Trophic Niche Shifts in Mountain Feirana Frogs under Human-mediated Habitat Transformations

Urbanization can induce environmental changes, disturbing habitat transformation process, and resulting in niche shift of species and local extinctions. Amphibians have experienced worldwide population declines, with ha bitat loss acting as one of the most disruptive causes. How amphibian species response to changing habitats could be reflected in their utilization and assimilation of resources. Using stable isotopes, we explored trophic niche variation between natural and transformed habitats for three closely related frog species in the genus Feirana(F. quadranus, F. taihangnica and F. kangxianensis). Our results indicated that the δ~(13)C value was negatively correlated with body size(snout-vent length) and the δ~(15)N value increased along with the ontogenetic process. The δ~(13)C values were significantly different among habitat types, and the variation of δ~(15)N values was relatively limited in different disturbed gradients. Urban groups displayed broader trophic niche width than both rural and natural groups. When species in sympatry, their resource utilization and trophic niche overlap probability were more similar in rural habitats than their natural counterparts. Our findings would be conducive to understand trophic niche and function variation in amphibians during the urbanization process, allowing for effective predictions of ecological consequences of habitat transformation. This study can also provide insight into conservation strategies for mountain amphibians in the Anthropocene.

Urbanization strengthens the edge effects on species diversity and composition of woody plants in remnant forests

Background:Urban remnant forests are embedded in urban areas and are threatened directly and indirectly by urbanization.The direct effects(e.g.,loss of area)have been well studied.However,knowledge about the indirect influence of urbanization through edge effects on the biodiversity in remnant forests is limited.Methods:In this study,we surveyed woody plant species in 72 plots in nine remnant forest patches in Guiyang,China.We examined the influences of urbanization and edge effects on the species diversity and composition of woody plants in remnant forests.We compared alpha diversities and quantified compositional dissimilarities in interior and edge sites at different levels of urbanization.We also measured the niche width of the recorded plant species and assessed whether high levels of urbanization and edge effects increased the number of generalist species.Results and conclusions:The Shannon index,the Simpson index and the Pielou index of adult trees were lowest in the edge habitat under high levels of urbanization.Significant differences in the Shannon index and the Simpson index of sapling/seedling were detected between interior and edge sites under low urbanization.The edge effects on the species composition of adult trees were intensified by high levels of urbanization.Woody plant species with wide niche widths were more abundant at edge sites under high levels of urbanization.Therefore,we recommend that urban expansion surrounding remnant patches should be strictly controlled to alleviate edge effects on biodiversity.

Revealing the role of microalgae-bacteria niche for boosting wastewater treatment and energy reclamation in response to temperature

Conventional biological treatment usually cannot achieve the same high water quality as advanced treatment when conducted under varied temperatures.Here,satisfactory wastewater treatment efficiency was observed in a microalgae-bacteria consortia(MBC)over a wide temperature range because of the predominance of microalgae.Microalgae contributed more toward wastewater treatment at low temperature because of the unsatisfactory performance of the accompanying bacteria,which experienced cold stress(e.g.,bacterial abundance below 3000 sequences)and executed defensive strategies(e.g.,enrichment of cold-shock proteins).A low abundance of amoA-C and hao indicated that conventional nitrogen removal was replaced through the involvement of microalgae.Diverse heterotrophic bacteria for nitrogen removal were identified at medium and high temperatures,implying this microbial niche treatment contained diverse flexible consortia with temperature variation.Additionally,pathogenic bacteria were eliminated through microalgal photosynthesis.After fitting the neutral community model and calculating the ecological niche,microalgae achieved a maximum niche breadth of 5.21 and the lowest niche overlap of 0.38,while the accompanying bacterial community in the consortia were shaped through deterministic processes.Finally,the maximum energy yield of 87.4 kJ L^(-1)and lipid production of 1.9 g L^(-1)were achieved at medium temperature.Altogether,this study demonstrates that advanced treatment and energy reclamation can be achieved through microalgae-bacteria niche strategies.

Ontogenetic resource use and trophic dynamics of endangered juvenile Tachypleus tridentatus among diversified nursery habitats in the northern Beibu Gulf,China

Horseshoe crabs,the most well-known example of“living fossils”,are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems.Their blood is a crucial resource for manufacturing Limulus or Tachypleus amebocyte lysate to detect bacterial endotoxins or fungal contamination in drug and medical devices.An enhanced understanding of their ecological roles and trophic interactions in the food webs is fundamental to facilitate resource management for the declining populations in Asia.Foraging information of the Asian species,however,is mainly derived from preliminary,scattered reports from a limited number of study locations.In this study,resource utilization,trophic niche dynamics,and trophic interaction of the juvenile tri-spine horseshoe crab,Tachypleus tridentatus(instars 1–12,approximately 0.5–8 years old)across ontogeny was assessed in diversified nursery habitats along the northern Beibu Gulf,China,using carbon and nitrogen stable isotopes.Our results suggest that:(i)T.tridentatus are ecological generalists given the vast range of carbon isotopic values and trophic niche width estimates exhibited between multiple instar groups;(ii)juvenile T.tridentatus across most habitat types predominantly assimilated energy from a variety of basal production sources in the food web,but primarily depended on sedimentary organic matter and seagrass resource pools;(iii)ontogenetic shifts in juvenile dietary proportions were evident,with decreased reliance on sedimentary organic matter,coupled with increased reliance on benthic macroinvertebrate grazers,detritivores,and omnivores with age;and(iv)nearly all juvenile instars occupied similar trophic positions in the food web with slight shifts in trophic position present with increasing size.Our findings indicate that resource availability and ontogenetic diet shifts strongly influence horseshoe crab trophic dynamics,and age should be accounted when formulating habitat conservation measures based on resource use for Asian horseshoe crabs.