Factors affecting the floristic relationships among Mexican pinyon woodlands
Luna-Cavazos, Mario; Romero-Manzanares, Angélica; García-Moya, Edmundo
We analyzed, by indirect and direct gradient analysis, the floristic relationships among different Mexican pinyon woodland communities dominated by Pinus cembroides, P. johannis, P. remota, P. maximartinezii, P. monophylla, P. quadrifolia, P. nelsonii, P. culminicola, and P. lagunae, belonging to distinct biogeographic provinces. We elaborated a presence-absence data matrix of 1153 taxa and 32 woodlands, and analyzed the pinyon woodland relationships in relation to various environmental factors by using Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA). The floristic differences among pinyon communities were tested by using Multiresponse Permutation Procedure (MRPP) analysis. Our results showed that the first DCA axis distinguished Operational Geographic Units (OGUs) based on a longitudinal and latitudinal patterns, while the second axis is related to mean annual temperature. Based on floristic relationships, three main groups were detected by DCA: a) pinyons from the California province; b) pinyons from Sierra Madre Oriental and Altiplano Norte and c) pinyons from Sierra Madre Occidental and Altiplano Sur. P. lagunae, from Del Cabo province, is more similar to this last group. Axis one of CCA correlated with longitude and latitude, axis two with elevation, mean annual precipitation, and aridity index. Overall, our data indicate that P. quadrifolia and P. monophylla communities are the pinyon woodlands floristically least similar to the other pinyon woodlands.