Reproductive biology in the endemic plants of the Juan Fernández Archipelago (Robinson Crusoe Islands)

BERNARDELLO G.

Congreso; XIX International Botanical Congress; 2017

We surveyed the reproductive features of the angiosperms of the archipelago including the pollination, breeding systems and sexual systems. The collection of original data was based on our team?s hundreds of hours of field and lab experiments and observations combined with data from the limited existing literature. This is the first and most comprehensive analysis of an entire island flora. The Juan Fernández flora is not large. It is notable in terms of the proportion of endemics per unit area (the greatest for any island archipelago), and for unusual species (e.g., Lactoris and many Asteraceae, e.g., Dendroseris and Robinsonia). The reproductive biology is notable for several reasons. Although, the level of dioecy is not particularly high (9%), it is higher than that on the Canaries, and significantly less than in Hawaii. As studies move beyond the necessary alpha-ecological first steps to careful in-depth analyses of various taxa, our understanding of breeding systems, and of the incidence of dioecy, will change (i.e., more reports of cryptic dioecy as we discovered with Pernettya rigida). The pollination is notable for two reasons. First, because bird pollination, hummingbirds in this case, is prominent, serving some 10% of the flora; one of the hummingbirds is the only hummingbird endemic to an oceanic island. Secondly, because other than the hummingbirds, there are virtually no animal pollinators. The impressive pioneering work by Skottsberg cited a number of likely zoophilous flowers in the flora, but, given that there are no virtually no bees (virtually, though the just discovered new species might become more important), or flower-visiting Lepidoptera or Diptera, animal pollination is restricted to birds. Thus, we have concluded that the island-ubiquitous autogamy or geitonogamy, and anemophily, are the key breeding systems and pollination syndrome. That lack of potential animal pollinators, coupled with a relatively young flora, has led to another particularly notable feature: many more of the island endemics and natives have retained features that are similar to their presumed ancestors than expected. To be sure, a significant portion of the flora fits the usual island model that Carlquist (1974) recognized, where many of the flowers are small, green and, in terms of pollination, are not showy. However, a number of the features would seem to manifest retention of features of the colonizing forms (e.g., larger brightly colored corollas, the expected pollen to ovule ratios for biotically pollinated taxa, and the presence of nectar ?all characteristic of zoophilous pollination)? presumably as a result of the lack of selection among species that are autogamous or geitonogamous and/or are wind pollinated. The flora of these little islands is indeed interesting in many ways. And, it seems, at least for the reproductive biology, to manifest an ability to ?make do?, to improvise success and sustainability, characteristics shared with its alternative namesake ? the Robinson Crusoe Islands? from the literature.