Coexistence mechanism of ecological specialists and generalists based on a network dimension reduction method

As an ecological strategy for species coexistence, some species adapt to a wide range of habitats, while others specialize in particular environments. Such 'generalists' and 'specialists' achieve normal ecological balance through a complex network of interactions between species. However, the role of these interactions in maintaining the coexistence of generalist and specialist species has not been elucidated within a general theoretical framework. Here, we analyze the ecological mechanism for the coexistence of specialist and generalist species in a class of mutualistic and competitive interaction ecosystems based on the network dimension reduction method. We find that ecological specialists and generalists can be identified based on the number of their respective interactions. We also find, using real-world empirical network simulations, that the removal of ecological generalists can lead to the collapse of local ecosystems, which is rarely observed with the loss of ecological specialists.

Species coexistence and niche interaction between sympatric giant panda and Chinese red panda: A spatiotemporal approach

The giant panda (Ailuropoda melanoleuca) and the Chinese red panda (Ailurus styani) are distributed in the same region in the mountain forest ecosystem on the eastern edge of the Qinghai Tibet Plateau and share the same food sources. In order to understand how sympatric giant pandas and Chinese red pandas maintain interspecific relationships to achieve stable coexistence, we used species distribution models and diurnal activity rhythms to analyze the spatial and temporal niche characteristics of giant pandas and Chinese red pandas in the Daxiangling Mountain system based on 187 camera traps data. The results show that: (1) In the Daxiangling Mountains, the total area of suitable habitats for giant pandas and Chinese red pandas is 717.61 km² and 730.00 km², respectively, accounting for 17.78% and 18.25%, respectively, of the study area. (2) The top five environmental factors contributing to the model of giant panda and Chinese red panda are precipitation seasonality, temperature seasonality, distance to the road, and elevation and vegetation type. (3) The total overlapping area of suitable habitats for giant pandas and Chinese red pandas is 342.23 km², of which the overlapping area of highly suitable habitats is 98.91 km². The overlapping index of suitable habitats is 0.472, and the overlapping index of highly suitable habitats is 0.348, which indicates that the two achieve spatial niches are separated to achieve stable coexistence. (4) The overlapping index of the daily activity rhythm of giant panda and Chinese red panda is 0.87, which is significantly different (p < .05). The existence of Chinese red panda will significantly affect the daily activity rhythm of giant panda (p < .001). This research can provide scientific reference for the researches about population and habitat protection of giant pandas and Chinese red pandas, so as to understand the driving mechanism of resource allocation and population dynamics of sympatric species.

Ecophysiological responses to different forest patch type of two codominant tree seedlings

According to gap-phase dynamics theory, forests can be divided into four distinct patch types: gap patch (G), building patch (B), mature patch (M), and degeneration patch (D). Varying light conditions across patch types are one of the most important factors affecting the coexistence of vegetation. Mechanisms of coexistence can be understood through detailed knowledge of ecophysiological responses of codominant tree seedlings to patch types. The following study was conducted to determine ecophysiological responses of Cyclobalanopsis glauca (an evergreen broad-leaved species) and Bothrocaryum controversum (a deciduous broad-leaved species) to four different patch types. During the gap-phase dynamics, light intensity and the magnitude of change in the four different patches followed the order of: G > B > D > M. Both species had the greatest photosynthetic capacity in the G patch. Dry leaf mass per area (LMA), Chlorophyll a + b concentration (Chl), carotenoids (Car), and nitrogen content per area (N a ) all responded to changes in light across patch type, but B. controversum showed greater sensitivity and changes than C. glauca. From G to M patch, the maximal quantum efficiency of PSII (F v /F m ) had a larger variation magnitude for B. controversum than for C. glauca. From G to M patch, B. controversum showed significant changes in gas exchange, while C. glauca showed only small changes. Ecophysiological trait partitioning of response to light in different patches provides a possible explanation of a coexistence mechanism.