Carbon Sources of Sediment and Epifaunal Food Sources in a Tropical Mangrove Forest in North Sulawesi, Indonesia

The stable isotope ratios of nitrogen(δ^(15)N) and carbon(δ^(13)C) were applied in this study to analyze sediment carbon sources and primary food sources of epifauna in an oceanic mangrove forest in tropical North Sulawesi, Indonesia. Proportional contribution of mangrove-derived carbon to the food sources was compared among epifauna belonging to different feeding guilds. The sediment in the mangrove site with a depleted δ^(13)C signature(-28.02‰± 0.24‰) mainly consists of mangrove-derived carbon. Analysis using Bayesian stable isotope mixing model in the R program shows that mangrove-derived carbon can dominate the food sources of a majority of the epifauna(11 out of the total 18 species), especially 2 sesarmid crabs Parasesarma semperi and Sesarma sp., crab Epixanthus dentatus, and snails Terebralia sulcata and Optediceros breviculum, which belong to various feeding guilds. Mangrove-derived carbon has a proportional contribution to the food sources of fiddle crab Tubuca coarctata and 3 littorinid snails(Littoraria spp.) close to that of suspended particulate organic matter. Three planktophagous bivalve species(Anadara antiquata, Anadara sp. and Callista erycina) were found to mainly feed on seagrass-derived materials. Mean proportional contributions of mangrove-derived carbon to the food sources were 50.15%, 59.60%, 46.20% and 27.58% for the carnivorous, omnivorous, phytophagous and planktophagous groups, respectively. The results suggest that mangrove-derived carbon can directly(via grazing plant tissues) or indirectly(via deposit feedings) make an important contribution to the food sources of epifauna in the oceanic mangrove forest where the allochthonous input of organic carbon is low.

Sexual Dimorphism, Length-Weight Relationships, Fecundity, and Diet of the Striped Eel Catfish Plotosus lineatus (Plotosidae) on Taiwan’s Southwest Coast

This study of feeding guild fish from the same coast of subtropics helps to suggest conservation of fishery resources. A total of 2,537 specimens of Plotosus lineatus (Plotosidae) were collected from July 2013 to March 2019 on the coast of Taiwan. The average total body length (TL) was 23.7 cm ± 4.7 cm and 20.3 cm ± 2.9 cm, and the average body weight (W) was 94.1 g ± 59.6 g and 56.6 g ± 30.8 g among 174 males and 630 females, respectively. The LWRs of male and female were ln(W)M = 3.2914 × ln (TL) −6.0395, and ln(W)F = 3.0917 × ln(TL) −5.3629. The male specimens were large than female in TL and W. The average OSW/TL ratios were 0.722 ± 0.044 and 0.649 ± 0.029 among 41 male and 49 female specimens, respectively. The OSW of the male head was wider than that of the female head (F = 91.5;p < 0.001), and the head widths of the male fish were significantly more than those of their female counterparts, causing the OSs to form granular protrusions. The average CFW/TL ratios were 0.198 ± 0.034 and 0.252 ± 0.032 among the male and female specimens, respectively. The CFW of the male specimens was narrower than that of the female specimens (F = 58.9;p < 0.001), and the CF gap of the male fish was narrower than that of the female fish. The P. lineatus exhibits significant sexual dimorphism. The average eggs number of each female was 2375.6 eggs/individual ± 1140.9 eggs/individual (N = 161). The major prey of P. lineatus were shrimps, crabs, and fishes;the total relative frequencies of occurrence of the prey were 57.1%, 32.6%, and 37.2%, respectively (N = 282), and their total relative abundance levels were 40.2%, 26.3%, and 25.8%, respectively (N = 445). Proper scientific knowledge management will improve the development of fisheries.

Habitat heterogeneity influences avian feeding guild composition in urban landscapes:evidence from Bhubaneswar,India

Background:Habitat heterogeneity clearly distinguished in terms of availability of food and habitat resources and landscape features(natural or human-modified)play a crucial role in the avian species composition and population structure.To examine this,a study was carried out in Bhubaneswar,India,to understand the ecological niche distinction in birds based on habitat heterogeneity.Regular sampling was conducted in 30 sampling sites covering six different habitat types in a predominantly urban landscape of Bhubaneswar for understanding the ecological niche in birds.The birds were classified into 11 types of foraging guilds.Results:The insectivorous guild had the highest bird species richness(181 species)and the omnivorous guild had the lowest(11 species).The piscivorous guild and wetland habitat had the strongest linkage,followed by the insectivorous guild and agricultural land.The frugivorous guild was significantly correlated with forest habitats(r=0.386,p<0.01)and park and garden habitats(r=0.281,p<0.01).This urban area hosted a higher number of bird species in certain habitat types,viz.,agricultural lands(52%,115 species)and forest patches(50%,111 species).Conclusion:The present study highlights the importance of agricultural lands,forest patches,parks and gardens,and wetlands inside the cityscape for supporting avifauna.It is therefore suggested that such habitats should be conserved inside an urban area to protect native avifauna.Thus,the city development plan must invariably include strategies for conserving the forest patches inside the urban area.Measures must be taken to restrain the degradation of agricultural lands and reduce their utilization for non-agricultural purposes,which will help in further reducing the bird population decline in the urban landscape.

Tree diversity increases levels of herbivore damage in a subtropical forest canopy:evidence for dietary mixing by arthropods?

Aims Plant diversity has been linked to both increasing and decreasing levels of arthropod herbivore damage in different plant communities.So far,these links have mainly been studied in grasslands or in artificial tree plantations with low species richness.Furthermore,most studies provide results from newly established experimental plant communities where trophic links are not fully established or from stands of tree saplings that have not yet developed a canopy.Here,we test how tree diversity in a species-rich subtropical forest in China with fully developed tree canopy affects levels of herbivore damage caused by different arthropod feeding guilds.Methods We established 27 plots of 30×30 m area.The plots were selected randomly but with the constraint that they had to span a large range of tree diversity as required for comparative studies in contrast to sample surveys.We recorded herbivore damage caused by arthropod feeding guilds(leaf chewers,leaf skeletonizers and sap feeders)on canopy leaves of all major tree species.Important Findings Levels of herbivore damage increased with tree species richness and tree phylogenetic diversity.These effects were most pronounced for damage caused by leaf chewers.Although the two diversity measures were highly correlated,we additionally found a significant interaction between them,whereby species richness increased herbivory mostly at low levels of phylogenetic diversity.Tree species with the lowest proportion of canopy leaf biomass in a plot tended to suffer the highest levels of herbivore damage,which is in contrast to expectations based on the resource concentration hypothesis.Our results are in agreement with expectations of the dietary mixing hypothesis where generalist herbivores with a broad spectrum of food plants benefit from increased resource diversity in tree species-rich forest patches.

Vertical and seasonal distribution of flying beetles in a suburban temperate deciduous forest collected by water pan trap

Vertical and seasonal distributions of flying beetles were investigated in asuburban temperate deciduous forest in Kanazawa, Japan using water pan traps to determine the abundance and composition among vertical strata, change in the abundance and composition through seasons and determinant factors in generating the distributions. Traps were placed at three levels (0.5 m, 10 m, and 20 m above ground) on a tower. Samplings were carried out seasonally from May to November in 1999 and 2000. Variations in the abundance of flying beetles were observed from different layers. The results showed that the abundance and composition of flying beetles varied among strata and seasons. In both 1999 and 2000,Elateridae was consistently most abundant in the bottom layer, while Attelabidae and Cantharidae were most abundant in the upper layer. In 1999, Eucnemidae and overall scavengers were most abundance in the bottom layer, but results were not consistent with those in 2000. In general, the abundance of herbivores reaches a peak in the early season(May/June) and decreases in the following months. Peaks of abundance in predators vary vertically. In the bottom layer a peak was observed in the early season (May/June), while in the upper layer this was observed in July. Scavengers had two peaks, in May/June and September. These patterns indicated that vertical distributions in the abundance of differentfeeding guilds varied through seasons.

Priority sites and conservation gaps of wintering waterbirds in the Yangtze River floodplain

The Yangtze River floodplain is critical for migratory waterbirds along the East Asian-Australasian Flyway (EAAF). Greater awareness of its global importance is urgently needed to ensure waterbird populations remain in favourable conservation status, as well as the enhancement of wider wetland biodiversity within this region. The designation of protected wetland areas and building a green ecological corridor in the Yangtze floodplain is now becoming a critical issue of interest to the Chinese government. Priority sites in this area were identified based on the criteria used to identify sites that qualify as Wetlands of International Importance (Ramsar Sites) and Important Bird and Biodiversity Areas (IBAs) by using multi-source data. The results show that 140 of the sites surveyed are priority sites. The Importance Index (/) for the whole floodplain decreased slightly from 2001–2005 and an unbalanced distribution pattern is evident with Jiangxi and Hunan provinces significantly higher than the other provinces in the floodplain. Although more than 60% of the priority sites are currently located outside protected areas, the average Conservation Effectiveness Index (C) of the whole floodplain is 75.6%, which suggests the coverage of protected areas for most wintering waterbird population is reasonable. Conservation of the Yangtze River floodplain needs to be further strengthened due to declining waterbird abundances and the mismatch between the distribution of protected areas and their importance for wintering waterbirds. A comprehensive system for priority site identification and protection and scientific review is needed. Multi-sourced data from regular, systematic and coordinated monitoring of waterbird distribution and abundance across the EAAF, as well as national scale citizen science programmes are also critically important.