Spatio‐temporal gradients in food supply help explain the short‐term colonisation dynamics of the critically endangered central rock‐rat (Zyzomys pedunculatus)

Abstract

Currently, the impact of introduced predators on small mammal population decline is a focal research direction in the Australian desert literature. In all likelihood though, single-factor explanation of population dynamics is inadequate, leaving gaps in our knowledge of the multitude of potential influences on small mammal abundance and occupancy patterns in time and space. Here, we investigated floristic gradients across four potential refuge sites of the central rock-rat, Zyzomys pedunculatus, a granivore rodent (50-120 g) that is endemic to central Australia and is categorised as critically endangered. The study took place in Tjoritja/West MacDonnell National Park in the MacDonnell Ranges bioregion. Floristic sampling was allocated across the four sites, the locations of which were predetermined by an established monitoring and management programme for the central rock-rat. Our aim was to examine the relationship between environmental gradients and floristic composition across the four sites, and thereby test the extent to which the patterns of food type and food availability can inform central rock-rat spatio-temporal dynamics. We found high site-scale floristic patterning that related foremost to elevation and then to antecedent rainfall and time-since-fire and fire-severity effects. To interpret these results, we applied the principles of refuge theory and we described a gradient from core refuge habitat to intermittent and then marginal habitat within the current central rock-rat stronghold area. Overall, our results implied a strong floristic basis to central rock-rat site occurrence, and they thus compel us to take explicit account of spatial (elevation) and temporal (rainfall-productivity and fire-disturbance) influences on the food axis of potential refuge sites of this critically endangered species.

Stability and predictability of bird assemblages in an arid riparian woodland during contrasting periods of resource availability

“…For flowering and fruiting, we constructed simple indices for each site, following Nano et al (2019), by multiplying each species cover abundance score by its fruiting and flowering score and then summing all scores for each plot. For insect abundance, we summed the number of invertebrates collected at each site for each survey.…”

“…Following Nano et al . (2019), we also recorded population‐level fruiting and flowering using the classes: 0 = no flowering/fruiting; 1 = low (<20% with low flowering/fruiting); 2 = moderate (20–100% with low flowering/fruiting or <20% with high flowering/fruiting); and 3 = high (20–100% with high flowering/fruiting).…”

The living heart: Climate gradients predict desert mountain endemism

“…These areas may have functioned as refugia by enabling upslope F I G U R E 5 Predicted endemism hotspots for (a) plants, (b) land snails, (c) vertebrates, and (d) all three guilds combined in the MacDonnell Ranges, Australian Arid Zone. Hotspots determined using Getis-Ord Gi in ArcGIS and 5 km grids selected at p = .01 movements during periods of warming (Lenoir et al 2008;Walther et al, 2005) and now support distinctive high elevation plant communities (Nano et al, 2019). Some of these high-elevation taxa occur on both quartzite and sandstone (e.g., Hakea grammatophylla, Hibbertia sp.…”