Reproductive Biology

ANDERSON G.J.; BERNARDELLO G.

Plants of oceanic islands: Evolution, Biogeography, and Conservation of the Flora of the Juan Fernández (Robinson Crusoe) Archipelago

Cambridge University Press

Año: 2017; p. 193 - 205

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; Lowry, 2009), and for unusual species (e.g., Lactoris and the many unusual composites in Dendroseris and Robinsonia; see Chapters 5, 13). In terms of reproductive biology it is notable for several reasons. The level of dioecy is not particularly high, higher than that on the Canaries, and significantly less than in Hawaii. As studies move beyond the necessary alpha-systematic, and 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. The pollination is notable for two reasons. First, because bird pollination, hummingbirds in this case, is prominent, serving some 10% of the flora. As noted, 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 newly discovered and newly described species might become more important), or flower-visiting Lepidoptera or Diptera, animal pollination is restricted to the ornithophilous species. Thus, we have concluded that the island-ubiquitous autogamy or geitonogamy, and anemophily, are the main sexual reproductive forces. That lack of potential animal pollinators, coupled with a relatively young flora, has lead to another particularly notable feature: many more of the island endemics and natives have retained features that are similar to their presumed ancestors than might be 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 least in a pollination sense, are not showy. However, a number of the features would seem to manifest retention of features of the colonizing forms (such things as 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, the Juan Fernández or Robinson Crusoe Islands-, is indeed interesting in so 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 from the literature.