scholarly journals Partner abundance controls mutualism stability and the pace of morphological change over geologic time

2017 ◽  
Vol 114 (15) ◽  
pp. 3951-3956 ◽  
Author(s):  
Guillaume Chomicki ◽  
Susanne S. Renner
Keyword(s):  
Morphological Change ◽  
Theoretical Models ◽  
Stabilizing Selection ◽  
Hole Size ◽  
Rates Of Evolution ◽  
Entrance Hole ◽  
Mutualism Stability ◽  
Related Trait ◽  
Different Levels ◽  
Mutualism Breakdown

Mutualisms that involve symbioses among specialized partners may be more stable than mutualisms among generalists, and theoretical models predict that in many mutualisms, partners exert reciprocal stabilizing selection on traits directly involved in the interaction. A corollary is that mutualism breakdown should increase morphological rates of evolution. We here use the largest ant-plant clade (Hydnophytinae), with different levels of specialization for mutualistic ant symbionts, to study the ecological context of mutualism breakdown and the response of a key symbiosis-related trait, domatium entrance hole size, which filters symbionts by size. Our analyses support three predictions from mutualism theory. First, all 12 losses apparently only occur from a generalist symbiotic state. Second, mutualism losses occurred where symbionts are scarce, in our system at high altitudes. Third, domatium entrance hole size barely changes in specialized symbiotic species, but evolves rapidly once symbiosis with ants has broken down, with a “morphorate map” revealing that hotspots of entrance hole evolution are clustered in high-altitude areas. Our study reveals that mutualistic strategy profoundly affects the pace of morphological change in traits involved in the interaction and suggests that shifts in partners’ relative abundances may frequently drive reversions of generalist mutualisms to autonomy.

scholarly journals Genetic constraints predict evolutionary divergence in Dalechampia blossoms

2014 ◽  
Vol 369 (1649) ◽  
pp. 20130255 ◽  
Author(s):  
Geir H. Bolstad ◽  
Thomas F. Hansen ◽  
Christophe Pélabon ◽  
Mohsen Falahati-Anbaran ◽  
Rocío Pérez-Barrales ◽  
...  
Keyword(s):  
Genetic Variance ◽  
Floral Morphology ◽  
Additive Genetic Variance ◽  
Genetic Data ◽  
Stabilizing Selection ◽  
Evolutionary Divergence ◽  
Genetic Constraints ◽  
Quantitative Genetic ◽  
Rates Of Evolution ◽  
Genetic Constraint

If genetic constraints are important, then rates and direction of evolution should be related to trait evolvability. Here we use recently developed measures of evolvability to test the genetic constraint hypothesis with quantitative genetic data on floral morphology from the Neotropical vine Dalechampia scandens (Euphorbiaceae). These measures were compared against rates of evolution and patterns of divergence among 24 populations in two species in the D. scandens species complex. We found clear evidence for genetic constraints, particularly among traits that were tightly phenotypically integrated. This relationship between evolvability and evolutionary divergence is puzzling, because the estimated evolvabilities seem too large to constitute real constraints. We suggest that this paradox can be explained by a combination of weak stabilizing selection around moving adaptive optima and small realized evolvabilities relative to the observed additive genetic variance.

Nest Box Entrance Hole Size Influences Prey Delivery Success by American Kestrels

2020 ◽  
Vol 54 (3) ◽  
Author(s):  
Logan B. Clark ◽  
Megan E. Shave ◽  
Melissa B. Hannay ◽  
Catherine A. Lindell
Keyword(s):  
Hole Size ◽  
Nest Box ◽  
American Kestrels ◽  
Entrance Hole

Supervision in Rehabilitation Counseling: Applications of Theory to Understand Supervision Style and the Supervisory Working Alliance

1995 ◽  
Vol 26 (2) ◽  
pp. 3-11
Author(s):  
Ruth Torkelson Lynch
Keyword(s):  
Rating Scales ◽  
Rehabilitation Counseling ◽  
Counseling Students ◽  
Theoretical Models ◽  
Supervisory Working Alliance ◽  
Major Theme ◽  
Rehabilitation Counselor ◽  
Perceptions Of Students ◽  
Supervisory Process ◽  
Different Levels

Recent years have evidenced an increased interest in developing theoretical models of supervision and empirically analyzing the supervisory process. The major theme underlying these efforts concerns the supervisory contexts - including style and relationships - which are most effective for trainees with varying needs and at different levels of experience. With the availability of models and instrumentation unique to supervision, it is now possible to more critically look at the perceptions of students and their respective supervisors regarding how supervision occurs. This study examines the current theoretical models of supervision, considers the linkages between the theoretical models and assessment instrumentation which has been developed, applies the models and rating scales toa sample of matched pairs of rehabilitation counseling students and their respective supervisors, and proposes applications for analyzing and improving supervision in rehabilitation counselor education.

Comparative variation of morphological and molecular evolution through geologic time: 28 S ribosomal RNA versus morphology in echinoids

1992 ◽  
Vol 338 (1286) ◽  
pp. 365-382 ◽  
Keyword(s):  
Molecular Evolution ◽  
Maximum Likelihood ◽  
Morphological Change ◽  
Rank Correlation ◽  
Morphological Data ◽  
Parsimony Analysis ◽  
Geological Time ◽  
Molecular Changes ◽  
Molecular Change ◽  
Rates Of Evolution

The comparatively good fossil record of post-Palaeozoic echinoids allows rates of morphological change to be estimated over the past 260 million years and com pared with rates of molecular evolution. Parsimony analysis of morphological data, based predominantly on skeletal characteristics, and parsimony, distance and maximum likelihood analyses of molecular data, from the first 380 bases from the 5' end of the 28 S rRNA molecule, for 10 species of echinoid produce congruent phylogenies. The m olecular sequence chosen is dem onstrably far from saturation and sister groups have divergence times ranging from about 15 to 260 Ma. Parsimony analysis allows the great majority of molecular and morphological apomorphies to be placed in one of 18 independent geological time intervals, providing a direct measure of rates of evolution for periods in the geological past. Because most molecular fixed point m utations in our sequences cannot be polarized unambiguously by outgroup comparison (making the outgroup states effectively random), distance and parsimony analyses both tend spuriously to root the echinoid tree on the longest internal branch. A topology identical to that derived from morphological data is, however, obtained using Maximum Likelihood and also parsimony analysis where outgroup rooting is restricted to more conserved regions. This is taken as the correct topology for assessing rates of evolution. Overall, both morphological and molecular changes show a m oderately strong correlation with time elapsed, but a weaker correlation with one another. Statistically significant differences in evolutionary rate are found between some, but not all, pair-wise comparisons of sister lineages for both molecular and morphological data. The molecular clock rate for echinaceans is three times faster than that for cidaroids and irregular echinoids. Spearm an’s rank correlation test, which requires only relative m agnitude of changes to be known, suggests that morphological change has a slightly better correlation with time than does molecular change, averaged over all ten species. However, when just echinaceans are considered an extremely good correlation is found between the num ber of molecular changes and time elapsed, whereas morphological change remains poorly correlated. Thus, molecular rates approxim ate to a clocklike model within restricted echinoid elades, but vary significantly between clades. Averaging results over all echinoids produces a correlation that is no better than the correlation between morphological change and time elapsed.

scholarly journals Identifying constraints in the evolution of primate societies

2013 ◽  
Vol 368 (1618) ◽  
pp. 20120342 ◽  
Author(s):  
Bernard Thierry
Keyword(s):  
Social Relations ◽  
Social System ◽  
Evolutionary History ◽  
Social Systems ◽  
Ecological Environment ◽  
Stabilizing Selection ◽  
Social Tolerance ◽  
Phylogenetic Methods ◽  
External Pressures ◽  
Different Levels

The evolutionary study of social systems in non-human primates has long been focused on ecological determinants. The predictive value of socio-ecological models remains quite low, however, in particular because such equilibrium models cannot integrate the course of history. The use of phylogenetic methods indicates that many patterns of primate societies have been conserved throughout evolutionary history. For example, the study of social relations in macaques revealed that their social systems are made of sets of correlated behavioural traits. Some macaque species are portrayed by marked social intolerance, a steep dominance gradient and strong nepotism, whereas others display a higher level of social tolerance, relaxed dominance and a weaker influence of kinship. Linkages between behavioural traits occur at different levels of organization, and act as constraints that limit evolutionary responses to external pressures. Whereas these constraints can exert strong stabilizing selection that opposes the potential changes required by the ecological environment, selective mechanisms may have the potential to switch the whole social system from one state to another by acting primarily on some key behavioural traits that could work as pacemakers.

scholarly journals Group Selection and Reciprocity among Kin

2009 ◽  
Vol 2 (1) ◽  
pp. 66-79 ◽  
Author(s):  
Neelesh Dahanukar ◽  
Milind Watve
Keyword(s):  
Kin Selection ◽  
Group Selection ◽  
Cooperative Behavior ◽  
Simple Game ◽  
Theoretical Models ◽  
Group Level ◽  
Group Competition ◽  
Different Types ◽  
Different Levels

The question how Darwinian mechanisms lead to the evolution of individually costly cooperative behavior has given rise to a number of hypotheses. However, attempts to build a synthesis where different types of mechanisms coexist and interact at different levels of selections are still scarce. Here we derive simple game theoretical models where the group level conflicts are resolved by group selection while simultaneously within group competition is resolved by kin selection and reciprocity. We show that none of the mechanisms, when alone, is as robust in evolving and maintaining cooperation as a synthesis of all. Furthermore, we show that initially within group conflicts can be overcome only by kin selection and not reciprocity. However, once common, different types of reciprocities can maintain high levels of cooperation even if average relatedness among individuals is lowered, groups become large, and the benefits of cooperation are reduced. Based on the synthesis we also propose a possible route to the evolution of social and eusocial systems.

scholarly journals Plastering mud around the entrance hole affects the estimation of threat levels from nest predators in Eurasian Nuthatches

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jiangping Yu ◽  
Li Zhang ◽  
Guodong Yi ◽  
Keqin Zhang ◽  
Jiyuan Yao ◽  
...  
Keyword(s):  
Nest Defence ◽  
Hole Size ◽  
Red Squirrels ◽  
Cavity Nesting ◽  
Sitta Europaea ◽  
Entrance Hole ◽  
Tamias Sibiricus ◽  
Threat Levels ◽  
Nest Predator ◽  
Nest Predators

Abstract Background For cavity-nesting birds, the nest entrance plays an important role in preventing predators from accessing nests. Several species of nuthatches use mud to narrow the entrance of cavities. In theory, the smaller the entrance hole size, the more effective it is against predators; however, few studies have tested whether narrowing the entrance hole size can affect the estimation of threat levels from nest predators in cavity-nesting birds. Methods Using dummy experiments, we tested whether Eurasian Nuthatches (Sitta europaea, narrow the entrance hole of cavities) and Cinereous Tits (Parus cinereus, do not narrow the entrance hole, as a control) perform different nest defence behaviours against Common Chipmunks (Tamias sibiricus, small nest predator) and Red Squirrels (Sciurus vulgaris, larger nest predator). Results Both nuthatches and tits exhibited stronger response behaviours (high dummy response scores) against chipmunks than against squirrels. Compared with tits, nuthatches exhibited more aggressive behaviours to chipmunks, but their responses to squirrels were similar. Conclusions Nest defence behaviours of nuthatches to chipmunks differed from tits, and the results suggested that nuthatches might estimate threat levels of nest predators according to their narrowed entrance-hole size.

scholarly journals The preeminent role of directional selection in generating extreme morphological change in Glyptodonts (Cingulata; Xenarthra)

2021 ◽  
Author(s):  
Fabio Andrade Machado ◽  
Gabriel Marroig ◽  
Alex Hubbe
Keyword(s):  
Morphological Evolution ◽  
Morphological Diversity ◽  
Directional Selection ◽  
Stabilizing Selection ◽  
Specialist Herbivore ◽  
Rates Of Evolution ◽  
Morphological Modification ◽  
Empirical Tests ◽  
Adaptive Zone

The prevalence of stasis on paleontological and comparative data has been classically taken as evidence of the strong role of stabilizing selection in shaping morphological evolution. When confronted against biologically informed predictions, empirical rates of evolution tend to fall below what is expected under genetic drift, suggesting that the signal for directional selection is erased at longer time scales. However, empirical tests of these claims are few and tend to focus on univariate traits, ignoring the potential roles of trait covariances in constraining evolution. Here we investigated the multivariate rates of morphological evolution in a fossil lineage that underwent extreme morphological modification, the glyptodonts. Contrary to what was expected, biologically informed models of evolution suggest a preeminent role of directional selection on the divergence of glyptodonts from living armadillos. Furthermore, the reconstruction of selection patterns shows that traits selected to generate a glytodont morphology are markedly different from those necessary to explain the extant armadillos' morphological diversity. Changes in both direction and magnitude of selection are probably tied to the invasion of a specialist-herbivore adaptive zone by glyptodonts. These results suggest that directional selection might have played a more important role in the evolution of extreme morphologies than previously imagined.

scholarly journals Determining the factors driving selective effects of new nonsynonymous mutations

2016 ◽  
Author(s):  
Christian D. Huber ◽  
Bernard Kim ◽  
Clare D. Marsden ◽  
Kirk E. Lohmueller
Keyword(s):  
Natural Populations ◽  
Evolutionary Genetics ◽  
Theoretical Models ◽  
Geometrical Model ◽  
Stabilizing Selection ◽  
Fundamental Parameter ◽  
Mutational Robustness ◽  
Medical Genomics ◽  
Multiple Phenotypes

AbstractThe distribution of fitness effects (DFE) of new mutations is a fundamental parameter in evolutionary genetics1–3. While theoretical models have emphasized the importance of distinct biological factors, such as protein folding4, back mutations5, species complexity6,7, and mutational robustness8 at determining the DFE, it remains unclear which of these models can describe the DFE in natural populations. Here, we show that the theoretical models make distinct predictions about how the DFE will differ between species. We further show that humans have a higher proportion of strongly deleterious mutations than Drosophila melanogaster. Comparing four categories of theoretical models, only Fisher’s Geometrical Model (FGM) is consistent with our data. FGM assumes that multiple phenotypes are under stabilizing selection, with the number of phenotypes defining a complexity of the organism. It suggests that long-term population size and cost of complexity drive the evolution of the DFE, with many implications for evolutionary and medical genomics.

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