Mechanisms underlying detection of seed dormancy by a scatter‐hoarding rodent

Plant hormones mediate the interaction between oak acorn germination and rodent hoarding behaviour

The interaction between animals and plants for seed dispersal and predation has received much attention; however, the underlying physiological mechanisms driving the responses of both seeds and animals remain unclear. We conducted a series of behaviour and physiology experiments to examine the role of plant hormones in regulating seed germination and rodent hoarding behaviour in the Quercus variabilis and Leopoldamys edwardsi systems. We found that acorns that were partially consumed by rodents had increased gibberellin (GA) levels and shortened germination time. Rodents preferred scatter-hoarded abscisic acid (ABA)-treated and intact acorns but consumed germinated and GA-treated acorns; such treatment differences disappeared for inactivated acorns by boiling water. Moreover, we found that seven potential compounds may be linked to seed germination and rodent hoarding behaviour. Our results indicate that acorns of oak showed rapid germination when facing predation risk, while rodents could identify the germination status of seeds for hoarding; GA and ABA may play an important role in regulating seed germination of oak and hoarding behaviour of rodents.

Odour-mediated Interactions Between an Apex Reptilian Predator and its Mammalian Prey

An important but understudied modality for eavesdropping between predators and prey is olfaction, especially between non-mammalian vertebrate predators and their prey. Here we test three olfactory eavesdropping predictions involving an apex reptilian predator, the sand goanna Varanus gouldii, and several species of its small mammalian prey in arid central Australia: 1) small mammals will recognize and avoid the odour of V. gouldii; 2) V. gouldii will be attracted to the odour of small mammals, especially of species that maximize its energetic returns; and 3) small mammals will be less mobile and will show higher burrow fidelity where V. gouldii is absent compared with where it is present. As expected, we found that small mammals recognized and avoided faecal odour of this goanna, feeding less intensively at food patches where the odour of V. gouldii was present than at patches with no odour or a pungency control odour. Varanus gouldii also was attracted to the odour of small mammals in artificial burrows and dug more frequently at burrows containing the odour of species that were energetically profitable than at those of species likely to yield diminishing returns. Our third prediction received mixed support. Rates of movement of three species of small mammals were no different where V. gouldii was present or absent, but burrow fidelity in two of these species increased as expected where V. gouldii had been removed. We conclude that olfaction plays a key role in the dynamic interaction between V. gouldii and its mammalian prey, with the interactants using olfaction to balance their respective costs of foraging and reducing predation risk. We speculate that the risk of predation from this apex reptilian predator drives the highly unusual burrow-shifting behaviour that characterizes many of Australia's small desert mammals.

Mutualism between antagonists: its ecological and evolutionary implications

Mutualism or antagonism between species is often investigated within the framework of monotonic interactions of either mutualism or antagonism, but studies on transition from mutualism to antagonism (within the context of nonmonotonic interactions) have been largely ignored. In this paper, through a brief review and synthesis, we highlighted the role of mutualism between antagonists in regulating the ecological and evolutionary processes, as well as maintaining the stability and complexity of ecosystems. Mutualism between antagonistic species represents the density-dependent transition between mutualism and antagonism, which is beneficial to species coexistence and stability of complex ecosystems; thus, it should be favored by natural selection. Species may face selection of conflicting pressure on functional traits in co-balancing mutualism and antagonism, which may result in evolution of the dual character of species with moderate mutualistic or antagonistic traits. Coevolution and co-balance of these traits are driving forces in shaping mutualism-antagonism systems. Rewards for mutualists, punishment for exploiters, and competition of meta-communities are essential in stabilizing mutualism between antagonists. We appeal for more studies on mutualism between antagonists and its ecological and evolutionary implications by expanding the conventional ecological studies from monotonic to nonmonotonic regimes.