fleshy fruits

Fleshy fruits involve plants in a mutualistic interaction with fruit eating animals. In return for the reliable food resource, fruit eating animals move seeds away from the mother plant often in a non-random pattern.
 
The evolution and variation of fleshy fruit types (berries, drupes etc.) have been ascribed to two different phenomena in the biological history; the radiation of fruit eating mammals and birds, and vegetation changes to more closed, shady plant communities.
 
Fruit eating animals are of course a precondition for fleshy fruit evolution, but that fleshy fruits originated as a response to frugivore radiations is just one of two possible hypotheses for fleshy fruit evolution. The competing hypothesis even suggests that the evolution of fleshy fruits may have initiated the radiation of fruit eating animals (Tiffney 2004). A conspicuos increase in fleshy fruit types and seed sizes occurred in the Cretaceous-Tertiary boundary. At the same time both mammals and birds went through rapid radiations. However, another big change characterized the biosphere in the Early Tertiary. Temperatures rose so that tropical forests became the dominating vegetation type on the globe. In multi-layered, shady plant communities as tropical forests, selection may favour large seed sizes. But evolving larger seed size then require additional dispersal attributes to maintain sufficient dispersal.
 
Testing the vegetation change hypothesis, I have pursued two related studies. The first was developed as part of my thesis and examines whether the evolution of fleshy fruit types were correlated with a change to more closed habitats (Bolmgren and Eriksson, 2005 pdf), and in the sequel we analyzed fruit type changes in relation to variation in seed masses (Bolmgren and Eriksson, 2010 pdf).
 
A consideration emerging from this project is that frugivore selection on fleshy fruits may be dependent on recruitment conditions. To the extent that seed mass and fruit size are correlated, frugivore selection on fruit size may be particularly strong when recruitment success is dependent on seed mass.

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In memory of Dr. Ted Stiles

I am continuing some worke on phylogenetic dispersal mode contrasts. Ted Stiles kindly shared his database with me, consisting of a list of species that, to the best of his knowledge, included all fleshy fruited species in the US (including Hawaii) and Canada.

Here is a OCR-scanned pdf copy (25 MB) of his list of North American fleshy fruited species. According to Dr. Stiles it is not a complete list of all fleshy fruited species in the US (including Hawaii) and Canada), but having used it I can assure it covers a lot. I can also provide a spread sheet version with taxonomy updated according to ITIS, which is the same as the one used in the USDA Plants database.


Kjell Bolmgren
PhD
  
E-mail:
kjell.bolmgren/at/esf.slu.se
 
 
Postal and Visiting Address:
Swedish University of Agricultural Sciences
c/o Department of Botany
Stockholm University
SE-106 91 Stockholm
SWEDEN
 
 
Telephone:
(INT + 46)-730-670365
(INT + 46)-8-164899