Sara Bumrungsri

Near-Complete Extinction of Native Small Mammal Fauna 25 Years After Forest Fragmentation

Futile Forest Fragments Most of the planets terrestrial biodiversity is found in tropical forests, but much of this critical habitat now persists as fragmented patches surrounded by agriculture. Smaller forest patches sustain fewer species than larger patches or contiguous forest. However, the numbers of species that will disappear from a forest fragment—and the rate of species loss—remain poorly understood. Gibson et al. (p. 1508) surveyed islands in a reservoir in Thailand to measure the rate of loss of small mammals from small forest fragments. Collapse of the entire native community (up to 12 species) from 16 forest fragments was observed after 25 years of isolation. Thus, small forest fragments hold little value for mammalian biodiversity, and conservation efforts should instead focus on the preservation of large forest expanses. The rapid loss of native mammals from isolated Thai forests suggests that forest fragments cannot maintain biodiversity. Tropical forests continue to be felled and fragmented around the world. A key question is how rapidly species disappear from forest fragments and how quickly humans must restore forest connectivity to minimize extinctions. We surveyed small mammals on forest islands in Chiew Larn Reservoir in Thailand 5 to 7 and 25 to 26 years after isolation and observed the near-total loss of native small mammals within 5 years from <10-hectare (ha) fragments and within 25 years from 10- to 56-ha fragments. Based on our results, we developed an island biogeographic model and estimated mean extinction half-life (50% of resident species disappearing) to be 13.9 years. These catastrophic extinctions were probably partly driven by an invasive rat species; such biotic invasions are becoming increasingly common in human-modified landscapes. Our results are thus particularly relevant to other fragmented forest landscapes and suggest that small fragments are potentially even more vulnerable to biodiversity loss than previously thought.

The pollination ecology of durian ( Durio zibethinus , Bombacaceae) in southern Thailand

The floral biology and pollination ecology of durian, Durio zibethinus , were determined in eight semi-wild trees in mixed-fruit orchards in southern Thailand during April-May 2003 and 2005. Flowers open fully at 16h00–16h30 and most androecia drop around 01h00. Anthers dehisce at 19h30–20h00 when the stigmata are already receptive. In a series of pollination experiments, fruit was set in all treatments within 10 d. The greatest pollination success occurred after hand-crossed (76.6%), open (54.4%) and emasculation pollination (53.3%). Consistently, hand-crossed (12.2%), emasculation (8.7%) and open pollination (5.1%) yielded a substantial fruit set 2 mo after the pollination experiments. Very low pollination success in facilitated autogamy suggests that most durian trees are highly self incompatible. No mature fruit was found after insect pollination and automatic autogamy. Fruit bats, especially Eonycteris spelaea , are the major pollinators of this durian although the giant honey bee ( Apis dorsata ) was the most frequent visitor to the flowers. Bats visited durian flowers at the rate of 26.1 (SD = 20.7) visits per inflorescence per night. Since this semi-wild durian depends on fruit bats as its pollinator, protecting fruit bat populations and their roosts is vital for the production of the durian fruit crop.

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.

Bird and bat predation services in tropical forests and agroforestry landscapes

Understanding distribution patterns and multitrophic interactions is critical for managing bat‐ and bird‐mediated ecosystem services such as the suppression of pest and non‐pest arthropods. Despite the ecological and economic importance of bats and birds in tropical forests, agroforestry systems, and agricultural systems mixed with natural forest, a systematic review of their impact is still missing. A growing number of bird and bat exclosure experiments has improved our knowledge allowing new conclusions regarding their roles in food webs and associated ecosystem services. Here, we review the distribution patterns of insectivorous birds and bats, their local and landscape drivers, and their effects on trophic cascades in tropical ecosystems. We report that for birds but not bats community composition and relative importance of functional groups changes conspicuously from forests to habitats including both agricultural areas and forests, here termed ‘forest‐agri’ habitats, with reduced representation of insectivores in the latter. In contrast to previous theory regarding trophic cascade strength, we find that birds and bats reduce the density and biomass of arthropods in the tropics with effect sizes similar to those in temperate and boreal communities. The relative importance of birds versus bats in regulating pest abundances varies with season, geography and management. Birds and bats may even suppress tropical arthropod outbreaks, although positive effects on plant growth are not always reported. As both bats and birds are major agents of pest suppression, a better understanding of the local and landscape factors driving the variability of their impact is needed.

The pollination ecology of two species of Parkia (Mimosaceae) in southern Thailand

Although the floral traits of Parkia conform to the bat-pollination syndrome, many visitors other than bats have been observed at their flowers. Some chiropterophilous plants are also pollinated by other animals; the syndrome is therefore best regarded as a hypothesis for which field observations and pollination experiments are required. The present study aimed, for the first time, to determine the breeding system of the economically important canopy trees, Parkia speciosa and P. timoriana , and to identify their pollinators. Pollination experiments carried out in Trang and Songkhla Provinces, in 28 trees of P. speciosa and four P. timoriana indicated that they are self incompatible. Open pollination resulted in the highest fruit set (average 60–67% of inflorescences per tree) although this was not significantly different from hand-crossed pollination (48–60%). Insect pollination resulted in fruit set in only 12% of P. speciosa inflorescences. Fruit bats, mainly Eonycteris spelaea , visit flowering plants continuously from dusk till after midnight. Nocturnal and diurnal insects (moths and stingless bees respectively) visit capitula, mostly at the nectar zone. Nectarivorous bats are the most effective pollinator for P. speciosa and P. timoriana . The fact that populations of E. spelaea appear to be declining throughout their distribution is therefore a matter of increasing concern.

The pollination ecology of the late-successional tree, Oroxylum indicum (Bignoniaceae) in Thailand

Although plant species that attract multiple species of pollinators predominate in tropical plant communities, pollination specialists appear to be at a greater advantage in tropical ecosystems in which pollinators are numerous and many plants flower synchronously. The present study determined the breeding system and legitimate pollinators of Oroxylum indicum Vent. in Songkhla and Patthalung Provinces, Thailand. Oroxylum indicum exhibits steady-state flowering, with one or two flowers per inflorescence opening each night. Flowers open in the evening and drop off shortly after midnight, while its bilabiate stigma is highly sensitive, and quickly close upon being touched. Oroxylum indicum is self-incompatible. Hand-cross pollination and open pollination yielded the highest pollination success (47.7% and 31.2% respectively, n = 7 trees). About 900 pollen grains are needed for initiating fruit set. It is confirmed that a fruit bat, Eonycteris spelaea , is the legitimate pollinator. Bats are responsible for all pollen load and the pollen load from only one visit is generally sufficient to initiate fruit set. Although Eonycteris spelaea is effective, it is an inefficient pollinator. Compared with plant species pollinated by multiple animal species, the likelihood of pollination failure resulting from the decline in populations of Eonycteris spelaea will be much more intense in Oroxylum indicum .

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.

The Dawn Bat, Eonycteris spelaea Dobson (Chiroptera: Pteropodidae) Feeds Mainly on Pollen of Economically Important Food Plants in Thailand

The diet of E. spelaea was determined for bats captured monthly between June 2002-June 2003 at a cave entrance in Songkhla Province, Southern Thailand. Faecal analysis and pollen collected from the bats’ fur were used to identify the plant species ingested. From 1,155 diet records from 506 samples, at least eleven plant taxa were identified. Individual bats feed on flowers of up to six plant species each night. Parkia spp. (34%) and Musa spp. (28%) have the highest percentage frequency followed by Eugenia spp. (9.4%), Oroxylum indicum (6.4%), Durio zibethinus (6.2%), Ceiba pentandra (5.5%), Sonneratia spp. (5.2%), while Cocos nucifera and an unknown plant species, made up a minor proportion (<2.5%). Parkia and Musa were the main dietary items of E. spelaea in nearly every month, while the remaining components of the diet varied seasonally. Durio spp. is an important contributor to the diet during March–April (39–42%). The results from pollen collected from fur generally corresponded with those from faecal analysis, but Musa spp. had a higher percentage frequency on the fur (34%) than Parkia spp. (23%). The dawn return patterns of the bats to their roosts differ significantly between sexes. Most mature males return early in the night while most females return at dawn. Earlier returning males were significantly heavier than those returning later. This return pattern is similar to that reported during the breeding period for those polygynous fruit bats that maintain a harem. Thus, these results suggest that E. spelaea may exhibit a resource-defence polygynous mating system.

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.

Parasite and viral species richness of Southeast Asian bats: Fragmentation of area distribution matters

Abstract Interest in bat-borne diseases and parasites has grown in the past decade over concerns for human health. However, the drivers of parasite diversity among bat host species are understudied as are the links between parasite richness and emerging risks. Thus, we aimed at exploring factors that explain macro and microparasite species richness in bats from Southeast Asia, a hotspot of emerging infectious diseases. First, we identified bat species that need increased sampling effort for pathogen discovery. Our approach highlights pathogen investigation disparities among species within the same genus, such as Rhinolophus and Pteropus. Secondly, comparative analysis using independent contrasts method allowed the identification of likely factors explaining parasite and viral diversity of bats. Our results showed a key role of bat distribution shape, an index of the fragmentation of bat distribution, on parasite diversity, linked to a decrease for both viral and endoparasite species richness. We discuss how our study may contribute to a better understanding of the link between parasite species richness and emergence.