Chutamas Satasook

The evolution of sensory divergence in the context of limited gene flow in the bumblebee bat

The sensory drive theory of speciation predicts that populations of the same species inhabiting different environments can differ in sensory traits, and that this sensory difference can ultimately drive speciation. However, even in the best-known examples of sensory ecology driven speciation, it is uncertain whether the variation in sensory traits is the cause or the consequence of a reduction in levels of gene flow. Here we show strong genetic differentiation, no gene flow and large echolocation differences between the allopatric Myanmar and Thai populations of the worlds smallest mammal, Craseonycteris thonglongyai, and suggest that geographic isolation most likely preceded sensory divergence. Within the geographically continuous Thai population, we show that geographic distance has a primary role in limiting gene flow rather than echolocation divergence. In line with sensory-driven speciation models, we suggest that in C. thonglongyai, limited gene flow creates the suitable conditions that favour the evolution of sensory divergence via local adaptation.

Molecular Evolution of the Odorant and Gustatory Receptor Genes in Lepidopteran Insects: Implications for Their Adaptation and Speciation

Lepidoptera (comprised of butterflies and moths) is one of the largest groups of insects, including more than 160,000 described species. Chemoreception plays important roles in the adaptation of these species to a wide range of niches, e.g., plant hosts, egg-laying sites, and mates. This study investigated the molecular evolution of the lepidopteran odorant (Or) and gustatory receptor (Gr) genes using recently identified genes from Bombyx mori, Danaus plexippus, Heliconius melpomene, Plutella xylostella, Heliothis virescens, Manduca sexta, Cydia pomonella, and Spodoptera littoralis. A limited number of cases of large lineage-specific gene expansion are observed (except in the P. xylostella lineage), possibly due to selection against tandem gene duplication. There has been strong purifying selection during the evolution of both lepidopteran odorant and gustatory genes, as shown by the low ω values estimated through CodeML analysis, ranging from 0.0093 to 0.3926. However, purifying selection has been relaxed on some amino acid sites in these receptors, leading to sequence divergence, which is a precursor of positive selection on these sequences. Signatures of positive selection were detected only in a few loci from the lineage-specific analysis. Estimation of gene gains and losses suggests that the common ancestor of the Lepidoptera had fewer Or genes compared to extant species and an even more reduced number of Gr genes, particularly within the bitter receptor clade. Multiple gene gains and a few gene losses occurred during the evolution of Lepidoptera. Gene family expansion may be associated with the adaptation of lepidopteran species to plant hosts, especially after angiosperm radiation. Phylogenetic analysis of the moth sex pheromone receptor genes suggested that chromosomal translocations have occurred several times. New sex pheromone receptors have arisen through tandem gene duplication. Positive selection was detected at some amino acid sites predicted to be in the extracellular and transmembrane regions of the newly duplicated genes, which might be associated with the evolution of the new pheromone receptors.

The impact of rubber plantations on the diversity and activity of understorey insectivorous bats in southern Thailand

Although a large proportion of tropical rain-forest in South-east Asia has been replaced by rubber plantations, there is very little information about the impact of such forest conversion on bat diversity. To address this deficiency, trapping and acoustic monitoring programmes were carried out in Ton Nga Chang and Khao Ban That wildlife sanctuaries in southern Thailand with the purpose of comparing species diversity and activity of understorey insectivorous bats at sites in forest and in nearby monoculture rubber plantations. Insect biomass in both habitats was assessed. Bat species diversity and activity were found to be much lower in rubber plantations than in forested areas and mean insect biomass was determined to be more than twice as high in the latter habitat than in the former. Bats utilising forest were shown to have significantly higher call frequencies but marginally lower wing loadings and aspect ratios than bats found in both habitats. Management strategies to increase biodiversity in rubber plantations are discussed.

A taxonomic review of Rhinolophus stheno and R. malayanus (Chiroptera: Rhinolophidae) from continental Southeast Asia: an evaluation of echolocation call frequency in discriminating between cryptic species

Abstract The taxon Rhinolophus microglobosus is elevated to specific rank on the basis of clearly defined morphometric and acoustic characters which differentiate it from Rhinolophus stheno. It is recorded from Cambodia for the first time. Rhinolophus malayanus exhibits considerable geographical variation in echolocation calls, with apparently two phonic types: a northern population with lower frequency calls and a predominantly southern population with higher frequencies. However, this acoustic divergence is not reflected in any morphometric divergence, and the taxonomic status of the two phonic populations remains unclear. Discriminating characters of all three species are given, together with distribution data and short ecological summaries. The value of echolocation as an indicator of cryptic species and the zoogeographical implications of the study are briefly discussed.

A review of bat research in Thailand with eight new species records for the country

ABSTRACT A review of the literature relating to the history of bat research in Thailand (1821–2006) is included, together with lists of the 119 bat species currently recorded from the country and the 16 that are omitted for lack of supporting data. The geographical distribution within Thailand of the some of the more significant bat field studies (1896–2004) is mapped and briefly discussed. Based on field work conducted in peninsular Thailand in 1993 and 2003–2004, eight bat species (Hipposideros ridleyi, Myotis hermani, Pipistrellus stenopterus, Hesperoptenus tomesi, Murina suilla, Murina aenea, Kerivoula pellucida, and Mops mops) are recorded from the country for the first time; information is provided on their taxonomy, distribution, and ecology. Recommendations are made for further bat studies in Thailand, with emphasis placed on selecting less well known species groups, such as forest bats, in under-researched habitats in neglected geographical areas (for example, the deciduous dipterocarp forests of eastern Thailand and the semi-evergreen forests of peninsular Thailand). A need to develop in-country skills in bat acoustics and taxonomy is also highlighted.

A Taxonomic Review of the Hipposideros bicolor Species Complex and H. pomona (Chiroptera: Hipposideridae) in Thailand

Following extensive field work in Thailand (2006–2008), this paper reviews the taxonomic status of the three species of the Hipposideros bicolor group. Based on morphometric characters and acoustic data, the two phonic types, H. bicolor (131 kHz) and H. bicolor (142 kHz) are treated as distinct species. Hipposideros bicolor (131 kHz) is designated as H. bicolor; H. bicolor (142 kHz) is provisionally designated as H. atrox. The morphometric characters, acoustic data, and geographical distribution of H. pomona are also reviewed. The diagnostic characters of these frequently confused taxa are discussed, with a detailed study of the external, cranio-dental, and bacular morphology, and acoustic features. New data on the conservation status, distribution and ecology of these three species are included.

Echolocation call analysis and presence-only modelling as conservation monitoring tools for rhinolophoid bats in Thailand

Bats are an important component of biodiversity in Southeast Asia, and are key indicators of habitat quality. Acoustic analysis of echolocation calls not only allows the identification of bat species that are difficult to capture, but also allows for rapid and standardised ways to survey and monitor bats over large areas. However keys based on call parameters must also account for geographic variation in call parameters, and consider any effects of morphology and sex on call frequency. Presence-only modelling can predict likely geographic locations of specific taxa, and can used to refine decision making so that species unlikely to occur in a specific region can be omitted from more localised acoustic libraries. Here we develop an acoustic library for the echolocation calls of rhinolophoid bats in Thailand, and use presence-only modelling (Maxent) to explore how species with similar calls in a library developed at the national level can sometimes be largely allopatric, and hence identifiable, once geographic range is predicted. Presence-only modelling can also be used to explore whether species with similar calls adjust call frequency in likely areas of sympatry. We analysed calls from fourteen species of rhinolophid and twelve hipposiderid species from Thailand. Calls from a further three rhinolophid and one hipposiderid species are also described but not analysed statistically because of small sample sizes. Even without considering geographic variation, 69% of rhinolophid (14 species with a minimum of five individuals/ species) and 91% of hipposiderid calls (12 species) could be classified successfully to species using two call parameters (frequency of most energy (FMAXE) and duration) in a discriminant function analysis. Most of the discrimination was achieved because species often utilised different frequency bands. Morphology can also affect call frequency both across and within species. In both rhinolophids and hipposiderid families there was a negative relationship between FMAXE and forearm length. Within species, FMAXE was negatively related to forearm length in Rhinolophus microglobosus, R. pusillus and R. thomasi, and positively related to forearm length in R. affinis and R. pearsonii. Male R. pusillus called at higher frequencies than females, although there was no sexual size dimorphism in forearm length. Call frequency was negatively related to relative humidity in R. pusillus, suggesting that bats called at lower frequencies in humid environments to counter increases in atmospheric attenuation. Presence-only modelling was used to show that some species with similar call frequencies (e.g., R. lepidus and R. microglobosus; R. yunanensis and R. trifoliatus are predicted to occur largely in allopatry, and so could be identified reliably in particular parts of the country. Presenceonly modeling can assist in predicting areas of overlap between species with similar call frequencies. Other species (e.g., R. malayanus, R. coelophyllus) overlap in frequency when data from all of Thailand are combined, but seem to avoid call overlap when syntopic. Hence acoustic identification can be improved by taking into account local distribution patterns and patterns of species coexistence. The creation of call libraries at a local scale would have extensive potential as a resource to monitor changes in species distributions through time.

A review of the Murina cyclotis complex (Chiroptera: Vespertilionidae) with descriptions of a new species and subspecies

Until recently, the taxon Murina cyclotis was considered to be a widespread species, albeit one that exhibited considerable individual, sexual and geographical variation. Subsequently however, it was recognised that this taxon was in fact a complex of species. As such, in 2012, two larger forms were recognised as separate and distinct species, namely: M. peninsularis in the Sunda region and M. fionae in Laos and Vietnam. In the current paper, a new cryptic species of the cyclotis-complex is described from peninsular Thailand based on a combination of external, craniodental and genetic differences. In addition, the population previously referred to M. cyclotis from the Nicobar Islands is described as a new subspecies of this new species. Despite this work and the research of others, the taxonomy of M. cyclotis still requires further study. The description of M. peninsularis is emended and the extensive variation in its morphological characters is addressed. The diagnostic characters of each taxon, as well as the additional data on ecology, zoogeography, distribution, echolocation and genetics, where available, are summarised and discussed.

Diversification of the ant odorant receptor gene family and positive selection on candidate cuticular hydrocarbon receptors

BackgroundChemical communication plays important roles in the social behavior of ants making them one of the most successful groups of animals on earth. However, the molecular evolutionary process responsible for their chemosensory adaptation is still elusive. Recent advances in genomic studies have led to the identification of large odorant receptor (Or) gene repertoires from ant genomes providing fruitful materials for molecular evolution analysis. The aim of this study was to test the hypothesis that diversification of this gene family is involved in olfactory adaptation of each species.ResultsWe annotated the Or genes from the genome sequences of two leaf-cutter ants, Acromyrmex echinatior and Atta cephalotes (385 and 376 putative functional genes, respectively). These were used, together with Or genes from Camponotus floridanus, Harpegnathos saltator, Pogonomyrmex barbatus, Linepithema humile, Cerapachys biroi, Solenopsis invicta and Apis mellifera, in molecular evolution analysis. Like the Or family in other insects, ant Or genes evolve by the birth-and-death model of gene family evolution. Large gene family expansions involving tandem gene duplications, and gene gains outnumbering losses, are observed. Codon analysis of genes in lineage-specific expansion clades revealed signatures of positive selection on the candidate cuticular hydrocarbon receptor genes (9-exon subfamily) of Cerapachys biroi, Camponotus floridanus, Acromyrmex echinatior and Atta cephalotes. Positively selected amino acid positions are primarily in transmembrane domains 3 and 6, which are hypothesized to contribute to the odor-binding pocket, presumably mediating changing ligand specificity.ConclusionsThis study provides support for the hypothesis that some ant lineage-specific Or genes have evolved under positive selection. Newly duplicated genes particularly in the candidate cuticular hydrocarbon receptor clade that have evolved under positive selection may contribute to the highly sophisticated lineage-specific chemical communication in each ant species.

Morphology, genetics and echolocation calls of the genus Kerivoula (Chiroptera: Vespertilionidae: Kerivoulinae) in Thailand

Abstract Following extensive field work in Thailand (2010–2013) and the examination of 155 museum specimens, this paper reviews and examines the taxonomy of the genus Kerivoula in Thailand, based on morphology, genetics, and echolocation call characteristics. Seven species (as currently understood), Kerivoula papillosa, K. kachinensis, K. hardwickii, K. titania, K. pellucida, K. krauensis and K. minuta, were analysed in detail. Thai specimens of two species, K. picta and K. whiteheadi, were not available for study. Morphological data suggested a complex pattern of possible cryptic species, with at least five morphotypes, based on cranial data for K. papillosa, and nine for K. hardwickii, as currently understood. An analysis of the mitochondrial DNA (COI) from Thai specimens identified three genetic lineages in K. papillosa and K. hardwickii, respectively. The echolocation calls data differed significantly, albeit with individual acoustic parameters overlapping considerably, among genetic lineages. The taxonomic status of the various lineages and morphotypes are discussed.