Abstract
Alonso, C. & Garcia-Sevilla, M. 2013. Strong inbreeding depression and individually variable mating system in the narrow endemic Erodium cazorlanum (Geraniaceae). Anales Jard. Bot. Madrid 70(1): 72-80. Angiosperms evolved different systems to attract effective pollinators while reducing selfing in hermaphroditic flowers. Selfing ability can be advantageous when pollinators and/or mates are scarce, although inbreeding depression may largely reduce those advantages. Recent comparative analyses suggested endemic species tend to evolve self-compatibility but a better understanding of the associated reproductive and genetic tradeoffs is required. Experimental hand-pollinations under greenhouse conditions were conducted to investigate the selfing ability and estimate inbreeding depression up to the offspring’ first reproductive event in Ero dium cazorlanum, a narrow endemic species restricted to dolomite outcrops in SE Spanish mountains. We found autonomous selfing ineffective. Further, when experimentally applied, pollen of the same flower produced significantly fewer fruits and seeds compared to geitonogamous and cross pollinations. The number of seeds per fruit was significantly higher after cross pollinations and strong inbreeding depression accumulated through the life-cycle. Interestingly, individual plants exhibited broad variation in selfing ability with six out of 14 individuals producing no seed after geitonogamy. Understanding the consequences of individual variation in self compatibility deserves further investigation in the field now that we know that strong inbreeding depression may limit recruitment of selfed progeny.
Highlights
The hermaphrodite flowers, characteristic of many Angiosperms, facilitate the deposition and collection of pollen by pollinators in just one visit but they open the possibility that self pollination eventually reduce the benefits of outcrossing
Research on plant mating system of hermaphroditic species during the last two decades has revealed that intermediate mixed mating systems prevail among animal pollinated species, and intraspecific variation in realized mating system can be substantial depending on reproductive traits and ecological conditions making it more a population trait than a species attribute, at least in some cases
In the following paragraphs we discuss the implications that high inbreeding depression may have in the evolution of mating system and population persistence of a non-autonomous habitat specialist endemic species
Summary
The hermaphrodite flowers, characteristic of many Angiosperms, facilitate the deposition and collection of pollen by pollinators in just one visit but they open the possibility that self pollination eventually reduce the benefits of outcrossing. Species with well-characterized selfincompatibility (SI) systems such as those found in the Brassicaceae and Solanaceae present some ability to set seeds with self pollen in some populations (Good-Avila & al., 2008, and references therein) In these pseudo self compatible (PSC) species SI operates as a quantitative, rather than a qualitative, trait due to the segregation of unlinked genes that modify the strength of SI (Good-Avila & al., 2008). Whether such intermediate strategies are widespread, artefactual or evolutionary labile is under debate (see Raduski & al., 2012 and references therein). PSC could be an evolutionary stage in the path towards self-compatibility (Allen & Hiscock, 2008) favored when mates are limiting (Busch & Schoen, 2008), for instance in small populations of endemic species (e.g., Byers, 1995)
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