Symposium proposal | |
Organizer: | Jun Kitano (National Institute of Genetics) |
Co-organizer: | Yo Y. Yamasaki (National Institute of Genetics) |
Speciation is the evolution of reproductive isolation. Because reproductive isolation is a continuous phenomenon rather than an all-or-nothing one, any species pairs can be placed along an axis called the "speciation continuum." The term "speciation continuum" is used in an increasing number of recent papers. However, it is often vague what is the axis of speciation continuum. We revisit this issue and then discuss how speciation proceeds along the continuum and what factors complete speciation. Dr. Mark Ravinet from University of Nottingham (UK) will talk about the definition of speciation continuum and set a stage for this symposium. Dr. Claudia Bank from University of Bern (Switzerland) will talk about her theoretical work on progress along the speciation continuum towards completion. Dr. Aya Takahashi from Tokyo Metropolitan University (Japan) will talk about her empirical genetic studies on the evolution of reproductive isolation in Drosophila species pairs. We will select other speakers, considering the balance in terms of gender, geographical location, carrier stage, and research topics (theoretical vs empirical or taxonomic groups etc), to cover diverse opinions in this research field. |
S5-1
What do we mean when we talk about a speciation continuum?
Mark Ravinet1, Sean Stankowski2
1University of Nottingham, UK
2IST Austria, Austria
2IST Austria, Austria
Concepts and definitions are fundamentally important to speciation research. They help us frame our thinking and our understanding of the processes and phenomena we observe or infer. This is especially true for speciation, a process that in most cases occurs on a timescale too great for us to see to completion. The idea of a speciation continuum as model to reconstruct the process of speciation has become increasingly popular over the last two decades, yet there is surprisingly little consensus about how it is defined or what it can be used for to help improve our understanding of speciation. Here I will examine what it is we mean when we talk about the speciation continuum, drawing on a survey that was conducted of speciation researchers to actually quantify the level of understanding of the concept. I will explore what the speciation continuum can and can’t tell us. Finally, I will propose our straightforward definition for the speciation continuum and explain how it can be used to understand how reproductive isolation evolves.
S5-2
Evolutionary consequences of hybridization
Claudia Bank1
1Institute of Ecology and Evolution, University of Bern, Switzerland
2Swiss Institute of Bioinformatics
3Gulbenkian Science Institute, Portugal
2Swiss Institute of Bioinformatics
3Gulbenkian Science Institute, Portugal
Hybridization is common in nature. Empirical evidence suggests that populations of hybrids can persist for many generations and occasionally even develop into separate species (hybrid speciation). In my talk, I will present theoretical work in which we study the probability of homoploid hybrid speciation by sorting of parental hybrid incompatibilities, and a new statistical method to detect such hybrid incompatibilities in genomic data from hybrid populations. We find that the location and arrangement of interacting genes in the genome is a major determinant of the fate of the hybrid population, and that intermediate recombination distances are most amenable to hybrid speciation. Screening genomic data from hybrid fish, we identify many candidate incompatibilities both within and between chromosomes.
S5-3
Mechanical incompatibility and reproductive isolation between a pair of fruit-damaging Drosophila species
Aya Takahashi1,2
1Department of Biological Sciences, Tokyo Metropolitan University
2Research Center for Genomics and Bioinformatics, Tokyo Metropolitan University
2Research Center for Genomics and Bioinformatics, Tokyo Metropolitan University
Mechanical incompatibility between female and male genitalia during copulation is a form of barrier that prevents gene flow between species. The morphology of genital structures is known to evolve rapidly, especially in males of various animal taxa, including fruit flies. We have shown that such mechanical reproductive isolation is present between Drosophila suzukii and its sibling species, D. subpulchrella, and that it is a consequence of the evolution of the serrated and elongated ovipositors in the females of the former species, which are used to pierce the hard skin of ripening fruits. The hard ripening fruits are not preferred by most other fruit flies that lay eggs onto soft decaying fruits. The elongation of the ovipositors in D. suzukii females has forced the males to adjust their copulating postures and coupling positions of their genitalia, resulting in incompatible shapes with those of its sibling species. The genital structures involved in this incompatibility were inferred from a detailed observation of the spatial configuration of the coupled genitalia during copulation. Thus, we conducted a QTL mapping analysis to elucidate the genetic bases of the interspecific differences in genital morphologies involved in this mechanical isolation. Interestingly, interspecific differences of many morphological traits mapped to a particular genomic region in these species. The peculiar characteristics of this region may be responsible for the accumulation of genetic changes underlying the rapid morphological divergence of the genital structures involved in mechanical isolation between these species.
S5-4
Parallel allochronic speciation by old genetic variants
Satoshi Yamamoto1,2, Seiya Kudo3, Nozomu Sato4, Hiroshi Ikeda3, Tomochika Fujisawa5, Teiji Sota1
1Department of Zoology, Graduate School of Science, Kyoto University
2Institute for Agro-Environmental Science, NARO
3Faculty of Agriculture and Life Science, Hirosaki University
4Faculty of Urban Environmental Sciences, Tokyo Metropolitan University
5Center for Education and Research of Data Science, Shiga University
2Institute for Agro-Environmental Science, NARO
3Faculty of Agriculture and Life Science, Hirosaki University
4Faculty of Urban Environmental Sciences, Tokyo Metropolitan University
5Center for Education and Research of Data Science, Shiga University
Parallel allochronic speciation by old genetic variants
Parallel speciation is a phenomenon in which the same pattern of speciation occurs in independent lineages. Repeated evolution of the same reproductive isolation in similar environments provides strong evidence that natural selection promotes speciation. However, even in the same situation, some taxa show parallel speciation, while others do not. Therefore, we have to understand factors that allow the divergence of reproductive isolation traits other than natural selection. Here we report that genetic variations established during an old speciation event promoted a second new speciation event using Japanese winter geometrid moths (Inurois punctigera), in which reproductive isolation is caused by differentiation of reproductive timing.
I. punctigera reproduce in cold season (i.e., winter), and their reproductive season is divided in early- and late-winter seasons in northern Japan and the high-altitude areas of southern Japan due to the harsh mid-winter environment. Seasonal races in those regions are reproductively isolated although they occur in sympatry. We collected adult moths in three localities: northern, central and southern Japan. Localities of northern and southern Japan showed separated reproductive timing into early- and late-winter, whereas the central Japan population showed a continuous reproductive season during winter. Phylogenetic analysis suggested that divergence of reproductive timing in high-altitude regions of southern Japan is independent event from that in northern Japan. GWAS and genome scan revealed that six genomic regions were associated with reproductive timing of this species. Furthermore, those reproductive timing-related genes were diverged between early- and late-winter types of I. punctigera. ADMIXTURE analysis suggested that central and southern Japan populations were admixture of early- and late-winter moths in northern Japan. In the central Japan population (i.e., continuous reproductive season), individuals emerge early in their reproductive season had alleles of the early-winter type for the six reproductive timing-related genes. Also, individuals emerge late had alleles of the late-winter type. In addition, individuals emerge in intermediate season in central Japan have both early- and late-winter alleles, indicating those old genetic variants cause standing variation of reproductive timing in the central Japan population. Our finding suggests that early- and late-winter I. punctigera have been diverged under harsh mid-winter environment in northern Japan but they were fused in central Japan where winter condition is much milder than northern Japan. The standing variation in reproductive timing retained in the admixed lineage facilitated further reproductive timing divergence under harsh mid-winter environment in high-altitude regions of southern Japan.
S5-5
Identifying evolutionary driver and disentangling population history among hybridizing zone of two Phasianidae birds
Pengcheng Wang1, Nan Wang2, Zhengwang Zhang3
1Institute of Zoology, Chinese Academy of Sciences
2School of Ecology and Nature Conservation, Beijing Forestry University
3College of Life Sciences, Beijing Normal University
2School of Ecology and Nature Conservation, Beijing Forestry University
3College of Life Sciences, Beijing Normal University
Hybrid zones offer insight into the speciation process by providing a rare opportunity to identify the evolutionary drivers of lineage divergence. Here, we integrate population genomic data (19,960 SNPs), generalized dissimilarity modeling, and dense geographic sampling (154 samples) to infer population structure and demographic history, document hybrid zones, and explore the evolutionary drivers of lineage divergence in Tibetan Eared Pheasant (Crossoptilon harmani) and White Eared Pheasant (C. crossoptilon). Our population genomic data suggest that C. crossoptilon consists of two genetic groups, which correspond to the subspecies C. c. dolani and C. c. crossoptilon. We document two hybrid zones, one between C. c. dolani and C. harmani in the eastern Tibetan Plateau, and another between C. c. dolani and C. c. crossoptilon in Hengduan mountains. Demographic inference showed that both hybrid zones formed following secondary contact. Genome-wide hybrid index and heterozygosity revealed that both hybrid zones lack early-generation (F1) hybrids and are instead composed of late-generation hybrids and backcrosses. Generalized dissimilarity models uncovered geographical distance, not environmental distance or landscape resistance, as the best predictor of genetic differentiation between populations, suggesting natural selection has been less important than genetic drift in driving genetic divergence among the populations of C. harmani and C. crossoptilon. To our knowledge, it is the first documentation of Galliform hybrid zones with population genomic data. Collectively, our findings contribute to a growing literature on the ecological and genetic basis of speciation, and represent the detailed investigation into the drivers of genetic divergence in pheasants.