A review of research on the interactions between dugongs (<Emphasis Type="Italic">Dugong dugon</Emphasis> Müller 1776) and intertidal seagrass beds in Indonesia

Research on dugong–seagrass interactions in Indonesia was done during the period 1990 until 2005 in respectively East Aru, Maluku Province and East Kalimantan, Indonesia. This research investigated intensive rotational grazing by dugongs in intertidal inshore Halodule univervis seagrass meadows, dugong movements in relation to these grazing swards, and analyses of parameters explaining the temporal and spatial patterns of grazing in these meadows. In this paper, we report the findings of this long-term study. The patterns of movement and the results of snorkelling surveys confirmed a practice of regular recropping of restricted grazing swards by small feeding assemblages of dugongs. Dugong grazing showed a significant correlation with carbohydrate content of the below-ground biomass and no significant relation with total N. The timing of dugong grazing in these intertidal meadows coincides with high below-ground biomass and high carbohydrate content in the rhizomes of H. uninervis in the upper 0–4 cm sediment layer. Our findings support the hypothesis that temporal dugong grazing is ruled by carbohydrate content in below-ground biomass. The mechanisms of rotational grazing in restricted grazing swards are not yet well understood, and the maximisation of carbohydrates does not fully explain this phenomenon. Our research confirms that intertidal H. univervis seagrass meadows form a crucial resource for dugong survival. These relatively unknown biotopes need therefore more attention in research and conservation programmes.     

Dugong foraging behavior on tropical intertidal seagrass meadows: the influence of climatic drivers and anthropogenic disturbance

Hydrobiologia - Foraging strategies of dugongs in tropical areas are not yet well understood, and that is particularly true for grazing of fast-growing pioneer seagrass meadows in the intertidal...     

Habitat collapse due to overgrazing threatens turtle conservation in marine protected areas

Marine protected areas (MPAs) are key tools for combatting the global overexploitation of endangered species. The prevailing paradigm is that MPAs are beneficial in helping to restore ecosystems to more ‘natural’ conditions. However, MPAs may have unintended negative effects when increasing densities of protected species exert destructive effects on their habitat. Here, we report on severe seagrass degradation in a decade-old MPA where hyper-abundant green turtles adopted a previously undescribed below-ground foraging strategy. By digging for and consuming rhizomes and roots, turtles create abundant bare gaps, thereby enhancing erosion and reducing seagrass regrowth. A fully parametrized model reveals that the ecosystem is approaching a tipping point, where consumption overwhelms regrowth, which could potentially lead to complete collapse of the seagrass habitat. Seagrass recovery will not ensue unless turtle density is reduced to nearly zero, eliminating the MPA''s value as a turtle reserve. Our results reveal an unrecognized, yet imminent threat to MPAs, as sea turtle densities are increasing at major nesting sites and the decline of seagrass habitat forces turtles to concentrate on the remaining meadows inside reserves. This emphasizes the need for policy and management approaches that consider the interactions of protected species with their habitat.     

Ethnobotanical Study of Traditional Building Materials from the Island of Bali,Indonesia

Ethnobotanical Study of Traditional Building Materials from the Island of Bali, Indonesia. Local knowledge of plant-based building materials has long been part of Balinese tradition. In order to better understand this particular tradition, we carried out a comprehensive ethnobotanical study of 13 aga villages. The data were obtained through semi-structured interviews and questionnaires. Seventy-eight species of plants were identified, comprising 63 genera and 34 families, of which 46% are native to the Flora Malesiana floristic region, 20% to the Indian floristic region, and 17% to the Indochinese floristic region. Ninety-one percent were trees. The most frequently used part was the stem (88%). The main use categories reported for building materials were houses (58%), religious uses (Balinese Hindu temple; 35%), stables (5%), and barns (2%). Thirty-eight percent appeared in more than one use category. Arenga pinnata (Wurmb) Merr. and Magnolia champaca (L.) Baill. ex Pierre were the two species that possessed the highest values in the preference ranking for use value (UV) followed by Artocarpus heterophyllus Lam. Species richness differed substantially between villages according to their different levels of traditional knowledge preservation. Despite the impact of the fast-growing tourist industry and the decline of local knowledge, the Balinese who live in the study areas still depend on locally available indigenous plant species for their building materials. The cultivation of these indigenous plants is in a period of crisis, especially with regard to conservation.     

Estuarine gradients determining the quality of tidal marsh halophytes as host plants for endophagous insect larvae: Experimental evidence

Phytophagous insects of estuarine tidal marshes which live inside their host plants, are, in contrast to the plants, not directly exposed to the estuarine salinity gradient. Previous field studies, however, have shown that patterns of growth and development ofAgapanthia villosoviridescens larvae, stem-borers of the halophyteAster tripolium, gradually change on tidal marshes along the Westerschelde estuary (HEMMINGA and VAN SOELEN, 1988). In the present study we carried out a laboratory experiment in which we followed growth ofA. villosoviridescens larvae from two different Westerschelde tidal marshes; the larvae either were kept inA. tripolium stems from their own marsh, or they were kept in stems from the other marsh. It was found that larvae from both tidal marshes showed larger weight increases inA. tripolium stems from the least saline marsh. Apparently, differences in host plant quality between stems of the two marshes exist. The results lend support to the hypothesis that growth and development, and distribution and abundance of phytophagous insects in estuarine tidal marshes may be indirectly influenced by estuarine gradients,via the host plant quality which changes along the estuary.     

Quantifying killing of orangutans and human-orangutan conflict in Kalimantan, Indonesia

Human-orangutan conflict and hunting are thought to pose a serious threat to orangutan existence in Kalimantan, the Indonesian part of Borneo. No data existed prior to the present study to substantiate these threats. We investigated the rates, spatial distribution and causes of conflict and hunting through an interview-based survey in the orangutan's range in Kalimantan, Indonesia. Between April 2008 and September 2009, we interviewed 6983 respondents in 687 villages to obtain socio-economic information, assess knowledge of local wildlife in general and orangutan encounters specifically, and to query respondents about their knowledge on orangutan conflicts and killing, and relevant laws. This survey revealed estimated killing rates of between 750 and 1800 animals killed in the last year, and between 1950 and 3100 animals killed per year on average within the lifetime of the survey respondents. These killing rates are higher than previously thought and are high enough to pose a serious threat to the continued existence of orangutans in Kalimantan. Importantly, the study contributes to our understanding of the spatial variation in threats, and the underlying causes of those threats, which can be used to facilitate the development of targeted conservation management.     

Combination of edible vegetable oil and artificial fruit to reduce Bactrocera dorsalis oviposition in chilli fruits

Bactrocera dorsalis (Hendel) is a major pest of a wide variety of fruits and vegetables. This study aimed to evaluate the potency of combining edible vegetable oil application and artificial fruit provision to reduce the oviposition of B. dorsalis in chilli fruits. Experiments were conducted in laboratory using a 20‐L plastic container provided with chilli fruits and in semi field using a fruit‐bearing chilli plant caged with insect screen. The laboratory test revealed that the combination of coconut oil application and artificial fruit provision significantly reduced fruit fly visits, eggs laid and the number of infested chilli fruits no matter when the chilli fruits were without prepuncture or with prepuncture. Further study using a caged chilli plant also found that this combination had significant effects on fruit fly visits and infestation in chilli fruits. These results provide an indication that coconut oil and artificial fruit can work together to reduce fruit fly attacks on chilli fruits. Combining the use of coconut oil and artificial fruit is likely to create an integrated behavioural manipulation (push and pull) of female B. dorsalis that lead to a much lower fruit fly infestation in chilli fruits.     

Genetic analysis and molecular mapping of low amylose gene du12(t) in rice (Oryza sativa L.)

Key message

We obtained interesting results for genetic analysis and molecular mapping of the du12(t) gene.

Abstract

Control of the amylose content in rice is the major strategy for breeding rice with improved quality. In this study, we conducted genetic analysis and molecular mapping to identify the dull gene in the dull rice, Milyang262. A single recessive gene, tentatively designated as du12(t), was identified as the dull gene that leads to the low amylose character of Milyang262. To investigate the inheritance of du12(t), genetic analysis on an F₂ population derived from a cross between the gene carrier, Milyang262, and a moderate amylose content variety, Junam, was conducted. A segregation ratio of 3:1 (χ ² = 1.71, p = 0.19) was observed, suggesting that du12(t) is a single recessive factor that controls the dull character in Milyang262. Allelism tests confirmed that du12(t) is not allelic to other low amylose controlling genes, wx or du1. Recessive class analysis was performed to localize the du12(t) locus. Mapping of du12(t) was conducted on F₂ and F₃ populations of Baegokchal/Milyang262 cross. Linkage analysis of 120 F₂ plants revealed that RM6926 and RM3509 flank du12(t) at a 2.38-Mb region. To refine the du12(t) locus position, 986 F₂ and 289 F₃ additional normal plants were screened by the flanking markers. Twenty-six recombinant plants were identified and later genotyped with four additional adjacent markers located between RM6926 and RM3509. Finally, du12(t) was mapped to an 840-kb region on the distal region of the long arm of chromosome 6, delimited by SSR markers RM20662 and RM412, and co-segregated by RM3765 and RM176.