Phylogenetic analysis of mutualistic filamentous bacteria associated with fungus-growing ants

The attine ant-microbe system is a quadripartite symbiosis, involving a complex set of mutualistic and parasitic associations. The symbiosis includes the fungus-growing ants (tribe Attini), the basidiomycetous fungi the ants cultivate for food, specialized microfungal parasites (in the genus Escovopsis) of the cultivar, and ant-associated mu tualistic filamentous bacteria that secrete antibiotics specifically targeted to suppress the growth of Escovopsis. In this study, we conduct the first phylogenetic analysis of the filamentous mutualistic bacteria (actinomycetes) associated with fungus-growing ants. The filamentous bacteria present on 3 genera of fungus-growing ants (Acromyrmex, Trachy myrmex, and Apterostigma) were isolated from 126 colonies. The isolated actinomycetes were grouped into 3 distinct morphological types. Each morphological type was specific to the ant genus from which it was isolated, suggesting some degree of host specificity. The phylogenetic position of the 3 morphotypes was estimated using 16S rDNA for representative strains. The 8 isolates of actinomycetes sequenced are in the family Pseudonocardiaceae (Actino mycetales) and belong to the genus Pseudonocardia. Transmission electron microscopy examination of the actino mycete associated with the cuticle of Acromyrmex sp. revealed bacterial cells with an outer electron-dense membrane, consistent with actinomycetes in the genus Pseudonocardia. Ant-associated Pseudonocardia isolates did not form a monophyletic group, suggesting multiple acquisitions of actinomycetes by fungus-growing ants over their evolutionary history.     

Flood control by ants: a Southeast Asian bamboo-dwellingTetraponera (Formicidae,Pseudomyrmecinae) bails water from its internode nests

Summary The Southeast Asian antTetraponera sp. nearattenuata F. Smith inhabits internodes of large bamboo species that it shares with symbiotic pseudococcids. It finds access to this nesting habitat via small holes made by wood-boring insects. During heavy rain, runoff water collects in these punctured internodes. TheTetraponera workers remove the water by ingesting it, walking to the entrance hole, and regurgitating it to the outside. In this way, they 1) reduce the danger of colony members drowing, 2) enable their symbionts to feed also on the internode floor, and 3) prevent excessive growth of microbes in the nest.     

Geographical variation in mutualistic networks: similarity,turnover and partner fidelity

Although species and their interactions in unison represent biodiversity and all the ecological and evolutionary processes associated with life, biotic interactions have, contrary to species, rarely been integrated into the concepts of spatial β-diversity. Here, we examine β-diversity of ecological networks by using pollination networks sampled across the Canary Islands. We show that adjacent and distant communities are more and less similar, respectively, in their composition of plants, pollinators and interactions than expected from random distributions. We further show that replacement of species is the major driver of interaction turnover and that this contribution increases with distance. Finally, we quantify that species-specific partner compositions (here called partner fidelity) deviate from random partner use, but vary as a result of ecological and geographical variables. In particular, breakdown of partner fidelity was facilitated by increasing geographical distance, changing abundances and changing linkage levels, but was not related to the geographical distribution of the species. This highlights the importance of space when comparing communities of interacting species and may stimulate a rethinking of the spatial interpretation of interaction networks. Moreover, geographical interaction dynamics and its causes are important in our efforts to anticipate effects of large-scale changes, such as anthropogenic disturbances.     

The effects of leaf deprivation on leaf-cutting ants and their mutualistic fungus

1. When leaf-cutting ants were deprived of leaves for 5 days, they increased their consumption rates of 'staphylae', the nutritive bodies produced by their mutualistic fungus. They also pruned their fungus garden more intensively, presumably stimulating increased staphyla production.
2. Depriving fungus gardens of leaves for 5 days led to greater rates of staphyla production compared with control gardens. The rate of substrate exhaustion also increased, possibly because of this increased staphyla production, which led to greater removal of fungal resources by the ants.
3. The availability of leaf substrate directly affected staphyla production by the fungus garden. When leaf fragments were inserted into fungus garden samples, staphyla production was depressed, suggesting that the fungus can allocate resources either to hyphal colonization of fresh substrate or to staphyla production.
4. Under conditions of leaf deprivation, food production for the ants effectively increased, due to the combined effects of increased pruning by the ants and the response of the fungus to lack of substrate. This will allow nests to survive for long periods in the field when forage availability is reduced.
5. Exposing parts of the colony to the stress of leaf deprivation showed that there is a high level of flexibility in the fungus garden's ability to produce staphylae. This may be important during the cyclic production of broods, when demands for larval food will fluctuate widely. Under normal conditions, the optimal strategy may be for the fungus garden to have a moderate rate of production with a low rate of turnover, unless demand for staphylae increases dramatically.     

Ant-plant-homopteran mutualism: how the third partner affects the interaction between a plant-specialist ant and its myrmecophyte host

By estimating relative costs and benefits, we explored the role of the homopteran partner in the protection mutualism between the myrmecophyte Leonardoxa africana T3, the ant Aphomomyrmex afer, and sap-sucking homopterans tended by ants in the tree''s swollen hollow twigs. The ants obtain nest sites and food from their host-plant (food is obtained either directly by extrafloral nectar or indirectly via homopterans). Aphomomyrmex workers patrol the young leaves of L. africana T3 and protect them against phytophagous insects. Because ants tended, either solely or primarily, coccids in some trees and pseudococcids in others, we were able to study whether the nature of the interaction was dependent on the identity of the third partner. First, the type of homopteran affects the benefits to the tree of maintaining a large ant colony. Larger colony size (relative to tree size) confers greater protection against herbivory; this relationship is more pronounced for trees whose ants tend pseudococcids than for those in which ants tend coccids. Second, for trees (and associated ant colonies) of comparable size, homopteran biomass was much larger in trees harbouring coccids than in trees with pseudococcids. Thus, the cost to the tree of maintaining ants may be greater when ants are associated with coccids. The net benefits to the plant of maintaining ants appear to be much greater with pseudococcids as the third partner. To explore how the type of homopteran affects functioning of the system, we attempted to determine which of the resources (nest sites, extrafloral nectar, and homopterans) is likely to limit ant colony size. In trees where ants tended coccids, ant-colony biomass was strongly dependent on the number of extrafloral nectaries. In contrast, in trees whose ants tended only pseudococcids, colony biomass was not related to the number of nectaries and was most strongly determined by the volume of available nest sites. We present hypotheses to explain how the type of homopteran affects functioning of this symbiosis, and discuss the implications of our study for the evolutionary ecology of ant–plant–homopteran relationships.     

The geography of diversification in mutualistic ants: a gene's-eye view into the Neogene history of Sundaland rain forests

We investigate the geographical and historical context of diversification in a complex of mutualistic Crematogaster ants living in Macaranga trees in the equatorial rain forests of Southeast Asia. Using mitochondrial DNA from 433 ant colonies collected from 32 locations spanning Borneo, Malaya and Sumatra, we infer branching relationships, patterns of genetic diversity and population history. We reconstruct a time frame for the ants' diversification and demographic expansions, and identify areas that might have been refugia or centres of diversification. Seventeen operational lineages are identified, most of which can be distinguished by host preference and geographical range. The ants first diversified 16-20 Ma, not long after the onset of the everwet forests in Sundaland, and achieved most of their taxonomic diversity during the Pliocene. Pleistocene demographic expansions are inferred for several of the younger lineages. Phylogenetic relationships suggest a Bornean cradle and major axis of diversification. Taxonomic diversity tends to be associated with mountain ranges; in Borneo, it is greatest in the Crocker Range of Sabah and concentrated also in other parts of the northern northwest coast. Within-lineage genetic diversity in Malaya and Sumatra tends to also coincide with mountain ranges. A series of disjunct and restricted distributions spanning northern northwest Borneo and the major mountain ranges of Malaya and Sumatra, seen in three pairs of sister lineages, further suggests that these regions were rain-forest refuges during drier climatic phases of the Pleistocene. Results are discussed in the context of the history of Sundaland's rain forests.     

Zoogeography of the Southeast Asian Rotifera

The distribution and taxonomic composition of Rotifera in Southeast Asia is reviewed. For some countries, records are poor: Brunei, Cambodia and Laos are almost terra incognitafor rotifers (<10 taxa recorded), while the Thai rotifer fauna is the best documented (ca. 310 taxa on record). However, analysis of the available data is impeded by fuzzy taxonomy and the questionable reliability of many records. Most studies focus on the pelagic or littoral of freshwater habitats. Other habitats are largely ignored. Similarly, few studies deal comprehensively with illoricate Monogononta, sessile Flosculariacea and Collothecacea and, especially, Bdelloidea. The genera Lecane, Brachionus and Trichocerca are the best represented, with littoral taxa predominant. Fisheries-related studies dealing with highly productive pelagic environments tend to over report the contribution of Brachionus. Most taxa are thermophilic character, exemplified by the dominance of tropic-centred Lecaneand Brachionus. Some cold-water taxa have been recorded, but the relative climatological homogeneity of the region and low number of studies on high-altitude environments prevent the discrimination of clear latitudinal or altitudinal variation in the distribution of rotifers within Southeast Asia. The majority of Southeast Asian rotifers are widely distributed, including true cosmopolites and thermophilic taxa. There are several local or Oriental endemic Rotifera, mostly Lecane. The American Brachionus havanaensis and Keratella americana appear to have been introduced to the region. The taxonomy of some Rotifera described from the region is commented upon; Brachionus murphyiSudzuki is recognised as senior synonym of B. niwati Sanoamuang et al. (syn. nov.). Some cases of geographical and/or ecological vicariant species-pairs are suggested. The Southeast Asian rotifer fauna contains a sizeable fraction of taxa occurring in the tropical regions of the Old World, most of which also occur in tropical Australia or the Austro-Malayan region. A tropical Australasian faunal component is present, but consists of few taxa only. Hence, affinities between the rotifer fauna of the Ethiopian, Oriental and tropical Australian and Austro-Malayan regions are supported, rather than an affinity between the Indo-Asian or Indo-Malaysian and tropical Australian fauna.     

Health Status of Southeast Asian Refugees

The rates of several diseases have been reported to be higher among Southeast Asian refugees compared with those of indigenous North Americans. When we prospectively evaluated 991 refugees new to the Denver metropolitan area for their health and immunization status over a 12-month period, 38% were found to be tuberculin-positive, 71% carried one or more enteric parasites, 15% were HBsAg-positive, 13% had anemia and 31% either presented without immunization records or required continuation of vaccination sequences begun in overseas camps. Age and ethnicity were important variables with regard to tuberculosis, hepatitis B and anemia. The rates of specific parasitic infestations varied among the four ethnic groups, though the overall rates of parasitosis remained constant across ethnic lines.     

Mitochondrial DNA diversity in Southeast Asian populations

In a previous study of Southeast Asian genetic variation, we characterized mitochondrial DNAs (mtDNAs) from six populations through high-resolution restriction fragment length polymorphism (RFLP) analysis. Our analysis revealed that these Southeast Asian populations were genetically similar to each other, suggesting they had a common origin. However, other patterns of population associations also emerged. Haplotypes from a major founding haplogroup in Papua New Guinea were present in Malaysia; the Vietnamese and Malaysian aborigines (Orang Asli) had high frequencies of haplogroup F, which was also seen in most other Southeast Asian populations; and haplogroup B, defined by the Region V 9-base-pair deletion, was present throughout the region. In addition, the Malaysian and Sabah (Borneo) aborigine populations exhibited a number of unique mtDNA clusters that were not observed in other populations. Unfortunately, it has been difficult to compare these patterns of genetic diversity with those shown in subsequent studies of mtDNA variation in Southeast Asian populations because the latter have typically sequenced the first hypervariable segment (HVS-I) of the control region (CR) sequencing rather than used RFLP haplotyping to characterize the mtDNAs present in them. For this reason, we sequenced the HVS-I of Southeast Asian mtDNAs that had previously been subjected to RFLP analysis, and compared the resulting data with published information from other Southeast Asian and Oceanic groups. Our findings reveal broad patterns of mtDNA haplogroup distribution in Southeast Asia that may reflect different population expansion events in this region over the past 50,000-5,000 years.     

Amphibian Pathogens in Southeast Asian Frog Trade

Amphibian trade is known to facilitate the geographic spread of pathogens. Here we assess the health of amphibians traded in Southeast Asia for food or as pets, focusing on Batrachochytrium dendrobatidis (Bd), ranavirus and general clinical condition. Samples were collected from 2,389 individual animals at 51 sites in Lao PDR, Cambodia, Vietnam and Singapore for Bd screening, and 74 animals in Cambodia and Vietnam for ranavirus screening. Bd was found in one frog (n = 347) in Cambodia and 13 in Singapore (n = 419). No Bd was found in Lao PDR (n = 1,126) or Vietnam (n = 497), and no ranavirus was found in Cambodia (n = 70) or Vietnam (n = 4). Mild to severe dermatological lesions were observed in all East Asian bullfrogs Hoplobatrachus rugolosus (n = 497) sampled in farms in Vietnam. Histologic lesions consistent with sepsis were found within the lesions of three frogs and bacterial sepsis in two (n = 4); one had Gram-negative bacilli and one had acid-fast organisms consistent with mycobacterium sp. These results confirm that Bd is currently rare in amphibian trade in Southeast Asia. The presence of Mycobacterium-associated disease in farmed H. rugolosus is a cause for concern, as it may have public health implications and indicates the need for improved biosecurity in amphibian farming and trade.     

Phylogeography of Asian weaver ants, Oecophylla smaragdina

The phylogeography of Oecophylla smaragdina was studied using the mitochondrial cytochrome b gene (Cytb), cytochrome oxidase subunit I (COI), and nuclear long-wavelength opsin gene (LW Rh). Weaver ants were collected from 35 localities and from one to nine colonies per locality. Neighbor-joining trees inferred from 647 bp of Cytb and 1,026 bp of COI using Oecophylla longinoda as an outgroup indicated that the haplotypes of O. smaragdina were clearly separated into seven groups: group 1 of India excluding West Bengal; group 2 of Bengal, Indochinese Peninsula, Malay Peninsula and Greater Sunda Islands, including Lombok and Sumbawa; group 3 of the Philippines; group 4 of Flores; group 5 of Sulawesi; group 6 of Halmahera; and group 7 of New Guinea and Australia. This grouping was also supported by a strict consensus tree derived from maximum parsimony and maximum likelihood trees. In addition, two haplotypes of LW Rh were found in O. smaragdina: one in group 2 and another in all the other groups. Comparison to haplotypes in other hymenopteran species suggests that group 2 is younger than other groups of O. smaragdina. The clustering of the seven groups was coincident with geological evidence of the distribution of continents, islands, and seas during glacial periods.     

Foraging behavior of ants: Theoretical considerations

This paper describes models of behavior for two ant species recruiting to very different sorts of resource. One species, Solenopsis geminata, recruits to sugar solution. The other, Pogonomyrmex occidentalis, recruits to patches of seeds. The models clarify the assumptions entering into the theoretical analysis of these behaviors and point to measurements that should be made for their experimental analysis.Both models assume that the colony gains energy when a forager gets a load of resource. Energy is lost during the trip to a patch of resource in a manner dependent upon the current physical conditions of the environment. The only factor counterbalancing an ever increasing net energy gain when the recruitment rates are increased is interference among workers at a patch. As the rate of recruitment is elevated this interference decreases the efficiency with which the resource can be used and, thus, sets an optimum at some intermediate rate of recruitment.The limitation of considerations in this paper to energetic efficiency is discussed and justified in terms of components of fitness and ant physiology. It is found that several qualitative predictions can be experimentally tested, but that quantitative predictions require fine measurement of metabolic costs to individual foragers and of complicated gains to the colony as a whole. Both models can be differentiated experimentally from corresponding time minimization models.     

东南亚留学生神经病学见习课教学浅谈

目的:探讨如何上好东南亚留学生神经病学见习课,为促进医学高等教育国际化提供依据.方法:在神经病学见习课教学中采用提高教师英语素质、充分准备病例、采用肢体语言及结合影像学资料等方法对东南亚留学生神经病学见习课进行教学.结果:上述方法能使这些留学生对神经病产生兴趣,从而达到较好的教学效果.结论:根据东南亚留学生的特殊情况,在神经病学见习中多种教学方式的灵活运用能达到理想的教学效果.     

The state and conservation of Southeast Asian biodiversity

Southeast Asia is a region of conservation concern due to heavy losses of its native habitats. In this overview, we highlight the conservation importance of Southeast Asia by comparing its degree of species endemism and endangerment, and its rate of deforestation with other tropical regions (i.e., Meso-America, South America, and Sub-Saharan Africa). Southeast Asia contains the highest mean proportion of country-endemic bird (9%) and mammal species (11%). This region also has the highest proportion of threatened vascular plant, reptile, bird, and mammal species. Furthermore, not only is Southeast Asia’s annual deforestation rate the highest in the tropics, but it has also increased between the periods 1990–2000 and 2000–2005. This could result in projected losses of 13–85% of biodiversity in the region by 2100. Secondary habitat restoration, at least in certain countries, would allow for some amelioration of biodiversity loss and thus potentially lower the currently predicted extinction rates. Nonetheless, urgent conservation actions are needed. Conservation initiatives should include public education, sustaining livelihoods, and ways to enhance the sustainability of agriculture and increase the capacity of conservation institutions. Furthermore, these actions should be country-specific and not ignore areas heavily populated by humans, as they can also harbour high numbers of threatened species. We urge that cooperative conservation initiatives be undertaken and support (e.g., capacity-building) be given by more developed countries in the region and beyond.     

Deep Whole-Genome Sequencing of 100 Southeast Asian Malays

Whole-genome sequencing across multiple samples in a population provides an unprecedented opportunity for comprehensively characterizing the polymorphic variants in the population. Although the 1000 Genomes Project (1KGP) has offered brief insights into the value of population-level sequencing, the low coverage has compromised the ability to confidently detect rare and low-frequency variants. In addition, the composition of populations in the 1KGP is not complete, despite the fact that the study design has been extended to more than 2,500 samples from more than 20 population groups. The Malays are one of the Austronesian groups predominantly present in Southeast Asia and Oceania, and the Singapore Sequencing Malay Project (SSMP) aims to perform deep whole-genome sequencing of 100 healthy Malays. By sequencing at a minimum of 30× coverage, we have illustrated the higher sensitivity at detecting low-frequency and rare variants and the ability to investigate the presence of hotspots of functional mutations. Compared to the low-pass sequencing in the 1KGP, the deeper coverage allows more functional variants to be identified for each person. A comparison of the fidelity of genotype imputation of Malays indicated that a population-specific reference panel, such as the SSMP, outperforms a cosmopolitan panel with larger number of individuals for common SNPs. For lower-frequency (<5%) markers, a larger number of individuals might have to be whole-genome sequenced so that the accuracy currently afforded by the 1KGP can be achieved. The SSMP data are expected to be the benchmark for evaluating the value of deep population-level sequencing versus low-pass sequencing, especially in populations that are poorly represented in population-genetics studies.     

Subcutaneous fat remodelling in Southeast Asian infants and children

Longitudinal data on 1,048 Thai children were evaluated for evidence of subcutaneous fat remodelling. Fat distribution, as defined by 100 (triceps/[triceps + subscapular]), was more pronounced in the limbs during infancy but shifted toward the trunk thereafter. Subsequent stepwise regression analysis indicated that biological age--as measured by Gruelich-Pyle bone age--and weight together explained between 0.8% and 14.5% of variance in fat distribution, with generally larger R2 values over age and for males. Relationships were curvilinear, with sex differences in slope. Path analysis supported the model that weight was a major causal agent primarily after infancy, whereas biological age had a small influence both in infancy and in late childhood. These findings indicate that trunk fat deposition is a normal feature of childhood. They also suggest that hypotheses which associate elevated trunk fatness with disorders of glucose metabolism are invalid for younger children.     

Phylogeny and cryptic diversification in Southeast Asian flying geckos

The closed-canopy forests of Southeast Asia are home to an impressive number of vertebrates that have independently evolved morphologies that enhance directed aerial descent (gliding, parachuting). These assemblages include numerous mammal, frog, snake, and lizard clades. Several genera of gekkonid lizards, in particular, have evolved specialized structures such as cutaneous expansions, flaps, and midbody patagia, that enhance lift generation in the context of unique gliding and parachuting locomotion. The genus Ptychozoon represents arguably the most morphologically extreme, highly specialized clade of gliding geckos. Despite their notoriety and celebrated locomotor ability, members of the genus Ptychozoon have never been the subject of a species-level molecular phylogenetic analysis. In this paper, we utilize molecular sequence data from mitochondrial and nuclear gene fragments to estimate the evolutionary relationships of this unique group of flying geckos. Capitalizing on the recent availability of genetic samples for even the rarest of known species, we include the majority of known taxa and use model-based phylogenetic methods to reconstruct their evolutionary history. Because one species, P. kuhli, exhibits an unusually wide distribution coupled with an impressive range of morphological variation, we additionally use intensive phylogeographic/population genetic sampling, phylogenetic network analyses, and Bayesian species delimitation procedures to evaluate this taxon for the possible presence of cryptic evolutionary lineages. Our results suggest that P. kuhli may consist of between five and nine unrecognized, distinct species. Although we do not elevate these lineages to species status here, our findings suggest that lineage diversity in Ptychozoon is likely dramatically underestimated.     

The place of Tam Hang in Southeast Asian human evolution

In February 1934, Jacques Fromaget of the Geological Service of Indochina discovered the Tam Hang rockshelter during prospecting work in Northern Laos. During his excavations, the geologist discovered seventeen anatomically modern human skulls. Ten of these skulls have been recovered in association with six largely-complete skeletons. These fossils, which are dated by ¹⁴C to 15.7 ka, are used to address issues related to anatomical variation and migration in Southeast Asia during the Late Pleistocene. Excellent preservation of the skeletal material allows for estimation of body size and shape in a sample of young adults. Cranial metrics are also used to assess affiliations between Tam Hang and other Southeast Asian fossil samples in an effort to address questions about population migration. This fossil sample demonstrates that Late Pleistocene human activity may be productively addressed by continued work in the highlands of mainland Southeast Asia.