Phenotypic changes in plants during domestication may disrupt plant–herbivore interactions. Because wild and cultivated plants have different habitats and some anti-herbivore defences exhibit some plasticity, their defences may be also influenced by the environment. Our goal was to assess the effects of domestication and the environment on herbivory and some anti-herbivore defences in chaya (Cnidoscolus aconitifolius) in its centre of domestication. Herbivores, herbivory, and direct and indirect anti-herbivore defences were assessed in wild and cultivated plants. The same variables were measured in the field and in a common garden to assess environmental effects. Our results show that domestication increased herbivory and herbivore abundance, but reduced direct and some indirect defences (ants). The environment also affected the herbivore guild (herbivore abundance and richness) and some direct and indirect defences (trichome number and ants). There was also an interaction effect of domestication and the environment on the number of trichomes. We conclude that domestication and the environment influence herbivory and anti-herbivore defences in an additive and interactive manner in chaya.
Tropical home gardens are widely recognized as reservoirs of biodiversity. Typically, Maya home gardens have an area of intensive management and one of extensive management. In the latter, some wild plant species may find safe sites for establishment, since they exhibit a high degree of similarity (in terms in plant species composition) to the surrounding forest and are dominated by plants with fleshy fruit. Therefore, this may attract frugivorous animals, which in turn may generate some seed rain. The objective of our study was to compare seed rain in the extensively managed areas of home gardens and in the surrounding forest during the fruiting peak in a rural landscape in the Yucatan. We assessed seed rain using seed traps in two habitats: the extensively managed areas of home gardens and an adjacent tropical forest. Seed rain was more abundant, denser and more diverse in the home gardens than in the adjacent forest. Approximately one quarter of the seeds recorded are from species shared between the forest and home gardens, suggesting there is notable seed exchange between these habitats. Also 50% of the seed species exclusively found in home gardens are allochthonous, likely rare species from the forest. In general, our results suggest that home gardens—particularly their extensively managed areas—are effective seed traps for forest species.
Abstract:Forest fragmentation, habitat loss and isolation may have a strong effect on biodiversity in tropical forests. This can include modification of the genetic diversity and structure of plant populations. In this study, we assessed the genetic diversity and structure of the treeManilkara zapotain 15 naturally formed fragments of semi-evergreen tropical forest, as well as in an adjacent continuous forest for comparison. Forest fragments were scattered within a matrix of wetlands and were highly variable in terms of size and degree of isolation. The naturally fragmented populations ofM.zapotahad slightly less allelic diversity (Ar: 3.4) than those of the continuous forest (Ar: 3.6), when corrected for sample size. However, populations in the fragments and continuous forest had very similar heterozygosity levels (HE: 0.59 in both cases). Low levels of genetic differentiation were observed among populations (FST: 0.026) and genetic structure was not consistent with isolation by distance, indicating high levels of gene flow. Genetic diversity was not explained by fragment size or degree of isolation. The relatively high genetic diversity and low inter-population genetic differentiation observed inM. zapotamay be the result of long-distance pollen and seed dispersal, as well as the high proximity among patches.
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