Pollination ecology and breeding system of two Calceolaria species in Chile
© Murúa et al.; licensee Springer. 2014
Received: 11 October 2013
Accepted: 24 March 2014
Published: 15 July 2014
Many angiosperms are exclusively dependent on pollinators for its reproduction (Matallana et al. 2010; Arroyo et al. 2006). However, pollinators sometimes could be erratic and variable in relation to the ecological context (e.g., plant community composition), especially in alpine zones where it is known that pollinators decline in abundance with the increment in altitude (Arroyo and Squeo 1990; Totland 1994). The latest could be critical in specialized pollination system and more over when specialized flowering plants inhabit in sympatry, potentially sharing the specialized floral visitors. In this context, it is expected that plant species develop reproductive strategies to ensure reproduction and/or exhibit some differences in their pollination ecology.
This study was conducted during the summer season of 2012 at the National Reserve Altos de Lircay (35°36′ S, 71°00′ W) in the Región del Maule, Chile. The sample site is located in the Reserve at 2,200 m a.s.l. and has a Mediterranean-type climate, with most rainfall concentrated in the winter season (di Castri and Hajek 1976). In the study site, C. filicaulis and C. arachnoidea inhabit in sympatry and are distributed in monospecific patches, surrounded by a vegetation matrix that includes Mimulus luteus Linnaeus (Schrophulareaceae), Mimulus cupreus Dombrain (Schrophulareaceae), Hypochoeris acaulis Britton (Asteraceae), Pozoa coriacea Lagasca & Segura (Apiaceae), and Azorella incisa Weddell (Apiaceae).
where, , , and represents the average number of seed per fruit on each treatment. The significance of treatment effects was evaluated on log-transformed data by two-way ANOVA. Statistical differences among treatments were evaluated in a post hoc Tukey test in R package version 2.15 (R development Core Team, 2011). To characterize pollination ecology, all flower visitors of both Calceolaria species were recorded. Focal observations of 15 min per plant were realized during six consecutive sunny days between 0900 and 1800 hours (50 h of observation per specie). All floral visitors contacting the reproductive structures of the flowers were captured and taken to the laboratory for taxonomic identification.
Floral visitors of each studied Calceolaria species
Proportion of visits
0.29 ± 0.07
0.06 ± 0.03
0.30 ± 0.04
0.04 ± 0.20
Chalepogenus sp. 1
0.002 ± 0.002
0.001 ± 0.001
In general, our results showed that Calceolaria species are highly dependent on pollinator for reproduction; however, they are able to self-fertilize and showed differences in their reproductive strategies. C. filicaulis is allogamous and self-incompatible, whereas C. arachnoidea is partially autogamous and present an incomplete self-compatibility. The latest seems to be frequent in flowering plants, in particular in specialized pollination systems (Perez et al. 2009), where the evolution of mixed mating strategies has evolved as stable strategy to deal with variable pollinator environments (see review in Goodwillie et al. 2005). In addition, both Calceolaria species were mainly visited by oil-collecting bees, but they differ in their principal pollinator. Globally, this finding suggest that Calceolaria and their oil-collecting bees could represent a highly specialized system, where plant species develop different reproductive strategies possibly in response to their ecological context. The latest could be explained by the frequency, consistency, and efficiency of their pollinators, which are known to decrease with the increase of elevation (Arroyo et al. 1985, 2006). In fact, in the study site, oil-collecting bees are present in low abundance, and they visit different plant species searching for pollen (MM, personal observation); it is known that this can interfere in plant fecundation through pollen interference and/or competition (Kunin 1997).
Despite that Calceolaria species are one of the most diverse genus in Chile (Fuentes et al. 1995), their biology, systematics, and evolution have been recently the subject of detailed research (Molau 1988; Sérsic 2004; Cosacov et al. 2009). Consequently, although this work represents a preliminary view of the breeding system and pollination ecology of Chilean Calceolaria species, this can be a starting point in the study of ecology and even evolution (e.g., reproductive barriers to speciation) of the genus. In this context, more studies are needed to determine proximal and ultimate mechanisms that are determining this finding in one of the most specialized plant-pollinator systems in Chile.
We thank Catalina González Brown for commenting the manuscript and CONAF for the sampling permission. This research was funded by the grant Beca de Apoyo a la Realización de la Tesis Doctoral (Folio 24110094, CONICYT) to MM.
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