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Abstract Detail

Questioning Species and Species Complexes: A Colloquium in Honor of Dr. R. James Hickey

Barcelona, Julie Fenete [1], Nickrent, Daniel [2], Pelser, Pieter [3].

Large flowers, big secrets: unravelling the biological mysteries of Philippine Rafflesia.

Rafflesia (Rafflesiaceae) is a small endoholoparasitic genus of c. 30 species found in the Philippines, Indonesia, Malaysia, and Thailand. This presentation will present the results of our 15 years of research on the taxonomy, population genetics, host specificity, and reproductive biology of Philippine Rafflesia. Nine new Philippines Rafflesia species were discovered since 2002 and two were resurrected from synonymy. The country now has 13 endemic species of which 12 are island endemics. Microsatellite data provided support for recognizing R. lagascae as a species that is distinct from R. manillana and revealed a potentially cryptic Rafflesia species. We studied patterns of genetic diversity and differentiation of two Rafflesia species. Rafflesia lagascae is the most widespread species of all Philippine Rafflesia. It is known from 14 disjunct, small-sized populations in Luzon. Except for the Mt. Labo population, the largest populations are the most genetically diverse and there is no evidence of low genetic diversity and inbreeding in smaller populations. Although most R. lagascae populations have little gene flow between them, this has not yet resulted in inbreeding. Rafflesia speciosa populations show similar patterns of genetic diversity and connectivity. This species has a more limited range: most populations are found in the central part of Panay I., but a single population is found in the adjacent Negros I. The Negros population is genetically quite distinct from those in Panay suggesting a lack of gene flow for quite some time. There is little genetic structure among Panay populations, suggesting recent gene flow. Rafflesia speciosa populations are better genetically connected than R. lagascae, perhaps because of smaller geographical distances between them. In an extensive host-specificity study, we provided support for the hypothesis that Rafflesia are exclusively parasitic to Tetrastigma (Vitaceae). The phylogenetic relationships between the Philippine Tetrastigma species that are parasitized by Rafflesia and those that are not infected failed to provide evidence for co-evolution. Rafflesia demonstrates some level of host specificity although its species do not seem to be limited to individual Tetrastigma species or clades. We advanced the understanding of the reproductive biology of Rafflesia by revealing that R. lagascae, R. manillana, and R. speciosa are monoecious and that individual host plants can be infected by more than one Rafflesia plant. Lastly, we observed ants transporting seeds of R. philippensis and R. speciosa. However, how these seeds infect host plants still remains a mystery.

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1 - Canterbury University, School of Biological Sciences, Private Bag 4800, Christchurch, 8140, New Zealand
2 - Southern Illinois University, Department Of Plant Biology, 1125 Lincoln Drive, Life Science II Room 420, Carbondale, IL, 62901, United States
3 - University of Canterbury, School of Biological Sciences, Private Bag 4800, Christchurch, 8140, New Zealand

Philippine Rafflesia
parasitic plant
Host specificity
population genetics
Rafflesia speciosa
Rafflesia lagascae
reproductive biology.

Presentation Type: Colloquium Presentations
Session: CO12, Questioning Species and Species Complexes: A Colloquium in Honor of Dr. R. James Hickey
Location: San Luis 1/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 2:45 PM
Number: CO12006
Abstract ID:630
Candidate for Awards:None

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