Kaori Murase

Chemical Recognition of Partner Plant Species by Foundress Ant Queens in Macaranga–Crematogaster Myrmecophytism

The partnership in the Crematogaster–Macaranga ant–plant interaction is highly species-specific. Because a mutualistic relationship on a Macaranga plant starts with colonization by a foundress queen of a partner Crematogaster species, we hypothesized that the foundress queens select their partner plant species by chemical recognition. We tested this hypothesis with four sympatric Macaranga species and their Crematogaster plant-ant species. We demonstrated that foundress Crematogaster queens can recognize their partner Macaranga species by contact with the surface of the seedlings, that they can recognize compounds from the stem surface of seedlings of their partner plant species, and that the gas chromatographic profiles are characteristic of the plant species. These findings support the hypothesis that foundress queens of the Crematogaster plant-ant species select their partner Macaranga species by recognizing nonvolatile chemical characteristics of the stem surfaces of seedlings.

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.

Effects of the Fukushima Daiichi nuclear accident on goshawk reproduction

Although the influence of nuclear accidents on the reproduction of top predators has not been investigated, it is important that we identify the effects of such accidents because humans are also top predators. We conducted field observation for 22 years and analysed the reproductive performance of the goshawk (Accipiter gentilis fujiyamae), a top avian predator in the North Kanto area of Japan, before and after the accidents at the Fukushima Daiichi nuclear power plant that occurred in 2011. The reproductive performance declined markedly compared with the pre-accident years and progressively decreased for the three post-accident study years. Moreover, it was suggested that these declines were primarily caused by an increase in the air dose rate of radio-active contaminants measured under the nests caused by the nuclear accidents, rather than by other factors. We consider the trends in the changes of the reproductive success rates and suggest that internal exposure may play an important role in the reproductive performance of the goshawk, as well as external exposure.

Non-ant antiherbivore defenses before plant-ant colonization in Macaranga myrmecophytes

Abstract We examined changes in the intensity of non-ant defenses of three myrmecophytic Macaranga species before and after the initiation of symbiosis with ants in a Bornean dipterocarp forest. The intensities of non-ant defenses at different growth stages of each Macaranga species were estimated by measuring the survival rate of larvae of the common cutworm, Spodoptera litura, when the larvae were fed on fresh leaves from seedlings (saplings) at three growth stages of each Macaranga species. In all species, the intensity of the non-ant defenses when seedlings had not yet received symbiont foundress queens was significantly higher than that after ant defense was well established. These results support the hypothesis that myrmecophytic Macaranga may defend themselves sufficiently via non-ant defenses before beginning symbiosis with ants and that the intensity of non-ant defenses may decrease as the symbiont colony size increases. We suggest that, where the status of myrmecophytism changes as plant–ant colonies grow, the decrease in the intensity of non-ant defenses which we detected after the establishment of ant colonies might generate an optimal allocation of metabolic cost to ant and non-ant defenses under resource limitations. We also measured leaf toughness, which is considered to be one of the most important agents of non-ant defenses against herbivorous insects, at different plant stages to assess its contribution to the change in the intensity of non-ant defenses after ant colonization. However, we found no evidence that changes in leaf toughness have a significant effect on the change in balance of the two antiherbivory mechanisms.

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.

Intraspecific variation in the status of ant symbiosis on a myrmecophyte, Macaranga bancana, between primary and secondary forests in Borneo

A tree species, Macaranga bancana , distributed in South East Asian tropics has a mutualistic relationship with specific symbiotic ant species, which defend the plant from herbivores. To examine the intraspecific variation in the status of the ant-plant symbiosis among microhabitats of different light conditions, we investigated the species composition of nesting ants and the herbivory damage on M. bancana saplings by field observations and sampling in primary and secondary forests in Sarawak. In addition, the effectiveness of non-ant (physical and chemical) defenses were estimated by feeding the larvae of a polyphagous lepidopteran with M. bancana leaves from saplings in the two types of forests. All saplings in the primary forest were colonized by two Crematogaster ant species that had been known to be the obligate symbionts of M. bancana, while in the secondary forest, about half of the saplings were occupied by several ant species that were not obligate symbionts. There was little herbivory damage on saplings colonized by the two Crematogaster symbiont ants in both forest types, while the saplings colonized by the other ant species suffered a 10–60% loss of leaf area. Larval mortality of the polyphagous lepidopteran Spodoptera litura was significantly higher when larvae fed on leaves of M. bancana saplings in the secondary forest than when fed on leaves of M. bancana saplings in the primary forest. These results suggest that the symbiosis between ants and M. bancana is looser and the non-ant-defenses are stronger in secondary forests, where light is more intense, than in primary forests.

Species specificity in settling-plant selection by foundress ant queens in Macaranga – Crematogaster myrmecophytism in a Bornean dipterocarp forest

Previous studies have demonstrated that the obligate myrmecophytism between Macaranga ant-plants and Crematogaster plant-ants is highly species specific, although multiple Macaranga species can coexist in a microhabitat. However, the species specificity has been described based on the study of trees with established plant-ant colonies. We studied how the process of settling into the partner Macaranga seedlings by single foundress Crematogaster queens contributes to species specificity. By sampling seedlings of three sympatric Macaranga myrmecophytes species in the field, we tested two hypotheses. The first is that foundresses correctly select their specific partner plant species when they settle into seedlings. The second hypothesis is that the seasons in which seedlings available for settling by foundresses appear are segregated among the Macaranga species, and the seasons in which foundress queens settle are synchronized to the appearance of seedlings of specific partner species; thus species specificity is consequently generated. Our results support the former hypothesis but not the latter: we always observed foundresses settling species-specific host plants, and seedlings suitable for settling were always available in each Macaranga species.

Do Japanese Queenless Ants Pristomyrmex punctatus (F. Smith) Exhibit Genotype-based Kin Recognition During Colony Formation?

The queenless ant, Pristomyrmex punctatus (F. Smith) reproduces parthenogenetically. Workers lay unfertilized eggs, which develop into female workers. This mode of reproduction generates hereditary clones, though a colony is not necessarily constructed from single clonal line. In a previous study, where a colony was separated into two subcolonies, it was found that genetically monomorphic colonies tended to reassemble but genetically polymorphic colonies did not. Here, we used multiple clonal colonies to investigate whether P. punctatus could recognize “individual” relatedness and assemble with subcolony members of the same clonal type. Results show individuals did not assemble with individuals of the same clonal type in each subcolony. This suggests they cannot recognize individual relatedness.

Spatially heterogeneous distribution of mtDNA haplotypes in a sika deer (Cervus nippon) population on the Boso Peninsula, central Japan

ABSTRACT We used variation in the mitochondrial DNA (mtDNA) control region (D-loop) to examine the genetic structure of the sika deer (Cervus nippon) population on the Boso Peninsula, central Japan. A total of four haplotypes was found. In order to examine whether or not artificial barriers such as roads, dams, and golf courses affect the spatial heterogeneity of mtDNA haplotypes, we implemented two exclusive spatial analyses (SAMOVA and network analysis based on Monmonier’s algorithm) for searching genetic discontinuities between artificial barriers. Prior to the analyses, the whole distribution area was divided into meaningful eight blocks. Analysis of molecular variance (AMOVA) detected significant spatial heterogeneity in the constitution of the haplotypes among the blocks. The subsequent spatial analyses detected some significant spatial discontinuities on borders of the blocks. In particular, the largest discontinuity was observed in the area including motorway Line 81, but the traffic density of Line 81 is generally not very heavy compared to other major roads. These findings suggest that roads could be one of major barriers to hamper migration of sika deer to some extent, but other potential factors such as the location of food resources and/or the history of bottleneck event are also likely to more or less contribute to configure the present patterns of haplotype distribution.

Broad-Leaved Forest Selection of the Japanese Marten (Martes melampus) in Central Japan Revealed by Camera Trapping

1 Carnivore Ecology and Conservation Research Group, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu City, Tokyo 183-8509, Japan 2 Laboratory of Ecometry and Ecoinformatics, Graduate School of Natural Sciences, Nagoya City University, and Research Center for Biological Diversity, Nagoya City University, 1 Yamanohata, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8501, Japan 3 Laboratory of Applied Ecological Techniques, 3-2, Enokuma, Oita City, Oita 870-0889, Japan 4 The Nature Conservation Society of Japan, Mitoyo Bldg. 2F 1-16-10 Shinkawa, Chuo-ku, Tokyo 104-0033, Japan