Print PageThe Arava desert valley constitutes an area whose rich biodiversity mandates energetic conservation and restoration efforts. Despite harsh climate conditions this highly arid region provides a habitat to an extremely rich variety of flora and fauna. While the artificial barrier dividing the area between Israel and Jordan has little environmental effect, significant cross-border differences in biodiversity have been documented and are attributed primarily to various human activities.
The pit-building ant lion (Neuroptera, Myrmeleontidae) is common in the Arava valley salt flats. Survival of the predatory ant lion larvae is largely dependent on their ability to dig a pit trap which is often prevented by a hard soil crust forming following rain or morning dew. Recent studies suggested that by breaking the soil crust with its hoofs, thus enabling pit-building, the Dorcas gazelle (Gazella dorcas) serves as an allogenic ecosystem engineer for the ant lion group. Significantly higher numbers of both gazelles and ant lions were documented on the Israeli side than in comparable landscape units in Jordan. Nonetheless, Areas where soil crust is seldom formed maintain a similar abundance dichotomy, implying more complex interactions exist between these species. We've conducted a series of comprehensive surveys documenting ant lion settlement patterns relative to vegetation and gazelle-made modifications: tracks and scent stations.
Results/Conclusions
A clear tendency of ant lion larvae to settle in surroundings of gazelle scent stations was observed: A density 35 times higher was documented within the station area compared to a randomly selected point. Most stations (91%, N=57) were located in close proximity (87.1cm in average) to Nitraria retusa bushes around which the highest ant lion density (4.959 per m2) was documented, nearly double the density found around bushes of the same species not directly adjacent to the station. Similar trends were documented in soil crust-free plots.
These results confirm that ant lions evidently benefit from gazelle presence. Gazelles modify the ecosystem by breaking the soil crust as well as creating favorable settlement sites. While the Israeli side of the border supports a large population of gazelles, their absence on the Jordanian side due to over hunting, consequently results in decreased ant lion abundance, making the latter group reliable indicators for anthropogenic pressure. Furthermore, if ant lions have a pivot ecological role in the ecosystem both as predator and as prey, then the presence of gazelles can lead to a cascade of trophic levels interactions.
