Shouhei Ueda

An ancient tripartite symbiosis of plants, ants and scale insects

In the Asian tropics, a conspicuous radiation of Macaranga plants is inhabited by obligately associated Crematogaster ants tending Coccus (Coccidae) scale insects, forming a tripartite symbiosis. Recent phylogenetic studies have shown that the plants and the ants have been codiversifying over the past 16–20 million years (Myr). The prevalence of coccoids in ant–plant mutualisms suggest that they play an important role in the evolution of ant–plant symbioses. To determine whether the scale insects were involved in the evolutionary origin of the mutualism between Macaranga and Crematogaster, we constructed a cytochrome oxidase I (COI) gene phylogeny of the scale insects collected from myrmecophytic Macaranga and estimated their time of origin based on a COI molecular clock. The minimum age of the associated Coccus was estimated to be half that of the ants, at 7–9 Myr, suggesting that they were latecomers in the evolutionary history of the symbiosis. Crematogaster mitochondrial DNA (mtDNA) lineages did not exhibit specificity towards Coccus mtDNA lineages, and the latter was not found to be specific towards Macaranga taxa, suggesting that patterns of associations in the scale insects are dictated by opportunity rather than by specialized adaptations to host plant traits.

Phylogeography of the Coccus scale insects inhabiting myrmecophytic Macaranga plants in Southeast Asia

Comparative historical biogeography of multiple symbionts occurring on a common host taxa can shed light on the processes of symbiont diversification. Myrmecophytic Macaranga plants are associated with the obligate mutualistic symbionts: Crematogaster (subgenus Decacrema) ants and Coccus scale insects. We conduct phylogeographic analyses based on mitochondrial cytochrome oxidase I (COI) from 253 scale insects collected from 15 locations in Borneo, Malaya and Sumatra, to investigate the historical biogeography of the scales, and then to draw comparisons with that of the symbiotic, but independently dispersing, Decacrema ants which are not specific to different Coccus lineages. Despite the different mode of ancient diversification, reconstruction of ancestral area and age estimation on the Coccus phylogeny showed that the scales repeatedly migrated between Borneo and Malaya from Pliocene to Pleistocene, which is consistent with the Decacrema ants. Just as with the ants, the highest number of lineages in the scale insects was found in northern northwest Borneo, suggesting that these regions were rainforest refugia during cool dry phases of the Pleistocene. Overall, general congruence between the Plio–Pleistocene diversification histories of the symbiotic scales and ants suggests that they experienced a common history of extinction/migration despite their independent mode of dispersal and host-colonization.

Congruence of Microsatellite and Mitochondrial DNA Variation in Acrobat Ants (Crematogaster Subgenus Decacrema, Formicidae: Myrmicinae) Inhabiting Macaranga (Euphorbiaceae) Myrmecophytes

A previously reported mitochondrial DNA (mtDNA) phylogeny of Crematogaster (subgenus Decacrema) ants inhabiting Macaranga myrmecophytes indicated that the partners diversified synchronously and their specific association has been maintained for 20 million years. However, the mtDNA clades did not exactly match morphological species, probably owing to introgressive hybridization among younger species. In this study, we determined the congruence between nuclear simple sequence repeat (SSR, also called microsatellite) genotyping and mtDNA phylogeny to confirm the suitability of the mtDNA phylogeny for inferring the evolutionary history of Decacrema ants. Analyses of ant samples from Lambir Hills National park, northeastern Borneo, showed overall congruence between the SSR and mtDNA groupings, indicating that mtDNA markers are useful for delimiting species, at least at the local level. We also found overall high host-plant specificity of the SSR genotypes of Decacrema ants, consistent with the specificity based on the mtDNA phylogeny. Further, we detected cryptic genetic assemblages exhibiting high specificity toward particular plant species within a single mtDNA clade. This finding, which may be evidence for rapid ecological and genetic differentiation following a host shift, is a new insight into the previously suggested long-term codiversification of Decacrema ants and Macaranga plants.

Phylogeny and Phylogeography of Myrmica rubra Complex (Myrmicinae) in the Japanese Alps

We investigated the genetic diversification of the mountain ant, Myrmica kotokui, in the Japanese Alps by using molecular phylogenetic analyses. Myrmica kotokui is widely distributed in Japan, and in the central Japanese Alps it is found only between elevations of approximately 1000 to 2000 m. We hypothesized that genetically distinct clades of this ant species might inhabit different mountain ranges in central Japan. To test this hypothesis, we reconstructed a molecular phylogeny using the DNA sequences of the mitochondrial cytochrome oxidase I gene and the nuclear long-wavelength rhodopsin gene of M. kotokui specimens collected from six mountain ranges in the Japanese Alps. The phylogeny showed four highly differentiated clades. However, the correspondence between the clades and morphological species was a little confusing. Two clades were composed only of M. kotokui specimens, whereas the other two clades were composed of multispecies, suggesting the possibility of multispecies composition of putative M. kotokui. The distribution pattern of these clades did not support our hypothesis of geographical differentiation, because two were distributed across all ranges, and a third was distributed in five of the six ranges. On the other hand, we found a pattern in the altitudinal distribution of the clades: one clade was distributed only at higher elevations, and the others were distributed at lower elevations. Thus, the ant clades do not show geographical segregation by mountain range, but they do show altitudinal differences.

New Pilophorus species associated with myrmecophilous Macaranga trees from the Malay Peninsula and Borneo (Heteroptera: Miridae: Phylinae)

Seven new species of the phyline plant bug genus Pilophorus Hahn, 1926, namely, P. aurifasciatus Nakatani & Komatsu, P. gracilipennis Nakatani & Komatsu, P. lambirensis Nakatani & Komatsu, P. laticollaris Nakatani & Komatsu, P. longirostris Nakatani & Komatsu, P. multivillus Nakatani & Komatsu, and P. unifasciatus Nakatani & Komatsu, are described from the Malay Peninsula and Borneo (Sarawak). These new species are associated with myrmecophilous Macaranga spp. (Euphorbiaceae), which are well-known as myrmecophytes. All the new species have a uniquely protruded scutellum; the phylogenetic significance of this modification is discussed.

First report of seed dispersal by ants in Dicentra peregrina (Papaveraceae), an alpine plant in the Japanese Alps

Seed dispersal by ants, known as myrmecochory, is commonly observed among various plant taxa. The seeds of these plants have an elaiosome to attract ants. In Japan, myrmecochory has been well studied in several lowland plant species, but not in highland plant species that grow above the tree line. We investigated whether the seeds of Dicentra peregrina, known as the “queen of the alpine plants” in Japan, are carried by Formica gagatoides ants at 2510 m a.s.l. on Mt Norikura, Kita‐Alps, Japan. We observed F. gagatoides workers picking up D. peregrina seeds by grasping the elaiosome and carrying the seeds into their nests. We inferred from the observed ant behavior and the seed morphology that D. peregrina is a myrmecochorous species.

Corrigendum: Host-ant specificity of endangered large blue butterflies ( Phengaris spp., Lepidoptera: Lycaenidae) in Japan

Scientific Reports 6: Article number: srep36364; published online: 03 November 2016; updated: 30 March 2017 This Article contains typographical errors in Table 1. For Location E, the ‘L1’ value “2 (0%)” should read “2 (100%)”. Additionally, the Region for ‘P. arionides’, “Chu-bu” should read “Chubu”.

Additional species and records of the “horn-backed” Pilophorus plant bugs in Southeast Asia (Heteroptera: Miridae: Phylinae)

Three new species of the “horn-backed” phyline plant bug genus Pilophorus Hahn, namely, P. erinaceulus , P. maruyamai and P. parvolus , are described from Borneo, Malaysia and Sumatra, Indonesia. The following species are newly recorded within Southeast Asia: P. lambirensis from the Malay Peninsula; P. laticollaris from Sumatra; P. longirostris and P. multivillus from Borneo. A supplementary key to the key by Nakatani et al. (2013) is provided.Y. Nakatani * , Natural Resources Inventory Center, National Institute for Agro-Environmental Sciences, Kannondai, 3-1-3, Tsukuba, Ibaraki, 305-8604, Japan. nakatany@affrc.go.jpT. Komatsu, Institute of Tropical Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan. corocoro1232000@yahoo.co.jpU. Shimizu-kaya, Center for Ecological Research, Kyoto University, Hirano, Otsu, Shiga 520-2113, Japan. shimizu.kaya.55c@st.kyoto-u.ac.jpT. Itioka, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan. ichioka.takao.5m@kyoto-u.ac.jpT. Itino, S. Ueda, Department of Biology, Faculty of Science, Shinshu University 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan. ueda32@shinshu-u.ac.jpR. Hashim, Institute of Biological Science, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. rh4758@gmail.comW. Asfiya, S. Hartini, Division of Zoology, Research Center for Biology, Indonesian Institute of Sciences, Jl. Raya Jakarta-Bogor Km. 46, Cibinong, Bogor, 16911, Indonesia. wara.asfiya@lipi.go.idH. Herwina, Laboratorium Riset Taksonomi Hewan, Jurusan Biologi, Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Andalas, Kampus UNAND Limau Manis, Padang, 25163, Indonesia. hennyf91@gmail.com

Host-ant specificity of endangered large blue butterflies ( Phengaris spp., Lepidoptera: Lycaenidae) in Japan

Large blue butterflies, Phengaris (Maculinea), are an important focus of endangered-species conservation in Eurasia. Later-instar Phengaris caterpillars live in Myrmica ant nests and exploit the ant colony’s resources, and they are specialized to specific host-ant species. For example, local extinction of P. arion in the U. K. is thought to have been due to the replacement of its host-ant species with a less-suitable congener, as a result of changes in habitat. In Japan, Myrmica kotokui hosts P. teleius and P. arionides caterpillars. We recently showed, however, that the morphological species M. kotokui actually comprises four genetic clades. Therefore, to determine to which group of ants the hosts of these two Japanese Phengaris species belong, we used mitochondrial COI-barcoding of M. kotokui specimens from colonies in the habitats of P. teleius and P. arionides to identify the ant clade actually parasitized by the caterpillars of each species. We found that these two butterfly species parasitize different ant clades within M. kotokui.