Hybridization in Mexican Pinus - implications for management and conservation
ID: 613 / 268
Proposed Symposium Title: Hybridization in Mexican Pinus - implications for management and conservation
M. Socorro González-Elizondo1, Martha González-Elizondo1, Norma L. Piedra Leandro2, Jorge A. Tena-Flores1, Christian A. Wehenkel3, José J. Corral-Rivas4, Lluvia Flores-Rentería5
Affiliations: 1 CIIDIR, Instituto Politécnico Nacional, Durango, México 2 Jardín Etnobiológico Estatal de Durango, Durango, México 3 ISIMA, Universidad Juárez del Estado de Durango, Durango, México 4 FCF, Universidad Juárez del Estado de Durango, Durango, México 5 Department of Biology, San Diego State University, San Diego, CA, U.S.A.
Hybridization is common in plants. Its outcomes are wide and contrasting, from detrimental or causing merging of species, to increasing their evolutionary and ecological resilience and even resulting in hybrid speciation. In western and northern Mexico, hybridization frequency among Pinus species ranges from occasional (e.g., isolated individuals of Pinus chihuahuana × P. lumholtzii) to stable populations (e.g., of P. arizonica × P. cooperi). There is also a wide range of fitness outcomes, from hybrid swarms composed by low fitness individuals (e.g., P. arizonica × P. engelmannii) to populations exhibiting hybrid vigor (e.g., P. herrerae × P. luzmariae). Some are recent (isolated F1s), and others are part of ancient introgressions (e.g., P. cembroides × P. discolor; P. strobiformis × P. flexilis); a syngameon encompassing pinyons has been recently recorded showing how sequential hybridization might have accelerated the speciation in this group. Gene flow among these species increases along ecological or geographical range edges and in disturbed communities. The high rate of hybridization in the zone may be owed to the facts that: a) Mexican pines are relatively recent (6 - 10.5 Ma), allowing for species to hybridize in absence of genetic incompatible systems, b) northwestern Mexico is a very rugged region offering multiple and diverse niches that favor diversification, and c) it is a boundary area for many species reaching there their northern or southern limits. Despite the evidence about their commonness, natural hybrids are not yet considered in forestry policies in Mexico. Combined names indicating hybridization or introgression are not allowed in inventories and monitoring reports nor in official paperwork. A shift of paradigm is needed to adjust forestry policies and management to the real situation in which genetically merged biological entities are common in forest ecosystems.