We tested whether species endemic to Sri Lanka were less able than non-endemics to tolerate disturbed habitats. Small mammals were surveyed in four habitat types along a disturbance gradient (unlogged forest, selectively logged forest, cultivated areas and areas abandoned after cultivation) within and around the Sinharaja rain forest in south-west Sri Lanka. Twenty 90-m×40-m plots were live trapped in each of these habitat types. Twelve taxa: nine rodents (Srilankamys ohiensis, Rattus rattus kelaarti, R. r. kandianus, Mus mayori, M. cervicolor, Bandicota indica, Funambulus layardi, F. sublineatus and F. palmarum) and three insectivores (Crocidura miya, Suncus zeylanicus and Feroculus feroculus) were recorded. Of these, five were endemic to Sri Lanka at the species level (species confined to the island) and six at subspecies level (subspecies confined to the island; other subspecies occurring on the Indian subcontinent). Species richness of small mammals decreased with the magnitude of forest disturbance. The endemic species selectively utilized sites within the forest whilst the majority of the other taxa used both forest and non-forest habitat types or were restricted to the latter. Bird surveys were carried out in the same plots, using sightings and calls. Sixty-six bird species were recorded, of which 21 were endemic species. Twenty endemic bird species preferentially used sites within the forest. The findings suggest that the forest-dwelling endemic species of both small mammal and bird encounter difficulties in tolerating modified landscapes, whilst other taxa are less affected. This highlights the vulnerability of endemic species to forest conversion.

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This study investigates the effects of continuous exposure to a widely used organophosphate pesticide, chlorpyrifos, on survival, growth, development, and activity of larvae of the Asian common toad, Duttaphrynus melanostictus Schneider 1799. Larvae were continuously exposed to six different concentrations (1-1,500 μg l(-1)) of commercial-grade chlorpyrifos for 14 days and monitored for 1 additional week. Chlorpyrifos at ≥1,000 μg l(-1) caused significantly high and dose-dependent mortality, and the weekly LC50(7 day-21 day) values ranged from 3,003 to 462 μg l(-1). Larvae surviving exposure to ≥500 μg l(-1) chlorpyrifos showed significant growth impairment, delays in metamorphosis, and decreased swimming activity. Tail abnormalities were the most common morphologic deformity at concentrations of 1,000 and 1,500 μg l(-1) chlorpyrifos. The findings of the present study highlight the need to recognize the potential risk that agrochemicals pose to amphibians inhabiting agricultural landscapes in Sri Lanka and other Asian countries.

Continuous subchronic exposure experiments were conducted to assess the effects of diazinon, an organophosphate pesticide, on the survival, growth and activity of larvae of the Asian common toad Bufo melanostictus. Two larval stages, the gill stage (Gosner stages 21 and 22) and gill-atrophy stage (Gosner stages 24 and 25), were continuously exposed to 4 microg/L, 400 mirog/L, and 10 mg/L of commercial-grade diazinon for 30 d. Treatments and untreated controls were maintained in triplicate with water changed and pesticide concentrations renewed every 3 d. Observations showed that subchronic exposure to 400 microg/L and 10 mg/L diazinon caused a significant dose-dependent increase in mortality compared to the control, regardless of the age at which larvae were exposed. One hundred percent mortality was observed in larvae exposed to 10 mg/L. No clear age-related sensitivity was evident in this study. The lethal concentrations at which 50% of the tadpoles (LC50) died during 30 d of continuous exposure were 6 and 7.5 mg/L for gill stage and gill-atrophy stage larvae, respectively. Diazinon impaired larval growth and activity. Tail abnormalities were apparent in larvae exposed to 400 microg/L and 10 mg/L of diazinon. This investigation provides the first empirical evidence of the negative effects of diazinon on the survival, growth and activity of B. melanostictus. The high degree of diazinon toxicity in this study highlights the need to consider important nontarget groups when recommending safe levels of pesticide application.

Around the world, endemic species with restricted ranges seem to be at particular risk of extinction. When range size is controlled, lowland continental species may be especially at risk, more so than island or montane species. Our study aimed to investigate reasons behind the high vulnerability of endemic species. In Sri Lanka, largescale national surveys and intensive localized fieldwork established that endemic plant and animal species are mostly associated with undisturbed rainforest habitats. On the other hand, non-endemic species used both forest and non-forest habitats almost equally, suggesting they are less likely to suffer from deleterious edge effects. To understand the different distribution of endemic and non-endemic species, our study focused on rats. Compared to the widespread species, the endemic rat species had a larger home range and fed on fewer species of forest fruit, possibly indicating greater specialization. The abundance of the endemic species was also negatively correlated with the abundance of the non-endemic species, to which it was behaviourally subordinate. Greater specialization and competitive inferiority could both contribute to the vulnerability of endemic species.