Abstract
Amazonian rainforests sustain some of the richest tree communities on Earth, but their ecological and evolutionary responses to human threats remain poorly known. We used one of the largest experimental datasets currently available on tree dynamics in fragmented tropical forests and a recent phylogeny of angiosperms to test whether tree communities have lost phylogenetic diversity since their isolation about two decades previously. Our findings revealed an overall trend toward phylogenetic impoverishment across the experimentally fragmented landscape, irrespective of whether tree communities were in 1-ha, 10-ha, or 100-ha forest fragments, near forest edges, or in continuous forest. The magnitude of the phylogenetic diversity loss was low (<2% relative to before-fragmentation values) but widespread throughout the study landscape, occurring in 32 of 40 1-ha plots. Consistent with this loss in phylogenetic diversity, we observed a significant decrease of 50% in phylogenetic dispersion since forest isolation, irrespective of plot location. Analyses based on tree genera that have significantly increased (28 genera) or declined (31 genera) in abundance and basal area in the landscape revealed that increasing genera are more phylogenetically related than decreasing ones. Also, the loss of phylogenetic diversity was greater in tree communities where increasing genera proliferated and decreasing genera reduced their importance values, suggesting that this taxonomic replacement is partially underlying the phylogenetic impoverishment at the landscape scale. This finding has clear implications for the current debate about the role human-modified landscapes play in sustaining biodiversity persistence and key ecosystem services, such as carbon storage. Although the generalization of our findings to other fragmented tropical forests is uncertain, it could negatively affect ecosystem productivity and stability and have broader impacts on coevolved organisms.
Highlights
The current biodiversity crisis driven by human-induced species loss is likely to drastically alter the tree of life [1,2], but this is still poorly understood due to the historical gap between ecology and phylogenetics [3]
Important advances in this field are helping us to understand the effects of fires on community assembly [11,12,13], the processes involved in community organization during forest regeneration [14,15], and the outcome of species loss and gain on community phylogenetic diversity [16,17]
Thirty-two out of 40 communities (80%) experienced a decrease in mean phylogenetic distance (MPD) over the period of tree monitoring, as indicated by negative rates of change in MPD (Fig. 2). In these impoverishing tree communities, the loss of phylogenetic diversity was positively correlated with the increase in importance value of increasing genera (r = 0.38; P,0.05) and marginally correlated with the reduction in importance value of decreasing genera (r = 0.34; P = 0.059), suggesting that both the proliferation of increasing genera and the reduction of decreasing genera are partially underlying the loss of phylogenetic diversity at the study landscape
Summary
The current biodiversity crisis driven by human-induced species loss is likely to drastically alter the tree of life [1,2], but this is still poorly understood due to the historical gap between ecology and phylogenetics [3]. In the context of conservation, community phylogenetics is a powerful tool to understand how biological communities respond to human disturbances of varying type, intensity, and frequency [10] Important advances in this field are helping us to understand the effects of fires on community assembly [11,12,13], the processes involved in community organization during forest regeneration [14,15], and the outcome of species loss and gain on community phylogenetic diversity [16,17]. We are still far from drawing general conclusions about the organization and persistence of biodiversity in our rapidly changing world [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
