Abstracts (first author)
Fitness returns of inflorescence architecture in a wind pollinated annual plant
Male fitness in outcrossing wind-pollinated plants is indirectly influenced by the efficiency of pollen delivery. Many wind-pollinated plant species present adaptations for efficient pollen dispersal. A typical example is provided by Mercurialis annua, where male individuals disperse pollen from erect inflorescences held above the plant. In contrast, hermaphrodite individuals usually release their pollen from sessile axillary inflorescences (axillary hermaphrodites), but pollen production and the length of inflorescences on hermaphrodites in some populations resembles that found in males (pedunculate hermaphrodites). The ability of males to invade and establish in populations with hermaphrodites is expected to depend directly on their relative ability to disperse pollen successfully. Thus, enhanced pollen production and dispersal ability by pedunculate hermaphrodites might prevent male invasion. Here, we estimated the pollen production and siring success of males and hermaphrodites of M. annua that varied in their inflorescence architecture in experimental mating arrays. Males sired four times more offspring when growing in populations with axillary hermaphrodites than with pedunculate hermaphrodites. We use these results, and those from previous work, to model the fate of males and hermaphrodites with different inflorescence architectures. Our results have important implications for the maintenance of males with hermaphrodites in this species (androdioecy). They also raise questions about the genetic architecture and the geographic distribution of inflorescence morphology in M. annua.
Life history trade-offs and human-driven microevolution in Maritime pine, a managed forest tree
Trees are massive organisms, with great maintenance costs, long lifespan, delayed reproduction and long life cycles. Just as any other organism on Earth, they must cope with different environments by finely tuning their relative allocation of resources to growth, reproduction and maintenance. Forests -and hence forest trees- are facing new challenges due to climate warming and other human-derived impacts like forest fires. Under this scenario, selection for earlier and enhanced reproduction is predicted by life history theory. Importantly, forest management can also modify and even counteract adaptive selective pressures in natural, largely undomesticated populations. For example, traditional breeding for high timber yield is predicted to delay reproduction, and lower resistance to biotic or abiotic stressors. In spite of the sound scientific background on life history theory, forest management has largely overlooked these biological principles. Here, we review the existing evidence for how breeding interferes on microevolutionary processes of forest trees. We also provide novel examples focusing on a Mediterranean pine (Pinus pinaster), a species for which detailed quantitative genetic information for key life history traits (growth, size at reproduction, investment in chemical defences) is available. We will present two practical examples derived from breeding programs to illustrate indirect impacts of one event of artificial selection for growth already found in the following generation: first, a correlated genetic response of increased size at first reproduction and reduced reproductive allocation; and second, a reduced ability to cope a harmful forest pest. These evidences suggest that current forest tree breeding can counteract natural selective pressures, thus compromising the resilience of forest populations to future challenges. On the other hand, these finding support that assisted micro-evolution can be considered in dynamic genetic conservation programs.