Extrafloral nectaries in the genus Macaranga (Euphorbiaceae) in Malaysia: comparative studies of their possible significance as predispositions for myrmecophytism

Some species of the paleotropical tree genus Macaranga (Euphorbiaceae) live in close association with ants. The genus comprises the full range of species from those not regularly inhabited by ants to obligate myrmecophytes. In Malaysia (Peninsular and Borneo) 23 of the 52 species are known to be ant-associated (44%). The simplest structural adaptation of plants to attract ants are extrafloral nectaries. We studied the distribution of extrafloral nectaries in the genus Macaranga to assess the significance of this character as a possible predisposition for the evolution of obligate myrmecophytism. All species have marginal glands on the leaves. However, only the glands of non- myrmecophytic species function as nectaries, whereas liquids secreted by these glands in myrmecophytic species did not contain sugar. Some non-myrmecophytic Macaranga and transitional Macaranga species in addition have extrafloral nectaries on the leaf blade near the petiole insertion. All obligatorily myrmecophytic Macaranga species, however, lack additional glands on the lamina. The non-myrmecophytic species are visited by a variety of different ant species, whereas myrmecophytic Macaranga are associated only with one specific ant-partner. Since these ants keep scale insects in the hollow stems, reduction of nectary production in ant-inhabited Macaranga seems to be biologically significant. We interpret this as a means of (a) saving the assimilates and (b) stabilization of maintenance of the association's specificity. Competition with other ant species for food rewards is avoided and thereby danger of weakening the protective function of the obligate ant- partner for the plant is reduced. A comparison with other euphorb species living in the same habitats as Macaranga showed that in genera in which extrafloral nectaries are widespread, no myrmecophytes have evolved. Possession of extrafloral nectaries does not appear to be essential for the development of symbiotic ant-plant interactions. Other predispositions such as nesting space might have played a more important role.     

Microgeographic evolution of snail shell shape and predator behavior

Genetic divergence in geographically isolated populations is a prerequisite for allopatric speciation, one of the most common modes of speciation. In ecologically equivalent populations existing within a small, environmentally homogeneous area, an important role for environmentally neutral divergence is often found or inferred. We studied a species complex of conspicuously shaped Opisthostoma land snails on scattered limestone outcrops within a small area of lowland rainforest in Borneo. We used shell morphometrics, mitochondrial and nuclear DNA sequences, and marks of predation to study the factors involved in allopatric divergence. We found that a striking geographic divergence exists in shell morphology, which is partly associated with neutral genetic divergence. We also found geographic differentiation in the behavior of the snails' invertebrate predator and evidence of an evolutionary interaction between aspects of shell shape and predator behavior. Our study shows that adaptation to biotic aspects of the environment may play a more important role in allopatric speciation than previously suspected, even on a geographically very small scale.     

马来西来番荔枝科紫玉盘属(Uvaria Linn.)、杯冠木属(Cyathostemma Griff.)和Ellipeia Hook.f.et Thomson叶的比较解剖学

对紫玉盘属8种,杯冠木属3种和Ellipeia属1种进行了叶的比较研究,以调查不同种之间解剖学的不同点,这对种的鉴别和了解它们的分类学意义可能是有用的.有意义的解剖学特征是末端石细胞,表皮细胞的晶簇,毛状体,在中脉和叶柄的薄壁组织内的短石细胞以及中脉和叶柄横切面的形状.有某些特征仅出现在某些种中,这对种的鉴别是有用的.结果亦显示这三个属的联系十分紧密.     

Noxious floating weeds of Malaysia

After ten years of field surveys on various water bodies ranging from stagnant water ponds, pools and man-made lakes to flowing waters such as rivers, streams and canals, there is a clear evidence of four problematic weeds in Malaysia. These species are Eichhornia crassipes, Salvinia molesta, Lemna perpusilla, and Pistia stratiotes. Among these weeds, E. crassipes and S. molesta are widely distributed througout Malaysia. E. crassipes generally dominates canals and rivers although, recently, this species has spread to man-made lakes. The favourable tropical climate and conducive environmental factors help to trigger the massive growth of these weeds. The high nutrient concentrations, notably phosphate which has a soluble reactive concentration greater than 0.1 mg l^–1, initiate a high productivity. Manual control methods are generally used and several herbicides including 2,4-D and glyphosate are frequently employed to eradicate these weeds.     

The reproductive biology of the cyprinid, Thynnichthys thynnoides (Bleeker), in the Chenderoh Reservoir — a small tropical reservoir in Malaysia

The reproductive biology and breeding cycle of a tropical cyprinid, Thynnichthys thynnoides (Bleeker), from Chenderoh Reservoir, Malaysia was studied from June 1991 to November 1992. A total of 329 and 246 mature females and males and 167 immature females were sampled during the study. Three breeding cycles were observed and the cycles coincided with high reservoir water level which resulted in the floodings of the littoral zone. Five and four gonad developmental stages were observed for females and males, respectively. Oocyte diameter distribution study indicated the species was a total spawner although clutches of ripe oocytes might be released over an extended time period. Fecundity was related to body weight and both absolute and relative fecundity increased with body size. Absolute fecundity ranged from 26962 ± 1484 to 173520 ± 127420 eggs fish^–1, whereas relative fecundity ranged from 121 ± 53 to 451 ± 259 eggs g^–1 body weight, respectively.     

Diversity and conservation of blackwater fishes in Peninsular Malaysia,particularly in the North Selangor peat swamp forest

One of the most extreme freshwater habitats in Peninsular Malaysia is the peat swamp forest, with dark-coloured and highly acidic waters. Surprisingly, little is known about blackwater fishes in Peninsular Malaysia. Until 1968, only 26 fish species were known from blackwaters throughout Peninsular Malaysia, of which only one can be regarded as stenotopic. A recent intensive survey of part of the North Selangor peat swamp forest yielded 47 species, of which 14 are probably stenotopic taxa. These include four undescribed species and several new records for western Peninsular Malaysia. These discoveries are significant in that they include the family Chaudhuriidae which until 1985, was not reported from Sundaic Southeast Asia, and the rare genus Encheloclarias which had not been encountered for over 50 years. The rapid rate of destruction of the peat swamp forest owing to development, forestry and agricultural activities must be halted or slowed significantly to enable the proper zoological surveys and studies to be conducted. Conservation plans and environmental impact assessments based on inadequate sampling and knowledge of species present is acutely dangerous. There are no longer substantial undisturbed blackwater peat swamp forests left in most of Peninsular Malaysia. Conservation of the remaining blackwater biotopes is critically important if extinction of many species, here regarded as economically valuable renewable resources, is to be prevented.     

The genusSavoryella from freshwater habitats,includingS. grandispora sp. nov.

The species ofSavoryella from freshwater are discussed and a key is provided.Savoryella grandispora sp. nov. from Malaysia is described and illustrated with interference contrast micrographs.     

Antimicrobial susceptibility and pulsed-field gel electrophoresis of Shigella sonnei strains in Malaysia (1997-2000)

AIMS: Antimicrobial resistance of Shigella sonnei from Malaysia was determined and subtyping was carried by pulsed-field gel electrophoresis (PFGE) to assess the extent of genetic diversity of these strains. METHODS AND RESULTS: A total of 62 isolates of S. sonnei from sporadic cases of shigellosis in different parts of Malaysia were studied by antimicrobial susceptibility test and PFGE. Approximately 35.5% of the strains showed resistance to three or more antimicrobial agents. Eight resistant phenotypes, i.e. RI to RVIII, was defined. Resistant phenotype RV and RVIII only appeared in year 2000. PFGE analysis with NotI and XbaI restriction showed that a great heterogeneity existed at the DNA level among Malaysian S. sonnei isolates. Fifty-eight NotI and 61 XbaI-PFGE profiles were observed in 63 S. sonnei isolates, including ATCC 11060 isolate. Drug sensitive isolates displayed very different profiles from drug-resistant isolates, with a few exceptions. Isolates of resistant phenotype RVI (SXTr.TETr.STRr) showed a greater similarity among each other compared with isolates of resistant phenotype RI and drug-sensitive isolates. CONCLUSION: Multi-drug-resistant S. sonnei were circulated in different parts of Malaysia and the emergence of new resistant phenotype was observed. Wide genetic variations among Malaysian S. sonnei were observed and the drug-sensitive strains could be differentiated from drug-resistant strains by PFGE. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study verifies the usefulness of PFGE in characterizing and comparing strains of S. sonnei. Minor variations among S. sonnei isolates could be detected by PFGE.     

Survey of plasmid profiles of <Emphasis Type="Italic">Shigella</Emphasis> species isolated in Malaysia during 1994–2000

Summary Plasmid profiling was used to characterize 219 strains of Shigellaspecies isolated from sporadic cases of shigellosis in Malaysia during the period 1994–2000. Heterogeneous plasmid patterns were observed in all Shigella spp. There was a correlation between plasmid patterns and serotypes of S. flexneri, S. dysenteriaeand S. sonnei. Five common small plasmids (>20.0 kb) were observed in S. flexneri1b and 2a, whereas six common small plasmids were found in serotype 3a. Some of these plasmids appeared to maintain their existence stably in each individual serotype. Plasmids of size 11.40 and 4.20 kb were present only in S. flexneri2a isolates, whereas the 4.40 kb plasmid was unique for serotype 3a. Large (>150 kb) or mid-range plasmid (20.0–150 kb) was not observed from any S. flexneri1b isolates. Eighty-nine percent of S. flexneriof various serotypes harboured the plasmid of 3.20 kb. All S. dysenteriaetype 2 isolates harboured the 9.00 kb plasmid, while four common small plasmids were found in S. sonneiisolates. The 2.10 kb plasmid was only seen in S. sonnei. Streptomycin resistance in S. dysenteriaetype 2 and multi-drug resistance in S. sonneimay be associated with the 9.00 and 14.8 kb plasmids, respectively. Plasmid profiling provided a further discrimination beyond serotyping and a useful alternative genotypic marker for differentiation of Shigellaspecies. To the best of our knowledge, this is the first report on the plasmid prevalence of the Malaysian Shigellaspecies.