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HETEROSIS IN AN ISOLATED, EFFECTIVELY SMALL, AND SELF‐FERTILIZING POPULATION OF THE FLOWERING PLANT LEAVENWORTHIA ALABAMICA
Author(s) -
Busch Jeremiah W.
Publication year - 2006
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2006.tb01092.x
Subject(s) - biology , heterosis , genetic load , population , small population size , offspring , outcrossing , human fertilization , reproductive isolation , reproductive success , genetic drift , inbreeding depression , effective population size , outbreeding depression , genetics , hybrid , inbreeding , ecology , agronomy , genetic variation , pollen , gene , demography , pregnancy , sociology , habitat
Mildly deleterious mutations are thought to play a major role in the extinction of natural populations, especially those that are small, isolated, or inbred. Self‐fertilization should reduce the effective size of populations and simultaneously reduce migration between populations. A history of self‐fertilization should therefore cause a population to harbor a substantial local drift load caused by the fixation of mildly deleterious mutations. This hypothesis was tested in Leavenworthia alabamica , which contains large, self‐incompatible populations and smaller self‐compatible populations with adaptations for self‐fertilization. The fitness of offspring from within‐ and between‐population crosses was compared to quantify heterosis caused by the masking of deleterious alleles in the heterozygous state. Little heterosis was observed in crosses between five large, self‐incompatible populations and two of the three small, self‐fertilizing populations of L. alabamica . However, the most geographically isolated and genetically divergent self‐fertilizing population (Tuscumbia) exhibited a 110.2% increase in germination and a 73.6% increase in fitness, which is consistent with a sizeable local drift load. The finding of substantial heterosis for fitness supports the idea that small effective size, reproductive isolation, and self‐fertilization can make populations particularly vulnerable to mutation accumulation.