Amazonian White‐Sand Forests Show Strong Floristic Links with Surrounding Oligotrophic Habitats and the Guiana Shield

Abstract

Amazonian white‐sand forests occur on quartzitic sandy soils, are distributed as an archipelago of habitat islands across the rain forests of Amazonia and contain many endemic plant species. Surprisingly, we found that only 23 percent of plant species in western Amazon white‐sand forests are white‐sand specialists, while the remaining species (77%) also occur in other habitat types. Overall, our analyses revealed: (1) somewhat unexpected composition similarity of white‐sand forests with nearby non‐white‐sand forests; (2) phytogeographical connections among distant white‐sand forests; and (3) a large proportion of western Amazon white‐sand specialists occurring in floras of the western and central Guiana Shield region (7–43%). These results suggest that dispersal from both neighboring oligotrophic non‐white‐sand habitats and distant white‐sand forests is fundamental in shaping western Amazonian white‐sand forests’ species composition and diversity. Although endemism in Amazonian white‐sand forests may be lower than previously estimated, conservation of this unique and fragile environment should remain a priority. Such conservation will require the maintenance of regional dispersal processes that connect these archipelagos of habitat islands and other ecologically similar oligotrophic habitats across the Amazon and the Guiana Shield.

Imaging spectroscopy predicts variable distance decay across contrasting Amazonian tree communities

“…In this way, white‐sand forest tree communities may be functioning as meta‐communities, separated by terra firme forests (Adeney, Christensen, Vicentini, & Cohn‐Haft, ; Palacios et al, ). The lack of declining similarity with increasing distance beyond 800 m is consistent with some published distance decay curves for white‐sand forests in this region (Draper, Honorio Coronado, et al, ), while others that have been developed for much broader spatial scales appear to show a more constant decay (García‐Villacorta, Dexter, & Pennington, ; Guevara et al, ), presumably because they include several compositionally distinct floras.…”

Biogeographic Barriers in the Andes: Is the Amotape—Huancabamba Zone a Dispersal Barrier for Dry Forest Plants?

“…The abundance of exclusive species was two to three times as high as the abundance of shared species (Quintana et al, 2017). The patterns found in DIAVs, with the majority of species shared with neighboring habitats but the minority of ecological specialized species as dominants in terms of abundance, has also recently been documented for palm swamp forests (Pitman et al, 2013) and white sand forests (García-Villacorta et al, 2016) in Amazonia. Dispersal from neighboring ecosystems is fundamental in shaping DIAV species composition, which is also true for Amazonian forests, where dispersal from non-white sand forests is fundamental in DIAVs located in the northern limits of the AmotapeHuancabamba zone have the highest numbers of species endemic to Ecuador.…”

The White‐sand Vegetation of Acre, Brazil

“…Although there is a growing corpus of research on white‐sand formations, addressing large‐scale floristics ( e.g ., García‐Villacorta et al . ), their ecology, and their role in speciation in Amazonia ( e.g ., Fine et al . ), there is still a great deal to be learned about patterns of variation within white‐sand areas.…”