Kazuya Kobayashi

Kazuya Kobayashi
Kyoto University | Kyodai · Field Science Education and Research Center

PhD

About

104
Publications
10,572
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
554
Citations
Citations since 2017
63 Research Items
433 Citations
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080
Introduction
Junior associate professor at the Field Science Education and Research Center, Kyoto University. Main research fields are Evolutionary Biology, Bioinformatics and Ecology. https://scholar.google.com/citations?user=yoUypoMAAAAJ
Additional affiliations
February 2017 - December 2017
Kyoto University
Position
  • Professor
April 2009 - March 2012
Hokkaido University
Position
  • PhD Student

Publications

Publications (104)
Article
Full-text available
Many sexual differences are known in human and animals. It is well known that females are superior in longevity, while males in athletic performances. Even though some sexual differences are attributed to the evolutionary tradeoff between survival and reproduction, the aforementioned sex differences are difficult to explain by this tradeoff. Here w...
Article
Full-text available
Sex is a paradoxical phenomenon because it is less efficient compared with asexual reproduction. To resolve this paradox we need a direct comparison between sexual and asexual forms. In many organisms, however, sexual and asexual forms do not occur in the same habitat, or at the same time. In a few cases where sexual and asexual forms are found in...
Article
Full-text available
Inclusive fitness theory, also known as kin selection theory, is the most general expansion of Darwin's natural selection theory. It is supported by female-biased investment by workers in the social Hymenoptera where relatedness to sisters is higher than to brothers because of haplodiploidy. However, a strong test of the theory has proven difficult...
Article
In colonies of the queen-polymorphic ant Vollenhovia emeryi, some colonies produce only long-winged (L) queens, while others produce only short-winged (S) queens. At four nuclear microsatellite loci, males in the S colony had alleles that were different from those of their queen. This suggests that the nuclear genome of males is not inherited from...
Article
Full-text available
Selfish genetic elements (SGEs) increase their transmission efficiency relative to the rest of the individual genome, which is often deleterious to individual fitness. Theoretical studies have suggested that intragenomic conflict over the sex ratio distortion between SGEs and the rest of the genome should lead to the evolution of sex-determining sy...
Article
Full-text available
Sex allocation is one of the most studied traits in evolutionary biology because its theoretical predictions match the empirical data. Here, using the Ryukyu dry-wood termite Neotermes sugioi, we investigated several factors that could bias the sex allocation in three populations (Okinawa, Ishigaki/Iriomote, and Yonaguni). Our survey showed that th...
Preprint
Full-text available
The origin of eusociality, altruistically foregoing personal reproduction to help others, has been a long-standing paradox ever since Darwin. Most eusocial insects and rodents likely evolved from subsocial precursors, in which older offspring "helpers" contribute to the development of younger siblings without a permanent sterile caste. The driving...
Article
Synergy is known to be vital for the group collaboration among non-kin individuals. In order to evaluate the condition of synergy that initiates group living, we build a model of food intake based on three types of functional response. We show that type III functional response is prerequisite for synergy to allow group living. The optimal number of...
Chapter
Sexual reproduction is a common feature of eukaryotes which include dominant members in many biological communities, especially on the hot spots of biodiversity. Given its ubiquity, sex may have an important role to characterize the community structures. In this chapter, we explore the possibility that sex plays an important role to sustain the com...
Article
Full-text available
Sex‐determination systems often show remarkable diversity in upstream signals, although downstream genes are broadly conserved. Therefore, the downstream genes have been investigated in various taxa, but the most upstream signals determining sex in insects have been well‐described mainly in model organisms, including fruit flies and honey bees, and...
Article
Evolutionary ecological theory suggests that selection arising from interactions with conspecifics, such as sexual and kin selection, may result in evolution of intraspecific conflicts and evolutionary ‘tragedy of the commons’. Here, we propose that such an evolution of conspecific conflicts may affect population dynamics in a way that enhances spe...
Article
Full-text available
Sexual dimorphism is a pervasive form of variation within species. Understanding how and why sexual dimorphism evolves would contribute to elucidating the mechanisms underlying the diversification of traits. In flowering plants, pollinators are considered a driver of sexual dimorphism when they affect female and male plant fitness in distinct ways....
Article
Full-text available
We surveyed the nest site characteristics, density and success rates of breeding crows in the study site in and around Hokkaido University campus (253.6 ha) in 2003. This site has rich vegetation in a highly urbanized area of Sapporo City. The results were compared with those of a previous study in Tokyo. Two species of crows (Jungle and Carrion Cr...
Article
To clarify how intraspecific competition over fertilization affects population growth rates and community dynamics in plants, Kobayashi (Journal of Ecology, 2019) proposed analytical and simulation models based on the game theory. Within this framework, it is suggested that the negative density‐dependent effect arising from sexual selection is an i...
Article
Full-text available
Self-sacrifice is very rare among organisms. Here, we report a new and astonishing case of adaptive self-sacrifice in a polyembryonic parasitic wasp, Copidosoma floridanum. This wasp is unique in terms of its larval cloning and soldier larvae. Male clone larvae have been found to be killed by female soldier larvae, which suggests intersexual confli...
Article
Sexual reproduction is a mysterious phenomenon. Most animals and plants invest in sexual reproduction, even though it is more costly than asexual reproduction. Theoretical studies suggest that occasional or conditional use of sexual reproduction, involving facultative switching between sexual and asexual reproduction, is the optimal reproductive st...
Article
Mechanisms for maintaining biodiversity are still unclear despite considerable research. The classic theory predicts that stable co‐occurrence of competitive species requires niche differentiation. In fact, the co‐occurring species are often differentiated from each other. However, the neutral theory assuming equivalence of the reproductive rate of...
Article
Full-text available
Identifying traits that facilitate species introductions and successful invasions of ecosystems represents a key issue in ecology. Following their establishment into new environments, many non‐native species exhibit phenotypic plasticity with post‐introduction changes in behavior, morphology or life history traits that allow them to overcome the pr...
Article
Full-text available
Aging is associated with the accumulation of DNA damage. High expression of DNA repair genes has been suggested to contribute to prolonged lifespan in several organisms. However, the crucial DNA repair genes contributing to longevity remain unknown. Termite kings have an extraordinary long lifespan compared with that of non-reproductive individuals...
Article
Full-text available
Background: Sexual reproduction is the norm in almost all animal species, and in many advanced animal societies, both males and females participate in social activities. To date, the complete loss of males from advanced social animal lineages has been reported only in ants and honey bees (Hymenoptera), whose workers are always female and whose mal...
Article
Eusocial insects display a caste system in which different castes are morphologically and physiologically specialised for different tasks. Recent studies have revealed that epigenetic modifications, including DNA methylation and histone modification, mediate caste determination and differentiation, longevity, and polyethism in eusocial insects. Alt...
Article
Full-text available
Eusocial insects exhibit the most striking example of phenotypic plasticity. There has been a long controversy over the factors determining caste development of individuals in social insects. Here we demonstrate that parental phenotypes influence the social status of offspring not through genetic inheritance but through genomic imprinting in termit...
Article
Full-text available
In most organisms, superoxide dismutases (SODs) are among the most effective antioxidant enzymes that regulate the reactive oxygen species (ROS) generated by oxidative energy metabolism. ROS are considered main proximate causes of aging. However, it remains unclear if SOD activities are associated with organismal longevity. The queens of eusocial i...
Data
Figure S2: maximum likelihood molecular phylogenetic tree of Cu/Zn-SOD sequences. We inferred the evolutionary history of the Cu/Zn-SODs using the maximum likelihood method based on the Whelan and Goldman model. The tree with the highest log likelihood (−2592.76) is shown. The percentage of trees in which the associated taxa clustered together is s...
Data
Figure S1: alignment and structure conservation of Mn-SOD sequences. Multiple sequence alignment of Homo sapiens, Mus musculus, Caenorhabditis elegans, Drosophila melanogaster, Zootermopsis nevadensis, and Reticulitermes speratus. Conserved functional residues are highlighted in bold characters in grey (circled M = manganese-binding site).
Article
Full-text available
The study of collective decision-making spans various fields such as brain and behavioural sciences, economics, management sciences, and artificial intelligence. Despite these interdisciplinary applications, little is known regarding how a group of simple 'yes/no' units, such as neurons in the brain, can select the best option among multiple option...
Article
Full-text available
Insects protect themselves from microbial infections through innate immune responses, including pathogen recognition, phagocytosis, the activation of proteolytic cascades, and the synthesis of antimicrobial peptides. Termites, eusocial insects inhabiting microbe-rich wood, live in closely-related family groups that are susceptible to shared pathoge...
Data
Differential expression of apolipophorinIIIs, SPIs, calpains, and LRPs among castes. The heatmap indicates the differential expression of three apolipophorinIIIs, seven SPIs, five calpains, and eight LRP transcripts among castes. Abbreviations are referred to in Fig 1. Relative expression level indicates the mean normalized Count per Million (CPM),...
Data
Differential expression of other signalling proteins among castes. The heatmap indicates the differential expression of two MHA and three 14-3-3 protein transcripts among castes. Abbreviations are referred to in Fig 1. Relative expression level indicates the mean normalized Count per Million (CPM), ranging from black (scaled expression of 0) to whi...
Data
Summary results of BLAST homology searches. BLAST homology searches of amino acid sequences in R. speratus were performed on the sequences of 6 termites (Z. nevadensis, C. secundus, C. formosanus, R. flavipes, R. chinensis, N. comatus), 2 cockroaches (P. americana, E. sinensis), a beetle (T. castaneum), a honeybee (A. mellifera), a silk moth (B. mo...
Data
Statistical results of differential expression among castes for each gene. Comparison of normalized counts per million (CPM) among castes (A: alates, Y: young primary kings (PKs) and queens, M: mature PKs and secondary queens (SQs), S: soldiers, W: workers) was conducted using edgeR package. Bold letters mean significant difference (FDR < 0.05). “C...
Data
Statistical results of age-dependent expression changes in male or female reproductives. Comparison of normalized counts per million (CPM) among male reproductives (alates (A), young primary kings (Y) and mature primary kings (M)) or female ones (alates (A) and young primary queens (Y)) was conducted using edgeR package. Bold letters mean significa...
Data
Statistical results of differential expression between reproductive and neuter castes and between males and females. Comparison of normalized counts per million (CPM) between reproductive statuses (reproductive castes: alates, young PKs and PQs, and mature PKs and SQs; neuter castes: soldiers and workers) and between sexes was conducted by edgeR pa...
Data
Statistical results of sexual difference of expression in each caste. Comparison of normalized counts per million (CPM) between sexes in each caste (PK: primary king, PQ: primary queens, SQ: secondary queen) was conducted using edgeR package. Bold letters mean significant difference (FDR < 0.05), and red and blue letters indicate the female- and ma...
Data
Differential expression of other immune-related genes among castes. The heatmap indicates the differential expression of transcripts of 11 carboxypeptidases, 2 metacaspase-like cysteine peptidases, 14 cysteine-rich proteases, 4 ferritins, 3 transferrins, and 10 other effectors among castes. Abbreviations are referred to in Fig 1. Relative expressio...
Data
Molecular phylogenetic analysis of lysozyme sequences. The maximum likelihood trees based on the amino acid sequences of C- and P-type lysozymes (a) and those of I-type lysozymes (b) are shown. These trees include the lysozyme sequences of termites (C. formosanus, R. speratus, and Z. nevadensis) and the American cockroach (Periplaneta americana) ob...
Article
Full-text available
Biodiversity has long been a source of wonder and scientific curiosity. Theoretically, the co-occurrence of competitive species requires niche differentiation, and such differences are well known; however, the neutral theory, which assumes the equivalence of all individuals regardless of the species in a biological community, has successfully recre...
Article
Full-text available
The trade-off between reproduction and longevity is known in wide variety of animals. Social insect queens are rare organisms that can achieve a long lifespan without sacrificing fecundity. The extended longevity of social insect queens, which contradicts the trade-off, has attracted much attention because it implies the existence of an extraordina...
Data
Measurement of CAT activity in several insects. Termite queens (n = 12) had higher CAT activity than D. melanogaster adult males (n = 3; P = 0.013), D. melanogaster adult females (n = 3; P = 0.011), B. mori larvae males (n = 3; P = 0.016), B. mori larvae females (n = 3; P = 0.011), B. mori pupae males (n = 3; P = 0.014), B. mori pupae females (n =...
Data
Sequences of primers used in this study. (DOCX)
Data
Target gene information for this study. (DOCX)
Data
Results of Thiobarbituric acid reactive substances (TBARS) assay. TBARS assays demonstrated that queens had lower levels of malondialdehyde (MDA) than workers (P = 0.002) and nymphs (P = 0.002) in control conditions. Moreover, after UV irradiation, we found that queens also had a potential to maintain lower MDA levels than workers (P < 0.001) and n...
Data
Survival rate after UV irradiation in R. speratus workers. Average survival was calculated immediately after 0, 5, 10, 15, 20, 15, and 30 min UV-B irradiation (312 nm, 10.4 kJ/ m2; Vilber Lourmat TF-20M). Although we observed 100%, 98%, and 93% survival of workers after 0–15, 20, and 25 min irradiation, respectively, workers irradiated for 30 min s...
Data
Results of unsaturated fatty acids quantification assay. Queens had higher levels of UFAs susceptible to oxidation than non-reproductive workers (P = 0.003) but not nymphs (P = 0.719). These data suggested why irradiation cannot increase the malondialdehyde (MDA) levels in workers (S3 Fig). We used pooled samples, shown as below (S1 Table), for 3 r...
Data
Measurement of Prx activity in several insects. There is no difference in Prx activity between termite queens and other insects. Termite queens had almost the same activity as D. melanogaster adult males (n = 3; P = 0.396), D. melanogaster adult females (n = 3; P = 0.359), B. mori larvae males (n = 3; P = 0.267), B. mori larvae females (n = 3; P =...
Data
The level of GPX genes RsGPX and RsPHGPX expression in R. speratus. The levels of GPx gene expression were equal or lower in queens compared with non-reproductive individuals. W, workers; S, soldiers; N, nymphs; Q, queens (A) Queens (n = 6) had no significant difference in the levels of RsGPX expression in comparison with soldiers (n = 12; P = 0.06...
Article
Full-text available
Despite being a central issue in evolutionary biology, few studies have examined the stasis of characters in populations with no gene flow. A possible mechanism of such stasis is stabilizing selection with similar peaks in each population. This study examined the evolutionary patterns of morphological characters with and without strong selection in...
Data
Full-text available
Inclusive fitness theory, also known as kin selection theory, is the most general expansion of Darwin’s natural selection theory. It is supported by female-biased investment by workers in the social Hymenoptera where relatedness to sisters is higher than to brothers because of haplodiploidy. However, a strong test of the theory has proven difficult...
Conference Paper
The sophisticated colony organization of eusocial insects is primarily maintained through the utilization of pheromones. The regulation of these complex social interactions requires intricate chemoreception systems. The recent publication of the genome of Zootermopsis nevadensis opened a new avenue to study molecular basis of termite caste systems....
Article
Full-text available
Parthenogenesis is a relatively rare reproductive mode in nature compared to sex. In social insects, the evolution of parthenogenesis has a notable impact on their life histories. Some termites with parthenogenetic ability produce numerous non-dispersing supplementary queens asexually, whereas other castes are produced via sexual reproduction. This...
Article
Full-text available
The evolution of sexual reproduction remains a fascinating enigma in biology. Theoretically, populations of sexual organisms investing half of their resources into producing male offspring that don't contribute to reproduction should grow at only half the rate of their asexual counterparts. This demographic disadvantage due to male production is kn...
Article
Full-text available
Optimality theory predicts the maximization of productivity in social insect colonies, but many inactive workers are found in ant colonies. Indeed, the low short-term productivity of ant colonies is often the consequence of high variation among workers in the threshold to respond to task-related stimuli. Why is such an inefficient strategy among co...
Article
Full-text available
The sophisticated colony organization of eusocial insects is primarily maintained through the utilization of pheromones. The regulation of these complex social interactions requires intricate chemoreception systems. The recent publication of the genome of Zootermopsis nevadensis opened a new avenue to study molecular basis of termite caste systems....
Data
Expression levels of ORs other than RsOr3. Comparison of the mean CPM of OR transcripts among castes and between the sexes (black: female, white: male) of each caste. Young reproductives refer to young PQs and PKs. Mature reproductives indicate mature secondary queens and mature PKs. Error bars denote standard errors. Results of statistical analyse...
Data
Length frequency distribution of R. speratus contigs. Histogram presentation of sequence-length distribution for significant matches that was found. The horizontal axis indicates sequence sizes from 200 to ≥3000 nucelotides. The vertical axis indicates the number of contigs for each size. (EPS)
Data
Phylogenetic tree of ORCO sequences from various insects. The tree was constructed based on the ORCO sequence of R. speratus and that of other insect species obtained from the protein database of NCBI. The evolutionary history was inferred using the Maximum Likelihood method based on the JTT matrix-based model [55]. The tree with the highest log li...
Data
Expression levels of IRs other than RsIR1 and RsIR11. Comparison of the mean CPM of IR transcripts among castes and between the sexes (black: female, white: male) of each caste. Young reproductives are referred to as young PQs and PKs. Mature reproductives indicate mature secondary queens and mature PKs. Error bars denote standard errors. Results o...
Data
Summary results of blast homology searches. Blast homology searches of amino acid sequences in R. speratus were performed on the sequences of a grasshopper (L. migratoria), a cockroach (P. americana), a termite (Z. nevadensis), bugs (R. prolixus and A. lineolatus), a honeybee (A. mellifera), beetles (T. castaneum, M. caryae, H. oblita, and D. ponde...
Data
Statistical results of differential expression levels among castes and sexes for each gene. Comparison of normalized counts per million (CPM) among castes and sexes was conducted using edgeR package. Bold letters means significant difference (FDR < 0.05). LR: likelihood ratio, FDR: false discovery rate, OR: odorant receptor, GR: gustatory receptor,...