Grasses are one of the most successful and dispersed plant families worldwide and their environmental and economic values are widely acknowledged. They dominate the landscape of Cabo Verde, the southernmost and driest archipelago of Macaronesia, and are relevant natural resources for local populations, but a comprehensive evaluation of their distribution patterns is still lacking. In this study, we aim to evaluate the potential effects of climate changes using the long-term data concerning grass distribution in Cabo Verde and the widely recognized climatic variability of this archipelago, which entails a huge irregularity in spatial and temporal rainfall. We identified two contrasting climatic periods (wet, from 1929 to 1968, and dry, from 1969 to 2007) and gathered all the information available from the bibliography, herbaria and fieldwork concerning spontaneous grass species recorded in Cabo Verde during those two periods, which amounted to 107 taxa.  This information was then used to disclose the patterns of grass diversity as related to climatic and topographic variables (altitude and windward vs leeward aspects). Different altitudinal shifts in the distribution patterns of grass species assemblages and an assemblage specific to the wet period were revealed by comparing the two climatic periods. The role of exposure in delimiting the altitudinal distribution of the various assemblages was highlighted; the trade winds clearly determine the distribution of grass assemblages. We detected shifts in the distribution of grass assemblages according to the climatic periods (related to the macroclimate) and local topographic factors (associated with mesoclimates). Also, functional traits (i.e., annuals vs. perennials, C3 vs. C4 grasses, and tropical vs. temperate species) were found to vary between wet and dry periods, as well as with altitude and with slope aspect. Understanding species distributions and the role of the climatic variability of Cabo Verde is crucial to predict how climate change will affect them and thus to support effective management and conservation actions.

These data were mainly compiled from: 1) herbarium specimens housed in the following Herbaria: Instituto de Investigação Científica Tropical, University of Lisbon (LISC), which holds the main collections from this geographical region; University of Coimbra (COI); Muséum National d’Histoire Naturelle, Paris (P); and Royal Botanic Gardens, Kew (K); local collections (e.g. Herbarium of the Parque Natural do Monte Gordo (PNMG), São Nicolau Island); 2) online databases such as the GBIF website that provide data on herbarium specimens and field observations (GBIF.org, 2020); 3) published works (namely Duarte, 1998; Duarte et al., 2005; Rivas-Martínez et al., 2017); and 4) unpublished data, including collected specimens and field observations dating from 1992 to 2006, done by the authors in Cabo Verde (mainly M.C. Duarte along with other collectors such as I. Gomes and J.C. Costa).

References

Duarte, M. C. 1998. A vegetação de Santiago (Cabo Verde): Apontamento histórico, composição florística e interpretação ecológica das comunidades. PhD thesis. Lisboa: Universidade Técnica de Lisboa, Instituto Superior de Agronomia.

Duarte, M. C., F. Rego, and I. Moreira. 2005. “Distribution patterns of plant communities on Santiago Island, Cape Verde.” Journal of Vegetation Science 16(3): 283-292. https://doi.org/10.1111/j.1654-1103.2005.tb02366.x

GBIF.org (30 June 2020). GBIF Occurrence Download https://doi.org/10.15468/dl.9gm3g3

Rivas-Martinez, S., M. Lousã, J. C. Costa, and M. C. Duarte. 2017. “Geobotanical survey of Cabo Verde Islands (West Africa).” International Journal of Geobotanical Research 7: 1-103.