View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by St Andrews Research Repository The University of Chicago Sex Allocation and Reproductive Success in the Andromonoecious Perennial Solanum carolinense (Solanaceae). II. Paternity and Functional Gender. Author(s): Elizabeth Elle and Thomas R. Meagher Source: The American Naturalist, Vol. 156, No. 6 (December 2000), pp. 622-636 Published by: The University of Chicago Press for The American Society of Naturalists Stable URL: http://www.jstor.org/stable/10.1086/316997 . Accessed: 12/08/2014 09:52 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press, The American Society of Naturalists, The University of Chicago are collaborating with JSTOR to digitize, preserve and extend access to The American Naturalist. http://www.jstor.org This content downloaded from 138.251.162.242 on Tue, 12 Aug 2014 09:52:28 AM All use subject to JSTOR Terms and Conditions vol. 156, no. 6 the american naturalist december 2000 Sex Allocation and Reproductive Success in the Andromonoecious Perennial Solanum carolinense (Solanaceae). II. Paternity and Functional Gender Elizabeth Elle1,* and Thomas R. Meagher2,² 1. Department of Biological Sciences, Simon Fraser University, primarily by mating opportunity, while ®tness gain Burnaby, British Columbia V5A 1S6, Canada; through female function is limited primarily by resource 2. Institute of Environmental and Evolutionary Biology, University availability for offspring production. This idea has been of St. Andrews, St. Andrews, Fife, Scotland integrated with sex allocation theory (Charnov 1982). Submitted November 22, 1999; Accepted July 20, 2000 When applied to plants, sex allocation theory predicts that ¯oral attractiveness (e.g., large petals, nectar availability) is more important to ®tness gain through male function than female function because attracting pollinators will increase mating opportunities. Although male success abstract: According to Bateman's principle, male ®tness in en- tomophilous plant species should be limited by mating opportunity, should be correlated with mating opportunities, one or a which is in¯uenced by the size or number of ¯owers. We determined few visits by pollinators may be adequate to fertilize all male-speci®c ®tness consequences of ¯oral phenotype in andro- ovules; thus, female ®tness should not be as strongly af- monoecious Solanum carolinense, examined the relationship between fected by ¯oral attractiveness. Because male success relies male and female reproductive success within plants, and evaluated on both pollinator response to ¯oral attractiveness and the distribution of functional gender among plants. A maximum another plant's resource base for seed production, male likelihood-based paternity analysis, based on multilocus allozyme phenotypes of parents and offspring from four experimental plots, reproductive success is also predicted to be more variable was used to determine male reproductive success and its relationship than female reproductive success. to ¯oral phenotype. Male success was enhanced by an increase in Empirical support for Bateman's principle in plant species the proportion of male ¯owers produced but not by an increase in is limited and has been equivocal (see reviews in Wilson et total ¯ower number, even though all ¯owers contain male parts. al. 1994; Campbell 2000). Fitness through male function Larger ¯ower size increased male success in only one plot. Male and has been shown to increase with increased pollen production female reproductive success were negatively correlated, and plants varied in functional gender from completely female to completely (Devlin et al. 1992) or the number of ¯owers producing male. This gender specialization may occur because hermaphroditic pollen (Queller 1983; Schoen and Stewart 1986). For en- and male ¯owers differ in their ability to contribute to male and tomophilous plants, ¯ower size (Bell 1985; Young and Stan- female success. Although sex allocation theory predicts a positive ton 1990) and overall ¯oral display (Broyles and Wyatt 1990, relationship between the size or number of plant parts and repro- 1995; Fishbein and Venable 1996) are also considered to be ductive success, this study indicates that aspects of ¯oral morphology important for male success. Some studies, however, have that affect gender specialization should also be considered. found that ¯ower size can be as important for female success Keywords: andromonoecy, Bateman's principle, functional gender, as it is for male success (Campbell 1989; Stanton et al. 1991; paternity analysis, sex allocation, Solanum carolinense. Wilson et al. 1994; Conner et al. 1996a, 1996b) and that display size is not always correlated with male success (Meagher 1991). In studies comparing variance in male and Bateman's principle (Bateman 1948; Wilson et al. 1994) female performance, male success has been found to be asserts that ®tness gain through male function is limited more variable than female success (MuÈller-Starck and Ziehe 1984; Meagher 1986), less variable than female success (Dev- * E-mail: [email protected]. lin and Ellstrand 1990; Dudash 1991), and more variable ² E-mail: [email protected]. or less variable in different years (Conner et al. 1996b). Am. Nat. 2000. Vol. 156, pp. 622±636. q 2000 by The University of Chicago. In hermaphroditic species, male and female reproduc- 0003-0147/2000/15606-0005$03.00. All rights reserved. tive success are often positively correlated, although weakly This content downloaded from 138.251.162.242 on Tue, 12 Aug 2014 09:52:28 AM All use subject to JSTOR Terms and Conditions Paternity and Functional Gender 623 (Broyles and Wyatt 1990; Devlin and Ellstrand 1990; Con- fruit (Solomon 1986). Hermaphroditic ¯owers are pro- ner et al. 1996b). It has been assumed that some traits, duced basally, the male ¯owers (when present) at the tips such as ¯ower production or overall plant vigor, in¯uence of in¯orescences. Pollen viability does not differ between both sex functions. However, some characteristics of the the two ¯ower types (Solomon 1985). The showy anthers ¯oral display may disproportionately increase success are attractive to pollinators, for whom pollen is the only through one or the other sex function, as predicted by sex reward (Solomon 1987). Flowers are buzz pollinated by allocation theory. Thus, individuals that differ in their ¯o- large-bodied bees, which hang from the ¯owers and vibrate ral phenotype may differ in their functional gender, the their ¯ight muscles, causing pollen to be ejected from a relative amount of reproductive success gained through terminal pore in the anther (Buchmann 1983; Solomon female function (Lloyd 1980, 1984). 1986). Fruit contain an average of 160 seeds (E. Elle, un- In order to address the relationship between ¯oral phe- published data). notype and male success as well as the relationship between Ripe fruit were collected from 12 source plants in each male and female success, it is necessary to measure male of three natural populations: a sheep pasture at Cook Col- success using paternity analysis (e.g., Meagher 1986, 1991; lege, Rutgers University, New Jersey; Brook®eld Land®ll Schoen and Stewart 1986; Broyles and Wyatt 1990; Devlin on Staten Island, New York; and an old ®eld (»15 yr since and Ellstrand 1990; Adams and Birkes 1991; Stanton et abandonment) at Hutcheson Memorial Forest, Franklin al. 1991; Karron et al. 1995a, 1995b; Conner et al. 1996b; Township, New Jersey. Three distinct populations were Burczyk and Prat 1997; Kaufman et al. 1998; Morgan used as seed sources to increase the genetic and phenotypic 1998). On the basis of multilocus genotype pro®les for a variation among plants used in this experiment. Source set of offspring, their known mothers, and the array of populations were 20±70 km distant from one another. potential fathers, one can determine maximum likelihood Source plants were chosen that were spatially separated so fertility estimates for all of the males in a population (Roe- as to minimize the probability of choosing multiple ramets der et al. 1989; Smouse and Meagher 1994). Recently, the from single genets. maximum likelihood approach has been extended to en- able direct regression of male characters on fertility (Ad- Experimental Plots ams and Birkes 1991; Adams et. al. 1992; Smouse et al. 1999), allowing us to address more effectively the as- Experimental design has been described elsewhere (Elle sumptions of sex allocation theory. 1999), with the most relevant information repeated here. This article is part of a series exploring the relationship Two plots were set up in opposite corners of a30 # 70 -m between sex allocation and sex-speci®c success in the an- rectangle in each of two sites. Plots A and B were in an old dromonoecious perennial plant Solanum carolinense. Prior ®eld at Hutcheson Memorial Forest (HMF), Franklin Town- work has shown that ¯oral characters are heritable in this ship, New Jersey, in a 10-yr-old experimental ®eld. Plots C species (Elle 1998) and that