Beyond vegetation-based habitat restoration for a threatened giant Spirostreptid millipede

Abstract

Vegetation-based restoration efforts often fail to provide suitable habitat for many invertebrates. Restoring habitat for target invertebrates requires an understanding of their resource and condition requirements. The Seychelles giant millipede (SGM), Sechelleptus seychellarum, is a functionally important millipede which is Red Listed as ‘Vulnerable’. Here, we studied the habitat requirements of this macro-detritivore in relation to the ongoing forest restoration programme on Cousine Island, Seychelles. SGM spatial density did not significantly correlate with edaphic and litter properties, but did positively correlate with the toposcape (i.e. elevation and granitic rock cover). Granite rock crevices in forest covered areas were important diurnal refuges for the SGM, as microclimate conditions in non-forest covered rock refuges were unsuitable. SGM physical condition was significantly lower in non-shaded crevices compared to those shaded by forest. Low granite rock cover in the restored forest limited the SGM colonisation of this area in large numbers, despite canopy cover in the restored forest being comparable with that in the reference natural forest. As most restoration practices are primarily vegetation-based, this study demonstrates that such an approach can be inadequate for restoring habitat for target invertebrates, as many species habitat requirements extend beyond that of vegetation. For the SGM, selecting restoration sites that already have abundant rock cover would be the most practical way to increase SGM habitat through forest restoration practices. Taking into consideration the habitat requirements of target invertebrates can help in setting or redirecting restoration goals and thus enhance the conservation value of such practices.