Implications of seed traits for restoration of ultramafic plant taxa from the Goro plateau in the subtropical hotspot of New Caledonia

The biodiversity hotspot of New Caledonia faces extensive landscape fragmentation. Progress of restoration practices is critical to address this problem for reestablishment of ecological continuities. The objective of our study, which can be considered as a first step, was to support appropriate species selection for restoration of fragmented habitats. We assessed seed dispersal, seed dormancy, and seed desiccation tolerance of 407 species from Forest (F) and Maquis (M) vegetation on ultramafic soils in southern New Caledonia. The primary seed dispersal mode was animals (zoochory, 53%). Overall, we found 34% of the taxa had some seed dormancy, and 72.9% had orthodox seeds. Wind-dispersed (anemochorous) species had predominantly non-dormant and orthodox seeds, whereas zoochorous species had seeds with at least some dormancy potential and higher recalcitrance. Further assessments were performed on 70 of the taxa, those currently used in ecological restoration. Their primary seed dispersal mode was found to be anemochory, 42.5% in Maquis (M) alone, and 40% in Forest and Maquis (FM) combined. Non-dormant seeds were prevalent both in M (82.5%) and FM (90%), and orthodoxy was the seed desiccation tolerance type most common in both vegetation types (95% and 66%, respectively in M and FM). Thus, the seeds currently used in restoration projects are mainly wind-dispersed orthodox seeds. To enhance both functional and phylogenetic diversity in restored areas, we recommend including fleshy-fruited, animal-dispersed taxa in restoration programs.