Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help
 

GeoTreesearch


Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

(933 KB bytes)

Title: Recent evolution and divergence among populations of a rare Mexican endemic, Chihuahua spruce, following holocene climatic warming

Author: Ledig, F. Thomas; Jacob-Cervantes, Virginia; Hodgskiss, Paul D.

Date: 1997

Source: Evolution 51(6): 1815-1827

Publication Series: Miscellaneous Publication

Description: Fragmentation and reduction in population size are expected to reduce genetic diversity. However, examples from natural populations of forest trees are scarce. The range of Chihuahua spruce retreated northward and fragmented coincident with the warming climate that marked the early Holocene. The isolated populations vary from 15 to 2441 trees, which provided an opportunity to test whether census number is a good predictor of genetic diversity. Mean expected heterozygosity, He, based on 24 loci in 16 enzyme systems, was 0.093 for 10 sampled populations, which is within the range reported for conifers. However, estimates varied more than two-fold among populations and He was closely related to the logarithm of the number of mature trees in the population (rHe,N = 0.93). Diversity among populations, FST, was 24.8% of the total diversity, which is higher than that observed in almost all conifer species studied. Nei's genetic distance, D, was not related to geographic distance between populations, and was 0.033, which is higher than estimates for most wide-ranging species. Most populations had excess homozygosity and the fixation index, FIS, was higher than that reported for all but one species of conifer. NM, the number of migrants per generation, was 0.43 to 0.76, depending on estimation procedure, and is the smallest observed in conifers. The data suggest that populations of Chihuahua spruce have differentiated by drift and that they are effectively isolated. The results illustrate how a combination of paleontological observation and molecular markers can be used to illuminate recent evolutionary events. Multilocus estimates of outcrossing for two small populations were zero (complete selfing) and 0.153, respectively, which are in striking contrast to the near complete outcrossing observed in most conifers. The high fixation index and a high proportion of empty seeds (45%) suggest that inbreeding may be a serious problem for conservation of Chihuahua spruce.

Keywords: Gene flow, genetic diversity, genetic drift, inbreeding, isozymes, Picea, population decline

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
  • You may send email to rschneider@fs.fed.us to request a hard copy of this publication. (Please specify exactly which publication you are requesting and your mailing address.)

XML: View XML

Citation:


Ledig, F. Thomas; Jacob-Cervantes, Virginia; Hodgskiss, Paul D. 1997. Recent evolution and divergence among populations of a rare Mexican endemic, Chihuahua spruce, following holocene climatic warming. Evolution 51(6): 1815-1827

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.