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Anales del Jardín Botánico de Madrid ISSN: 0211-1322 [email protected] Consejo Superior de Investigaciones Científicas España Torices, Rubén; Agudo, Alicia; Álvarez, Inés Not only size matters: achene morphology affects time of seedling emergence in three heterocarpic species of Anacyclus (Anthemideae, Asteraceae) Anales del Jardín Botánico de Madrid, vol. 70, núm. 1, enero-junio, 2013, pp. 48-55 Consejo Superior de Investigaciones Científicas Madrid, España Available in: http://www.redalyc.org/articulo.oa?id=55628039005 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative 2351 anacyclus.7.qxp:Anales 70(1).qxd 22/07/13 16:27 Página 48 Anales del Jardín Botánico de Madrid 70(1): 48-55, enero-junio 2013. ISSN: 0211-1322. doi: 10.3989/ajbm. 2351 Not only size matters: achene morphology affects time of seedling emergence in three heterocarpic species of Anacyclus (Anthemideae, Asteraceae) Rubén Torices1*, Alicia Agudo2 & Inés Álvarez2 1Centro de Ecologia Funcional, Universidade de Coimbra, 3001– 455 Coimbra, Portugal 2Real Jardín Botánico, CSIC(RJB-CSIC), Plaza de Murillo 2, E-28014 Madrid, Spain [email protected]; [email protected]; [email protected] Abstract Resumen Torices, R., Agudo, A. & Álvarez, I. 2013. Not only size matters: achene Torices, R., Agudo, A. & Álvarez, I. 2013. No sólo importa el tamaño: la morphology affects time of seedling emergence in three heterocarpic morfología del aquenio afecta al tiempo de emergencia de la plántula en species of Anacyclus (Anthemideae, Asteraceae). Anales Jard. Bot. Madrid tres especies heterocárpicas de Anacyclus (Anthemideae, Asteraceae). 70(1): 48-55. Anales Jard. Bot. Madrid 70(1): 48-55 (en inglés). The production of two or more distinct fruit types by an individual, i.e. hete- La producción de dos o más tipos de frutos diferentes por un mismo indivi- rocarpy, is considered as a mixed dispersal strategy in which a proportion duo, i.e. heterocarpia, es considerada como una estrategia mixta de dis- of the offspring is able to colonize new sites, whilst others remain near the persión en la que una parte de la descendencia es capaz de colonizar nue- maternal location. Here, we aimed to explore the effects of achene mor- vos sitios, mientras que la otra permanece cerca de la planta madre. En este phology (winged vs. unwinged achenes) and achene size –measured here trabajo, nuestro objetivo fue explorar los efectos de la morfología del aque- as achene mass– on post-dispersal life-history traits (probability and time nio (aquenios alados vs. no alados) y de su tamaño –medido aquí como of seedling emergence) in three heterocarpic Anacyclus species (An- masa del aquenio– en la etapa del ciclo de vida siguiente a la dispersión themideae, Asteraceae). Morphology, size and germination performance (probabilidad de germinación y tiempo de emergencia de las plántulas) de were studied in achenes from six populations of Anacyclus clavatus (Desf.) tres especies heterocárpicas del género Anacyclus (Anthemideae, Astera- Pers., A. homogamos (Maire) Humphries, and A. valentinus L. Our results ceae). Se estudió la morfología, el tamaño y la germinación en aquenios de show that achene morphology and size were related to their position with- seis poblaciones de Anacyclus clavatus (Desf.) Pers., A. homogamos (Mai- in the capitulum, such that outer, winged achenes were significantly hea- re) Humphries y A. valentinus L. Nuestros resultados indican que tanto la vier than the inner, unwinged ones. Additionally, winged achenes germi- morfología del aquenio como su tamaño estaban relacionados con su po- nated faster than unwinged ones. This pattern may be related to the se- sición en el capítulo, de manera que los aquenios más externos –alados– quential achene time of release displayed by these species. Finally, our eran significativamente más pesados que los internos –sin alas–. Además, findings cast doubt on the role of wings as structures that favor dispersal los aquenios alados germinaron más rápidamente que los no alados. Este by wind in these three species of Anacyclus. patrón puede estar relacionado con la liberación secuencial de los aquenios que ocurre en estas especies. Por último, nuestros resultados ponen en duda la función de las alas como estructuras que favorecen la dispersión por viento de los aquenios en estas tres especies de Anacyclus. Keywords: bet-hedging, Compositae, heterocarpy, mixed strategy, posi- Palabras clave: bet-hedging, Compositae, heterocarpia, estrategia mix- tion effects, weeds, winged fruits. ta, efectos de posición, malas hierbas, frutos alados. INTRODUCTION dual phenotypes may have a relatively lower mean fitness (Gillespie, 1977; Venable, 1985; Venable & al., 1987; Ven- Seed dispersal is mainly determined by fruit characteris- able, 2007; Simons, 2011; Tielbörger & al., 2012). tics, which usually vary continuously within an individual Among members of Asteraceae, the occurrence of hetero- plant (Herrera, 2009). However, some plants produce two or carpy is relatively high (Mandák, 1997; Imbert, 2002). Hetero- more defined fruit types, a condition known as heterocarpy, carpic species in this family usually produce different achene in which distinct fruit morphs may show different behavior morphs within the same capitulum (reviewed in Imbert, 2002), for dispersal, germination recruitment or seedling survival although exceptions in which achene variation occurs between (Imbert, 2002). Heterocarpy is usually interpreted as a bet- aerial and subterranean capitula are known in Gymnarrhena hedging or mixed strategy in which different seed subsets of micrantha (Koller & Roth, 1964) and Catananche lutea (Ruiz one individual may successfully germinate under different de Clavijo, 1995; Ruiz de Clavijo & Jiménez, 1998), and in Cen- conditions in time and space. This offers the chance to colo- taurea melitensis (Porras & Muñoz, 2000) between cleistoga- nize new sites, free from sibling competition or other local mous and chasmogamous capitula. Apart from these excep- sources of stress, whereas the remainder of the offspring stays tions, most of achene variation is found within capitula. Be- in the same habitat (Gadgil, 1971; Levin & al., 1984; Schoen sides variation in morphology, achenes may also vary marked- & Lloyd, 1984; Venable & Brown, 1993; Imbert & Ronce, ly in size (Venable & al., 1987; McGinley, 1989; Maxwell & al., 2001). Various authors have proposed that a bet-hedging 1994; Imbert & al., 1996; Van Mölken & al., 2005; Brändel, strategy is likely to be favored in temporally variable environ- 2007). Both traits, achene size and morphology, usually co- ments because it increases geometric fitness, even if indivi- vary, such that achenes without dispersal structures are usual- * Corresponding author. 2351 anacyclus.7.qxp:Anales 70(1).qxd 22/07/13 16:27 Página 49 Time of emergence in heterocarpic Anacyclus 49 ly the heaviest ones, whereas those adapted for greater disper- ences between the central unwinged achenes and the periphe- sal are generally lighter (McEvoy, 1984; Tanowitz & al., 1987; ral winged ones were not significant and also both morphs Venable & al., 1987; Imbert & al., 1996; Imbert & Ronce, had non-dormant seeds. 2001; Brändel, 2004, 2007; Bastida & Menéndez, 2004, Basti- We aimed to explore the effects of achene morphology da & al., 2010; among others). With regard to germination per- (presence vs. absence of wings in achenes) and achene size on formance, recent research suggests that variation in achene size two important post-dispersal life-history traits in three Anacy- may be the main driver of divergent behavior exhibited by clus species: probability and time of seedling emergence. Fi- seeds from different achene morphs (Van Mölken & al., 2005; nally, we discuss the implications that winged achenes may Torices & Méndez, 2010). Achene size can also affects perfor- have on different dispersal mechanisms and germination per- mance in post-dispersal life-history traits, particularly in com- formance with regard to bet-hedging strategies in Anacyclus petitive conditions (McEvoy, 1984; Andersson, 1996; Ruiz life-history. de Clavijo & Jiménez, 1998; Meyer & Carlson, 2001; Ruiz de Clavijo, 2005; Van Mölken & al., 2005; Benard & Toft, 2007). MATERIAL AND METHODS Alternatively, seeds might have different behaviors in germina- Study species and plant material tion that are linked to the achene morphology, regardless of size, and which might also affect later stages in plant develop- Morphology, size and germination performance were stud- ment (Imbert, 2002). In order to distinguish which of these sit- ied in achenes from a total of 6 different natural populations uations applies in any particular species, we need to determine in Anacyclus clavatus, A. homogamos, and A. valentinus whether the achene morphology within a capitulum has direct (Table 1). A total of 9-10 mature capitula of several individu- effects on post-dispersal life-history traits, or whether this ef- als in each site were collected and preserved in darkness at fect is solely mediated by achene size. –4 ºC with silica gel until their use. In spite of the high incidence of heterocarpy in the Astera - These three species (Fig. 1) occur in Western Mediter- ceae and its known influence on dispersal ability and germi- ranean and their distribution areas partially