Open Collections

Paajanen, Mikko Pasi Tapani

University of British Columbia

Native ecosystems on St Helena have had a limited instrumental (i.e., economical) value for human exploitation during the island’s ~500 years of anthropic influence. This has led to introduction of many animal and plant species to the island, which in turn has led to the almost complete replacement of the native ecosystems with introduced ones. Conservation of the remaining native ecosystems rely on a combination of intrinsic and instrumental values for the native species both by the island community and by international funding agencies, and requires continuity in funding and effort. The current zonal vegetation structure of St Helena is comparable to the past structure of the native vegetation, based on modern floristic surveys and a model of the pre-anthropic vegetation, although the species composition has completely changed. The modern zones can be used to indicate potential areas for restoring different native vegetation types. I introduce the concept of indicator species for St Helena, and suggest a set of currently widely spread and easy to identify species that could be used in restoration planning on the island. The arborescent daisies in the sister genera Commidendrum and Melanodendron (family Asteraceae) have been foundation species in most native ecosystems of St Helena. I present genetic evidence of hybridization among the five species in these genera. I propose that the species in the two genera may form a syngameon, an evolutionary unit where closely related species can exchange genetic material via occasional hybridization and introgression. I discuss the significance of the potential syngameon for the conservation of these endangered and ecologically central species. I present preliminary evidence that there may be differences in pollinators between the two species C. robustum and C. rugosum, with the former being especially attractive to moths, and the latter being visited predominantly by flies. I suggest that the structure of the capitula and individual florets can nudge flower visitation preferences of moths and flies. Differences in pollinator fauna may reinforce the reproductive isolation of these closely related and ecologically partly overlapping species, and promote limited hybridization.

Text

2024-09-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89281

Botany

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/