Testing multiple assembly rule models in avian communities on islands of an inundated lake, Zhejiang Province, China

Abstract

Aim A fundamental question in community ecology is whether general assembly rules determine the structure of natural communities. Although many types of assembly rules have been described, including Diamond's assembly rules, constant body-size ratios, favoured states, and nestedness, few studies have tested multiple assembly rule models simultaneously. Therefore, little is known about the relative importance of potential underlying factors such as interspecific competition, inter-guild competition, selective extinction and habitat nestedness in structuring community composition. Here, we test the above four assembly rule models and examine the causal basis for the observed patterns using bird data collected on islands of an inundated lake.Location Thousand Island Lake, China.Methods We collected data on presence-absence matrices, body size and functional groups for bird assemblages on 42 islands from 2007 to 2009. To test the above four assembly rule models, we used null model analyses to compare observed species co-occurrence patterns, body-size distributions and functional group distributions with randomly generated assemblages. To ensure that the results were not biased by the inclusion of species with extremely different ecologies, we conducted separate analyses for the entire assemblage and for various subset matrices classified according to foraging guilds. ResultsThe bird assemblages did not support predictions by several competitively structured assembly rule models, including Diamond's assembly rules, constant body-size ratios, and favoured states. In contrast, bird assemblages were highly significantly nested and were apparently shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of bird assemblages was not a result of passive sampling or selective colonization. These results were very consistent, regardless of whether the entire assemblage or the subset matrices were analysed.Main conclusions Our results suggest that bird assemblages were shaped by extinction processes mediated through area effects and habitat nestedness, rather than by interspecific or inter-guild competition. From a conservation point of view, our results indicate that we should protect both the largest islands with the most species-rich communities and habitat-rich islands in order to maximize the number of species preserved.

Ecological correlates of vulnerability to fragmentation in forest birds on inundated subtropical land-bridge islands

“…The archipelago and the adjacent mainland have similar vegetation, climate, topography and faunas (Wang and Feng, 2009). The major vegetation type on the islands is a successional forest dominated by the Masson pine (Pinus massoniana) (Wang et al, 2011(Wang et al, , 2012. The climate is typical of the subtropical monsoon zone and is highly seasonal, with hot summers and cold winters.…”

“…The maximum elevations of the study islands ranged from 106.7 m to 298.5 m (Table A1). To account for the greater habitat variability associated with larger areas, sampling effort was roughly proportional to log (island area) (Wang et al, 2011(Wang et al, , 2012. Accordingly, eight transects were sampled on the largest study island 1 (area N 1000 ha), four on islands 2-3 (1000 N area N 100 ha), two on islands 4-7 (100 N area N 10 ha), and one on each of the remaining small islands (area ≈ 1 ha for most islands; Table A1) (Wang et al, 2011(Wang et al, , 2012.…”

“…These islands were selected to represent a range of area size and degree of isolation from the mainland (Table A1) (Wang et al, 2011(Wang et al, , 2012. To facilitate surveys, we cut transects (c. 20 cm wide) that traversed the small islands entirely and the mountain ridges of large islands (Wang et al, 2010(Wang et al, , 2011.…”

The structure of mixed-species bird flocks, and their response to anthropogenic disturbance, with special reference to East Asia

“…For example, Grubb and colleagues were able to remove species from flocks that are found in small pockets of forest in an agricultural landscape, and then measure the effects on the body condition of the remaining birds (Cimprich and Grubb 1994;Grubb 1998, 1999). One can imagine potential experiments on the Thousand Island Lake landscape (Wang et al 2011), discussed above, where fulvettas could be removed from islands, or even added to islands where they were not before, with the one complicating problem that the resulting flocks would not only be different in the presence of this one species, but also in the number of individuals per flock (due to the species being highly gregarious).…”

“…This gradient could be elevation, or fragmentation, or land-use intensification. For example, the Thousand Island Lake system in eastern China (Wang et al 2011) could be an excellent system in which to look for fragmentation effects. The flock leading species Alcippe hueti is found on 35 of these 42 islands (Wang et al 2011), so it would be interesting to see what happens to flocks and the pool of bird species on the remaining seven islands.…”