was tested in a dataset of 1,301 rodent species. We used adult body mass as a measure of body size and normalized difference vegetation index (NDVI) as a measure of habitat productivity. We utilized a cross-species approach to investigate the association between these variables. This was done at both the order level (Rodentia) and at narrower taxonomic scales. We applied phylogenetic generalized least squares (PGLS) to correct for phylogenetic relationships. The relationship between body mas and NDVI was also investigated across rodent assemblages. We controlled for spatial autocorrelation using generalized least squares (GLS) analysis. The cross-species approach found extremely low support for the resource availability hypothesis. This was reflected by a weak positive association between body mass and NDVI at the order level. We find a positive association in only a minority of rodent subtaxa. The best fit GLS model detected no significant association between body mass and NDVI across assemblages. Thus, our results do not support the view that resource availability plays a major role in explaining geographic variation in rodent body size.

scholarly journals Evidence that gestation duration and lactation duration are coupled traits in primates

2012 ◽  
Vol 8 (6) ◽  
pp. 998-1001 ◽  
Author(s):  
Evgenia Dubman ◽  
Mark Collard ◽  
Arne Ø. Mooers
Keyword(s):  
Body Size ◽  
Linear Regression ◽  
Metabolic Rate ◽  
Least Squares ◽  
Generalized Least Squares ◽  
Related Factor ◽  
Scaling Exponent ◽  
Metabolic Theory ◽  
Lactation Duration ◽  
Duration Of Gestation

Gestation duration and lactation duration are usually treated as independently evolving traits in primates, but the metabolic theory of ecology (MTE) suggests both durations should be determined by metabolic rate. We used phylogenetic generalized least-squares linear regression to test these different perspectives. We found that the allometries of the durations are divergent from each other and different from the scaling exponent predicted by the MTE (0.25). Gestation duration increases much more slowly (0.06 < m < 0.12), and lactation duration much more quickly (0.36 < m < 0.52) with body mass than the MTE predicts. By contrast, we found that the combined duration of gestation and lactation is consistent with the MTE's predictions (0.22 < m < 0.35). These results suggest that gestation duration and lactation duration might best be viewed as distinct but coupled adaptations. When transferring energy to their offspring, primate mothers must meet metabolically dictated physiological requirements while optimizing the timing of the switch from gestation to lactation in relation to some as-yet-unidentified body-size-related factor.

scholarly journals Teeth complexity, hypsodonty and body mass in Santacrucian (Early Miocene) notoungulates (Mammalia)

2015 ◽  
Vol 106 (4) ◽  
pp. 303-313 ◽  
Author(s):  
Guillermo H. Cassini ◽  
Santiago Hernández Del Pino ◽  
Nahuel A. Muñoz ◽  
M. V. Walter G. Acosta ◽  
Mercedes Fernández ◽  
...  
Keyword(s):  
Surface Area ◽  
Body Mass ◽  
Tooth Enamel ◽  
Tooth Wear ◽  
Occlusal Surface ◽  
South American ◽  
Strongly Correlated ◽  
Size Dependent ◽  
Dental Traits ◽  
The Relationship

ABSTRACTNotoungulates, native South American fossil mammals, have been recently objective of several palaeoecological studies. Ecomorphology and biomechanics of the masticatory apparatus, together with micro and mesowear analyses on tooth enamel, were applied in order to understand their palaeobiology. In particular, the relationship between some dental traits (hypsodonty, occlusal surface area and complexity) and body mass is still poorly understood. These features were measured by means of the hypsodonty index (HI), occlusal surface area (OSA) and tooth area (OTA), enamel crest complexity (ECC) and length (OEL). The relationships between these indices were evaluated in five pan-contemporaneous Santacrucian Notoungulata genera from Patagonia: Adinotherium and Nesodon (Toxodontia), Interatherium, Protypotherium and Hegetotherium (Typotheria). While OSA, OTA and OEL were size dependent and strongly correlated, HI and ECC were size independent. All notoungulates analysed have very hypsodont teeth, indicating high rates of tooth wear in response to an increase of abrasives consumed with the food; their tooth occlusal area and complexity could be related to chewing efforts associated with the toughness of the plants consumed. HI, OSA and ECC were considered useful for palaeoecological reconstructions, but the results presented here show that these three features are integrated as a complex, so should not be evaluated separately.

scholarly journals Quantifying the relationship between genetic diversity and population size suggests natural selection cannot explain Lewontin's paradox

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Vince Buffalo
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Phylogenetic Signal ◽  
Neutral Theory ◽  
Negative Relationship ◽  
Abundant Species ◽  
Census Size ◽  
Population Sizes ◽  
The Relationship ◽  
Linked Selection

Neutral theory predicts that genetic diversity increases with population size, yet observed levels of diversity across metazoans vary only two orders of magnitude while population sizes vary over several. This unexpectedly narrow range of diversity is known as Lewontin’s Paradox of Variation (1974). While some have suggested selection constrains diversity, tests of this hypothesis seem to fall short. Here, I revisit Lewontin’s Paradox to assess whether current models of linked selection are capable of reducing diversity to this extent. To quantify the discrepancy between pairwise diversity and census population sizes across species, I combine previously-published estimates of pairwise diversity from 172 metazoan taxa with newly derived estimates of census sizes. Using phylogenetic comparative methods, I show this relationship is significant accounting for phylogeny, but with high phylogenetic signal and evidence that some lineages experience shifts in the evolutionary rate of diversity deep in the past. Additionally, I find a negative relationship between recombination map length and census size, suggesting abundant species have less recombination and experience greater reductions in diversity due to linked selection. However, I show that even assuming strong and abundant selection, models of linked selection are unlikely to explain the observed relationship between diversity and census sizes across species.

scholarly journals Exceptional body sizes but typical trophic structure in a Pleistocene food web

2016 ◽  
Vol 12 (5) ◽  
pp. 20160228 ◽  
Author(s):  
Angel M. Segura ◽  
Richard A. Fariña ◽  
Matías Arim
Keyword(s):  
Body Size ◽  
Trophic Position ◽  
Negative Relationship ◽  
Additional Energy ◽  
Quaternary Period ◽  
Species Vulnerability ◽  
Body Sizes ◽  
Energetic Constraints ◽  
The Relationship

In this study, we focused on the exceptionally large mammals inhabiting the Americas during the Quaternary period and the paramount role of body size in species ecology. We evaluated two main features of Pleistocene food webs: the relationship between body size and (i) trophic position and (ii) vulnerability to predation. Despite the large range of species sizes, we found a hump-shaped relationship between trophic position and body size. We also found a negative trend in species vulnerability similar to that observed in modern faunas. The largest species lived near the boundary of energetic constraints, such that any shift in resource availability could drive these species to extinction. Our results reinforce several features of megafauna ecology: (i) the negative relationship between trophic position and body size implies that large-sized species were particularly vulnerable to changes in energetic support; (ii) living close to energetic imbalance could favour the incorporation of additional energy sources, for example, a transition from a herbivorous to a scavenging diet in the largest species (e.g. Megatherium ) and (iii) the interactions and structure of Quaternary megafauna communities were shaped by similar forces to those shaping modern fauna communities.

scholarly journals Permutation tests for comparative data

2020 ◽  
Author(s):  
James G. Saulsbury
Keyword(s):  
Least Squares ◽  
Permutation Test ◽  
Phylogenetic Signal ◽  
Cyclic Permutation ◽  
Permutation Tests ◽  
Generalized Least Squares ◽  
Comparative Data ◽  
Least Squares Regression ◽  
Data Points ◽  
Restricted Permutation

AbstractThe analysis of patterns in comparative data has come to be dominated by least-squares regression, mainly as implemented in phylogenetic generalized least-squares (PGLS). This approach has two main drawbacks: it makes relatively restrictive assumptions about distributions and can only address questions about the conditional mean of one variable as a function of other variables. Here I introduce two new non-parametric constructs for the analysis of a broader range of comparative questions: phylogenetic permutation tests, based on cyclic permutations and permutations conserving phylogenetic signal. The cyclic permutation test, an extension of the restricted permutation test that performs exchanges by rotating nodes on the phylogeny, performs well within and outside the bounds where PGLS is applicable but can only be used for balanced trees. The signal-based permutation test has identical statistical properties and works with all trees. The statistical performance of these tests compares favorably with independent contrasts and surpasses that of a previously developed permutation test that exchanges closely related pairs of observations more frequently. Three case studies illustrate the use of phylogenetic permutations for quantile regression with non-normal and heteroscedastic data, testing hypotheses about morphospace occupation, and comparative problems in which the data points are not tips in the phylogeny.

scholarly journals The evolution of vocal duets and migration in New World warblers (Parulidae)

The Auk ◽  
2019 ◽  
Vol 136 (2) ◽  
Author(s):  
Liam R Mitchell ◽  
Lauryn Benedict ◽  
Jakica Cavar ◽  
Nadje Najar ◽  
David M Logue
Keyword(s):  
New World ◽  
Common Ancestor ◽  
Phylogenetic Signal ◽  
Negative Relationship ◽  
Last Common Ancestor ◽  
Shared Resources ◽  
Significant Negative Relationship ◽  
Explicit Correlation ◽  
And Migration ◽  
Vocal Duets

Abstract Vocal duets occur when 2 individuals vocalize in temporal coordination. In birds, duet participation functions to cooperatively defend shared resources, localize mates, and in some species, guard the mate. Previous work indicates that duetting tends to co-evolve with a non-migratory lifestyle, probably because the absence of migration facilitates greater cooperation between mates. We examined the evolution of duetting and migration in New World warblers (Parulidae), a group that has been largely ignored by duetting research. Of the 95 species in our analysis, we found evidence of duetting in 19 (20%) species, and evidence of migration in 45 (47.4%) species. Ancestral character reconstruction indicated that the last common ancestor of the New World warblers did not duet. Duetting evolved multiple times in this group, including 2 early origins and several more recent origins. Migration was present in the last common ancestor and was lost several times. Both duetting and migration exhibit phylogenetic signal. A phylogenetically explicit correlation analysis revealed a significant negative relationship between duetting and migration, in keeping with findings from other avian taxa. This study, the first description of the evolution of duetting in a large avian family with a temperate-zone origin, supports the hypothesis that duetting co-evolves with a sedentary natural history in birds.

scholarly journals On being the right size: increased body size is associated with reduced telomere length under natural conditions

2015 ◽  
Vol 282 (1820) ◽  
pp. 20152331 ◽  
Author(s):  
Thor Harald Ringsby ◽  
Henrik Jensen ◽  
Henrik Pärn ◽  
Thomas Kvalnes ◽  
Winnie Boner ◽  
...  
Keyword(s):  
Body Size ◽  
Telomere Length ◽  
Natural Populations ◽  
Negative Relationship ◽  
House Sparrows ◽  
Selection Regime ◽  
Trade Offs ◽  
Length Changes ◽  
The Relationship ◽  
Telomere Dynamics

Evolution of body size is likely to involve trade-offs between body size, growth rate and longevity. Within species, larger body size is associated with faster growth and ageing, and reduced longevity, but the cellular processes driving these relationships are poorly understood. One mechanism that might play a key role in determining optimal body size is the relationship between body size and telomere dynamics. However, we know little about how telomere length is affected when selection for larger size is imposed in natural populations. We report here on the relationship between structural body size and telomere length in wild house sparrows at the beginning and end of a selection regime for larger parent size that was imposed for 4 years in an isolated population of house sparrows. A negative relationship between fledgling size and telomere length was present at the start of the selection; this was extended when fledgling size increased under the selection regime, demonstrating a persistent covariance between structural size and telomere length. Changes in telomere dynamics, either as a correlated trait or a consequence of larger size, could reduce potential longevity and the consequent trade-offs could thereby play an important role in the evolution of optimal body size.

scholarly journals Good Things Come in Larger Packages: Size Matters for Adult Fruit-Feeding Butterfly Dispersal and Larval Diet Breadth

Diversity ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 664
Author(s):  
Geraldo B. Freire ◽  
Thayane Silva ◽  
Hernani Oliveira ◽  
Chloe Collier ◽  
Hanna P. Rodrigues ◽  
...  
Keyword(s):  
Body Size ◽  
Phylogenetic Signal ◽  
Large Population ◽  
Species Abundance ◽  
Generalized Least Squares ◽  
Species Traits ◽  
Diet Breadth ◽  
Dispersal Ability ◽  
Larval Diet ◽  
Dispersal Capacity

Introduction: In animals, body size is correlated with many aspects of natural history, such as life span, abundance, dispersal capacity and diet breadth. However, contrasting trends have been reported for the relationship between body size and these ecological traits. Methods: Fruit-feeding butterflies were used to investigate whether body size is correlated with species abundance, dispersal, permanence, and larval diet breadth in a Neotropical savanna in Brazil (Cerrado). We used Blomberg’s K and Phylogenetic Generalized Least Squares models (PGLS) to measure phylogenetic signal strength in species traits and to estimate size–dispersal–diet breadth associations, while also taking shared ancestry into account. Results: 539 individuals from 27 species were captured, and 190 individuals were recaptured, representing a 35% recapture rate. We found body size to be negatively associated with butterfly abundance, and positively associated with dispersal level, distance traveled, number of traps visited, individual permanence, and diet breadth. These results indicate that larger butterflies are more likely to disperse over longer distances. Moreover, larger butterflies have more generalized larval diets, based on the number of host plant families, genera, and phylogenetic diversity of the host plants they consume as larvae. Smaller butterflies rely on fewer resources, which is reflected in their higher survival in small patches and may explain their lower dispersal ability and higher diet specialization. Nevertheless, lower dispersal ability may, if not compensated by large population sizes, threaten small-bodied species inhabiting environments, such as the Cerrado, which have intense deforestation rates. Conclusions: Body size is positively associated with dispersal and diet breadth for the fruit-feeding butterflies collected in this study.

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