Kyle Summers - Academia.edu (original) (raw)

Papers by Kyle Summers

Evolutionary ecology, Apr 12, 2024

bioRxiv (Cold Spring Harbor Laboratory), Jul 21, 2019

Assortative or disassortative aggression – when individuals display more aggression towards consp... more Assortative or disassortative aggression – when individuals display more aggression towards conspecifics with similar or different phenotypic characteristics – can either maintain polymorphisms or facilitate gene flow between populations depending on which direction the aggression is aimed. Deciphering which factors elicit or prevent aggression is crucial to improving our knowledge of the origin and maintenance of reproductive barriers and subsequent speciation. The Peruvian mimic poison frog, Ranitomeya imitator, is a monogamous and territorial species that has evolved into four distinct color-pattern morphs in a mimetic radiation. Here we use historical landscape genetic data and competition trials between male individuals sourced from different populations and color-pattern morphs to show that the level of aggression between individuals is not associated with color morph or body size but rather with source population. Individuals spent more time in combat with individuals from th...

Journal of Evolutionary Biology

bioRxiv (Cold Spring Harbor Laboratory), Apr 21, 2023

Parental care has evolved repeatedly and independently across animals. While the ecological and e... more Parental care has evolved repeatedly and independently across animals. While the ecological and evolutionary significance of parental behavior is well recognized, underlying mechanisms remain poorly understood. We took advantage of behavioral diversity across closely related species of South American poison frogs (Family Dendrobatidae) to identify neural correlates of parental behavior shared across sexes and species. We characterized differences in neural induction, gene expression in active neurons, and activity of specific neuronal types in three species with distinct parental care patterns: male uniparental, female uniparental, and biparental. We identified the medial pallium and preoptic area as core brain regions associated with parental care, independent of sex and species. Identification of neurons active during parental care confirms a role for neuropeptides associated with parental care in other vertebrates as well as identifying novel candidates. Our work highlights the p...

Frontiers in Ecology and Evolution

Darwin posited that social competition among conspecifics could be a powerful selective pressure.... more Darwin posited that social competition among conspecifics could be a powerful selective pressure. Alexander proposed a model of human evolution involving a runaway process of social competition based on Darwin’s insight. Here we briefly review Alexander’s logic, and then expand upon his model by elucidating six core arenas of social selection that involve runaway, positive-feedback processes, and that were likely involved in the evolution of the remarkable combination of adaptations in humans. We discuss how these ideas fit with the hypothesis that a key life history innovation that opened the door to runaway social selection, and cumulative culture, during hominin evolution was increased cooperation among individuals in small fission-fusion groups.

Animal Behaviour, 2016

Begging, the behavior by which offspring solicit food and parental care, is a good model for stud... more Begging, the behavior by which offspring solicit food and parental care, is a good model for studying parent-offspring conflict (POC) and the evolution of signaling. According to POC theory, conflict arises over the amount of parental investment provided, with offspring soliciting more resources than parents are selected to give

Aim Comparison of Epipedobates bassleri (Myers, 1987), which occurs on highaltitude mountain ridg... more Aim Comparison of Epipedobates bassleri (Myers, 1987), which occurs on highaltitude mountain ridges ('sky peninsulas') in the Andean transition zone and demonstrates high levels of divergence in colouration among populations, and Epipedobates hahneli (Schulte, 1999), which occurs throughout the lowland regions of the Amazon basin and is morphologically conserved, using phylogenetic analysis of mitochondrial sequence data and comparison of colour pattern. Location Central cordilleras of Peru (near Tarapoto, San Martin). Methods DNA was extracted from individuals of E. bassleri from the central cordilleras of Peru, and from individuals of E. hahneli from across Peru. The cytochrome b mitochondrial gene region was amplified and sequenced for individuals of each species, and phylogenetic analysis was carried out using Bayesian inference. Genetic distances among populations and geographic distances of each species were examined and compared using Mantel tests. Parametric bootstrapping was used to test the monophyly of E. bassleri. Results Epipedobates bassleri formed a well-supported monophyletic group and showed higher levels of genetic divergence among populations than was shown among populations of E. hahneli from the same region. Distinct clades representing different geographic regions were recovered for E. hahneli. Levels of divergence among more geographically distant populations of E. hahneli were higher than levels of divergence among E. bassleri populations. We found a significant correlation between genetic divergence and geographic distance as measured along a 1000-m contour line, but not as measured by direct routes (crossing putative biogeographical barriers). Main conclusions Levels of genetic divergence were higher among populations of morphologically conservative E. hahneli than among populations of morphologically variable E. bassleri, suggesting rapid divergence in colouration among populations of E. bassleri. These patterns support previous arguments concerning the role of the montane transition zone between the high mountains and lowlands in divergence and speciation. High levels of both genetic and phenotypic divergence among populations of E. bassleri indicate that ecological or behavioural factors may be responsible for the high levels of colour variation seen among E. bassleri, but not among E. hahnleli, populations.

PeerJ

Aposematism continues to be a phenomenon of central interest in evolutionary biology. The life hi... more Aposematism continues to be a phenomenon of central interest in evolutionary biology. The life history of the mimic poison frog, Ranitomeya imitator, relies heavily on aposematism. In order for aposematic signals to be effective, predators must be able to learn to avoid the associated phenotype. However, in R. imitator, aposematism is associated with four different color phenotypes that mimic a complex of congeneric species occurring across the mimic frog’s geographic range. Investigations of the underlying mechanics of color production in these frogs can provide insights into how and why these different morphs evolved. We used histological samples to examine divergence in the color production mechanisms used by R. imitator to produce effective aposematic signals across its geographic range. We measured the coverage of melanophores and xanthophores (the area covered by chromatophores divided by total area of the skin section) in each color morph. We find that morphs that produce ora...

PLOS ONE

Neural crest cell genes control the migration of neural crest cells to multiple parts of developi... more Neural crest cell genes control the migration of neural crest cells to multiple parts of developing vertebrate embryos. A recent hypothesis posits that the “domestication syndrome” characteristic of domesticated animals is driven by selection for tameness acting on neural crest cell genes, particularly those affecting cell migration. This is posited to explain why this syndrome involves many disparate phenotypic effects. These effects can be connected to deficits in neural crest cell migration. This hypothesis predicts that patterns of selection on these neural crest cell genes will differ between domesticated species and related wild species. Specifically, it predicts higher levels of positive selection on these genes in domesticated species, relative to closely related wild species. Here we test this prediction in a comparative framework. We obtained DNA sequences from a public database (NCBI) for eleven key neural crest cell genes from a set of thirty domesticated vertebrates and...

Encyclopedia of Evolutionary Psychological Science, 2021

condition-specific and asymmetric competition in a

Schizophrenia poses an evolutionary-genetic paradox because it exhibits strongly negative fitness... more Schizophrenia poses an evolutionary-genetic paradox because it exhibits strongly negative fitness effects and high heritability, yet it persists at a prevalence of approximately 1% across all human cultures. Recent theory has proposed a resolution: that genetic liability to schizophrenia has evolved as a secondary consequence of selection for human cognitive traits. This hypothesis predicts that genes increasing the risk of this disorder have been subject to positive selection in the evolutionary history of humans and other primates. We evaluated this prediction using tests for recent selective sweeps in human populations and maximum-likelihood tests for selection during primate evolution. Significant evidence for positive selection was evident using one or both methods for 28 of 76 genes demonstrated to mediate liability to schizophrenia, including DISC1, DTNBP1 and NRG1, which exhibit especially strong and well-replicated functional and genetic links to this disorder. Strong evidence of non-neutral, accelerated evolution was found for DISC1, particularly for exon 2, the only coding region within the schizophrenia-associated haplotype. Additionally, genes associated with schizophrenia exhibited a statistically significant enrichment in their signals of positive selection in HapMap and PAML analyses of evolution along the human lineage, when compared with a control set of genes involved in neuronal activities. The selective forces underlying adaptive evolution of these genes remain largely unknown, but these findings provide convergent evidence consistent with the hypothesis that schizophrenia represents, in part, a maladaptive by-product of adaptive changes during human evolution.

Comparative and experimental field studies of species in the genus Dendrobates were carried out t... more Comparative and experimental field studies of species in the genus Dendrobates were carried out to test predictions from two hypotheses that propose to explain the selective pressure causing female-female competition for mates in species of Dendrobates with male parental care. The sex role reversal hypothesis (Trivers, 1972; Wells, 1978) proposes that males invest so much time and energy in parental care that receptive males are rare relative to receptive females, and females compete to find and mate with receptive males. The parental quality hypothesis (Summers, 1989) proposes that females compete to monopolize the parental effort of particular males, because they potentially suffer a cost when their mates care for the offspring of other females. Comparisons of males and females in species with male parental care (Dendrobates auratus and Dendrobates leucomelas) did not support the sex role reversal hypothesis, but were consistent with predictions of the parental quality hypothesis: Males defended territories to attract and mate with females; females did not compete for mates more aggressively than males; males were less selective about mating than females; some females guarded their mates for long periods (over a month). Comparisons between species with male (D. leucomelas) and female (Dendrobates histrionicus) parental care contradicted predictions from the sex role reversal hypothesis, but were consistent with predictions from the parental quality hypothesis: Male D. histrionicus did not compete for mates more aggressively than male D. leucomelas; male D. leucomelas were not more selective about mating than male D. histrionicus, female D. leucomelas and D. histrionicus were both selective about mating; female D. leucomelas associated with, and competed for particular males, whereas female D. histrionicus did not. Observations of male parental care revealed that males will deposit more than one tadpole in the same pool. Field experiments demonstrated that increasing the number of tadpoles in a pool decreases tadpole growth rate and survivorship. Hence, male polygyny potentially imposes a cost on offspring growth and survivorship, and consequently on female reproductive success, as predicted by the parental quality hypothesis.Ph.D.Biological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105291/1/9116304.pdfDescription of 9116304.pdf : Restricted to UM users only

Parent-offspring conflict theory predicts continuing conflict between maternal and fetal interest... more Parent-offspring conflict theory predicts continuing conflict between maternal and fetal interests during pregnancy. This is thought to contribute to risks of diseases like hypertension and preeclampsia during pregnancy. Genes expressed in the maternal and fetal genomes are predicted to have conflicting effects on various aspects of maternal physiology, including blood pressure. The genes are predicted to undergo continuous antagonistic coevolution, which should leave signals of positive selection in the short and long term. We tested for such signals in the FLT1 gene (previously argued to be a locus involved maternal-fetal conflict), and in several other suites of genes found to be significantly associated with preeclampsia in large-scale GWAS analyses. The FLT1 gene showed strong signals of positive selection at multiple levels of analysis. The suites of genes did not show an overall enhanced probability of positive selection (relative to a control set of genes), but a number of g...

Richard D. Alexander, T.H. Hubbell Distinguished University Professor of Biology at the Universit... more Richard D. Alexander, T.H. Hubbell Distinguished University Professor of Biology at the University of Michigan, Curator of Insects at the Museum of Zoology there, a member of the National Academy of Sciences, and a pioneer in the study of the evolutionary basis of human behavior, died on the 20th of August 2018 at age 88. Alexander is survived by his wife of 68 years Lorraine Kearnes Alexander; his brother Noel (Donna); his daughters Susan (Sarita) and Nancy; his grandchildren Morgan, Lydia, Lincoln, and Winona; and his great-grandson Ezekiel; several nieces and nephews; and “young” Tom Pyle who lived with Alexander's family for years while growing up (Fig. 1). Alexander's life is an iconic American success story. He rose from humble beginnings, having been born on November 18th, 1929 and raised on a small, single-family farm in rural Illinois, without electricity or indoor plumbing. Although his early schooling took place in a one room school house, and he had no thought of...