J Plant Ecol ›› 2013, Vol. 6 ›› Issue (6): 489-498 .

• Research Articles •

### Spatial patterns of distribution and abundance of Harrisia portoricensis, an endangered Caribbean cactus

Julissa Rojas-Sandoval1,2,* and Elvia J. Meléndez-Ackerman2,3

1. 1 Department of Biology, University of Puerto Rico, Río Piedras Campus, PO Box 23360, San Juan, Puerto Rico 00931-3360, USA; 2 Center for Applied Tropical Ecology and Conservation, University of Puerto Rico, PO Box 70377, San Juan, Puerto Rico 00936-8377, USA; 3 Department of Environmental Sciences, College of Natural Sciences, University of Puerto Rico, PO Box 70377, San Juan, Puerto Rico 00936-8377, USA
• Received:2012-12-04 Accepted:2013-02-10 Published:2013-11-21
• Contact: Rojas-Sandoval, Julissa

### Spatial patterns of distribution and abundance of Harrisia portoricensis, an endangered Caribbean cactus

Abstract: Aims The spatial distribution of biotic and abiotic factors may play a dominant role in determining the distribution and abundance of plants in arid and semiarid environments. In this study, we evaluated how spatial patterns of microhabitat variables and the degree of spatial dependence of these variables influence the distribution and abundance of the endangered cactus Harrisia portoricensis.
Methods We used geostatistical analyses of five microhabitat variables (e.g. vegetation cover, soil cover and light incidence) and recorded the abundance of H. portoricensis in 50 permanent plots established across Mona Island, Puerto Rico, by the United States Department of Agriculture Forest Service as part of the Forest Inventory and Analysis (USDA–FIA). We also used partial Mantel tests to evaluate the relationships between microhabitat variables and abundance of H. portoricensis, controlling for spatial autocorrelation.
Important findings Abundance of H. portoricensis showed strong affinities with microhabitat variables related to canopy structure, soil cover and light environment. The distribution of this cactus species throughout the island was consistent with the spatial variation patterns of these variables. In general, landscape-level analyses suggested a predictive value of microhabitat traits for the distribution and abundance of this endangered species. For sensitive cacti species, wherein abundance may be influenced by similar variables, these types of analyses may be helpful in developing management plans and identifying critical habitats for conservation.

Aims The spatial distribution of biotic and abiotic factors may play a dominant role in determining the distribution and abundance of plants in arid and semiarid environments. In this study, we evaluated how spatial patterns of microhabitat variables and the degree of spatial dependence of these variables influence the distribution and abundance of the endangered cactus Harrisia portoricensis.
Methods We used geostatistical analyses of five microhabitat variables (e.g. vegetation cover, soil cover and light incidence) and recorded the abundance of H. portoricensis in 50 permanent plots established across Mona Island, Puerto Rico, by the United States Department of Agriculture Forest Service as part of the Forest Inventory and Analysis (USDA–FIA). We also used partial Mantel tests to evaluate the relationships between microhabitat variables and abundance of H. portoricensis, controlling for spatial autocorrelation.
Important findings Abundance of H. portoricensis showed strong affinities with microhabitat variables related to canopy structure, soil cover and light environment. The distribution of this cactus species throughout the island was consistent with the spatial variation patterns of these variables. In general, landscape-level analyses suggested a predictive value of microhabitat traits for the distribution and abundance of this endangered species. For sensitive cacti species, wherein abundance may be influenced by similar variables, these types of analyses may be helpful in developing management plans and identifying critical habitats for conservation.