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INDIVIDUAL DIFFERENCES IN PROGENY VIABILITY IN LAVANDULA LATIFOLIA : A LONG‐TERM FIELD STUDY
Author(s) -
Herrera Carlos M.
Publication year - 2000
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(2000)081[3036:idipvi]2.0.co;2
Subject(s) - seedling , biology , fecundity , survivorship curve , population , evergreen , sowing , shrub , juvenile , natural population growth , ecology , agronomy , demography , genetics , cancer , sociology
Despite its potential importance as a source of fitness variation in natural plant populations, few studies have so far examined long‐term patterns of individual differences in progeny viability under natural conditions. This paper reports on a six‐year field study on the differences in progeny viability (defined here as the probability of seeds contributing an established, prereproductive juvenile to the population), and its two components (seedling emergence and seedling survivorship), for the Mediterranean evergreen shrub Lavandula latifolia. The main objectives of the study were (1) to assess whether individual plants actually differ in the viability of their progeny under natural conditions, and (2) to determine if naturally occurring levels of variation in viability may modify individual differences in fecundity. Seed progenies from 14 maternal parents belonging to one population were sown at 10 field sites differing broadly in habitat type and soil characteristics, and seedling emergence and survival subsequently were monitored for six years. Maternal parents differed significantly in progeny viability because of both differential seedling emergence and seedling survivorship, and variation in either of these parameters was not significantly related to maternal differences in seed size. Differences in seedling survivorship were more important than differences in seedling emergence as determinants of maternal variation in progeny viability. While individual differences in seedling emergence remained consistent across sowing sites, there was a strong parent × sowing site interaction on seedling survivorship, and the rank of maternal parents with regard to this variable varied erratically among sowing sites. A significant inverse relationship existed across maternal parents between seed production and progeny viability, which was not mediated by differences in seed size, thus suggesting a trade‐off between the number and quality of the progeny produced by L. latifolia plants. Although maternal differences in seed production were about twice as important as differences in progeny viability in determining maternal differences in juvenile recruitment, viability differences should not be disregarded a priori as unimportant sources of fitness differences. Results of this study stress the importance of conducting long‐term, direct field assessments of individual differences in progeny viability across a range of environments encompassing the conditions actually faced by the species.