Impact of Alien Plant Invaders on Pollination Networks in Two Archipelagos

Mutualistic interactions between plants and animals promote integration of invasive species into native communities. In turn, the integrated invaders may alter existing patterns of mutualistic interactions. Here we simultaneously map in detail effects of invaders on parameters describing the topology of both plant-pollinator (bi-modal) and plant-plant (uni-modal) networks. We focus on the invader Opuntia spp., a cosmopolitan alien cactus. We compare two island systems: Tenerife (Canary Islands) and Menorca (Balearic Islands). Opuntia was found to modify the number of links between plants and pollinators, and was integrated into the new communities via the most generalist pollinators, but did not affect the general network pattern. The plant uni-modal networks showed disassortative linkage, i.e. species with many links tended to connect to species with few links. Thus, by linking to generalist natives, Opuntia remained peripheral to network topology, and this is probably why native network properties were not affected at least in one of the islands. We conclude that the network analytical approach is indeed a valuable tool to evaluate the effect of invaders on native communities

Sounds Scary? Lack of Habituation following the Presentation of Novel Sounds

Animals typically show less habituation to biologically meaningful sounds than to novel signals. We might therefore expect that acoustic deterrents should be based on natural sounds

Impact of Alien Plant Invaders on Pollination Networks in Two Archipelagos

Mutualistic interactions between plants and animals promote integration of invasive species into native communities. In turn, the integrated invaders may alter existing patterns of mutualistic interactions. Here we simultaneously map in detail effects of invaders on parameters describing the topology of both plant-pollinator (bi-modal) and plant-plant (uni-modal) networks. We focus on the invader Opuntia spp., a cosmopolitan alien cactus. We compare two island systems: Tenerife (Canary Islands) and Menorca (Balearic Islands). Opuntia was found to modify the number of links between plants and pollinators, and was integrated into the new communities via the most generalist pollinators, but did not affect the general network pattern. The plant uni-modal networks showed disassortative linkage, i.e. species with many links tended to connect to species with few links. Thus, by linking to generalist natives, Opuntia remained peripheral to network topology, and this is probably why native network properties were not affected at least in one of the islands. We conclude that the network analytical approach is indeed a valuable tool to evaluate the effect of invaders on native communities

The integration of bioacoustic indicators and artificial fear cues for the strategic management of kangaroo herbivory following fire and mining

Western grey kangaroos (Macropus fuliginosus) have not previously been subject to tests for susceptibility to auditory based deterrents. This study presented a mob of western grey kangaroos with a series of treatments to determine behavioural responses towards artificial and biologically-significant acoustic deterrents. I observed and quantified nine common behaviours, including stablestate, feeding, vigilance, and alarm behaviour before, during and after presentation of each stimulus through three experiments.In the first experiment, four sounds were tested individually (each pre-recorded sound played once) to evaluate potentially effective deterring signals. Two sounds were artificial (an aerosol can hiss and a bullwhip crack) and two were natural (a kangaroo alarm footstomp and a raven call, a presumed benign control). Despite the promising literature on the potential for natural alarm stomps as non-invasive deterrents, artificial sounds were at least as evocative as bioacoustic sounds. A whip crack was more efficient deterring western grey kangaroos than their alarm stomp at generating flight and vigilant behaviours. Foraging behaviour was reduced from 71% to 1% within one minute of play back, whereas the foot stomp reduced feeding from 57% to 22%. An artificial hiss reduced feeding effort from 89% to 65% and the raven call dropped percentage of time spent foraging from 70% to 47% in the first minute post- treatment.In a second experiment, I tried to artificially enhance the rate of habituation to ascertain the likelihood of habituation to acoustic signals, by playing back the most fear-inducing sounds (the whip crack and the alarm foot stomp) at 5 s intervals for two full minutes. Feeding behaviour did not return to normal levels following either signal.In the third experiment, to evaluate if rate of applications has an effect, I then focused on the most aversive signal (whip) and varied the rate at 3 s, 15 s and 30 s intervals. More animals left the area overall, with the highest rate of stimulus, though not significantly so. There were no other effects of rate of playback on behaviour.The outcomes of these experiments suggest that artificial sounds may be at least as effective as bioacoustic sounds in generating alarm and flight among kangaroos while the rate of playback may influence a sound's ability to deter animals from a targeted area. Animals did not fully habituate to either signal during the timeframe of these experiments (three weeks; up to twice daily, but often less as dependent on weather; two minutes duration) despite my having replayed the signal repetitively at close intervals without reinforcing fear with any other effects.Despite the failures of commercial ultrasonic kangaroo deterrents, I was unable to find any reason that auditory deterrents cannot successfully form part of astrategic repellent program for the non-lethal management of kangaroos, ifmanaged appropriately. I have characterised and quantified changes in behaviourin response to several sounds, some that may be effective in fashioning anauditory based repellent. My results, mainly in regard to the whip crack, arepromising, but the overall efficacy of auditory based deterrents requires furtherresearch, especially in regard to rate of habituation, alternation of different signalsand to intensity, rate, frequency and duration of the signal

Sounds scary? Lack of habituation following the presentation of novel sounds.

BackgroundAnimals typically show less habituation to biologically meaningful sounds than to novel signals. We might therefore expect that acoustic deterrents should be based on natural sounds.MethodologyWe investigated responses by western grey kangaroos (Macropus fulignosus) towards playback of natural sounds (alarm foot stomps and Australian raven (Corvus coronoides) calls) and artificial sounds (faux snake hiss and bull whip crack). We then increased rate of presentation to examine whether animals would habituate. Finally, we varied frequency of playback to investigate optimal rates of delivery.Principal findingsNine behaviors clustered into five Principal Components. PC factors 1 and 2 (animals alert or looking, or hopping and moving out of area) accounted for 36% of variance. PC factor 3 (eating cessation, taking flight, movement out of area) accounted for 13% of variance. Factors 4 and 5 (relaxing, grooming and walking; 12 and 11% of variation, respectively) discontinued upon playback. The whip crack was most evocative; eating was reduced from 75% of time spent prior to playback to 6% following playback (post alarm stomp: 32%, raven call: 49%, hiss: 75%). Additionally, 24% of individuals took flight and moved out of area (50 m radius) in response to the whip crack (foot stomp: 0%, raven call: 8% and 4%, hiss: 6%). Increasing rate of presentation (12x/min ×2 min) caused 71% of animals to move out of the area.Conclusions/significanceThe bull whip crack, an artificial sound, was as effective as the alarm stomp at eliciting aversive behaviors. Kangaroos did not fully habituate despite hearing the signal up to 20x/min. Highest rates of playback did not elicit the greatest responses, suggesting that 'more is not always better'. Ultimately, by utilizing both artificial and biological sounds, predictability may be masked or offset, so that habituation is delayed and more effective deterrents may be produced

Parameters for the bi-modal and uni-modal networks.

<p><b>Note</b>: Abbreviations: <b>P</b>, number of plant species; <b>A</b>, number of animals species; <b>S</b> (species richness) = A+P; <b>M</b> (network size) = A*P; <b>I</b>, number of links in 2-mode networks; <b>C</b> (connectance) = I/M; <b>n></b>, average number of links per plant species and standard deviation; <b>m></b>, average number of links per pollination species and standard deviation; <b>MN</b>, matrix nestedness using Aninhado program; <b>N*</b>, relative matrix nestedness (see text for more explanations); <b>BR</b>, Brualdi and Sanderson index; *, <i>P</i><0.05; <b>ns</b>, non-significance; <b>N</b>, community size; <b>m</b>, number of links between N; <b>d</b> (link density) = 2*m/(N*(N−1)); <b></b>, average shortest path length, i.e. average shortest distance among any pair of species; <b>D</b>, diameter, i.e. longest shortest path among any pair of species; <b></b>, average clustering coefficient, i.e. link density among neighbours to a species (X±SD); <b></b>, degree centrality (X±SD); <b></b>,closeness centrality (X±SD); <b></b>,betweenness centrality (X±SD); <b>DC</b>, degree centralization; <b>CC</b>, closeness centralization; <b>BC</b>, betweenness centralization; <b>CCO</b>, connectivity correlation (R²); *, <i>P</i><0.05; <b>ns</b>, non-significance. All values are absolute, i.e. not corrected by network size.</p

Location of the study sites in the Canary and the Balearic Islands.

<p>Ravine and Windmill localities are in the <i>Teno Bajo</i> area (Tenerife) and Cardona and Llimpa localities are in <i>S'Albufera des Grau</i> Natural Park area (Menorca).</p

Parameters included in the analyses.

<p>Parameters included in the analyses.</p

Results of Wilcoxon's tests analysing differences in the bi-modal and uni-modal network parameters.

<p>Alien effects were tested using pairs of sites (invaded <i>vs.</i> non-invaded) observed in 2005. Year-to-year variation was observed comparing only the pairs of sites observed two consecutive seasons. <i>C</i>, <i>BR</i> and <i>d</i> have been corrected for network size when performing the analyses.</p