Density-dependent migration and human population structure in historical Massachusetts

✍ Scribed by John H. Relethford

• Book ID: 102704310
• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 959 KB
• Volume: 69
• Category: Article
• ISSN: 0002-9483
• DOI: 10.1002/ajpa.1330690309

✦ Synopsis

Studies of population structure often focus on the effects of population size and migration rates on genetic variation. Few studies, however, have investigated the relationship between these two factors. The purpose of this paper is to determine the extent to which migration (and gene flow) is density-dependent (that is, affected by population size) for populations in historical Massachusetts. Data from 4,859 marriage records were analyzed from four populations in north-central Massachusetts during the time period 1741 to 1849. These data were placed into 29 samples defined in terms of population and time cohort. Within each cohort the overall exogamy rate was computed along with three estimates of gene flow based on marital migration: local migration (k), long-distance migration (m), and effective migration rate (me).

Three samples show unusually low rates that reflect the history of settlement.

Regression analyses were used with the remaining samples, and they show nonlinear density-dependent migration that is unrelated to temporal trends. Migration is highest in samples with small population sizes (< 800) and large population sizes ( > 1,600). Migration is lowest in medium-sized populations.