When to help juveniles, adults, or both: analyzing the evolutionary models of stage-structured mutualism

Mutualism is common in nature and is crucial for population dynamics, community structure, and ecosystem functioning. Studies have recently pointed out that life-history stage structure (e.g., juveniles and adults) is a key factor to better understand the ecological consequences of mutualism (termed stage-structured mutualism). Despite the potential importance, little is known about what kinds of stage-structured mutualism can evolve and when it is likely to occur. Here, we theoretically investigated how a mutualistic partner species should allocate efforts of mutualistic associations for different life-history stages of its host species to maximize its fitness. We assessed the partner’s optimal strategy by using a one host–one partner model with the host’s juvenile-adult stage structure. The results showed that different forms of stage-structured mutualism can evolve, such as juvenile-specialized association, adult-specialized association, and inter-stage partner sharing (i.e., the partner associates with both the juvenile and adult stages of the host) depending on the shape of association trade-off, i.e., how much association with one stage is weakened when the partner strengthens its association with the other stage. In general, stage-specialized association (either juvenile-specialized or adult-specialized association) tends to evolve when being associated with that stage is relatively beneficial. Meanwhile, when the association trade-off is weak, inter-stage partner sharing can occur if the mutualistic benefits of juvenile-specific and adult-specific associations are sufficiently large. We also found that when the association trade-off is strong, alternative stable states occur in which either juvenile-specialized or adult-specialized associations evolve depending on the initial trait value. These results suggest that pairwise interspecific mutualism is more complicated than previously thought, implying that we may under-or overestimate the strength of mutualistic interactions when looking at only certain life-history stages. This study provides a conceptual basis for better understanding the mechanisms underlying ontogenetic shifts of mutualistic partners and more complex mutualistic networks mediated by the life-history stages of organisms and their stage-structured interactions

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

International Collaborative Study on Ecology and Evolution in Plant-Insect Interactions

Collaborative research in science has been conducted for over 300 years, which international collaboration having grown in importance throughout the past century. International collaboration offers some important opportunities and advantages in ecological research. This is because ecosystems have complexity, variety, and ubiquity across boarder, and the insights of a variety of disciplinary experts are required to understand these ecosystems. In particular, today, our societies face global problems, including biodiversity loss, climate changes, and biological invasion, in which multidisciplinary, international approaches are needed. In my talk I will introduce two topics of our collaborative studies on ecology and evolution in plant-insect interactions: (1) biodiversity and microevolutionary divergence in a community context, and (2) plant genetics and insect population dynamics of exotic species in their native range. First, we have conducted collaborative study between Japan and Finland. In this collaboration we have investigated how species diversity of herbivorous insects affects trait evolution of a community member. Despite growing concerns of biodiversity loss, the question of how biodiversity influences evolutionary dynamics within species remains understudied. Plagiodera versicolora is a specialist leaf beetle on willow trees (Salix spp), and is widely distributed across Eurasia, including Japan and Finland. We found that the leaf beetle populations in Japan evolutionally developed divergent adaptive foraging traits, depending on local herbivore community structure. We also confirmed a similar pattern in Finland. Our results suggest that changes in local biodiversity may rapidly change evolutionary trajectories of species, and that this may be ubiquitous phenomenon. Second, we have conducted collaborative study between Japan and US to investigate interactions between the tall goldenrod (Solidago altissima) and its specialist aphid (Uroleucon nigrotuberculatum), both of which are exotic species in Japan from North America. We examined consequences of genotypic diversity of the tall goldenrod for spatial population dynamics of the aphids in their native range. As a result we found that plant genotypic diversity increased population size of the aphid due to enhancement of movement. Motivation of the collaboration arises from the following reasons: (1) genetic variation and spatial spreading dynamics are important issues in biological invasion processes, (2) knowledge and collection of a variety of Solidago genotypes are accumulated in the US collaborator’s lab, and (3) comparison of ecological and evolutionary dynamics between native and introduced range may provide insights toward management of exotic species as well as fundamental ecological theory.Session 2.1: Biodiversity and Environmental Protection in the Nort

Spatial heterogeneity in genetic diversity and composition of bacterial symbionts in a single host species population

Aims Revealing genetic diversity in a root nodulation symbiosis under field conditions is critical to understand the formation of ecological communities of organisms associated with hosts and the nitrogen cycle in natural ecosystems. However, our knowledge of the genetic diversity of bacterial mutualists on a local scale is still poor because of the assumption that the genetic diversity of mutualistic bacteria is constrained by their hosts. Methods We thoroughly investigated the genetic diversity ofFrankiain a local forest stand. We collected root nodules from 213Alnus hirsutaseedlings covering the spatial range of the continuous population, which means thatAlnusindividuals occurred in a relatively homogeneous distribution in a continuous forest. Then, a phylogenetic and diversity analysis was performed for thenifD-K IGS region, including globalFrankiasequences fromAlnushosts. Results The genetic diversity ofFrankiadetected even on a local scale measured as high as that shown by previous studies conducted on local and regional scales. Moreover, a genetic structure analysis revealed a spatially mosaic-like distribution of genetic variation inFrankiadespite the small spatial scale. Conclusions The genetic diversity and composition of bacterial mutualists are heterogeneous on a local scale. Our findings demonstrate that genetically different bacterial symbionts simultaneously interact with a single host population and interaction partnerships spatially vary. The standing variation could produce dynamic ecological and evolutionary outcomes in a heterogeneous forest ecosystem

ショクガイ ガ ユウドウスル ヤナギ ノ サイセイチョウ ハンノウ ガ セッソク ドウブツ グンシュウ ニ アタエル エイキョウ ニ カンスル セイタイガクテキ ケンキュウ

京都大学0048新制・課程博士博士(理学)甲第13633号理博第3291号新制||理||1485(附属図書館)UT51-2008-C551京都大学大学院理学研究科生物科学専攻(主査)教授 大串 隆之, 教授 今福 道夫, 教授 椿 宜高学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

Data from: Feeding evolution of a herbivore influences an arthropod community through plants: implications for plant-mediated eco-evolutionary feedback loop

1. Genetic variation in individual species can have important ecological consequences, and sometimes, these interactions are mediated through another species. For example, genetic variation in an herbivore could alter plant responses that then influence other plant-associated arthropods. However, few systems have experimentally tested the ecological consequences of genetic variation as mediated through other species, especially within the same trophic community context. 2. I studied how evolution of feeding preference in the willow leaf beetle (Plagiodera versicolora), which occurs under selection in a herbivore community context, feeds back to an arthropod community through plant-mediated indirect interactions. Previous studies show beetle populations locally adapt distinct preferences ranging from the gourmet-type, which feeds exclusively on new leaves of willows, to the no-preference (no-pref) type, which displays non-preferential feeding on leaves of different ages. 3. I conducted field experiments at two sites that mimicked evolutionary changes in the feeding preference of the leaf beetle. I manipulated the composition of leaf beetle feeding types for 6 days in spring and then investigated subsequent development of arthropod communities. I found that initial herbivory by a higher proportion of gourmet-type beetles led to lower subsequent abundance of conspecific beetle larvae. In contrast, a higher proportion of gourmet-type beetles resulted in higher abundance of aphids. Aphid-tending ants also increased with the increasing abundance of aphids. As a result, species diversity of arthropod communities decreased with the proportion of gourmet-type beetles in the initial beetle treatment. 4. Community assembly dynamics were significantly influenced by interactive effects between the initial beetle treatment and subsequent colonizer species identities. Thus, beetle genetic variation had long-lasting effects through a temporal chain of indirect interactions likely mediated through induced plant responses and the abundance of aphids. 5. Synthesis. Evolutionary changes in feeding traits within an herbivore species had profound but predictable impact on local arthropod communities. Because the feeding evolution of herbivores nearly always occurs in a community context, plant-mediated feedback loops between the evolution and ecological community of arthropods may be widespread in nature