AOBPreview originally published online on February 14, 2009
Annals of Botany 2009 103(7):1077-1089; doi:10.1093/aob/mcp033
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Effect of variation in self-incompatibility on pollen limitation and inbreeding depression in Flourensia cernua (Asteraceae) scrubs of contrasting density
1 Departmento de Ecología, Universidad Autónoma de Yucatán, Km. 15·5 Carretera Mérida Xtmacuil, Mérida, Yucatán, 97000, México
2 Department of Biology, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB R3B2E9, Canada
3 Instituto de Ecología A.C., Apartado Postal 63, Xalapa, Veracruz, CP 91070, México
4 Departamento de Ecología Evolutiva, Instituto de Ecología, UNAM, Apartado Postal 70-275 México D. F., CP 04510, México
* For correspondence. E-mail mferrer{at}uady.mx or trigoamarillo{at}gmail.com
Received: 24 June 2008 Returned for revision: 27 August 2008 Accepted: 5 January 2009 Published electronically: 14 February 2009
Background and Aims: Selection may favour a partial or complete loss of self-incompatibility (SI) if it increases the reproductive output of individuals in the presence of low mate availability. The reproductive output of individuals varying in their strength of SI may also be affected by population density via its affect on the spatial structuring and number of S-alleles in populations. Modifiers increasing levels of self-compatibility can be selected when self-compatible individuals receive reproductive compensation by, for example, increasing seed set and/or when they become associated with high fitness genotypes.
Methods: The effect of variation in the strength of SI and scrub density (low versus high) on seed set, seed germination and inbreeding depression in seed germination (
germ) was investigated in the partially self-incompatible species Flourensia cernua by analysing data from self-, cross- and open-pollinated florets.
Key Results: Examination of 100 plants in both high and low scrub densities revealed that 51% of plants were strongly self-incompatible and 49 % varied from being self-incompatible to self-compatible. Seed set after hand cross-pollination was higher than after open-pollination for self-incompatible, partially self-incompatible and self-compatible plants but was uniformly low for strongly self-incompatible plants. Strongly self-incompatible and self-incompatible plants exhibited lower seed set, seed germination and multiplicative female fitness (floral display x seed set x seed germination) in open-pollinated florets compared with partially self-incompatible and self-compatible plants. Scrub density also had an effect on seed set and inbreeding depression: in low-density scrubs seed set was higher after open-pollination and germ was lower.
Conclusions: These data suggest that (a) plants suffered outcross pollen limitation, (b) female fitness in partially self-incompatible and self-compatible plants is enhanced by increased mate-compatibility and (c) plants in low-density scrubs received higher quality pollen via open-pollination than plants in high-density scrubs.
Key words: Flourensia cernua, population density, seed set, seed germination, female fitness, partial self-incompatibility, Mapimí Biosphere Reserve
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