Field observations indicate that La Palma Stick Grasshopper (Acrostira euphorbiae) strictly depends on its only known host plant (Euphorbia lamarckii), the dominant shrub in the highly reduced distribution area of this grasshopper. It is a flightless species, with a reduced jumping capacity due to its heavy body and weak hind limbs compared to other grasshoppers. It is therefore a species with low dispersal ability, being strongly affected for any threat on its habitat. In the last decades, populations of Acrostira euphorbiae have had an important decline mainly due to the alteration of its habitat (wildfire, illegal logging of vegetation, and grazing), that has affected both this grasshopper and its host plant. As a result of this situation, Acrostira euphorbiae is included as “Endangered” in both the Spanish National and the Canary Regional official lists of threatened species, this being the maximum category of threat in these catalogues. Furthermore, this species has recently been assessed as Critically Endangered in the IUCN Red List (Jakobs, 2012).

Since 2001 our scientific team GIET (in English, Group of Entomological Research from Tenerife) has carried out several studies on this critically endangered species to improve the scarce knowledge about its biology and ecology. In 2001 the local Government commissioned us a study about the situation of Acrostira euphorbiae. The results showed a restricted distribution of this endangered species, and some aspects about its phenology and habitat use were discovered. In 2003 we performed a second project to know the reproductive biology and ecology of this extremely scarce species. In this project we worked out all stages of their life cycle and the environmental requirements for their breeding. In subsequent years we performed several monitoring programs to check if populations of this grasshopper had declined due to alteration of its habitat (wildfire, logging of vegetation, and grazing), that has affected both this grasshopper and its host plant.

We have now enough knowledge about its distribution, phenology, reproduction, some ecological aspects and the threats to its habitat. But in order to preserve this species, we still need to know the potential plants it feeds on, and its precise trophic preferences to perform an appropriate restoration of its habitat for a recovery plan of Acrostira euphorbiae.

Objectives

To clarify the trophic preferences of Acrostira euphorbiae and their ecological implications either in altered and non-altered areas are key objectives for correct conservation policies. To accomplish the study we have considered the following objectives:

1. To know the seasonal diet of Acrostira euphorbiae by means of microhistological analysis of their faeces, to test if this grasshopper is really monophagous or polyphagous.

2. To clarify the trophic preferences of A. euphorbiae with experiments of selection, to check whether they depend on the relative abundance or on the nutritional quality of the plant species available in its habitat.

3. To test if the habitat alteration cause negative effects on the populations of A. euphorbiae. For such purpose we will check if this grasshopper is capable to feed on the remaining plants in the altered habitat, and if these plants afford them enough nutrients for survival.

4. To design the habitat restoration according these results.

After being finished this project, as a result of all our studies we will have a more complete information about biology, ecology, behaviour and genetic aspects of this grasshopper. The Government could start a successful recovery plan for this species considering our results about the genetic diversity of the populations, the trophic and habitat preferences, its reproductive and behaviour characteristics, and our experience on its captive breeding.