Browsing by Autor "Olivier Honnay"

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Genetic diversity of Andean<i>Polylepis</i>(Rosaceae) woodlands and inferences regarding their fragmentation history
(Oxford University Press, 2013) Edgar E. Gareca; Peter Breyne; Katrien Vandepitte; Jennifer R. A. Cahill; Milton Fernández; Olivier Honnay
There is a long-standing debate on whether the occurrence of the iconic high-Andes Polylepis woodlands as small and isolated fragments is of natural or anthropogenic origin. We make inferences regarding the fragmentation history based on both a new population genetic study on P. besseri and a synthesis of available studies on the population genetics of Polylepis woodlands. We infer the timing of the main woodland fragmentation event by analysing: (1) the remaining levels of population genetic diversity and the relation to population size; (2) among-population genetic differentiation; and (3) the difference in genetic diversity between the offspring and adult generation. We retrieved seven publications on the population genetics of five Polylepis spp. We did not find a relationship between population size and genetic diversity, and genetic differentiation was low compared with that reported for similar plant species. These findings do not support a history of long-term fragmentation. The offspring showed a loss of genetic diversity and increasing differentiation compared with adults, suggesting that the main habitat fragmentation event is of relatively recent origin. For P. besseri, no significant differences were found between the adult and offspring genetic variation. We discuss the conservation and restoration consequences for this important high-Andean genus.
Polylepis woodland remnants as biodiversity islands in the Bolivian high Andes
(Springer Science+Business Media, 2010) Edgar E. Gareca; Martin Hermy; Jon Fjeldså; Olivier Honnay
Seed germination, hydrothermal time models and the effects of global warming on a threatened high Andean tree species
(Cambridge University Press, 2012) Edgar E. Gareca; Filip Vandelook; Milton Fernández; Martin Hermy; Olivier Honnay
Abstract Seed germination is a crucial event in a plant's life cycle. Because temperature and water availability are important regulators of seed germination, this process will likely be influenced by global warming. Insight into the germination process under global warming is thus crucial, and requires the study of a wide range of water availability and temperature conditions. As hydrothermal time (HTT) models evaluate seed germination for any combination of water potential and temperature, they can be suitable to predict global warming effects on seed germination. We studied the germination characteristics of the high Andean endemic tree species Polylepis besseri (Rosaceae), using HTT models. We were especially interested in the potential effects of global warming on seed germination. Assembly of HTT models for P. besseri was fairly straightforward due to the lack of a seed dormancy mechanism. The models allowed prediction of Polylepis germination under constant and alternating temperatures. Initially, a global warming induced increase in the field minimum and mean temperature will increase P. besseri germination, but as maximum temperatures rise above the optimum temperature for the species, seed germination will become jeopardized. Effects of global warming on seed germination are currently considerably underexplored. HTT models prove to be useful tools to study a plant species' general germination characteristics, and how they may become affected under global warming. For the endemic mountain tree species P. besseri , we predict an increase, followed by a decrease of seed germination under global warming.